JP2018148052A - Remaining life assessment method of oil-filled transformer and diagnostic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diagnostic method and a diagnostic system, capable of gripping a life of a transformer.SOLUTION: A transformer diagnostic method performs diagnostic by: dividing a longitudinal section including a region where an existence region in a transformer without an iron core and an insulation oil are existed into a plurality of divisions in a longitudinal direction and a lateral direction; gripping distribution of a winding coil, a solid insulation material, and the insulation oil which are existed in each division; gripping a relationship that water is alternately diffused between the solid insulation material and the insulation oil in each division; gripping a status where the insulation oil including a predetermined water flows in each division; gripping a counter diffusion relationship of a water amount in each division; comparing an actual measurement value of the water amount in the insulation oil actually fetched from one part of the divisions obtained by dividing during the driving of the oil-filled transformer with a value of the water amount in the insulation oil conducted from the counter diffusion relationship to the division where the insulation oil is fetched; and defining a water distribution in the insulation oil in each division even when a difference of the actual value of the water amount in the oil and the water amount in the oil conducted by the counter diffusion relationship is a predetermined threshold value or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a diagnostic method and a diagnostic apparatus for obtaining the remaining life of an oil-filled transformer from the average polymerization degree residual rate of winding insulation paper accommodated in the oil-filled transformer.

It is considered that the life of the transformer depends on a decrease in mechanical strength of the coil insulating paper, in particular, a decrease in tensile strength (tensile strength).
When a short circuit failure occurs outside the transformer, a large electromagnetic mechanical force is generated in the coil inside the transformer. The transformer is designed so that the stress applied to the coil copper wire at this time is 1200 kgf / cm ² or less, and the coil insulating paper breaks when it becomes unable to withstand the expansion and contraction of the coil copper wire at this time. The internal insulation of the machine will be threatened. When the insulating paper enters such a state, the transformer is judged to have a life.

It is known that the mechanical strength of the winding insulation paper has a correlation with the average degree of polymerization (DP) of the cellulose molecules constituting it. In the Japan Electrical Manufacturers' Association standard JEM 1463, the life level is DP450 and the danger level is It is defined as DP250. In addition, the electric cooperative study group recommends DP450 as the life level of the winding insulating paper (Non-patent Document 1, P177).
As a method for predicting the remaining life of a transformer, the current degree of deterioration of the transformer is investigated, and when the same operation is continued in the future, the DP of the winding insulation paper decreases and its minimum value reaches the life level. It has been made to predict the time until (Non-Patent Document 2, P40).

Current methods of investigating the degree of deterioration of transformers include the method of estimating the degree of deterioration of winding insulation paper by collecting portions of insulation paper that do not affect insulation from inside the transformer, and the generation of insulation paper deterioration in insulating oil. Non-Patent Document 2 describes a method for measuring the amount of CO ₂ + CO, furfural and the like of a product.
Although the former is direct, it is difficult to extract insulating paper unless the transformer is stopped. Therefore, the latter method that can be collected even during operation is widely implemented.

If the transformer continues to operate in the future, the method of predicting the time until the DP of the winding insulation paper decreases and the minimum value reaches the life level is described in P180 to P181 of Non-Patent Document 1. It is described as a life prediction method. There are two types of life prediction methods: a method based on an estimated DP value, and a method (ARY-Map method) for mapping the generation amount (A), generation rate (R), and operation years (Y) of an insulating paper deterioration product. It is shown.
However, as shown in P172 to P174 of Non-Patent Document 1, the method for estimating the deterioration degree of a transformer from components in oil such as CO ₂ + CO and furfural has a certain range of diagnosis, There is a need for a highly accurate degradation diagnosis method.

Therefore, a method for quantitatively evaluating the decrease in DP from the initial operation based on the operation results of the transformer without using the measured value of the deterioration product for the prediction of deterioration has been studied (Non-Patent Document 3). , P43-4, formula (2)).
In Non-Patent Document 2 and the like, the relationship between the deterioration temperature and the rate of decrease in DP has been clarified and reported by various experiments through tests in which insulating paper is thermally accelerated and deteriorated in a test tank simulating a transformer. It describes that the temperature rise history can be grasped from the load of the transformer and the ambient temperature, and the deterioration of the insulating paper can be accurately estimated by combining the thermal deterioration characteristics of the insulating paper.

On the other hand, it is known that the winding insulating paper used in the oil-filled transformer is accelerated by moisture, and its influence is formulated (Non-Patent Document 4, P21-17 to P21). (8) Formulas (1) to (3) and Non-Patent Document 5, P7-7 Formulas (4) and (5)).
Therefore, it is considered that it is important to grasp the moisture absorption state of the upper insulating paper of the winding, which is expected to have the highest temperature in the transformer, for the deterioration diagnosis.
However, it is usually difficult to collect insulation paper from a transformer in operation and measure the amount of moisture. Therefore, from the relationship between the amount of moisture in the insulation oil collected from the transformer and the moisture balance between insulation paper and insulation oil. A technique for indirectly estimating the moisture content in the winding upper insulating paper has been studied (Non-Patent Document 6, P335).

  Patent Document 1 describes a method of measuring the moisture content of insulating paper from the temperature and moisture content of insulating oil. The principle is: “Moisture moves from the higher vapor pressure to the lower one until the moisture vapor pressure of the insulating paper and the moisture vapor pressure of the insulating oil are equal. It reaches an equilibrium state. " In this Patent Document 1, a graph of the moisture vapor pressure in oil against the oil temperature and a graph of the moisture vapor pressure in paper against the oil temperature are shown in Tables 2 and 3, and the oil temperature and the moisture content in the oil are given. It is described that the amount of moisture in the paper is determined.

Non-Patent Document 7 Electric Cooperative Research Vol. 61, No. 2, P43 states, “Generally, oil is collected from a valve near the bottom of the tank. Therefore, in an operating transformer, the upper temperature indicated by a dial thermometer, There is a difference in the temperature of the insulating oil collected, but since this temperature difference is taken into consideration in the coefficient in the equation, the value of the dial thermometer at the time of oil extraction may be applied.
However, in Non-Patent Document 7, the moisture in the oil and the moisture in the paper in the transformer are represented by one representative value, but the aspect of the moisture in the oil and the moisture in the paper in the transformer is constant. However, there is a need for a more accurate method for estimating moisture in paper.

  Patent Document 2 is a document that describes a technique that aims to provide a new apparatus and method for estimating moisture in insulating paper at the upper part of a winding in consideration of the temperature distribution inside the oil-filled transformer. In the technique described in Patent Document 2, a change in temperature with time is taken into consideration, and it is described that the moisture content in oil and the moisture content in paper change with a first order delay with different time constants with respect to the changing oil temperature. ing.

  Patent document 3 relates to a remaining life diagnosis device and a remaining life diagnosis method for a power transformer, and estimates the history of the highest winding point temperature at which the transformer has been operated from the outside air temperature record and load history during operation. The technology to do is described. And, compared to the conventional method of measuring degradation products in insulating oil, it is a technology that claims that the use of heat history can improve diagnostic accuracy. However, Patent Document 3 still shows moisture in insulating paper. The effect of deterioration is not considered.

  Patent Document 4 proposes a method that considers moisture in the paper for DP estimation of the winding insulating paper. The method of estimating the moisture in the paper is a method of measuring the moisture content in oil during operation of the transformer and obtaining it using a diagram showing the relationship between the moisture content in oil and the moisture content in paper. At that time, the upper insulator temperature is obtained by calculation, and the water equilibrium value in the paper at the insulating oil temperature and the moisture content in the oil is estimated from the relationship diagram.

  Patent Document 5 proposes a moisture content estimation method in paper that takes into account that the moisture equilibrium relationship between paper and oil changes due to aging of paper and oil. Assuming that the moisture in the oil circulating in the transformer is determined by the moisture content in the press board, when estimating the average value throughout the year, measure the moisture content in the oil several times during operation of the transformer, and between the paper and oil It is obtained using the water balance relationship. Since the moisture in oil corrected by the moisture content in the press board flows back through the transformer, it is used to estimate the moisture in the winding insulation paper.

Japanese Patent No. 3709444 JP 2008-192775 A Japanese Patent No. 4323396 Japanese Patent No. 4703519 Japanese Patent No. 5704965

Power Transformer Maintenance Management Committee, “4-1 Average Life Degree of Lifetime”, published by the Japan Electric Cooperative Research Association, February 1999, Vol. 54, No. 5 (Part 1), No. 1 Chapter 4, P177 Miyamoto Ikuo, “4. Transformer Life Diagnosis Method”, Lifetime Diagnosis Technology of Oil-immersed Transformer During Operation, IEEJ Research Material, Industrial Electric Power Application Study Group IEA-94-5, P40 Yoshinobu Mizutani et al., “Method of evaluating thermal degradation based on temperature history analysis of 154 to 275 kV oil-filled transformer insulation paper”, 2012 IEEJ Power and Energy Division No. 343, P43-3 to P43-4 Satoshi Nakatsuka et al., “Examination on Thermal Degradation Characteristics of Power Transformer Winding Insulation Paper by Accelerated Degradation Test”, 2006 IEEJ Power and Energy Division Conference 271, P21-17 to P21-18 Satoshi Nakatsuka et al., “Estimation of average degree of polymerization of power transformer winding insulation paper using thermal history”, 2007 IEEJ Power and Energy Division No. 158, P7-7 to P7-8 Noriyuki Sekiguchi et al., “Method for estimating moisture content in insulating paper of oil-filled transformer”, 2007 IEEJ National Convention No. 5-216, P335 "6-1-5 How to determine the limit value of insulating paper based on bubble generation temperature (1) Method for estimating the amount of moisture in insulating paper", Electric cooperative research, Electric cooperative Published by the Society, November 2005, Vol. 61, No. 2, P43

What is common to the patent documents and non-patent documents described above is that the moisture equilibrium relationship between paper and oil is utilized. In the conventional technology, the moisture content in the paper has been estimated on the assumption that an equilibrium relationship is established between the upper coil insulating paper and the moisture content in the oil.
However, in the transformer in operation, the insulation oil must be collected from the oil collection port (for example, the drain valve at the bottom of the tank) where the transformer is installed. It may be different from the value near.
Further, since the insulating oil in the transformer is always in convection, the moisture relationship between paper and oil is locally unbalanced. Therefore, when the moisture content in the oil near the upper part of the winding to be actually estimated from the moisture content in the insulating oil collected from the oil collection port of the transformer is estimated by the prior art, the problem is that the accuracy is lowered.

  Furthermore, in the case of the technique described in Patent Document 5, the average value throughout the year is used as the moisture content in the paper. However, in actuality, the moisture content in the paper changes every moment as the ambient temperature changes, and the moisture content in the paper decreases when the temperature of the insulating paper is high, and vice versa when the temperature of the insulating paper is low. Therefore, in order to accurately calculate the deterioration of the insulating paper, it is considered that the temperature and moisture value at the same time are required. Once the temperature and water content at the same time are obtained, the state of DP of the insulating paper that falls every time under that condition is calculated by a deterioration equation (average residual degree of polymerization) as shown in Non-Patent Document 5. Is possible.

  The object of the present invention is to propose a new method for estimating the amount of oil in the vicinity of the upper part of the winding to be actually estimated from the amount of moisture in the insulating oil, and based on that, the deterioration state of the winding insulating paper is estimated to estimate the oil content. A method for diagnosing the remaining life of a transformer and an apparatus for diagnosing the remaining life are provided.

  The method for diagnosing the remaining life of an oil-filled transformer according to the present invention includes an iron core, a winding coil provided around the iron core, a water-containing solid insulator including insulating paper for coil insulation, a press board, and a wooden object, A method for diagnosing the remaining life of an oil-filled transformer having a configuration in which an oil flow is generated in the insulating oil, wherein the transformer is provided with an oil-immersed transformer immersed in an insulating oil contained in a tank. In an incoming transformer, a longitudinal section including a region where the transformer contents excluding the iron core and a region where the insulating oil is present is divided into a plurality of sections in the longitudinal direction and the transverse direction, and each section is present. The distribution of the winding coil, the solid insulator, and the insulating oil is grasped, and in each area, the relationship in which moisture interdiffuses between the solid insulator and the insulating oil is grasped. Understand the situation where insulating oil containing moisture flows, The mutual diffusion relation of the moisture amount between each area is grasped for each zone, and the measured value of the moisture content in the oil of the insulating oil actually collected from a part of the divided zone during the operation of the oil-filled transformer, Compare the value of the moisture content in the oil of the insulating oil derived from the mutual diffusion relationship for the area where the insulating oil was sampled, and the measured value of the moisture content in the oil and the moisture content in the oil derived from the mutual diffusion relationship. If the difference is equal to or less than a predetermined threshold, the moisture distribution in the insulating oil for each of the areas is determined, and the remaining life diagnosis of the oil-filled transformer is performed based on the determined moisture distribution.

  The method for diagnosing the remaining life of an oil-filled transformer according to the present invention includes an iron core, a winding coil provided around the core, and a water-containing solid insulator including insulating paper for coil insulation, a press board, and a wooden object. A method for diagnosing the remaining life of an oil-filled transformer having a structure in which an oil flow is generated in the insulating oil, wherein the content of the provided transformer is immersed in an insulating oil housed in a tank. In the transformer, a division modeling step for dividing a longitudinal section including a region where the transformer contents are removed excluding the iron core and a region where the insulating oil is present into a plurality of sections in a vertical direction and a horizontal direction, and the solid insulation Physical distribution, the insulating oil distribution, the weight, thickness and average degree of polymerization of the solid insulator, the density and saturated water content of the insulating oil, the opening area between the adjacent areas, and the temperature distribution, Basic data assumptions that assume oil flow distribution and initial moisture distribution , The saturated moisture content of the insulating oil, the moisture diffusion coefficient in the insulating oil, the equilibrium moisture content between the solid insulator and the oil, the movement speed of the moisture in the solid insulator, and the The calculation parameter assumption step that assumes the temperature gradient and the moisture in the oil of the insulating oil of the transformer in the initial state mutually diffuse with respect to the solid insulator over time, but the total moisture content is constant. Grasping and interdiffusion grasping step for grasping the mutual diffusion relation between the moisture content in the oil of the insulating oil and the moisture content in the solid insulation for each zone, and from a part of the divided zone when the oil-filled transformer is operated. Compare the measured value of the moisture content of the insulating oil actually collected with the calculated value of the moisture content of the insulating oil derived from the mutual diffusion grasping step for the area where the insulating oil was sampled. If the difference between the value and the calculated value is less than a predetermined threshold The comparison step for determining the moisture distribution in the insulating oil for each area and the diagnosis for diagnosing the remaining life of the transformer from the moisture content in the paper of the winding coil upper insulating paper derived from the determined moisture distribution It is characterized by comprising steps.

In the present invention, in the mutual diffusion grasping step, the distribution of the insulating oil amount for each of the divided areas, the distribution of the solid insulator amount, the distribution of the opening area between adjacent areas, the oil flow distribution of the insulating oil, It is preferable to grasp the substantial movement speed of water molecules in the solid insulator for each zone, the moisture velocity gradient coefficient in the solid insulator, the thickness of the solid insulator for each zone, and the initial moisture content.
In the present invention, in the comparison step, when the difference between the measured value and the calculated value exceeds a predetermined threshold value, the initial moisture amount, the distribution of the insulating oil amount for each of the areas, the distribution of the solid insulator amount, Distribution of opening area between adjacent areas, oil flow distribution of insulating oil, substantial movement speed of water molecules in solid insulation per area, moisture velocity gradient coefficient in solid insulation, solid insulation per area A feature is added in which at least one of the thickness of the object and the dispersion coefficient is reviewed and recalculated, and the recalculation is repeated until the difference falls below a threshold value.

  In the present invention, in the mutual diffusion grasping step, it is preferable to grasp the mutual diffusion based on the following equation (1).

However, in the formula (1), x: position of the solid insulator from the copper wire (mm), y: moisture content in the solid insulator (%), yn: moisture in the solid insulator in the nth section (section) Amount (%), t: time from the start of operation (min), ∂t: minute time (min), ∂yn: increment of moisture content in the solid insulator in the n-th zone in minute time (%), v ₀ : Substantial moving speed of water molecules in solid insulator (mm / min) in insulating paper in contact with copper wire, k ′: Moisture velocity gradient coefficient in solid insulator (1 / mm), tp: solid insulation in section 1 It is defined as the thickness (mm) of the object.

  In the present invention, the amount of water contained in each region is the sum of the amount of water in the solid insulator and the amount of water in the oil, the sum of the amount of water in each region is the total amount of water contained in the oil-filled transformer, The increment of the amount of water in the area is an amount obtained by subtracting the amount of water flowing out from the amount of water flowing into the area, and it is preferable that the increment of the amount of water in oil satisfies the relationship of the following equation (2).

  The diagnostic device according to the present invention includes a transformer including an iron core, a winding coil provided around the core, and a water-containing solid insulator including insulating paper for coil insulation, a press board, and a wooden object. An oil-filled transformer immersed in insulating oil accommodated in a tank, wherein the oil-filled transformer has a remaining life diagnosis device configured to generate an oil flow in the insulating oil. A function of storing a plurality of sections obtained by dividing a longitudinal section including a region where the transformer contents are present and a region where the insulating oil is present in the longitudinal direction and the transverse direction, and the windings present in each of the divided areas. The function of storing the distribution of the wire coil, the solid insulator, and the insulating oil, and the relationship in which the moisture is interdiffused between the solid insulator and the insulating oil in each zone, and the predetermined moisture in each zone Understand the situation where insulating oil containing The function of calculating the interdiffusion relationship of the moisture content between these for each zone, and the actual measured value of the moisture content in the oil of the insulating oil actually taken from a part of the divided zone during operation of the oil-filled transformer And comparing the value of the moisture content in the oil of the insulating oil derived from the mutual diffusion relationship with respect to the area where the insulating oil was sampled, in the oil derived from the measured value of the moisture content in the oil and the mutual diffusion relationship If the difference in the amount of moisture is equal to or less than a predetermined threshold value, it has a function of determining the moisture distribution in the insulating oil for each area.

    A remaining life diagnosis apparatus according to the present invention includes an iron core, a winding coil provided around the core, and a water-containing solid insulator including insulating paper for coil insulation, a press board, and a wooden object. An oil-filled transformer whose contents are immersed in insulating oil contained in a tank, and a remaining life diagnosis device for an oil-filled transformer configured to generate an oil flow in the insulating oil, wherein the oil-filled transformer A division modeling function for storing each section obtained by dividing a longitudinal section including an existing area of the transformer content excluding the iron core and an area where the insulating oil exists into a plurality of areas in the vertical direction and the horizontal direction; Solid insulator distribution, the insulating oil distribution, the weight, thickness and average degree of polymerization of the solid insulator, the density and saturated water content of the insulating oil, the opening area between the adjacent areas, and the temperature distribution Basic data for storing oil flow distribution and initial moisture distribution Constant function, saturated moisture content of the insulating oil, moisture diffusion coefficient in the insulating oil, equilibrium moisture content between the solid insulator and oil, the movement speed of moisture in the solid insulator, Calculation parameter assumption function that stores the assumed value of the temperature gradient, and moisture in the oil of the insulating oil of the transformer in the initial state mutually diffuses over time with respect to the solid insulator, but the total moisture content is constant A mutual diffusion grasping function for grasping and storing a mutual diffusion relationship between the moisture content in the oil of the insulating oil and the moisture content in the solid insulator for each area, and the division during the operation of the oil-filled transformer. The measured value of the moisture content in the oil of the insulating oil actually collected from a part of the obtained area and the calculated value of the moisture content in the oil of the insulating oil derived from the mutual diffusion grasping step for the area where the insulating oil was collected. And the difference between the measured value and the calculated value is less than a predetermined threshold value. If so, the remaining life of the transformer is determined from the comparison function for determining the moisture distribution in the insulating oil for each section and the moisture content in the paper of the upper insulating paper of the winding coil derived from the determined moisture distribution. A diagnostic function for diagnosis is provided.

  In the interdiffusion grasp function of the remaining life diagnosis apparatus of the present invention, the distribution of the insulating oil amount for each divided area, the distribution of the solid insulator amount, the distribution of the opening area between adjacent areas, and the oil flow of the insulating oil It has the function of grasping the distribution, the substantial movement speed of water molecules in the solid insulator for each zone, the moisture velocity gradient coefficient in the solid insulator, the thickness of the solid insulator for each zone, and the initial moisture content. It is preferable.

  In the comparison function of the remaining life diagnosis apparatus of the present invention, when the difference between the actual measurement value and the calculated value exceeds a predetermined threshold value, the distribution of the insulating oil amount and the distribution of the solid insulation amount for each area are adjacent to each other. Distribution of open area between zones, oil flow distribution of insulating oil, substantial transfer rate of water molecules in solid insulators per zone, moisture velocity gradient coefficient in solid insulators, and solid insulators per zone It is preferable to add a function of recalculating and recalculating at least one of the thickness and the dispersion coefficient, and repeating the recalculation until the difference falls below a threshold value.

  The interdiffusion grasping function of the remaining life diagnosis apparatus of the present invention preferably has a function of grasping the mutual diffusion based on the following equation (1).

However, in the formula (1), x: position of the solid insulator from the copper wire (mm), y: moisture content in the solid insulator (%), yn: moisture in the solid insulator in the nth section (section) Amount (%), t: time from the start of operation (min), ∂t: minute time (min), ∂yn: increment of moisture content in the solid insulator in the n-th zone in minute time (%), v ₀ : Substantial moving speed of water molecules in solid insulator (mm / min) in insulating paper in contact with copper wire, k ′: Moisture velocity gradient coefficient in solid insulator (1 / mm), tp: solid insulation in section 1 It is defined as the thickness (mm) of the object.

According to the remaining life diagnosis method for a transformer according to the present invention, the conventional remaining life diagnosis method did not take into account moisture fluctuations in solid insulation such as insulating paper due to temperature change, whereas the temperature at the same time From the amount of moisture and the amount of moisture, it is possible to calculate the deterioration of the transformer by considering the moisture variation in the solid insulator such as insulating paper and press board, and grasping the distribution of the amount of moisture in the oil based on them.
Since temperature and moisture content behave in reverse, it was corrected that the deterioration of solid insulation was excessively calculated in the prior art, and the life of solid insulation such as insulating paper and pressboard, and thus the transformer As a result of accurately calculating the remaining life, it is possible to diagnose the remaining life of the transformer accurately.
Therefore, it is determined that the remaining transformer actually has a remaining life and is not replaced, and the transformer can be operated efficiently.
In addition, it is possible to accurately calculate fluctuations in temperature and moisture during overload operation of the transformer, and it is possible to diagnose the influence of overload operation on the life of the transformer.

The sectional side view which shows the outline | summary of the transformer used for implementation of the remaining life diagnostic method of 1st Embodiment which concerns on this invention. The flowchart which shows each step of the remaining life diagnostic method which concerns on 1st Embodiment. Explanatory drawing which shows the state divided | segmented into the several area with respect to the partial longitudinal cross-section of the transformer shown in FIG. Explanatory drawing which shows an example which assumed the distribution state of the insulating oil with respect to the division area of the transformer shown in FIG. Explanatory drawing which shows an example which assumed the distribution state of the winding insulation paper with respect to the division area of the transformer shown in FIG. Explanatory drawing which shows an example which assumed the total weight distribution state of a press board and a wooden thing with respect to the division area of the transformer shown in FIG. Explanatory drawing which shows an example which assumed the opening area between the division areas adjacent to the division area of the transformer shown in FIG. Explanatory drawing which shows the position which installed the thermocouple in paper, the thermocouple in oil, and the thermocouple for external temperature measurement separately with respect to the division area of the transformer shown in FIG. FIG. 4 is an explanatory diagram assuming a temperature distribution of insulating oil for each grouped area when the divided areas of the transformer shown in FIG. 3 are grouped into a larger area. Explanatory drawing which shows an example of the state which classified the flow of the insulating oil into six big flows with respect to the division area of the transformer shown in FIG. Explanatory drawing which shows the state which divided | segmented the flow of the insulating oil with respect to the gathered area into six big flows with respect to the case where the division | segmentation area of the transformer shown in FIG. 3 was gathered into the bigger area than the case of FIG. The graph which shows the mutual equilibrium relationship about the water | moisture content in the paper in the winding insulation paper with which the transformer shown in FIG. 1 was equipped, and the water | moisture content in the oil in the insulating oil which is contacting this winding insulation paper. The graph which shows a mutual equilibrium relationship about the water | moisture content in the paper in the press board with which the transformer shown in FIG. 1 was equipped, and the water | moisture content in the oil in the insulating oil which is contacting this press board. The result which the inventor calculated | required regarding the moving speed of the water | moisture content in the coil insulation paper with which the transformer shown in FIG. 1 was shown is shown, (A) is a graph which shows a step temperature rising experiment result, (B) is K '= The graph which shows the calculation result in the case of 0.15. The graph which shows the result of having calculated | required temperature dependence regarding the moving speed of the moisture in a coil insulating paper. The graph which compares and shows an experimental result and a calculation result about the moving speed of the moisture in a press board. The result of having calculated the moisture content in oil using the transformer of the composition shown in FIG. 1 and the experimental value are shown in comparison, (A) is a graph showing the experimental value, and (B) is a graph showing the calculated value. The graph which shows the change by the time of the insulation paper temperature and the moisture content in paper in the calculation result using the transformer of the structure shown in FIG. FIG. 3 shows the result of calculating the oil temperature and the amount of water in the oil corresponding to the transformer division shown in FIG. 3, (A) is a diagram showing the calculation result of the oil temperature in light and shade, (B ) Is a diagram showing the result of calculating the amount of water in oil in shades. The block diagram which shows an example of the remaining life judgment apparatus suitable for using when implementing this invention. A model of temperature distribution and moisture distribution when a winding coil (heater), winding insulation paper, and insulation oil are placed adjacent to each other and a film is formed at the boundary between the insulation paper and insulation oil. Illustration. Explanatory drawing which shows an example of a moisture distribution in case heater, insulating paper, pleura, and insulating oil are adjacent. Explanatory drawing shown about the temperature distribution model in a coil | winding insulation paper, and a moisture moving speed model. Explanatory drawing for grasping | ascertaining a water movement when the temperature gradient which changes temporally is given when a heater, insulating paper, a boundary film, and insulating oil are adjacent. The graph which shows the calculation result which estimated the temperature dependence of kinematic viscosity from the measured value of kinematic viscosity and temperature according to JIS specification. The graph which shows the result of having estimated the temperature dependence of the density using the thermal expansion coefficient of 1 type of insulating oil according to JIS specification from the density measured value of 15 degreeC. The kinematic viscosity and density are the values in FIGS. 25 and 26, the constant const. The graph which shows the result of having calculated the diffusion coefficient temperature dependence of the water | moisture content in oil by Formula (39) supposing that is 4. FIG.

<First Embodiment>
Hereinafter, a first embodiment of a method for diagnosing the remaining life of an oil-filled transformer according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an example of a model transformer used for carrying out the remaining life diagnosis method of an oil-filled transformer. This model transformer is composed of a collection of components of a transformer actually used. The coil winding 2 is provided around the iron core 1 arranged at the center. Each coil winding 2 is covered with insulating paper 3, and the coil winding 2 is sandwiched between the upper and lower press boards 5 and 5, and a clamping force is applied to the coil winding 2 from above and below by the press boards 5 and 5. Yes. A spacer press board is also sandwiched between turns between the windings.
In this embodiment, an iron core 1, a coil winding 2, an insulating paper 3 and a press board 5 are provided to form a transformer content 6, and the transformer content 6 is immersed in an insulating oil 8 filled in a cylindrical tank 7. Thus, the transformer A is configured. The transformer A is configured as a single-phase cylindrical transformer. In the transformer A, various wooden objects are provided in addition to the insulating paper 3 and the press board 5. The wooden objects will be described in detail later.

The coil winding 2 of the transformer A is wound around an insulating cylinder 4 arranged around the iron core 1 in a state of being insulated and separated by an insulating paper 3, and an upper yoke 9 is arranged on the upper side of the iron core 1. A lower yoke 10 is disposed on the side, and a disk-shaped press board 5 is disposed on the upper and lower portions thereof. The primary side coil winding and the secondary side coil winding are respectively supported in an insulated state around the insulating cylinder 4 via a solid insulator such as an insulating spacer (not shown).
Support members 11 are erected so as to penetrate the peripheral portions of the press boards 5 and 5, and these support members 11 press the upper and lower press boards 5 and 5 in a direction approaching each other and are provided inside them. A predetermined tightening force is applied to the coil winding 2.
Although omitted in FIG. 1, the coil winding 2 is surrounded by a winding spacer made of a wooden material equivalent to a press board, an insulating cylinder rail, an insulating cylinder duct rail, an upper yoke insulator, and a lower yoke insulator. Etc. are arranged. Although omitted in FIG. 1, an outer barrier made of a wooden material is disposed outside the winding coil 2. Since these wooden objects affect the diffusion and movement of moisture in the oil, they are analyzed as described below.

In the transformer A shown in FIG. 1, a vertical radiator (radiator) 13 is provided on the right side of the tank 7. The upper side of the radiator 13 and the upper side of the tank 7 are connected by an upper pipe 15. The lower discharge side and the lower part of the tank 7 are connected by a lower pipe 16.
With the above configuration, the insulating oil 8 accommodated in the tank 7 is sucked from the upper pipe 15 to the radiator 13 side and is radiated while passing through the radiator 13, and then passes through the lower pipe 16. Circulation is performed so as to return to the lower side of the tank 7.
Moreover, since the insulating oil 8 accommodated in the tank 7 is heated by the heat generated in the transformer 6, the heated insulating oil causes natural convection from the lower side to the upper side of the tank 7 by natural convection. . The natural convection and the return flow from the radiator 13 are combined, and the upper yoke 9, the lower yoke 10, the upper and lower press boards 5, the coil winding 2, and the like housed in the tank 7 are insulated oil. Since it becomes a flow resistance body with respect to the flow of 8, in the inside of the tank 7, the flow of a complicated some insulating oil arises. The analysis of the complicated flow of insulating oil will be described in detail later. Further, the insulating oil may be forced to circulate with a pump.

In the transformer A shown in FIG. 1 according to the present embodiment, the tank 7 used for the test has an insulating oil amount of 647 L on the upper space side in the tank, an insulating oil amount existing in the coil area of 1142 L, and a tank lower space side. This is a transformer having a total insulating oil amount of 2100 L and a rated capacity of 10.2 kVA. In this transformer A, the weight of the coil insulating paper 3 is 14.3 kg, and the total weight of the upper yoke insulator, the winding spacer, the insulating cylinder rail, the insulating cylinder duct rail, and the lower yoke insulator is 73.7 kg, wooden As a thing, the weight of the support | pillar member 11 is 27.3 kg, and the total weight of an insulating paper, a press board, and a wooden thing is 115.3 kg.
The insulating oil on the upper space side in the tank, the insulating oil on the coil section, and the insulating oil on the lower side of the tank have a total capacity including the insulating oil existing on the radiator 13 side and the pipes 15 and 16. Further, a conservator CS (see FIGS. 3 to 9) omitted in FIG. 1 is installed on the upper side of the tank 7, and 110 L of insulating oil is accommodated in the conservator CS. The insulating oil to be contained is included in the weight of the insulating oil on the upper space side in the tank.

The insulating paper 3 has a configuration in which a sheet having a thickness of 80 μm is wound around the coil winding 2 by a half wrap.
When the transformer A can be regarded as new immediately after the start of operation, the average degree of polymerization (DP) of the insulating paper is assumed to be all new values (around 1100). Since DP decreases as deterioration progresses over time, it is necessary to assume the DP distribution when calculating from the time when the influence of deterioration cannot be ignored after the start of operation. In the case of the transformer A of the present embodiment, the transformer A is regarded as a new product. In this embodiment, the DP of the insulating paper 3 is assumed to be 1174, and the DP of the press board and the wooden object is assumed to be 1101.
The insulating oil was used a density 0.866 g / ^cm 3, 40 insulating oil kinematic viscosity 2.17 mm ² / s in kinematic viscosity 7.68mm ² / s, 100 ℃ at ° C. at 15 ° C..

Transformer A described above was actually used, and after a 20-day operation at a load factor of 100%, a change in moisture in the oil was calculated by calculation for 10 days in a no-load state, and compared with an actual measurement value. Examples are described below.
In the present embodiment, as shown in the flowchart shown in FIG. 2, the oil-filled transformer A includes a region where the transformer contents 6 excluding the iron core 1 and a region where the insulating oil 8 exists. A division modeling step S1 for taking a longitudinal section and dividing the longitudinal section into a plurality of sections in the longitudinal direction and the lateral direction is performed.

“Partition modeling step: S1”
In this embodiment, in the division modeling step S1, as illustrated in FIG. 3, the vertical section on the right half side of the tank 7 is cut in 5 cm increments, and the vertical direction is 48 layers (the bottom side of the tank 7 is the area 1). And the inner top side of the tank 7 was set as a zone 48), and was divided into a total of 296 zones of 7 layers in the radial direction (set in zones A to G in order from the inside to the outside of the tank 7).
Since the transformer A of the present embodiment is single-phase and cylindrical, the structure can be approximated in two dimensions in the radial direction and the vertical direction assuming cylindrical symmetry. For this reason, cutting the mesh in 5 cm increments as shown in FIG. 3 takes a longitudinal section of the transformer A including the region where the transformer contents 6 excluding the iron core 1 and the region where the insulating oil is present, This means that the longitudinal section is divided into a plurality of areas in the longitudinal and lateral directions.

Moreover, as shown in FIG. 3, the internal space of the radiator 13 divides the height direction into R12 to 43 sections in order from the lower side, and the section RU indicates the upper pipe 15 at the upper end of the radiator 13. An area RL indicates the lower pipe 16 at the lower end of the radiator 13. Further, since the vertical direction of the tank 7 is divided into a total of 296 areas of 48 layers and 7 layers in the radial direction, the internal space of the tank 7 is A41 to A48, B1 to B48, C1 to C48, D1 to D48, It is divided into areas E1 to E48, F1 to F48, and G1 to G48.
In addition, since the area corresponding to A1-A40 is an area where the iron core 1 exists and the insulating oil does not exist, it is excluded from the area setting in this division modeling step S1. The internal space of the radiator 13 is divided into 32 regions (RU, RL) that are divided into 32 and connected by the upper pipe 15 and the lower pipe 16.

“Basic data assumption step: S2”
Next, in this embodiment, in the basic data assumption step S2, the volume of insulating oil in each area in the transformer A, solid insulation (coil winding insulation paper, press board, winding spacer, insulation cylinder rail, insulation) The tube duct rail, upper yoke insulator, lower yoke insulator, etc. are collectively referred to as solid insulator). The arrangement, thickness, and weight are examined in advance, and the known values are the values. It is assumed that what is not known is consistent with the survey results described later.
For the transformer A employed in this embodiment, the distribution of insulating oil (unit: L) is shown in FIG. 4, the distribution of winding insulating paper (unit: g) is shown in FIG. The distribution of the total weight of the wooden objects (unit: g) was assumed as shown in FIG.
Since these assumptions have revealed the details of the structure of the transformer A actually used, how much insulation oil, winding insulation paper, pressboard and wooden objects are present in each divided area. Is the result of allocating

In each area shown in FIGS. 3 to 6, the insulating oil convects through the opening area in contact with the adjacent area and the upper and lower areas, and moisture in the oil diffuses mutually. Therefore, the opening area between the sections is assumed as shown in FIG. 7 in consideration of the geometric shape of the transformer A and the structure of the transformer (unit: cm ² ).
In FIG. 7, areas B9 to B36 are areas where coil windings are provided, and the opening area between adjacent areas above and below is assumed to be half of the opening area of the upper and lower areas.
Also, the opening area between the B8 and B9 areas was considered to be more clogged with the winding support and was assumed to be a quarter of the geometric opening area of the B8 area. (864/4 = 216 cm ² ) Further, the boundary between the tank upper part and the coil winding area (the area under the upper black solid line in FIG. 7) is the upper yoke, and the boundary between the tank lower part and the coil winding area ( Since the lower yoke in the lower part of the figure has a lower yoke and is considered not to be open, it is assumed that the open area of C to F in these areas is zero. That is, it is assumed that the upper and lower black thick line portions in FIG. 7 become walls when insulating oil flows, and the insulating oil convects so as to avoid this wall.

The opening area at the boundary between the vertical direction and the horizontal direction of each region is shown as a numerical value in FIG.
The opening area of the vertical direction, A42～A48 is 1963cm ^2, A2~A8 is 864cm ^2, B10~B37 is 432cm ^2, B38~B48 is 864cm ^2, C2~C48 is 1021cm ^2, B10~B37 is 432 cm ^2, D2 ~D48 is 1178cm ^2, E2~E48 is 1335cm ^2, F2~F48 is 1492cm ^2, G2~G48 was set to 1649cm ^2.
The opening area of the left-right direction, the direction of B42~B48 from A42~A48 773cm ^2, the direction from B37~B48 to C37~C48 927cm ^2, the direction from C37～C48 to D37~D48 is 1082cm ^2, D37~ direction from D48 to E37~E48 is 1237cm ^2, the direction from E37~E48 to F37~F48 1391cm ^2, the direction from F37～F48 to G37~G48 was set to 1546 cm ^2.

The opening area of the left-right direction, the direction from B9~B36 to C9~C36 954cm ^2, direction 1113Cm ² from C9～C36 to D9～D36, direction from D9～D36 to E9~E36 is 1272cm ^2, E9 direction from ~E36 to F9~F36 is 1431cm ^2, the direction from F9~F36 to G9~G36 was set to 1590 cm ^2.
About the opening area of the left-right direction, the direction from B1-B8 to C1-C8 is 973 cm < ² >, the direction from C1-C8 to D1-D8 is 1135 cm < ² >, the direction from D1-D8 to E1-E8 is 1297 cm < ² >, E1 direction from ~E8 to F1~F8 is 1459cm ^2, the direction from F1~F8 to G1~G8 was set to 1621 cm ^2.
Radiator opening area of the vertical direction in 13 746cm ^2, the opening area of the opening area of the entrance portion of the upper pipe 15 and the lower pipe 16 connections to 150 cm ^2, CS was set to 13cm ^2.

  If the amount of insulating oil moving per one cycle of calculation exceeds half of the volume, the calculation may become unstable. Therefore, the calculation time is devised, and ∂t: minute time used in the diffusion equation described later is set to 10 seconds. The minute time may be 1 minute when the number of divisions is small, but is 10 seconds in order to increase the flow rate per area when dividing into 296 areas.

In addition, in the case of this embodiment, the time constant used in each formula described later was determined as follows. The numerical value on the right side of the following equation is a numerical value applied when the minute time is 10 seconds.
-Equilibrium time constant of moisture in paper-moisture in oil:
τp (81.5 ° C.) = 205.9 min = 205.9 × 60 sec = 1235.4 × 10 sec
・ Moisture movement speed in coil insulation paper:
ν ₀ (80 ° C.) = 0.015 mm / min = 0.015 mm / 60 sec = 0.005 mm / 10 sec
・ Moisture movement speed in press board:
ν (80 ° C.) = 0.0009 mm / 60 sec = 0.000 / 60 sec = 0.015 mm / 10 sec
As a result, in this embodiment, the flow rate of the insulating oil can be increased to 3 mm / s, as will be described later, and a convection closer to a real device can be set.
In this embodiment, the temperature dependence of the density and viscosity of the insulating oil used in the transformer A is measured in advance, and is used for calculation after grasping each value.

In this embodiment, the temperature dependence of the saturated moisture content of the insulating oil used in the transformer A is measured in advance.
In the case of the transformer A of this embodiment, the saturated water content of oil can be expressed by the Griffin equation. Let p be the actual moisture content of the insulating oil. An important indicator of moisture in oil is water saturation, which is relative humidity. Oil moisture saturation pr is given by the following equation (3).

In the formula (3), R represents a gas constant (1.987 cal / mol / K), and T represents an absolute temperature.
The insulating oil used in transformers A, use a density 0.866g / ^cm 3, 40 insulating oil kinematic viscosity 2.17 mm ² / s in kinematic viscosity 7.68mm ² / s, 100 ℃ at ° C. at 15 ℃ It was. From this measurement result, the temperature dependency of the insulating oil viscosity, which will be described later, is taken into consideration and can be used for the calculation described later.

  In the present embodiment, the initial moisture distribution in oil of the transformer A is assumed to be 4 ppm from the grasp of actual measurement results based on various tests by the present inventors. This assumption of moisture distribution in oil will be described in detail later.

  Next, since it is necessary to obtain and input the temperature distribution of each area in the transformer A, in each area of the transformer A shown in FIG. 8, a thermocouple (Double) is formed in the insulating paper in the areas B10, B22, and B35. (Moisture meter manufactured by Kogyo Co., Ltd.), thermocouples (Doble Moisture meter) are installed in the C10, C22, C35, D2, G43, and RL areas, and thermoelectrics for measuring the outside air temperature outside the G1 area. A pair was placed. In FIG. 8, the areas where the thermocouples are arranged are filled with dark gray using dots to indicate the respective positions.

In the transformer A of the present embodiment, the thermocouples on the surface of the winding insulating paper installed at three places, the upper part of the winding (B35), the middle part (B22), and the lower part (B10), and the six inserted at the above-mentioned positions In addition to the thermocouple, temperature data of a total of 10 locations including the thermocouple for measuring the outside air temperature is collected and used for the calculation described later.
As described above, in the tank 7 of the transformer A, a moisture sensor in oil (a moisture meter manufactured by Doble Co.) is disposed as indicated by reference numerals 20, 21, 22, 23, 24, and 25 in FIG. The oil-in-water sensor 20 is provided in the upper pipe 15, the oil-in-water sensor 21 is provided in the lower pipe 16, and the oil-in-water sensor 22 is an oil discharge valve 26 provided near the bottom of the tank side wall. It is provided in the vicinity. The oil-in-water sensor 23 is provided near the outside of the bottom of the coil winding 2, the oil-in-water sensor 24 is provided near the outside of the center of the coil winding 2, and the oil-in-water sensor 25 is outside the upper portion of the coil winding 2. It is provided nearby, and the amount of water in oil at each position can be measured.

  From previous studies on the transformers of the present inventors, it has been found that the surface temperature of the winding insulation paper is higher by about 10 ° C. than the insulation oil temperature, and therefore the oil temperature in the area where the coil winding 2 is located. Separately, the temperature in the paper was calculated. The outside temperature thermocouple indicates the temperature around the transformer. The moisture calculation requires the temperature of each area, but since there are only 10 measurement points, it is necessary to calculate the other areas for each area assuming the oil temperature and use it for the calculation for each area. Therefore, it was assumed that 10 temperatures measurable in the transformer A and the ambient temperature had a proportionally distributed temperature distribution.

In addition, although it is the above-mentioned temperature proportional distribution, the basic idea is demonstrated below based on FIG.
FIG. 9 is a simplified view of a structure in which the tank 7 is divided into a total of 296 areas of 48 layers in the vertical direction and 7 layers in the radial direction, as shown in FIG. It is a figure which shows the result of the temperature distribution proportional calculation at the time of dividing | segmenting into the area of a total of 74 of seven layers in a direction.
The area is divided into 12 in the vertical direction, and B to G in the tank 7 are divided into 12 areas, so that they are divided into 72 areas in total and divided into 74 areas together with the areas A11 and A12 located above the iron core 1. Yes.

  As shown in FIG. 9, thermocouples are arranged in C3, C6, C9, D1, G11, and RL, respectively, and the oil temperature in the sections C3 to C9 is the temperature of the moisture meter inserted in the transformer coil winding (Do2 to Do2). Assume proportional distribution using Do4). The oil temperatures in the sections A11 to A12, B1 to 12, and C10 to 12 were assumed by proportionally distributing the thermocouples (thermocouple positions C3, C6, and C9) and the moisture meter temperatures (Do2 to Do4). The temperature (Do1) of the moisture meter inserted in the tank bottom is assumed to be the oil temperature of D1, and the oil temperature of C1 to C2 is assumed from the surrounding oil temperature. Assuming that the moisture meter at the top of the radiator represents the oil temperature in the neighboring zone G11, zone G1 is close to the outside air temperature H1 (thermocouple TC84) but is also related to the tank bottom moisture meter temperature (Do1). It was assumed that the remaining area G can be represented by proportional distribution from G11 and G1. The remaining zones D to F were assumed to be a proportional distribution of zone C and zone G. The oil temperature of the radiator was proportionally distributed between the area G11 and the temperature of the moisture meter (Do6) at the bottom. The oil temperature of the conservator CS was assumed to be equal to the outside air temperature (thermocouple TC84).

Assuming the above, the oil temperature can be obtained by proportional distribution for each area into which the tank 7 is divided.
As shown in FIG. 3, the oil temperature obtained by simply proportionally allocating in this way is applied as the temperature of each area obtained by dividing the tank 7 into a total of 296 areas of 48 layers in the vertical direction and 7 layers in the radial direction. Apply. Of course, the method of calculating the temperature distribution when the tank 7 is divided into a total of 74 areas of 12 layers in the vertical direction and 7 layers in the radial direction is shown in FIG. It is preferable to calculate in detail by dividing into 7 layers totaling 296 areas to obtain and apply the temperature distribution.

In addition, when implementing the transformer remaining life diagnosis method described later, if it is necessary to obtain the temperature history of the transformer, the temperature rise history can be obtained from the load of the transformer and the ambient temperature. is necessary. In that case, the temperature history analysis of the oil-filled transformer insulating paper described in Non-Patent Document 3 may be performed.
Thus, the temperature history can be calculated by calculating from the load history of the transformer with respect to the polymerization degree of the insulating paper, and the polymerization degree can be calculated from the temperature history.
In a general transformer, only one thermometer is installed, and when there is only two temperature data in total of the outside air temperature as other data, the temperature history analysis described in Non-Patent Document 3 may be applied.

Since there is a temperature distribution in the tank 7 of the transformer A used for measurement as described above, natural convection occurs in the insulating oil 8. In the forced circulation type transformer, it is necessary to consider the convection for the forced circulation. However, the convection of the transformer A used in the present embodiment may be natural convection. As a result of hydrodynamic simulation of the flow of the insulating oil 8 in the tank 7, the convection distribution (oil flow distribution) is assumed to be a six-loop model (loops a to f) as shown in FIG.
It is considered that the convection flow rate of the insulating oil is proportional to the temperature difference between the upper and lower sides. Therefore, it is preferable to calculate the temperature difference for each loop and optimize the flow rate of each loop so that the calculation result is close to the experimental value.

  Regarding the flow of the insulating oil in the tank 7 in the transformer A, the tank 7 is simply divided into a total of 74 areas of 12 layers in the vertical direction and 7 layers in the radial direction, and the result of examining the flow of the insulating oil is shown in FIG. 11 shows. In FIG. 11, a press board as a partition plate for the lower yoke is provided on the upper side of the area from B2 to E2 as shown by a thick solid line, and a press board as a partition plate for the upper yoke is provided at the lower side of the area from B10 to E10. It is provided as shown by a thick solid line. The insulating oil at the upper part of the tank 7 is drawn into the radiator 13 through the upper pipe 15, passes through the radiator 13, and is returned to the lower part of the tank 7 through the lower pipe 16.

For this reason, it is considered that convection loops only in the upper tank area above the area where the upper yoke partition plate exists. In addition, since the partition plate of the lower yoke exists, it is considered that the oil inflow due to convection is small in the lower part of the tank. Since the gap between the iron core and the coil winding has a small opening area, it is considered that the flow rate of the insulating oil is high but the amount of oil is small. Rather, the convection outside the coil winding is faster and the flow rate is higher. Compared to the tank perimeter of about 3 m, the radiator 13 has a structure in which two pipes with a diameter of 15 cm are connected, so the amount of oil flowing through the radiator 13 is small, and the downward direction along the wall surface of the tank 7 The amount of oil flowing into the As a result of hydrodynamic simulation from this situation, it was determined that a 6-loop convection model as shown in FIG. 10 could be introduced to express convection.
In FIG. 11, loop a, loop b, loop c, loop d, loop e, and loop f when the area is divided into 74 are distinguished and described. It is assumed that the loop model divided into 74 shown in FIG. 11 can be applied to the transformer divided into 296 shown in FIG.

"Calculation method"
(Total calculation of total water content)
The sum of the amount of moisture in the solid insulator (the amount of moisture as the whole solid insulator including insulating paper, pressboard, wooden objects, etc.) and the amount of moisture in the oil is the amount of moisture contained in each zone. If moisture generation due to deterioration of solid insulation such as insulating paper or press board or moisture flowing into the transformer from the outside air can be ignored, the total moisture in the transformer is considered to be constant, and the amount of moisture in each area The sum is considered to be the total amount of water contained in the transformer. However, when the solid insulator deteriorates and moisture is added, it is necessary to consider the moisture to be added.
Further, the increment of the amount of water in each area is an amount obtained by subtracting the amount of water flowing out from the amount of water flowing into the area. Therefore, the water content in oil can be calculated by the following equation (4).

(Difference method of water diffusion equation in solid insulator)
The calculation of the solid insulator is obtained by the diffusion equation shown by the following equation (1).

However, in the formula (1), x: position of the solid insulator from the copper wire (mm), y: moisture content in the solid insulator (%), yn: moisture in the solid insulator in the nth section (section) Amount (%), t: time from the start of operation (min), ∂t: minute time (min), ∂yn: increment of moisture content in the solid insulator in the n-th zone in minute time (%), v ₀ : Substantial moving speed of water molecules in solid insulator (mm / min) in insulating paper in contact with copper wire, k ′: Moisture velocity gradient coefficient in solid insulator (1 / mm), tp: solid insulation in section 1 It is defined as the thickness (mm) of the object.
When the solid insulator is made of insulating paper, the nth section (section) means that when four layers of copper wire are wound with half wrap, eight layers of insulating paper exist outside the copper wire. It means the number in the insulating paper of the layer.

The moisture in the oil of the insulating oil in contact with the solid insulator is considered to be in equilibrium because the moisture saturation is equal to that of the outermost surface of the solid insulator. Water saturation _{p r} is a value obtained by dividing the in-oil water content p [mg / kg] in a saturation water content _{p 0} of the oil. The moisture content in oil can be converted into the moisture content y [%] in the solid insulator corresponding to the following equation (5) and used for calculation. The parameters used in the following formulas are kraft paper parameters used in general transformers. When the insulation paper is different, the calculation is performed by selecting parameters according to the type of insulation paper being applied, the manila paper, and the like.

"Diffusion formula of moisture in oil"
The diffusion equation shown in the following formula (6) holds for the moisture in the oil.

If there is a temperature gradient, the diffusion coefficient D _diffusion is calculated using the temperature of each zone. The diffusion coefficient and the moisture movement speed ν have the relationship of the following equation (7).

Therefore, when the moisture movement speed in the area 1 is expressed as ν ₁ and the density of the insulating oil in the area 1 is expressed as ρ ₁ , it is caused by the diffusion for 1 minute at the boundary between the area 1 and the area 2 in contact with a certain cross-sectional area S. The amount of moisture transfer is calculated as in the following equation (8).

(Dispersion formula of moisture in oil)
In liquid, it is considered that there is a micro flow with no directionality due to fluctuations in density and temperature, vibrations of the transformer itself (including sound waves), and the like. This mixing of oil by local flow is called dispersion.
If the dispersion coefficient is D _dispersion , the effect of dispersion expressed by the difference method is given by the following equation (9).

(Formula of moisture transfer by convection)
In convection, a certain volume of insulating oil flows with direction. The movement of moisture is considered to be the migration of moisture in the oil contained in the volume. Strictly speaking, if oil moves from one area to another where the temperature is different, the volume of the oil is considered to change due to thermal expansion, but the effect is considered to be small and the volume change is ignored. Think that moves.
As described above, in the transformer A of the present embodiment, a six-loop convection model is examined, but details of where the oil amount is set proportional to the oil temperature in which area will be described later. .

“Calculation parameter assumption step: S3”
Next, various parameters necessary for calculating the moisture content in the insulating oil are assumed in the calculation parameter assumption step S3.
(Moisture diffusion coefficient in insulating oil)
Eyring states that the liquid diffusion coefficient is proportional to absolute temperature and inversely proportional to viscosity. When the diffusion coefficient of the solute is D, the viscosity of the solvent is μ, and the absolute temperature T, the relationship of the following equation (10) is established.

Here, the constant was assumed to be 4 from various examination results that the present inventor has studied on transformers in the past. This constant 4 is a numerical value adopted from the constant of the organic liquid described in the physical handbook. The assumption of this constant 4 will be described in detail later.
As described above, the temperature dependence of the moisture diffusion coefficient in the insulating oil can be calculated using the temperature dependence of the viscosity of the insulating oil examined in advance.

Values for the coil insulating paper-oil equilibrium moisture content, the moving speed of moisture in the coil insulating paper, the temperature gradient in the coil insulating paper, and the like were obtained by experiments.
"Equilibrium water content between coil insulation paper and oil"
The equilibrium moisture content between the coil insulating paper and the insulating oil can be used as an equation in consideration of DP dependency in the BET equation represented by the following equation (11).

  The parameters A to D shown in the equation (11) are values shown in Table 1 below. The parameters shown in Table 1 are kraft paper parameters used for the transformer used in the experiment. Therefore, in the case of different types of insulating paper, for example, manila paper, the parameters corresponding to it may be selected.

The DP (average degree of polymerization) of the coil insulating paper and the press board is a newly measured value. It was assumed that the parameter A related to the monolayer saturated adsorption amount was different between the coil insulating paper and the press board, and B, C, and D were equal.
FIG. 12 shows a comparison between the results of the coil insulation paper-oil equilibrium experiment and the BET equation calculation results, and FIG. 13 shows a comparison between the results of the pressboard-oil equilibrium experiments and the BET equation calculation results. All of the calculated values roughly reproduce the experimental results.

"Water diffusion coefficient in oil"
The effect of dispersion is similar to that of diffusion, and the effect of dispersion can be included by multiplying the diffusion coefficient several times.
The dispersion coefficient can be obtained by optimizing to a value that satisfies the experimental results described later.

(Moving speed of moisture in coil insulating paper)
In the equation (1) of the diffusion equation described above, there are two parameters, v ₀ and k ′.
From the analysis of the test results shown in FIGS. 14A and 14B, it was judged that v ₀ = 0.015 mm / min and k ′ = 0.15 / mm were optimal and used for the calculation.
The test result shown in FIG. 14 (A) shows that a heating heater in which 6 wraps of insulating paper is wound is immersed in insulating oil after dehydration filled in a thermostatic bath, and a thermometer and a moisture meter are immersed in insulating oil and held for 8 hours. The relationship between the elapsed time obtained when the heater is energized and heated to the target temperature in 3 hours and then the constant energization is continued and the amount of moisture in the oil is displaced is shown.
As the heater heats, the temperature of the insulating oil rises to the target temperature, but the water content in the oil does not immediately rise to the equilibrium state, and gradually delays with time as shown in FIG. Get up and rise. From this relationship, the optimum values of v ₀ and k ′ can be obtained. As the calculation result in the case of k ′ = 0.15 / mm shown in FIG. 14B, the curve when the value of v ₀ is set to 0.015 mm / min is close to the experimental result, so these values are calculated. Using.

(Temperature dependence of moisture transfer rate in coil insulating paper)
According to a separate study by the present inventors, the time constant τ _{p of} moisture movement in the solid insulator was calculated as 204.4 min at 81 ° C. and 600 min at 35 ° C. Further, it is assumed that the temperature dependence of the time constant is approximated by the following equation (12). The relationship of equation (12) is shown in the graph of FIG.

  The experimental value of the time constant temperature dependency of the equation (12) was only two points of 81 ° C and 35 ° C. In particular, the time constant varies greatly at 25 ° C. or less.

(Moving speed of moisture in the press board)
Four press board pieces are immersed in insulating oil, and the insulating oil is heated by a heater, and the moisture content in the oil is measured with a moisture meter immersed in the insulating oil. The results were analyzed. Assuming that the moisture transfer time constant of the press board is equal to that of the coil insulating paper and the moisture transfer rate v is 0.009 mm / min at an oil temperature of 80 ° C., the experimental values can be reproduced well as shown in FIG.

"Interdiffusion grasping step: S4"
(Time evolution calculation of moisture distribution)
Next, the time evolution of the moisture distribution is calculated. Moisture in the solid insulator develops over time according to the diffusion equation shown in equation (1) above.
Moisture in the insulating oil evolves over time due to diffusion, dispersion and convection. If there is a difference in the moisture saturation between the solid insulator such as insulating paper and the insulating oil, the time will develop in the direction in which the moisture moves from the higher moisture saturation to the lower one. The total moisture content in the transformer is considered to be constant in time evolution, ignoring the intrusion from the outside and the generation of moisture due to the deterioration of the insulating paper. The calculation formula is shown by the following formula (1).

As a result of calculating by the above equation (1), the moisture content in the insulating oil collected during operation is compared with the moisture content in the insulating oil obtained by the calculation, and if the difference is less than the set value (threshold) The calculation is terminated assuming that the moisture distribution has been determined. In this embodiment, 3 ppm can be adopted as the threshold value.
In the transformer A of this embodiment, since the insulating oil collecting part is the oil discharge valve 26, the insulation of the section E1 divided as shown in FIG. Compare the calculation results of water content of oil. As described above, the initial condition of moisture in oil is set to 4 ppm (mg / kg), and the initial condition of moisture in paper is set to 1.45%.

Based on the above formula (1), after calculating the transformer A for 20 days at a load factor of 100% and then operating for 10 days in a no-load state, the change in moisture in the oil is obtained by calculation, and compared with the measured value. An example performed will be described below.
The measured values are the oil-in-water sensor 20 (upper radiator), the oil-in-water sensor 22 (tank bottom), the oil-in-water sensor 23 (in the lower part of the winding), and the oil-in-water sensor 24 (in the middle of the winding). The value measured from the oil-in-water sensor 25 (the upper part of the winding).

FIG. 17A shows actual measured values of moisture in oil obtained from each oil-in-water sensor, and FIG. 17B shows calculated values of moisture in oil calculated from the above equation (1).
As is clear from the comparison between FIGS. 17A and 17B, the actual measurement values and the calculation results almost coincided.
If it is in this state, it can move to the next step. If there is a difference between the calculated value and the actually measured value exceeding the aforementioned threshold value of 3 ppm, the value set as described above, assumed data and parameters are changed, and the above calculation is repeated.
The difference between the calculated value and the measured value is compared with the period in which the amount of water in oil is stable between 10 and 20 days from the start of transformer operation, and whether or not the difference exceeds 3 ppm within this period. I decided to compare them.
By this calculation, it is possible to calculate the moisture content in the paper of the winding upper insulating paper that is considered to be most deteriorated.
For example, in the case of the calculation example shown in FIG. 18, the moisture content in the winding upper insulating paper on the 20th day can be calculated as 0.87% on the copper wire side and 1.12% on the insulating oil side.

When the calculation is repeated, among the values determined as described above, the initial moisture amount, the distribution of the insulating oil amount for each area, the distribution of the solid insulation amount, and the distribution of the opening area between adjacent areas At least of the oil flow distribution of the insulating oil, the substantial moving speed of the water molecules in the solid insulator per area, the moisture velocity gradient coefficient in the solid insulator, the thickness of the solid insulator per area, and the dispersion coefficient Review one and recalculate and repeat the recalculation until the difference is below the threshold.
As an example, in this embodiment, the transformer A is used for model analysis, and among the variously determined values as described above, the distribution of the insulating oil amount for each of the areas, the distribution of the amount of solid insulation, and the distance between adjacent areas. Since it can be estimated that appropriate values have been introduced for the distribution of the opening area and the thickness of the solid insulator in each area, it is preferable to review other items first. For example, by reviewing either the substantial movement speed of water molecules in the solid insulator for each zone, the moisture velocity gradient coefficient in the solid insulator, or the dispersion coefficient, the oil between 10 to 20 days from the start of transformer operation Recalculate if the difference does not exceed 3 ppm within the period when the amount of moisture in the medium is stable. If the difference does not exceed 3 ppm, the recalculation is terminated.
If the difference does not exceed 3 ppm, the value of the item that has been presumed that the appropriate value has been introduced is reviewed and recalculated. When recalculating, it is preferable to review the initial moisture content, the number of dispersed systems, and the oil flow distribution as priority.
Regarding recalculation, in the case of this embodiment, if the division step is set well, it can be assumed that the calculation can be performed by parameter optimization, but if the calculation still does not end, the threshold value is reduced, We will review the division modeling step.

FIG. 18 shows the time variation of the temperature of the upper winding insulating paper and the moisture content in the insulating paper based on the above calculation.
From the calculation results shown in FIG. 18, immediately after the operation of the transformer A, the temperature of the upper insulating paper of the winding rises to the 80 ° C. level, the moisture content in the insulating paper decreases, and remains high temperature and high moisture until the 20th day. However, after the operation of the transformer A was stopped on the 20th day, the behavior of the insulation paper temperature decreased to about 20 ° C. and the moisture content in the insulation paper increased to 1.8% was calculated. The step of grasping the moisture history in the insulating paper in the transformer A is completed.

FIG. 19 shows an example of the distribution of the oil temperature and the moisture in the oil for each section obtained based on the above calculation in shades, and shows the value at 16:00 on the 20th day after the start of operation.
Although the oil temperature (° C.) and the water content in the oil (ppm) can be calculated in detail for each zone, detailed numerical values are not shown in FIG. 19, and FIG. It is displayed in dark gray and the low temperature side is displayed in light gray. In FIG. 19B, the high region for the moisture in the oil is displayed in dark gray, and the low region is displayed in light gray.
FIG. 19A shows that the oil temperature is high on the upper side of the tank 7 and the oil temperature is low on the lower side. From FIG. 19 (B), it can be seen that the water content in oil is high in the region above the region C14 to G14 and in the region below the region C38 to G38.

The next step is the calculation of the minimum winding insulation paper DP. In the case of the new transformer A used in the previous embodiment, the current winding insulation paper minimum DP is naturally a new value.
Since the embodiment shown above is such a calculation example, in the case of a new transformer A, the current winding insulation paper minimum DP is the new value used for the calculation (the winding insulation paper DP is all 1174, All press boards and wooden objects are 1101).

However, when the transformer in actual use which is not the transformer A shown in FIG. 1 is the measurement object, that is, when the transformer at the stage of use over time is the measurement object, for example, the moisture history which is the previous step In the calculation, it is necessary to appropriately substitute the DP distribution. However, since the DP distribution is unknown in a transformer in actual use, the calculation of the previous step at the present time cannot be executed immediately.
Therefore, first, assuming that the DP at the operation start time is a new value, the water content in the paper and the water content in the oil at the beginning of the operation are appropriately assumed, and the water content distribution in the paper at the operation start time in the above embodiment. Based on the described method, calculation is performed for a certain period of time, and a decrease in DP for a certain period of time is calculated for each divided area.

Various examination results have been reported for the rate at which DP of insulating paper decreases when moisture is present, and can be calculated with reference to, for example, a calculation formula shown in Non-Patent Document 5.
Non-Patent Document 5 discloses the following equations (13), (14), and (15).

In each equation, βm and γm are constants determined by the moisture content m [%] in the insulating paper, and βm and γm in the equation (13) substitute the moisture content m in the insulation paper for the equations (14) and (15). Thus, the average degree of polymerization residual ratio can be calculated by obtaining Vr (lifetime loss ratio).
In Non-Patent Document 5, the life loss ratio Vr is defined by the following equation (16).

In equation (16), V ₃₀ : life loss when heating (winding) temperature is 95 ° C. for 30 years continuously, θ _i : heating (winding) temperature [° C.], h: heating (winding) temperature θ _i Indicates the continuous time.
By using these formulas (13) to (16), a decrease in the average degree of polymerization DP can be calculated.

Subsequently, the moisture distribution in the paper for the next fixed time is calculated, and the calculation is performed using the lowered DP of each area previously calculated in the calculation.
The calculation can be sequentially repeated until the current time, and the DP distribution at the present time can be obtained. The assumed value is appropriately selected so that the difference between the experimental value and the calculated value of the moisture content in the insulating oil obtained from the result is equal to or less than a set value (threshold value, for example, 3 ppm).
The constant time chosen to execute the calculation for one cycle is considered to be one year or less for normal operation, but the transformer is considered to have rapidly deteriorated due to overload operation. In this case, it is necessary to shorten one cycle of calculation according to the degree.
When the calculation has converged, the current minimum winding insulation paper DP can be obtained.
When it is considered that the deterioration of the insulation paper has progressed suddenly due to overload operation, the calculation break is calculated in units of hours or 1 day, and when DP falls by 100 a day, the second day is the time when 100 drops Recalculate from

"Remaining life diagnosis step"
The next step is the remaining life calculation and diagnostic step.
Assume that transformer A is operated under the same conditions as before. In other words, it is assumed that the temperature history of the transformer A is that the average load and ambient temperature from the start of operation to the present will continue.
Using the current DP distribution calculated in the previous step, the DP distribution after the next fixed time is calculated to confirm the decrease in DP. By repeating the calculation every certain time until the minimum DP of the winding insulating paper reaches the life level, the remaining life of the transformer can be obtained, and the value becomes the result of the remaining life diagnosis of the converter. For example, when operating in the current state, the remaining life can be evaluated as 5 years.

FIG. 20 is an explanatory diagram showing an example of a remaining life diagnosis apparatus (personal computer) used for carrying out the steps outlined above.
The remaining life diagnosis apparatus 30 includes a processing unit 31, a storage unit 32, an interface unit 33, and a display unit 34 connected to the interface unit 33 by wire or wirelessly.
The storage unit 32 stores information on the areas divided in the division modeling step S1 described above, various basic data obtained in the basic data assumption step S2, various calculation parameters obtained in the calculation parameter assumption step S3, A plurality of pieces of information such as mathematical formulas set in the mutual diffusion grasping step S4 are individually stored, and the processing unit 31 has a function of performing a plurality of calculations and processes.
The calculation performed in each of the above steps can be performed using, for example, a commercially available spreadsheet software for personal computers.

As described above, each region divided into 296 areas in the division modeling step S1 is applied to each cell of the spreadsheet software, and a calculation formula is incorporated in each cell so that calculation can be performed for each region.
For each sheet of spreadsheet software, calculated oil amount, oil diffusion coefficient, oil density, moisture content in oil (g), moisture content in solid insulation (g), moisture content in oil (ppm) The numerical value input to each cell is displayed on the display device 34.
For example, in the transformer A shown in FIG. 1, the oil temperature calculation value is automatically measured at 10-minute intervals for 10 temperature measurement data, but for a minute time for all temperature data in each of the 296 areas, For example, since data is required at 10-second intervals, as described above, it is automatically calculated for each area (each cell) by proportional distribution, converted into temperature data at 10-second intervals for each 296 areas, and stored for each area and used for calculation. Is done.
Once the oil temperature in each area is determined, the oil diffusion coefficient for each area is calculated and stored in each cell of the oil diffusion coefficient sheet, and the density is calculated and stored in each cell of the oil density sheet for later calculation. Used for
The sheet of moisture content in oil records how much oil is contained in each divided area and is used for later calculations.

In the spreadsheet software, in addition to the above-mentioned sheets, sheets for each of 296 areas from A41 to R43 are set, and the weight and average polymerization degree are input and stored for the thickness of the press board and the wooden object for each area. The weight of the insulating paper and the average degree of polymerization are input and stored for each area.
Moreover, the opening area information between the areas described above based on FIG. 7 is recorded in correspondence with the boundary position of each area, and is used for later calculations.
Assuming that the initial moisture content in the oil starts from the same initial moisture content in all zones, 4.0 ppm is input at the start of the time axis and is used for later calculations.

The moisture content in the fixed insulator is divided into the moisture content in the coil insulating paper and the moisture content in the press board, and is recorded in the cells corresponding to the respective areas.
The coil insulating paper is calculated by taking, for example, four half-wrap windings of 80 μm thick insulating paper. In this case, the calculation is performed assuming that a total of eight layers of insulating paper are overlapped.
The side near the copper wire (coil winding) has a high temperature, so there is little moisture in the paper, and the insulating paper on the side in contact with the insulating oil has a low temperature, so the moisture in the paper tends to increase. The spreadsheet software is configured so that the moisture value in the coil insulation paper can be input for each piece of insulation paper. In the case of a press board, the moisture distribution differs in the thickness direction. Each cell corresponding to each region is configured so that medium moisture can be input.

Regarding the dispersion coefficient, the liquid is greatly affected by density, temperature fluctuations, transformer vibration, etc. and produces a micro flow, which causes dispersion due to the local oil flow. Since a large coefficient can be taken, it is necessary to make a provisional decision by calculating as a parameter so as to satisfy the result described later. Here, provisional values are selected and used for calculation as described later.
As for the oil flow velocity, the flow rate at a single time step was determined in the area of the smallest volume in the flow path of each area when the maximum flow velocity was 3 mm / s from the cross-sectional area of the area. Convection occurs when there is a temperature difference. In each of the six convection loops, a zone on the high temperature side and a low temperature side that determine the temperature difference is shown, and the convection flow rate is set to change at a ratio to the set temperature.

In order to solve the above-mentioned diffusion equation, the initial moisture content in oil (4.0 ppm), the initial moisture content in paper (1.45%), the coil insulation paper thickness (80 μm, 1.0 times), the dispersion coefficient Each cell of the spreadsheet software is assembled so that each flow velocity (mm / s) of convection af can be substituted as a calculation parameter (60 times).
Each cell of the spreadsheet software is set for every 30 minutes for the test operation period of the transformer for 30 days and up to the 4320th line by 10 minutes.

The details of each step that has been outlined so far will now be described in more detail.
The processing unit 31 and the storage unit 32 of the remaining life diagnosis apparatus described above are configured to be able to input the above-described items, calculation functions corresponding to them, equations and parameters necessary for calculation according to the following items, and the like. Is calculated.
"Specific calculation method of moisture in transformer winding insulation paper"
The moisture in the transformer is the sum of the moisture in the insulating oil and the moisture in the insulating paper. It is assumed that moisture does not enter from the outside, and the total amount of moisture in the transformer is assumed to be constant. However, in some cases, some moisture generated due to aging of the insulating paper is taken into consideration.

  There are three ways to move moisture in insulating oil: diffusion, dispersion, and oil flow. When there is a concentration gradient in the moisture in the oil, even if the insulating oil is stationary, the moisture moves from the high concentration side to the low concentration side. However, even when there is no oil flow as a whole, dispersion is actually caused by a local flow in the insulating oil due to local temperature fluctuations and transformer vibration. The local flow is the same as that of stirring the insulating oil, and the water moves from the high water concentration side to the low water side similarly to the diffusion. In addition, if there is a temperature distribution in the transformer even if there is no forced circulation of the insulating oil, convection occurs in the insulating oil, and moisture in the oil circulates in the transformer along the flow of the insulating oil.

Moisture in the insulating paper diffuses and moves through the insulating paper when there is a concentration distribution in the insulating paper. Further, it is known that when there is a temperature distribution in the insulating paper, moisture moves from the high temperature side to the low temperature side, and a moisture concentration distribution is generated in the insulating paper.
On the other hand, the moisture in the insulating oil and the moisture in the insulating paper move with each other. For example, when dry insulating paper is put into insulating oil containing moisture, the moisture moves from the insulating oil to the insulating paper, and the moisture in the insulating oil decreases. It is considered that moisture moves between the insulating oil and the insulating paper from the high relative humidity side to the low side. The higher the temperature, the more the insulating oil can contain moisture. On the other hand, the insulating paper does not adsorb moisture as the temperature increases. Therefore, as the temperature rises, the relative humidity of the insulating oil decreases and the relative humidity of the insulating paper increases, so that moisture in the insulating paper is released from the insulating paper and released into the insulating oil.

"Temperature distribution at the boundary of copper wire, insulating paper and insulating oil of winding coil"
There is a transition region at the boundary between paper and oil, and the oil is considered to be in contact with the paper at a temperature higher than the oil temperature to equilibrate moisture. When the temperature distribution situation in the coil winding is schematically shown, the insulating paper is wound around a copper wire. The copper wire constituting the coil winding is a heating element (heater) during the operation of the transformer and is considered to be higher than the oil temperature. Therefore, it is considered that the insulation paper (paper) has a high temperature on the copper wire side and a low temperature on the oil side, and there is a transition region (boundary film) between the paper and the oil. It is considered that there is a temperature difference of about 10 to 15 ° C. and about 15 to 20 ° C. in the oil-feeding transformer.
For example, assuming that the copper wire surface is 80 ° C., the temperature gradually decreases in the thickness direction of the insulating paper, and if the outermost surface of the insulating paper is 73 ° C., a transition region (boundary film) outside the insulating paper. As a result, the temperature drops rapidly, resulting in a temperature difference such that the temperature of the insulating oil at a position away from the transition region reaches 60 ° C.

“Details of Derivation of Diffusion Equation for Winding Insulation Paper with Temperature Gradient”
As shown in FIG. 21, the winding coil (heater) temperature T ₀ regarded as a heating element, the paper temperature changes linearly from T ₀ to T ₁ , and the film temperature changes from T ₁ to T ₂ , oil The moisture distribution when the temperature is T ₂ is calculated.
As for moisture, as shown in FIGS. 21 and 22, the moisture balance at a minute time ∂t in a minute section ∂x is considered per unit area. The moisture concentration at the position x in the paper is y (x), and the change in the moisture concentration at the minute interval に お け る t in the minute section ∂x is ∂y. Consider the moisture that passes x = x during ∂t. Moisture is in thermal motion in the ± x direction at a velocity v (T).

Since it is assumed that the paper temperature changes linearly from T ₀ to T ₁ , it can be expressed by the following equations (17) and (18).

  Although the average speed of water molecules is considered to be proportional to the square root of temperature, the average speed is given by the following formulas (19) and (20) by approximating a small temperature difference and a linear change with temperature. Suppose that FIG. 23 shows a temperature distribution model and moisture transfer rate model in the winding insulating paper.

  We think that half of the moving water molecules move to the right and half move to the left. The amount of moisture coming from the left per minute time ∂t is given as follows.

  Here, Δx1 is the movement distance of moisture coming from the left. The moisture velocity at the position x−Δx1 can be expressed by the following equation (22), and the moving distance per minute time ∂t can be expressed by the following equation (23).

  Solving Δx1 from this equation yields the following equation (24).

In the equation (24), the denominator k′v ₀ ∂t can be approximated to be sufficiently smaller than 1 and can be expressed by the following equation (25).

  Substituting this relationship into equation (21) yields the following equation (26).

  Further, if y (x−Δ) is expanded and the second term is taken, it can be expressed as the following equation (27), and the following equation (28) is obtained.

  The amount of water coming from the right can be expressed by the following equation (29).

  Here, Δx2 is the movement distance of moisture coming from the left, and can be expressed by the following equation (30). Therefore, the substantial water flow flowing from the left to the right can be expressed by the following equation (31).

When ∂t is extremely small, the content of the parenthesis of the second item of the equation (31) can be v _x ² . In that case, when (31) is rewritten, the substantial flow of water can be expressed by the following equation (32).

Next, non-equilibrium moisture movement is calculated when a time-varying temperature gradient is given. As shown in FIG. 24, in the thin film region between x and x + ∂x, the moisture balance between time t and t + ∂t is the amount of moisture entering from surface x: F (x), surface x + ∂x Moisture amount coming out of the water: F (x + ∂x).
The amount of moisture change in the region sandwiched between the two surfaces is obtained by the following equation (33), and the diffusion equation is obtained by the following equation (34).

  When the previous equation (19) is substituted into this equation (34), the diffusion equation is given by the following equation (35).

  In the equation (35), the first and second terms on the right side represent moisture movement caused by a temperature gradient. Due to the temperature gradient, the moisture velocity has a gradient k '. If it is assumed that there is no temperature gradient and the moisture velocity is constant, that is, k ′ = 0, the right side is only the third term, and equation (35) becomes the following equation (36).

  Here, if the following equation (37) is set, the equation (36) can be expressed as the following equation (38), which is an equation representing the diffusion phenomenon of the primary equation due to a constant temperature. It becomes (6) Formula demonstrated previously.

"Derivation of difference equations"
Since it is difficult to analytically solve the previous equation (35), it is considered to solve by the difference method. The difference method is a method of solving a continuum as a collection of minute regions and expressing a differential as a difference from an adjacent region, and is an analysis means usually used for simulation of a thermofluid phenomenon.
When the first-order differential ∂y / ∂x of y is expressed in a difference format, the following equation (39) is obtained.

The subscript n represents the nth minute region from the copper wire. For example, in the case of the previous experiment, the number of turns is 12 in the case of 6 wraps, and can be considered as n-th insulating paper. In that case _{t p} represents the thickness 0.167mm one sheet of paper.
Further, when the second-order differential ∂ ² y / ∂x ² of y is expressed in a differential format, the following equation (40) is obtained.

  Using the above relationship, the calculation formula (35) can be expressed by the following differential equation (41).

  Expression (41) is an expression for calculating moisture movement in the insulating paper. As the boundary condition, it is necessary to consider the calculation of paper that is wound directly on the coil winding (heater: copper wire) on the innermost side and paper that is in contact with oil on the outermost side. . In the first paper on the heater side, moisture movement occurs only between the second paper. Therefore, it was decided to approximate by the following equation (42) instead of the equation (39) as the calculation of the first derivative of the first y.

  Further, the second-order derivative of y of the first sheet is approximated to be substantially equal to that of the second sheet, and is calculated as a relationship represented by the following equation (43).

In the paper that is in contact with oil on the outermost side, moisture movement occurs so that the moisture in the paper and the moisture in the oil are in equilibrium. The outermost surface of the coil winding and oil are considered to be in contact with each other at the temperature of the outermost paper. When the heater temperature (copper wire temperature) is 80 ° C., it is considered that there is a temperature difference of about 13 ° C. from the oil temperature.
Strictly speaking, in the present embodiment, it is considered that the moisture in the oil in the film is not a constant value, but since the handling of the film is very difficult, the moisture in the oil in the film is also different from the moisture in the oil outside the film. We assume that they are equal.
The relative humidity of the moisture in the oil is the saturation _pr , and can be expressed by the following equation (44) using the Griffin equation.

  Here, R represents a gas constant, and T represents an absolute temperature. On the other hand, the moisture in the paper is given by the relationship of the following equation (45) based on the results of investigations by the present inventors.

Here, a represents 0.260, and k represents 8.49 × 10 ⁻⁴ e ^{2010 / RT} . However, here, R is calculated using 1.98 cal / mol / K. This is equal to or less than the expression (46) and solving for _{p r.} (46) y _r in expression may be considered a saturation Kamichu water.

On the contrary, the moisture content y _oil in the insulating paper calculated by the equation (45) using the moisture content p in the oil is regarded as the moisture concentration in the oil (corresponding to the insulating paper), and is used to insulate the outermost layer. Perform paper difference calculation. That is, as the calculation of the first derivative of y of the outermost insulating paper (12th sheet: in the case of 6 wrap winding as in the experimental example shown in FIG. 14A), instead of the equation (39), The following equation (47) can be used, and the following equation (48) can be used in place of equation (40) as the calculation of the second derivative of y.

In addition, the moisture content in the oil is calculated by subtracting the moisture content of the insulating paper from the moisture content of the entire system to obtain the total moisture content in the oil.
In the equation (41), there are two parameters, v ₀ and k ′. v ₀ represents the ease of moisture movement in the insulating paper, and is a physical quantity that is close in meaning to the diffusion constant as seen in equation (37).
In this embodiment, since the moisture in the oil is also considered to be the moisture concentration y _{oil in} the paper equivalent to that in the paper, the moisture movement is related to v ₀ even in the region where the paper and the oil are in contact. k ′ relates to a moisture velocity gradient, that is, a difference in moisture velocity between the high temperature portion (heater side) and the low temperature portion (oil side) of the insulating paper.

Therefore, both parameters are optimized from the experimental results. As an experimental result, v ₀ = 0.0025 mm / 10 s and k ′ = 0.15 / mm are adopted for the winding insulating paper as a parameter that gives a moisture change in oil close to the measured value. These are optimum values obtained from the experimental results, as described above based on FIGS. 14 (A) and (B).
Further, v ₀ is the result of an experiment of pressboard, is adopted 0.0015 mm / 10s, considered immersed in without insulating oil it pressboard wound directly copper, k 'was zero. V ₀ of the press board, as previously described based on FIG. 16, but reproducibility of the experimental values with a 0.009 mm / min was determined from it is good, the value of 10 seconds in the diffusion equation Therefore, 0.0015 mm / 10s is adopted.

"Time constant of insulating paper and temperature dependence of k and k '"
As approximated in the description of FIG. 15, the time constant τp of the insulating paper is approximated by the above equation (12). Here, the time constant and the moving speed of water molecules are assumed to be inversely proportional. That is, it is assumed that the following equation (49) holds for an arbitrary temperature T.

Therefore, if τ _p (80 ° C.) = 204.4 min and v ₀ (80 ° C.) = 0.015 mm / min from the experimental results so far, G = 204.4 min × 0.015 mm / min = 3.07 mm. Consider the following equation (50).

  When the heater temperature is 80 ° C., the following equation (51) is obtained. However, if the insulating paper and the insulating oil are assumed to be constant at 35 ° C. at 35 ° C., k has temperature dependence. Therefore, k is expressed by the following equation (52). Similarly, the velocity of water molecules disappears from position dependency at 35 ° C., so it is considered as the following equation (53).

"About diffusion"
According to Eyring, the liquid diffusion coefficient is considered to be proportional to absolute temperature and inversely proportional to viscosity. As described above, when the diffusion coefficient of the solute is D, the viscosity of the solvent is μ, and the absolute temperature is T, the relationship of the equation (10) is satisfied.
As shown in the equation (10), the viscosity of the insulating oil is represented by the product of kinematic viscosity and density. The results of measuring the kinematic viscosity and density of the insulating oil used in the experiment are shown in Table 2 below.

FIG. 25 shows the calculation result of the kinematic viscosity estimated from the temperature dependence from two points of 40 ° C. and 100 ° C. according to JIS K2283. FIG. 26 shows a calculation result of estimating the temperature dependence from the measured value of 15 ° C. using the thermal expansion coefficient 7.4 × 10 ⁻⁴ / ° C. (example described in JIS C2101) of one kind of insulating oil according to JIS C2101 .

The const. Is a constant due to the solvent and solute. Since there is no data on the value of moisture in oil, the value is assumed from constants due to different solvents and solutes. For three types of solvents, water, methanol, and ethanol (solute), the water diffusion coefficient and viscosity data were examined from the Chemical Handbook (Revised 4th Edition) and the Chemical Engineering Handbook (Revised 4th Edition). The results obtained are shown in Table 3 below.
Compared with the case where the solvent is water, methanol and ethanol are more constant const. It is considered that water tends to hardly diffuse in organic solvents. Therefore, the constant const. Is a constant const. The calculation was made assuming that 4 is 4.
The kinematic viscosity and density are the values in FIGS. 25 and 26, the constant const. FIG. 27 shows the result of calculating the diffusion coefficient temperature dependence of moisture in the oil by equation (39) assuming that is 4.

  From the results shown in FIG. 27, the viscosity of the insulating oil may be high at low temperatures, and the diffusion coefficient is smaller than that of high-temperature insulating oil. Therefore, it is necessary to consider moisture movement due to the difference in diffusion coefficient in addition to normal diffusion at the interface where the high temperature oil and the low temperature oil are in contact.

About dispersion
Although the moisture in the insulating paper was thought to move by diffusion, the moisture movement in the insulating oil has other effects. Moisture movement by diffusion alone is extremely slow, and when considering actual water propagation, it is necessary to consider the effect of local micro oil flow. Insulating oil is considered to have a myriad of micro vortices (considered as turbulent flow) that are constantly generated at a plurality of locations in the oil, and the oil is moving as a group. The phenomenon of moisture in oil due to such a non-directional micro oil flow is referred to herein as “dispersion”. As for dispersion, a dispersion coefficient can be considered like diffusion, and the dispersion coefficient is considered to be orders of magnitude greater than the diffusion coefficient.
With respect to the moisture in the insulating oil, the diffusion equation can be expressed in the same manner as the equation (40), and when the moisture concentration in the oil is p, it can be expressed by the following equation (54).

  However, since the diffusion coefficients of adjacent areas are different, it is necessary to devise a calculation method at the boundary. Rewriting equation (54) in differential form yields equation (55) below.

  Here, when the following equation (56) is set, equation (55) becomes a diffusion equation that can be expressed by the following equation (57).

Here, D _diffusion represents a diffusion coefficient, and v represents an average moving speed of water molecules.
If the temperature is continuously changing, the previous diffusion equation (35) can be used. However, in this example, since the diffusion coefficient is discontinuous at the boundary, the water movement at the boundary is calculated using the average movement speed of water molecules obtained from the diffusion coefficient.
Based on the diffusion coefficient of water in oil determined in the previous section, the average moving speed of water molecules is determined using equation (56). In the area divided into 296 as described above, when three areas n-1, n, and n + 1 are arranged, half of the water molecules contained in the nth area are half on the n-1 side. Thinks that it moves to the (n + 1) th side. When the water concentration in oil in the n-th area is _expressed as pn, the water molecule average velocity in the n-th area as v _n , the cross-sectional area of the boundary as S, and the density of the n-th area as ρ _n , the n-th area The amount of water W _{n → n + 1} (mg) that moves per unit time (1 minute) from the first to n + 1 is given by the following equation (58).

Similarly, the water W _{n + 1 → n} (mg) flowing into the n-th area from the n + 1-th area can be considered, and when subtracted, the n-th area increases the water content ΔW _n (mg) by the following equation (59). To do.

Assuming that the thickness of one divided area is tp, the amount of oil contained in the nth area is expressed as S × tp × ρ _n (kg), so the nth area is a value of the following equation (60). Only the moisture in oil Δw _n (ppm) will increase.

The oil flow in transformer A is considered to be mainly convective. However, even if there is no convection, it is considered that there is a micro oil flow with no directionality due to fluctuations in density and temperature, vibration of the transformer itself (including sound waves), and the like.
The dispersion considered here is the movement of water in the oil accompanying the movement of the oil, assuming that the mixing of the oil by the local oil flow always occurs.
Such a micro oil stream is considered to have an effect of averaging the local concentration regardless of the concentration gradient of moisture in the oil.

It is assumed that the water concentration in oil is _pn-1 , _pn , and _{pn + 1} , respectively, when three sections n-1, n, and n + 1 are arranged. The average water content in the oil in the three zones is (p _n-1 + p _n + p _{n + 1} ) / 3, and if the proportionality constant is A, the water content in the oil in zone n is {(p _n-1 + p _n + p _{n + 1} ) / 3-p _n } × A increments.
When this is modified, (p _n−1 −2p _n + p _n−1 ) / 3 × A is obtained, and if 3 × A is set as the dispersion coefficient D _dispersion , the effect of dispersion is given by the following equation.

  It can be seen that the equation (61) is similar to the following equation (62) in which the diffusion coefficient shown in the equation (56) is substituted into the equation (54).

Therefore, it is understood that the movement of moisture in oil due to dispersion can be calculated simply by replacing the diffusion coefficient in the diffusion equation (54) with the dispersion coefficient. In the boundary area, the dispersion effect can be added to the aforementioned diffusion effect.
Since the dispersion coefficient is unknown, the dispersion coefficient is changed as a parameter to take a value close to the experimental result.

"About convection"
In convection, a certain volume of insulating oil flows with direction. It is considered that the movement of moisture moves the moisture in the insulating oil contained in the volume. Strictly speaking, if the oil moves from one region to another region where the temperature is different, the volume of the oil is considered to change due to thermal expansion. I think so.
The state of convection can be numerically calculated, but it is very complicated and difficult to calculate because it is calculated with an actual transformer structure. Therefore, simulation was performed assuming a simple structure. as a result,
・ Independent convection in the upper part of the tank ・ Slight convection in the lower part of the tank ・ It was found that the flow between the iron core and the coil winding is smaller than the outside of the coil winding but the flow speed is larger. Therefore, as described above, a 6-loop model as shown in FIG. 10 was assumed and a convection model was examined.
The flow rate of convection is considered to be proportional to the temperature difference between the upper and lower sides. Therefore, an area name that is a basis for calculating a temperature difference for each loop and a temperature setting value that is 100% flow rate are assumed as shown in Table 4 below. Here, the temperature set value was the oil temperature of each region at 16:00 on the 20th day.

  From this result, it can be seen that there is no problem in judging that the convection of the 6-loop model described above occurs.

When each area divided into 296 described above is set, and based on the basic data assumption step and the mutual diffusion grasping step described above, calculation is performed so as to solve the diffusion equation by substituting the numerical values set in each cell of the spreadsheet software. The calculation result shown in FIG. 17B described above is obtained.
As is apparent from the comparison between FIGS. 17A and 17B, if the actual measurement value and the calculation result are substantially in agreement, the process can proceed to the next step.
If there is a difference between the calculated value and the actually measured value exceeding the aforementioned threshold value of 3 ppm, the value set as described above, assumed data and parameters are changed, and the above calculation is repeated.
This calculation allows you to calculate the moisture content in the paper of the upper winding insulation paper, which is thought to deteriorate most, and to determine the remaining life of the transformer by grasping the moisture content in the paper above the winding. .

  A ... transformer, 1 ... iron core, 2 ... coil winding, 3 ... insulating paper, 5 ... press board, 6 ... transformer contents, 7 ... tank, 8 ... insulating oil, 9 ... upper yoke, 10 ... lower yoke, DESCRIPTION OF SYMBOLS 11 ... Strut member, 13 ... Radiator, 15 ... Upper piping, 16 ... Lower piping, 20, 21, 22, 23, 24, 25 ... Moisture sensor in oil, 26 ... Drain valve, S1 ... Split modeling step, S2 ... Basic data assumption step, S3 ... Calculation parameter assumption step, S4 ... Mutual diffusion grasping step, S5 ... Comparison step, S6 ... Diagnosis step.

Claims (11)

Insulating oil in which the contents of a transformer including a core, a winding coil provided around the core, and a water-containing solid insulator including insulating paper for coil insulation, a press board, and a wooden object are contained in a tank An oil-filled transformer immersed in the oil-filled transformer, and a method for diagnosing the remaining life of an oil-filled transformer configured to generate an oil flow in the insulating oil,
In the oil-filled transformer, a longitudinal cross section including a region where the transformer contents excluding the iron core and a region where the insulating oil is present is divided into a plurality of sections in a vertical direction and a horizontal direction,
Grasp the distribution of the winding coil, the solid insulator and the insulating oil present in each of the divided areas;
In each area, grasp the relationship of moisture interdiffusion between the solid insulator and the insulating oil. In each area, grasp the situation where the insulating oil containing the predetermined moisture flows. Grasp the interdiffusion relationship of quantity for each area,
The measured value of the moisture content in the oil of the insulating oil actually collected from a part of the divided area during operation of the oil-filled transformer, and the insulating oil derived from the mutual diffusion relationship with respect to the area where the insulating oil was collected If the difference in the moisture content in oil derived from the measured value of the moisture content in oil and the mutual diffusion relationship is equal to or less than a predetermined threshold, A remaining life diagnosis method for an oil-filled transformer, wherein a moisture distribution of the oil-filled transformer is determined and a remaining life diagnosis of the oil-filled transformer is performed based on the determined moisture distribution. Insulating oil in which the contents of a transformer including a core, a winding coil provided around the core, and a water-containing solid insulator including insulating paper for coil insulation, a press board, and a wooden object are contained in a tank An oil-filled transformer immersed in the oil-filled transformer, and a method for diagnosing the remaining life of an oil-filled transformer configured to generate an oil flow in the insulating oil,
In the oil-filled transformer, a division modeling step that divides a longitudinal section including a region where the transformer content is excluded and a region where the insulating oil is present excluding the iron core into a plurality of sections in a vertical direction and a horizontal direction;
The solid insulator distribution, the insulating oil distribution, the weight, thickness and average degree of polymerization of the solid insulator, the density and saturated water content of the insulating oil, the opening area between the adjacent areas, and the temperature A basic data assumption step that assumes a distribution, an oil flow distribution, and an initial moisture distribution;
Assuming the saturated moisture content of the insulating oil, the moisture diffusion coefficient in the insulating oil, the equilibrium moisture content between the solid insulator and the oil, the movement speed of moisture in the solid insulator, and the temperature gradient in the solid insulator A calculation parameter assumption step to
Understand the relationship that the moisture in the oil of the insulating oil of the transformer in the initial state mutually diffuses over time with respect to the solid insulator, but the total water content is constant, and the oil of the insulating oil for each area A mutual diffusion grasping step for grasping the mutual diffusion relation between the moisture content in the solid and the moisture content in the solid insulator;
The measured value of the amount of moisture in the oil of the insulating oil actually collected from a part of the divided area during operation of the oil-filled transformer, and derived from the mutual diffusion grasping step for the area where the insulating oil was collected Comparing the calculated value of the moisture content in the oil of the insulating oil, if the difference between the measured value and the calculated value is less than a predetermined threshold, a comparison step for determining the moisture distribution in the insulating oil for each area;
A method for diagnosing the remaining life of an oil-filled transformer, comprising a diagnostic step of diagnosing the remaining life of the transformer from the amount of moisture in the paper of the winding coil upper insulating paper derived from the determined moisture distribution .   In the interdiffusion grasping step, the distribution of the insulating oil amount for each divided area, the distribution of the solid insulator amount, the distribution of the opening area between adjacent areas, the oil flow distribution of the insulating oil, and the solid for each area 3. The substantial movement speed of water molecules in the insulator, the moisture velocity gradient coefficient in the solid insulator, the thickness of the solid insulator in each area, and the initial moisture content are ascertained. A method for diagnosing the remaining life of oil-filled transformers.   In the comparison step, when the difference between the measured value and the calculated value exceeds a predetermined threshold, the initial moisture amount, the distribution of the insulating oil amount for each zone, the distribution of the solid insulator amount, and between adjacent zones Distribution of opening area, oil flow distribution of insulating oil, substantial movement speed of water molecules in solid insulation per area, moisture velocity gradient coefficient in solid insulation, and thickness of solid insulation per area The oil-filled transformer according to claim 2 or 3, further comprising a function of recalculating and recalculating at least one of the dispersion coefficients, and repeating the recalculation until the difference falls below a threshold value. Remaining life diagnosis method. 5. The method for diagnosing the remaining life of an oil-filled transformer according to claim 1, wherein in the mutual diffusion grasping step, the mutual diffusion is grasped based on the following expression (1).

However, in the formula (1), x: position of the solid insulator from the copper wire (mm), y: moisture content in the solid insulator (%), yn: moisture in the solid insulator in the nth section (section) Amount (%), t: time from the start of operation (min), ∂t: minute time (min), ∂yn: increment of moisture content in the solid insulator in the n-th zone in minute time (%), v ₀ : Substantial moving speed of water molecules in solid insulator (mm / min) in insulating paper in contact with copper wire, k ′: Moisture velocity gradient coefficient in solid insulator (1 / mm), tp: solid insulation in section 1 It is defined as the thickness (mm) of the object. The amount of water contained in each area is the sum of the amount of water in the solid insulator and the amount of water in the oil, and the sum of the amounts of water in each area is the total amount of water contained in the oil-filled transformer. The increment of is the amount obtained by subtracting the amount of moisture flowing out from the amount of moisture flowing into the area, and the increment of the amount of moisture in the oil satisfies the relationship of the following equation (2): The remaining life diagnosis method of the oil-filled transformer as described in any one of 5-5.

Insulating oil in which the contents of a transformer including a core, a winding coil provided around the core, and a water-containing solid insulator including insulating paper for coil insulation, a press board, and a wooden object are contained in a tank An oil-filled transformer immersed in the oil-filled transformer, and a remaining life diagnosis device for an oil-filled transformer configured to generate an oil flow in the insulating oil,
In the oil-filled transformer, a function of storing a plurality of areas obtained by dividing a longitudinal section including a region where the transformer contents are excluded and the region where the insulating oil is present, excluding the iron core, in a vertical direction and a horizontal direction;
A function of storing distribution of the winding coil, the solid insulator, and the insulating oil present in each of the divided areas;
In each area, grasp the relationship of moisture interdiffusion between the solid insulator and the insulating oil. In each area, grasp the situation where the insulating oil containing the predetermined moisture flows. The ability to calculate the interdiffusion relationship of quantities for each area;
The measured value of the moisture content in the oil of the insulating oil actually collected from a part of the divided area during operation of the oil-filled transformer, and the insulating oil derived from the mutual diffusion relationship with respect to the area where the insulating oil was collected If the difference in the moisture content in oil derived from the measured value of the moisture content in oil and the mutual diffusion relationship is equal to or less than a predetermined threshold, A remaining life diagnosis device for an oil-filled transformer having a function of determining the moisture distribution of the oil-filled transformer. Insulating oil in which the contents of a transformer including a core, a winding coil provided around the core, and a water-containing solid insulator including insulating paper for coil insulation, a press board, and a wooden object are contained in a tank An oil-filled transformer immersed in the oil-filled transformer, and a remaining life diagnosis device for an oil-filled transformer configured to generate an oil flow in the insulating oil,
In the oil-filled transformer, a division for storing each area obtained by dividing a longitudinal section including a region where the transformer contents are excluded and a region where the insulating oil is present excluding the iron core into a plurality of regions in the vertical direction and the horizontal direction. Modeling function and
The solid insulator distribution, the insulating oil distribution, the weight, thickness and average degree of polymerization of the solid insulator, the density and saturated water content of the insulating oil, the opening area between the adjacent areas, and the temperature Basic data assumption function to store the distribution, oil flow distribution, and initial moisture distribution;
Assumption of saturated moisture content of the insulating oil, moisture diffusion coefficient in the insulating oil, equilibrium moisture content between the solid insulator and oil, movement speed of moisture in the solid insulator, and temperature gradient in the solid insulator A calculation parameter assumption function for storing values;
Understand the relationship that the moisture in the oil of the insulating oil of the transformer in the initial state mutually diffuses over time with respect to the solid insulator, but the total water content is constant, and the oil of the insulating oil for each area Interdiffusion grasping function to grasp and memorize the mutual diffusion relation between the moisture content in the solid and the moisture content in the solid insulator,
The measured value of the amount of moisture in the oil of the insulating oil actually collected from a part of the divided area during operation of the oil-filled transformer, and derived from the mutual diffusion grasping step for the area where the insulating oil was collected Compare the calculated value of the amount of moisture in the oil of the insulating oil, and if the difference between the measured value and the calculated value is less than a predetermined threshold, the comparison function to determine the moisture distribution in the insulating oil for each area;
A remaining life diagnosis device for an oil-filled transformer comprising a diagnostic function for diagnosing the remaining life of the transformer from the amount of moisture in the winding coil upper insulating paper derived from the determined moisture distribution .   In the interdiffusion grasping function, the initial moisture amount, the distribution of the insulating oil amount for each divided area, the distribution of the solid insulator amount, the distribution of the opening area between adjacent areas, and the oil flow distribution of the insulating oil, And a function of grasping a substantial movement speed of water molecules in the solid insulator for each area, a moisture velocity gradient coefficient in the solid insulator, and a thickness of the solid insulator for each area. The remaining life diagnosis apparatus for oil-filled transformers according to 8.   In the comparison function, when the difference between the measured value and the calculated value exceeds a predetermined threshold value, the initial moisture amount, the distribution of the insulating oil amount for each zone, the distribution of the solid insulator amount, and between adjacent zones Distribution of opening area, oil flow distribution of insulating oil, substantial movement speed of water molecules in solid insulation per area, moisture velocity gradient coefficient in solid insulation, and thickness of solid insulation per area The oil-filled transformer according to claim 8 or 9, further comprising a function of recalculating and recalculating at least one of the dispersion coefficients, and repeating the recalculation until the difference falls below a threshold value. Remaining life diagnosis device. The residual diffusion diagnosis device for oil-filled transformers according to any one of claims 8 to 10, wherein the mutual diffusion grasping function has a function of grasping mutual diffusion based on the following equation (1). .

However, in the formula (1), x: position of the solid insulator from the copper wire (mm), y: moisture content in the solid insulator (%), yn: moisture in the solid insulator in the nth section (section) Amount (%), t: time from the start of operation (min), ∂t: minute time (min), ∂yn: increment of moisture content in the solid insulator in the n-th zone in minute time (%), v ₀ : Substantial moving speed of water molecules in solid insulator (mm / min) in insulating paper in contact with copper wire, k ′: Moisture velocity gradient coefficient in solid insulator (1 / mm), tp: solid insulation in section 1 It is defined as the thickness (mm) of the object.

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