JP6609134B2 - Estimation method of copper sulfide generation status of oil-filled cable by insulation oil analysis, risk diagnosis method - Google Patents

Description

  The present invention relates to a method for estimating the state of copper sulfide generation in an oil-filled cable by insulating oil analysis, and a risk diagnosis method.

  Oil-filled electrical equipment such as oil-filled transformers contain oil because conductive copper sulfide is generated (sulfurization corrosion) due to the reaction between the copper components of oil-filled electrical equipment and sulfur components in the insulation oil, causing dielectric breakdown. It is known that it can cause fatal damage to electrical equipment. Estimated sulfur components in insulating oil include sulfur components contained in insulating oil, eluted sulfur components eluted from members such as insulating paper, and added sulfur components such as antioxidants added later to insulating oil. Conceivable.

  In oil-filled electrical equipment such as large transformers, oil-impregnated paper is used as an insulator, so when copper sulfide adheres to this oil-impregnated insulating paper, a short circuit occurs between the coils, which causes destruction. It has been reported overseas as an example of dielectric breakdown. In addition, although deterioration of oil-filled cables using oil-impregnated paper as the same insulator has been considered to be very gradual, in recent years there have been confirmed cases of dielectric breakdown in aged oil-filled cable lines. However, it has not been reported that the breakdown factor is copper sulfide formation.

  The reaction mechanism related to copper sulfide formation has been studied in detail in relation to the antioxidant dibenzyl disulfide (hereinafter sometimes abbreviated as “DBDS”) added to the insulating oil. That is, DBDS is adsorbed on coil copper, and then DBDS reacts with coil copper to form a DBDS-copper complex, which is further decomposed into benzyl radical, benzylsulfenyl radical, and copper sulfide. It is reported that the reaction occurs (for example, see Patent Documents 1 to 3).

  In Patent Document 1 and Patent Document 2, insulating oil is collected from a transformer in operation, DBDS and its decomposition products, by-products, etc. are analyzed to predict the formation of copper sulfide. Discloses a method of diagnosing the risk level. Patent Document 3 discloses a method of measuring the concentration of dibenzyl sulfoxide in an insulating oil when the insulating oil is in an air atmosphere, and estimating the amount of copper sulfide generated based on the concentration. Yes.

  However, in the above diagnostic method, it is indispensable that DBDS is added to the insulating oil. Basically, in the case of an oil-filled cable using an insulating oil to which DBDS is not added, There is a problem that the amount of copper sulfide produced in insulating oil cannot be estimated from the amount of DBDS-copper complex produced. Conventionally, as an inspection technique for oil-filled cables, combustible gas generated by partial discharge (local breakdown of insulating oil) by measuring dielectric tangent (tan δ) of insulating oil and analyzing gas in insulating oil Gas analysis in oil using the amount of toxic gas as a measure of the degree of deterioration is common, and no method for diagnosing the risk from the state of copper sulfide formation has been implemented.

JP 2010-010439 A JP 2012-156232 A JP 2014-045212 A

  The present invention has been made in view of the above-described conventional problems, and estimates the state of copper sulfide generation in an oil-filled cable using insulating oil, and based on the state of copper sulfide generation estimated by the method, An object of the present invention is to provide a diagnostic method for evaluating the risk of occurrence of abnormality in an incoming cable.

In order to solve the above problems, the present inventors have intensively studied. As a result, from the results of dismantling investigation of oil-filled cables using insulating oil, copper sulfide is also produced in the oil-filled cable; the amount of copper dissolved in the oil and insulation that is considered to be the cause of copper sulfide formation. A correlation between the oil loss tangent (tan δ) and the trend graph showing the time-dependent changes in the amount of copper dissolved in the oil and the dielectric loss tangent (tan δ) at the time of copper sulfide formation decreases after reaching the maximum value. It paid attention to that there was a tendency; combustible gas in insulating oil was generated at the time of copper sulfide generation, and total combustible gas (TCG) increased.
And the copper sulfide production situation can be estimated from the amount of dissolved copper in the insulating oil collected from the oil-filled cable, the dielectric loss tangent (tan δ) and the amount of flammable gas (TCG), and was estimated by this method. Based on the state of copper sulfide generation, it has been found that it is possible to diagnose the risk of occurrence of an abnormality in an oil-filled cable, and the present invention has been completed.

That is, the method of estimating the copper sulfide production status of the present invention is
In an oil-filled cable using insulating oil, a method for estimating the production status of copper sulfide in the cable,
For the insulating oil collected from the oil-filled cable, including a step 1 for creating a trend graph showing a change with time of the amount of copper dissolved in the oil or the dielectric loss tangent (tan δ) and the total amount of combustible gas (TCG),
In the created trend graph, the period in which the amount of copper dissolved in oil or the loss tangent (tan δ) decreases after reaching the maximum value is estimated as the copper sulfide formation period, and the dissolution in oil shown in the trend graph The production state of copper sulfide is estimated from the maximum value of the amount of copper or dielectric loss tangent (tan δ) and the maximum value of the total amount of combustible gas (TCG) during the copper sulfide formation period.

Moreover, the estimation method of the copper sulfide production status of the present invention is:
In an oil-filled cable using insulating oil, a method for estimating the production status of copper sulfide in the cable,
Step 1 for creating a trend graph showing the change over time of the amount of copper dissolved in the oil or the dielectric loss tangent (tan δ) and the total amount of combustible gas (TCG) for the insulating oil collected from the oil-filled cable;
Create a graph showing the relationship between the amount of copper dissolved in the oil and the dielectric loss tangent (tan δ) of the insulating oil collected from the oil-filled cable of the actual equipment and the oil-filled cable before using the oil-filled cable. From step 2, find the maximum amount of copper dissolved in the oil,
Step 3 for determining a ratio of dielectric loss tangent (tan δ) of insulating oil collected from actual equipment and amount of dissolved copper in oil,
Estimate the period during which the amount of copper dissolved in the oil or dielectric loss tangent (tan δ) shown in the created trend graph decreases after reaching the maximum value as the copper sulfide formation period, and determine the maximum oil obtained in step 2 The amount of medium-dissolved copper, the ratio of the dielectric loss tangent (tan δ) obtained in step 3 and the amount of copper dissolved in oil, the value of the amount of copper dissolved in oil or dielectric tangent (tan δ) and the total amount of combustible gas (TCG) in step 1 Is used to estimate the production status of copper sulfide.

In the method for estimating the state of copper sulfide production according to the present invention, the conductor constituting the oil-filled cable reacts with the hydrocarbon or non-hydrocarbon compound in the insulating oil and dissolves in the insulating oil as a copper complex or a copper compound. This is based on the presumption that the copper complex aggregates on the insulating paper of the reinforcing insulating layer in the high electric field region to form copper sulfide.
In addition, for insulation oil before using an oil-filled cable, there is a positive linear correlation between the dielectric loss tangent (tan δ) and the amount of copper dissolved in the oil, so the maximum value of the dielectric loss tangent (tan δ) (maximum value) Is large, the amount of copper dissolved in the oil also increases, and this is based on the assumption that the amount of copper sulfide produced increases.
The amount of copper dissolved in oil and the trend of dielectric loss tangent (tan δ) are correlated. It is possible to estimate the copper sulfide production status using any parameter. It can be arbitrarily selected in consideration of the amount of stored data, high reliability, ease of data processing, and the like.

Moreover, the diagnostic method of the present invention comprises:
In an oil-filled cable using insulating oil, a diagnostic method for evaluating the risk of occurrence of abnormality in the cable,
Step 1 for creating a trend graph showing the change over time of the amount of copper dissolved in the oil or the dielectric loss tangent (tan δ) and the total amount of combustible gas (TCG) for the insulating oil collected from the oil-filled cable;
Create a graph showing the relationship between the amount of copper dissolved in the oil and the dielectric loss tangent (tan δ) of the insulating oil collected from the oil-filled cable of the actual equipment and the oil-filled cable before using the oil-filled cable. From step 2, find the maximum amount of copper dissolved in the oil,
Step 3 for determining a ratio of dielectric loss tangent (tan δ) of insulating oil collected from actual equipment and amount of dissolved copper in oil,
(A) Ratio of dielectric loss tangent (tan δ) obtained in step 3 and amount of copper dissolved in oil, (B) reference value of preset maximum amount of copper dissolved in oil, and (C) total amount of combustible gas set in advance ( The risk is evaluated based on a reference value of TCG).

In the diagnostic method of the present invention, an oil-filled cable whose dissolved copper amount or dielectric loss tangent (tan δ) shown in the trend graph created in Step 1 is in the decreasing process or in a substantially steady state after the decrease is diagnosed and evaluated. And then
(A) Ratio of dielectric loss tangent (tan δ) determined in step 3 to the amount of copper dissolved in oil, (B) preset reference value for maximum amount of copper dissolved in oil, C) It is preferable to evaluate the risk based on a preset reference value of the total amount of combustible gas (TCG).

  In the diagnostic method of the present invention, (A) the ratio of the dielectric loss tangent (tan δ) obtained in Step 3 and the amount of copper dissolved in oil, (B) a preset reference value for the maximum amount of copper dissolved in oil, and (C ) It is preferable to evaluate and rank the risk in the order of the reference value of the preset total amount of combustible gas (TCG).

  The relational expression obtained in Step 3 can be said to be a highly reliable index because a correlation with the sludge generation amount and sludge generation range (wide and narrow) in the actual equipment is recognized. Since the amount of copper dissolved in oil is an index that represents the amount of copper that is a factor for producing copper sulfide, it is a factor that directly leads to copper sulfide production. Moreover, since the amount of TCG is an index representing an increase in insulating oil dissolved gas, it is important in evaluating the risk of partial discharge.

According to the method for estimating the state of copper sulfide production according to the present invention, the amount of copper dissolved in oil or the value of dielectric loss tangent (tan δ) shown in the trend graph decreases after the maximum value is reached. Since the generation period is estimated, it is possible to estimate the state of copper sulfide generation from the amount of dissolved copper in the oil or dielectric loss tangent (tan δ) of the insulating oil collected from the oil-filled cable.
Further, according to the diagnostic method of the present invention, analysis of gas in oil (diagnosis of trend of gas generated by partial discharge or thermal deterioration), diagnosis of decrease in electrical characteristics of insulating oil (tan δ, TCG, volume resistivity, AC Oil that uses insulating oil that does not contain dibenzyl disulfide because it diagnoses based on the copper sulfide formation mechanism from a different viewpoint from conventional diagnostic methods such as pressure resistance measurement and water intrusion diagnosis (moisture content measurement). Degradation diagnosis is also possible for incoming cables.

Furthermore, since the measurement data of the dielectric loss tangent (tanδ) of the insulating oil and the total amount of combustible gas (TCG) in the insulating oil are used, a trend graph can be created from the measurement data accumulated since the operation of the oil-filled cable. .
In addition, the risk level is evaluated by associating the wide and narrow data of the copper sulfide generation range in the disassembled oil-filled cable with the relational expression of the amount of dissolved copper in oil and dielectric loss tangent (tan δ) created using unused insulating oil. Can be diagnosed.

  Therefore, it is possible to easily and accurately diagnose an oil-filled cable that reaches 30 to 40 years from the start of operation while utilizing conventional accumulated data.

It is a figure which shows an example of (a) sectional drawing of an OF cable, and (b) connection part structure. It is a figure which shows the sludge of a cable core part, and the copper sulfide production | generation example. (A): A photograph showing an example generated along an oil gap. (B) is a photograph showing an example generated on a cable core (whole insulating paper). It is a figure which shows the sludge and copper sulfide production | generation tendency in the reinforcement layer of the aged OF cable which carried out the dismantling investigation. It is a figure which shows the sludge and copper sulfide production | generation tendency in the reinforcement layer of the aged OF cable which carried out the dismantling investigation. It is a figure which shows an example of the trend graph which shows a time-dependent change of tan-delta and TCG. It is a correlation diagram of the amount of copper dissolved in oil and tan δ. It is a figure which shows the maximum melt | dissolution copper amount calculation method. It is a related figure of the amount of copper dissolved in oil, and a dismantling investigation result. It is a figure which shows the amount of copper dissolved in oil according to a trend graph shape, tan-delta, TCG, and H2.

  Hereinafter, a method for estimating the state of copper sulfide generation in an oil-filled cable (hereinafter referred to as an OF cable) according to the present invention and a diagnostic method for evaluating the risk of occurrence of abnormality will be described in detail.

≪Deterioration status of OF cable≫

  An example of the OF cable is shown in FIG. FIG. 1A is a cross-sectional view of an OF cable, and FIG. 1B shows an OF cable connecting portion structure. Since the OF cable simply uses oil-insulated insulating paper as an insulator, pressure drops in the insulating oil due to temperature changes cause bubbles in the insulating oil, which do not satisfy the required characteristics, so the inside of the conductor (or metal sheath) It is designed to withstand high electric field strength by providing an oil passage and constantly applying pressure above the atmospheric pressure to the insulating oil by an oil tank installed outside. The insulator of the OF cable is configured by winding a tape-shaped insulating paper and impregnating the insulating oil as shown in FIG. At this time, in order to improve the bending characteristics, the insulating paper is usually not wrapped and the gaps are evenly provided.

  Factors that decrease the insulation performance of OF cables are thought to be due to a decrease in the degree of insulation paper polymerization due to overheating, damage / deformation due to vibration / thermal expansion / contraction, collapse of insulation, negative pressure, oil leakage, and abnormal insulation oil characteristics. In the past, various inspection techniques have been reported and implemented. Examples of inspection techniques include gas analysis techniques in oil (trend trend diagnosis of gas generated by partial discharge and thermal degradation), and decreasing tendency of electrical characteristics (tan δ, TCG, volume resistivity, AC withstand voltage measurement) of insulating oil. Techniques for diagnosis, water intrusion diagnosis (moisture content measurement), and the like exist.

  The electrical characteristics of the OF cable have a tolerance for the AC voltage, but if there is a defect due to the shift or damage of the insulation paper due to the core shift etc., partial discharge occurs at the defective part due to the penetration of overvoltage, and gas is generated. If it is repeated, it may exist as a void in the defective part. Furthermore, since voids have a remarkably low dielectric strength, it is conceivable that partial discharge is continued by applying an AC voltage.

  Figure 2 shows the results of removing the OF cable that has been operating for 30 years or more in actual equipment and conducting a disassembly study. As a result, in the cable core (cable insulator), streaky sludge and copper sulfide (Fig. 2 (a)), or a photograph showing an example in which dotted sludge or copper sulfide (FIG. 2 (b)) is generated on the entire cable core (insulating paper). The sludge and copper sulfide in the cable core part tend to be most generated and deposited on the cable core part under the semi-stop.

  Further, as shown in FIG. 3, the most product is deposited and deposited in the gap portion, but there is a case where the product is deposited and deposited on the entire insulating paper. Sludge and copper sulfide are generated and deposited in the order of the outer layer to the inner layer to the middle layer of the cable core part. However, there is an example in which sludge is produced and deposited to the vicinity of the middle layer in a cable with dielectric breakdown.

  FIG. 4 shows an example of a generation situation that may lead to dielectric breakdown. As shown in FIG. 4, when copper sulfide is generated and deposited up to the middle layer in a situation where the upper and lower oil gaps are close to each other or connected, the copper sulfide production and deposition portion is also connected from the inner and outer layers to the middle layer. As a result, the insulation performance is significantly lowered and the possibility of dielectric breakdown increases.

≪Mechanism of copper sulfide formation in OF cable≫

  Conventionally, copper sulfide is produced in insulating oil to which DBDS is added. DBDS and copper of the conductor react, DBDS-copper complex diffuses into insulating oil, and DBDS-copper complex diffused in oil becomes insulating paper. It is presumed that this is due to the mechanism that copper sulfide is produced by being adsorbed on and decomposed by thermal energy.

On the other hand, in the present invention, the copper sulfide in the OF cable is produced by (i) the reaction between the conductor and the insulating oil, (ii) the copper complex or the copper compound being dissolved in the insulating oil, and (iii) the dissolved copper complex. Alternatively, the copper compound aggregates in the high electric field region, and (iv) the sludge of the insulating oil is generated by the catalytic effect of the copper complex or the copper compound, and (v) the copper complex or the copper compound is contained in the insulating paper or the insulating oil. It is presumed to be due to the mechanism that copper sulfide is produced by reacting with the sulfur component. And in this invention, the sulfur component which reacts with a copper complex or a copper compound is not restricted to the component added to insulating oil like DBDS, The sulfur component derived from the sulfur compound used at the time of manufacture of insulating paper It is also assumed that sulfur components derived from petroleum, which is a raw material for insulating oil, are also included.
That is, the copper sulfide production mechanism according to the present invention is based on the assumption that copper sulfide is produced over time, although the reaction rate is very slow even in the case of an insulating oil to which no sulfur compound such as DBDS is added. It is estimated that three conditions of copper + insulating oil + high electric field are necessary for the production of copper sulfide.

≪Diagnostic method based on copper sulfide formation mechanism≫

  According to the copper sulfide formation mechanism in the OF cable, (ii) when the copper complex or copper compound is dissolved in the insulating oil, the amount of copper dissolved in the oil and the dielectric loss tangent (tan δ) of the insulating oil increase. Thereafter, (iii) when the copper complex or the copper compound aggregates in the high electric field region, the dissolution amount reaches a maximum value, and eventually (iv) the sludge generation and (v) the copper sulfide generation, the dissolved copper amount in the oil And the dielectric loss tangent (tan δ) of the insulating oil decreases.

  On the other hand, the gas generated during the copper complex formation reaction, sludge and copper sulfide production reaction is absorbed by the insulating oil, so the gas concentration in the oil increases and the total amount of combustible gas (TCG) in the oil is measured. The value increases.

  FIG. 5 is an example of a trend graph showing changes in the dielectric loss tangent (tan δ) of insulating oil and the total amount of combustible gas (TCG) in oil as changes over time based on the copper sulfide generation mechanism in the OF cable. . Moreover, the trend graph of dielectric loss tangent (tan δ) correlates with the trend of the amount of copper dissolved in oil. That is, from the trend graph (FIG. 5) of the amount of copper dissolved in oil and the dielectric loss tangent (tan δ) of oil, the “decrease” period of these characteristic values corresponds to the copper sulfide formation period, and these characteristic values (absolute values) ) Is large, the amount of copper dissolved in oil that becomes copper sulfide is large, so that it can be estimated that the amount of copper sulfide produced is large. Therefore, it becomes possible to estimate the production state of copper sulfide in the OF cable from the amount of copper dissolved in oil or the maximum value of the dielectric loss tangent (tan δ) shown in the trend graph.

<Measurement and analysis of characteristic values necessary for diagnosis>

FIG. 6 is an example of a correlation diagram between the amount of copper dissolved in oil and the dielectric loss tangent (tan δ). As a simulation test, using insulating oil before use in an OF cable, an insulating oil in which copper is dissolved from a copper rod and an insulating oil in which a copper compound is dissolved are prepared with different amounts of copper dissolved in the oil. For each insulating oil, the amount of copper dissolved in the oil and the dielectric loss tangent (tan δ) value were measured, and the obtained measurement values were plotted to draw an approximate straight line to obtain the correlation coefficient. In addition, for the insulating oil collected from the actual equipment, the amount of copper dissolved in the oil and the tan δ value are measured, and the measured values obtained are plotted.
From the results of FIG. 6, in the insulating oil in which copper or a copper compound is dissolved, the correlation coefficient between the dissolved copper amount and the dielectric loss tangent (tan δ) is 0.9 or more, and the correlation coefficient is 0.9 or more. Since the linearity was confirmed, the maximum dissolved copper amount in oil can be estimated from the past maximum value of the tan δ value using the correlation coefficient, as shown in FIG. Therefore, it is possible to estimate the production status of copper sulfide using the value of the dissolved copper amount or the value of tan δ.

  However, it has been confirmed that the slope of the straight line is different when the form of copper dissolved in oil is different. In actual equipment, it has been confirmed that even if the amount of dissolved copper is the same, the dielectric loss tangent (tan δ) value varies depending on the equipment. Even with this same amount of dissolved copper, it is assumed that the dielectric loss tangent (tan δ) value varies depending on the equipment, but the dielectric loss tangent (tan δ) value increases due to deterioration of the insulating oil (moisture content or thermal deterioration). Insulating oil is rarely degraded. Therefore, it is presumed that the difference in dielectric loss tangent (tan δ) value depending on the equipment even with the same amount of dissolved copper is due to the difference in the form of dissolved copper in oil for each equipment. The slope of the straight line representing the correlation of) will be different for each facility. Thus, in actual operation, such measurement and plot need to be created for each OF cable equipment.

  As shown in FIG. 8, the inventors of the present invention dismantled the facility using insulating oil whose dielectric loss tangent (tan δ) value is higher than the correlation line with respect to the amount of copper dissolved in the oil. Therefore, it is confirmed that copper sulfide is generated in many places in the facility, and that copper sulfide is generated from a wide range of the reinforcing layer, from the inner and outer layers of the cable core to the vicinity of the middle layer.

  In addition, as shown in FIG. 8, the plot of the dielectric loss tangent (tan δ) of the equipment in which copper sulfide was generated in many places in the equipment is the dielectric loss tangent (tan δ) (%) and the amount of copper dissolved in oil (ppm). It exists in the part above the straight line (straight line with a slope of 0.9 (% / ppm)) representing the correlation of.

  That is, when 0.9 (% / ppm) is set as the reference value, the ratio of the amount of dissolved copper in the oil and the dielectric loss tangent (tan δ) measured for the unknown insulating oil is larger than the reference value (the measured value is more than a straight line). It is possible to estimate that copper sulfide is generated in many places in the facility. On the other hand, when the ratio of the amount of copper dissolved in oil to the dielectric loss tangent (tan δ) is smaller than the reference value (when the measured value is present below the straight line), copper sulfide formation is limited to a narrow range in the facility. Can be estimated.

<Diagnosis>
In diagnosis, evaluation is performed in the order of “diagnosis I” and “diagnosis II”.

In the first “diagnosis I”, equipment corresponding to the copper sulfide production period is extracted.
When extracting the relevant equipment, the trend graph shape of dielectric loss tangent (tan δ) is classified into the five types shown in Table 1, and the copper sulfide production status is estimated for each, and the equipment in and around the copper sulfide production period is extracted. .
When the diagnosis necessity item is “need diagnosis”, the following “diagnosis II” is performed. When “warning is required”, it is preferable to shorten the measurement interval and perform “diagnosis II” again when the graph tends to decrease (copper sulfide formation period). When “no need”, the measurement may be performed at a normal pace.

In the diagnostic method for evaluating the risk of occurrence of abnormality in the oil-filled cable of the present invention, as step 1, with respect to the insulating oil collected from the oil-filled cable, the amount of copper dissolved in the oil, the dielectric loss tangent (tan δ), and the total amount of combustible gas A trend graph showing changes with time is created for the amount of copper dissolved in oil or dielectric loss tangent (tan δ) and the amount of combustible gas (TCG) obtained by measuring (TCG).
Then, Steps 2 and 3 similar to the above are adopted, (A) the ratio of the dielectric loss tangent (tan δ) obtained in Step 3 and the amount of copper dissolved in oil, and (B) the maximum amount of copper dissolved in oil set in advance. The risk is evaluated based on the reference value and the reference value of (C) the preset total amount of combustible gas (TCG).
After the amount of copper dissolved in the oil or dielectric loss tangent (tan δ) shown in the trend graph created in Step 1 shows a maximum value, copper sulfide is generated for the oil-filled cable that is in the decreasing process or in the steady state after the decrease. Since it can be estimated that it is in a state of being in a state, it is better to evaluate as a diagnosis required.

In the next "Diagnosis II", the equipment risk level is diagnosed from the copper sulfide production location and production quantity.
As diagnostic criteria, the ratio of the tan δ to the amount of copper dissolved in oil, the maximum amount of copper dissolved in oil, the maximum value of TCG ( The copper sulfide generation period) is adopted, and the equipment risk level (5 categories A to E below) is diagnosed based on the criteria in Table 2.
Each reference value shown in Table 2 is an example, and the setting of the numerical value will be described later.
(Equipment risk diagnostic criteria)
A: Generated in many places and a large amount of accumulated paper on the insulating paper in each place B: Generated in many places, but a small amount of accumulated paper on the insulating paper in each place C: Generated in limited places, but insulation of the generated places Large amount of deposit on paper D: Generated at limited locations, small amount of deposit on insulating paper at generated locations E: Little generated

In the diagnosis II, it is preferable to first evaluate (A) the magnitude of the dielectric loss tangent (tan δ) obtained in step 3 and the ratio of the amount of dissolved copper in oil. This is because it is highly reliable because it is an evaluation standard that is also correlated with the dismantling survey results.
Next, from the maximum amount of copper dissolved in oil determined in Step 2, it is preferable to evaluate (B) the size of the preset maximum amount of copper dissolved in oil relative to the reference value. This is because it is estimated to correlate with the amount of copper sulfide produced.
Next, it is preferable to evaluate (C) the magnitude of the preset total amount of combustible gas (TCG) with respect to the reference value. This is because the total amount of combustible gas (TCG) during the copper sulfide generation period is estimated to correlate with the amount of copper sulfide generation.
By evaluating and ranking the risk level in the above order, the risk level of the facility can be evaluated and grasped in stages.

The estimation of the partial discharge occurrence is performed as “supplemental diagnosis”.
Using the trend graph showing the change over time in tan δ and TCG of insulating oil shown in FIG. 5, the TCG maximum after tan δ decrease for facilities where the copper sulfide generation status shown in Table 1 was extracted as after copper sulfide generation by diagnosis I From the value, the magnitude of the preset reference value of the total amount of combustible gas (TCG) is evaluated.
In the example illustrated in FIG. 5, the partial discharge occurrence state can be estimated by diagnosing the partial discharge generation facility when the TCG is 140 ppm or more after the measurement date 2010 after the decrease of tan δ.

  Next, although the confirmation result of the effect by the diagnostic method by this invention is demonstrated concretely, this invention is not limited only to a following example.

(1) Confirmation of the effect of this diagnostic method (see Table 3)
For actual equipment (OF cable 3-wire), the estimated diagnosis result diagnosed based on the diagnosis method of the present invention was compared with the dismantling investigation result. The results are shown in Table 3.
For each OF cable, measure the amount of dissolved copper in insulating oil collected separately from the B phase, R phase, and W phase (this value is the maximum amount of copper dissolved in oil) and compare it with the reference value (0.6 ppm). evaluated.

In the dismantling survey, the copper sulfide generation range was visually confirmed (blackened part on the insulating paper), and equipment with a wide generation range was evaluated as “wide” and equipment with a narrow range was evaluated as “narrow”. did.
In addition, the confirmation of copper sulfide generation is performed by specifying a place where both copper (Cu) and sulfur (S) are detected at the blackened portion on the insulating paper by an electron microscope and an X-ray fluorescence analyzer. This was confirmed by the detection of the Raman spectrum of copper sulfide by a microscopic Raman spectrometer.

(Measurement method of amount of copper dissolved in oil)
The sample oil was diluted 10 times with xylene, and the prepared solution was analyzed by ICP emission spectroscopy. The standard solution for the calibration curve was prepared by using a standard solution prepared by diluting a commercially available oily copper-containing standard solution in order with blank oil and xylene.

From the results shown in Table 3, it is possible to determine the risk “A / B” for facilities where copper sulfide has been generated up to a wide area of the reinforcing layer and near the middle layer of the cable core, and the risk “E” for facilities with a small amount of generation. It was determined that “No generation”.
It was confirmed by the diagnostic method of the present invention that an actual facility with a large amount of copper sulfide generation in the OF cable can be identified.

(2) Correlation confirmation of this diagnostic method and copper sulfide production | generation mechanism It confirmed that the diagnostic method of this invention had a correlation with the copper sulfide production | generation mechanism as follows by the dismantling test and each evaluation test of an actual facility.
(B) Calculation of maximum amount of copper dissolved in oil (see Fig. 6)
Insulating oils (sample insulating oils) with different amounts of dissolved copper in the oil in which copper is dissolved from copper bars, insulating oils (copper compound-dissolving sample insulating oils) in which different amounts of copper compounds are dissolved, and sampled from actual equipment FIG. 6 shows the results of measuring the amount of copper dissolved in the oil and tan δ for the insulating oil.
The amount of dissolved copper in the sample insulating oil was measured by the above-described ICP emission spectroscopic analysis after heating the insulating oil dipped in a copper rod at 80 ° C. in a nitrogen atmosphere and sampling it over time. The amount of copper dissolved in the insulating oil of the copper compound-dissolved sample was measured by ICP emission spectrometry using the above method after dissolving a commercially available copper compound reagent (copper alkylbenzene sulfonate or copper oleate) at an appropriate concentration. did. Tan δ was measured using a dielectric loss tangent measuring instrument.

FIG. 6 shows that the copper-dissolved sample insulating oil shows a linear correlation between the amount of copper dissolved in oil and the tan δ value. However, in actual equipment, the tan δ value varies depending on the equipment even if the amount of copper dissolved in oil is the same. Understand. Although the tan δ value increases due to the deterioration of the insulating oil (moisture content or heat deterioration), the deterioration of the insulating oil rarely occurs in the OF cable. On the other hand, FIG. 6 shows the slope (correlation coefficient) of a straight line indicating the correlation between the amount of copper dissolved in oil and the tan δ value depending on the type of copper compound used, even in the case of a copper-dissolved sample insulating oil in which a copper compound is dissolved. It has been shown that this is different, which indicates that the value of tan δ is influenced by the form of the copper compound dissolved in the insulating oil. Therefore, it is considered that the reason why the value of the dielectric loss tangent (tan δ) is different even if the amount of copper dissolved in oil is the same in actual equipment is that the form of copper dissolved in oil differs from equipment to equipment.
From the above, it is possible to calculate the amount of copper dissolved in oil from the tan δ value using the relational expression between the amount of copper dissolved in oil and the tan δ value. It can be seen that it is necessary to create a relational expression for each facility because the form of copper is different.

(B) Estimation of copper sulfide generation period According to the copper sulfide generation mechanism in the OF cable proposed in the present invention, the relationship with the risk of OF cable accompanying copper sulfide generation is as follows: It can be explained in relation to the quantity.
(I) The conductor reacts with the insulating oil. At this stage, the amount of copper dissolved in the oil does not change.
(Ii) When copper is dissolved in the insulating oil as a copper complex or a copper compound, the amount of copper dissolved in the oil gradually increases, and eventually the dissolution stops with time.
(Iii) The dissolved copper complex or copper compound aggregates in the insulator (insulating paper) oil gap in the high electric field region.
(Iv) Furthermore, since the copper complex or the copper compound is aggregated in a high electric field region, the catalytic effect of the copper complex or the copper compound in the insulator oil gap is increased.
(V) Due to an increase in the catalyst medium effect, the oil is combined with oxygen and sulfur and rapidly deteriorates, and sludge is generated in the insulator oil gap. At this stage, the amount of copper dissolved in the oil maintains the maximum value.
(Vi) A copper complex or a copper compound reacts with sulfur in the insulating paper or insulating oil (sulfur that is originally contained in the insulating oil) to form copper sulfide. As copper sulfide is produced, the amount of copper dissolved in the oil gradually decreases.
(Vii) When copper sulfide is generated in the oil gap portion, the amount of dissolved copper in the oil is reduced, and a partial discharge occurs due to the copper sulfide in the oil gap portion.

Since there is a correlation between the amount of copper dissolved in oil and the tan δ value, it can be said that there is also a correlation between the trend of tan δ and the amount of copper dissolved in oil. Moreover, from the copper sulfide production | generation mechanism estimated as mentioned above, when copper sulfide produces | generates, since the amount of melt | dissolved copper in oil will reduce, a tan-delta value will also reduce.
From the above, when the tan δ trend decreases, it can be determined that the amount of dissolved copper has decreased due to copper sulfide formation.

(C) Facility risk diagnosis from copper sulfide production location / production amount (a) Relationship between tan δ, amount of dissolved copper in oil and copper sulfide production location (see Table 4 and FIG. 8)
FIG. 8 shows the relationship between tan δ, the amount of copper dissolved in oil, and the locations where copper sulfide is generated. FIG. 8 is a graph showing the relationship between the amount of copper dissolved in oil and tan δ in the actual equipment subjected to the dismantling investigation, and a straight line is drawn so that the ratio of tan δ and the amount of copper dissolved in oil becomes 0.9. .
Furthermore, based on the results of the dismantling investigation, for facilities with many copper sulfide production sites (copper sulfide production is wide), graph plots 11 locations (sample name: A to K) are circled with tan δ and the amount of copper dissolved in oil Table 4 shows the results obtained for the ratio.
As a result, for equipment with many copper sulfide production sites, the minimum value (sample name: K) of the ratio of tan δ and the amount of dissolved copper in oil is “0.95”, above the straight line of the ratio 0.9. Plotted.

  However, even in the facilities where there were few copper sulfide generation sites, there were facilities plotted above the straight line with a ratio of 0.9. However, in the equipment (x plot) in which the amount of copper dissolved in oil was small and the maximum amount of copper dissolved in oil in the past could be calculated, the calculated maximum amount of copper dissolved in oil was as small as 0.1 ppm. That is, since the amount of copper dissolved in the original oil was small, it can be estimated that there were few production | generation locations.

  Similarly, in the equipment having an amount of dissolved copper in oil of 1 ppm or more, there is no past data and the trend tendency is unknown, but from this it can be inferred the possibility of reaching the copper sulfide production period.

  From the above, if the value of the ratio of tan δ and the amount of copper dissolved in oil is high, it can be judged that there is a possibility that copper sulfide may be generated in many places, and it is possible to identify deteriorated equipment that leads to dielectric breakdown It becomes.

(B) Relationship between the amount of copper dissolved in oil and the amount of copper sulfide produced From the copper sulfide production mechanism, it can be said that the amount of copper sulfide produced increases as the amount of copper dissolved in oil increases.
From the above, it can be determined that the amount of production increases when copper sulfide is produced by equipment having a large amount of copper dissolved in the maximum oil.

(C) Relationship between amount of dissolved copper in oil and TCG (see Table 5 and FIG. 9)
A trend graph of tan δ of actual equipment (1230 locations) was created, the graph shapes were classified, and the average value of each characteristic value for each category is summarized in Table 5 and FIG.
As a result, the amount of TCG tended to increase when tan δ increased or decreased. It was assumed that various chemical reactions occurred in the process of copper dissolution, sludge formation, and copper sulfide formation from the generation mechanism, and TCG was detected as a decomposition product gas generated during this chemical reaction. That is, it can be determined that the greater the amount of TCG, the greater the amount of copper dissolved, the amount of sludge produced, and the amount of copper sulfide produced.
From the above, it can be determined that the larger the amount of TCG when the dissolved copper is decreased (when tan δ is decreased), the greater the amount of copper sulfide produced.

(D) Each reference value (see Table 5)
Since each reference value described in the equipment risk diagnosis table of Table 2 does not have a clear correlation at present, it was determined as a provisional reference value from the current test data shown in Table 5. This point needs to be reviewed in the future according to the actual situation of the equipment.

(E) Supplementary diagnosis [partial discharge occurrence status] (See Table 1, Table 5, and FIG. 9)
The TCG amount (H ₂ amount), tan δ, and the amount of dissolved copper in oil are shown in FIG. 9 in association with the copper sulfide formation tendency (tan δ increase / decrease tendency) shown in Table 1.
As is apparent from FIG. 9, the amount of TCG (H ₂ ) tends to be large (not decreased) after copper sulfide is generated. In this case, since the later copper sulfide generation, not decomposed gas by various chemical reactions occur, the concept of the conventional insulating oil analysis, generated by the partial discharge gas (H ₂ discharge charge quantity is large partial discharge Gas). In particular, it can be inferred that partial discharge occurs at the copper sulfide generation site in terms of after copper sulfide generation.
From the above, it can be determined that a large amount of partial discharge is generated in equipment having a large amount of TCG after copper sulfide is generated.

  As described above, the diagnosis method for the risk of occurrence of an OF cable abnormality according to the present invention can be applied to insulating oil to which dibenzyl disulfide that is a copper sulfide generation factor is not added, as compared with the conventional diagnosis method. Since characteristic values (dissolved copper amount in oil, tan δ, TCG) by a conventional diagnostic method can be used, it can be said that the diagnostic method is simple and accurate. There is also consistency with actual equipment.

  However, since the value of tan δ is affected by the form of copper dissolved in oil, and the form of copper dissolved in oil varies from equipment to equipment, the above-described diagnosis method needs to be implemented for each OF cable equipment.

Claims (5)

In an oil-filled cable using insulating oil, a method for estimating the production status of copper sulfide in the cable,
For the insulating oil collected from the oil-filled cable, including a step 1 for creating a trend graph showing a change with time of the amount of copper dissolved in the oil or the dielectric loss tangent (tan δ) and the total amount of combustible gas (TCG),
In the created trend graph, the period in which the amount of copper dissolved in oil or the loss tangent (tan δ) decreases after reaching the maximum value is estimated as the copper sulfide formation period, and the dissolution in oil shown in the trend graph A method for estimating the production state of copper sulfide from the maximum value of copper amount or dielectric loss tangent (tan δ) and the maximum value of combustible gas total amount (TCG) in the copper sulfide production period. In an oil-filled cable using insulating oil, a method for estimating the production status of copper sulfide in the cable,
Step 1 for creating a trend graph showing the change over time of the amount of copper dissolved in the oil or the dielectric loss tangent (tan δ) and the total amount of combustible gas (TCG) for the insulating oil collected from the oil-filled cable;
Create a graph showing the relationship between the amount of copper dissolved in the oil and the dielectric loss tangent (tan δ) of the insulating oil collected from the oil-filled cable of the actual equipment and the oil-filled cable before using the oil-filled cable. From step 2, find the maximum amount of copper dissolved in the oil,
Step 3 for determining a ratio of dielectric loss tangent (tan δ) of insulating oil collected from actual equipment and amount of dissolved copper in oil,
Estimate the period during which the amount of copper dissolved in the oil or dielectric loss tangent (tan δ) shown in the created trend graph decreases after reaching the maximum value as the copper sulfide formation period, and determine the maximum oil obtained in step 2 The amount of medium-dissolved copper, the ratio of the dielectric loss tangent (tan δ) obtained in step 3 and the amount of copper dissolved in oil, the value of the amount of copper dissolved in oil or dielectric tangent (tan δ) and the total amount of combustible gas (TCG) in step 1 A method characterized by estimating the production state of copper sulfide using
In an oil-filled cable using insulating oil, a diagnostic method for evaluating the risk of occurrence of abnormality in the cable,
Step 1 for creating a trend graph showing the change over time of the amount of copper dissolved in the oil or the dielectric loss tangent (tan δ) and the total amount of combustible gas (TCG) for the insulating oil collected from the oil-filled cable;
Create a graph showing the relationship between the amount of copper dissolved in the oil and the dielectric loss tangent (tan δ) of the insulating oil collected from the oil-filled cable of the actual equipment and the oil-filled cable before using the oil-filled cable. From step 2, find the maximum amount of copper dissolved in the oil,
Step 3 for determining a ratio of dielectric loss tangent (tan δ) of insulating oil collected from actual equipment and amount of dissolved copper in oil,
(A) Ratio of dielectric loss tangent (tan δ) obtained in step 3 and amount of copper dissolved in oil, (B) reference value of preset maximum amount of copper dissolved in oil, and (C) total amount of combustible gas set in advance ( A diagnostic method characterized by evaluating a risk based on a reference value of TCG).
The oil-filled cable whose dissolved copper amount or dielectric loss tangent (tan δ) shown in the trend graph created in Step 1 is in the decreasing process or in a nearly steady state after the reduction is evaluated as a diagnosis required.
For the oil-filled cable, (A) the ratio of the dielectric loss tangent (tan δ) determined in step 3 and the amount of copper dissolved in oil, (B) a preset reference value for the maximum amount of copper dissolved in oil, and (C) preset 4. The diagnostic method according to claim 3, wherein the risk is evaluated based on a reference value of the total amount of combustible gas (TCG).   (A) Ratio of dielectric loss tangent (tan δ) obtained in step 3 and amount of copper dissolved in oil, (B) preset reference value of maximum amount of copper dissolved in oil, (C) preset total amount of combustible gas (TCG) The diagnosis method according to claim 4, wherein the risk levels are evaluated and ranked in the order of the reference values.