JP2009224579A - Deterioration diagnosis method of oil electrical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform a reliable and precise prediction diagnosis of oxidation deterioration in the characteristics of an insulating oil by evaluating gas shut-off performance by the deterioration multiplication coefficient of a nitrogen gas transmission coefficient in a diaphragm and quantitatively evaluating the amount of consumption of oxygen in the insulating oil using the deterioration multiplication coefficient. <P>SOLUTION: By using nitrogen concentration in oil, data of temperature in the insulating oil with time, and temperature characteristic data the nitrogen gas transmission coefficient of the diaphragm in a non-deteriorated conservator, the amount of penetration of nitrogen gas in the non-deteriorated diaphragm is obtained. The deterioration of an oil electrical apparatus is diagnosed by obtaining the amount of oxygen consumed by the oil electrical apparatus according to a coefficient for evaluating the amount of nitrogen gas comprising the ratio of an actual amount of penetration of nitrogen gas expressed by the product of the amount of penetration of nitrogen gas in the non-deteriorated diaphragm, the amount of change in the nitrogen concentration in oil of the oil electrical apparatus, and the volume of the insulating oil to the amount of penetration of nitrogen gas in the non-deteriorated diaphragm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for diagnosing deterioration of oil-filled electrical equipment, and more particularly to degradation diagnosis of oil-filled electrical equipment for deterioration of insulating oil characteristics.

  Conventionally, oil-filled electrical devices such as power capacitors and transformers have been provided with conservators. When the insulating oil sealed inside the oil-filled electrical device expands and contracts due to temperature changes during operation, the conservator absorbs the expansion and contraction of the insulating oil and reduces the pressure inside the oil-filled electrical device. It is a device that keeps it constant. When this conservator causes poor airtightness, gas or the like (for example, air) enters the oil-filled electrical device, which adversely affects the oil-filled electrical device. In particular, it is known that when oxygen in the air that has entered dissolves in the insulating oil inside the oil-filled electrical device, the deterioration of the insulating oil is promoted and the life of the oil-filled electrical device is greatly affected. Therefore, diagnosing the deterioration of the insulating oil in the oil-filled electrical device is important for predicting the life of the oil-filled electrical device.

As one of the techniques for diagnosing the deterioration of insulating oil in such oil-filled electrical equipment, the oxidation state of the solid insulator in the oil-filled electrical equipment is estimated from the nitrogen gas concentration in the insulating oil of the oil-filled electrical equipment, A method for diagnosing deterioration of insulating oil is disclosed (for example, see Patent Document 1). This is because the increase in the nitrogen gas concentration of the insulating oil and the increase in the amount of oxygen consumed in the insulating oil are qualitatively matched to evaluate the amount of oxygen consumed in the insulating oil from the nitrogen gas concentration. This is a method for diagnosing deterioration of insulating oil.
JP-A-2005-223104

  However, the method disclosed in Patent Document 1 has the following problems.

  In other words, the nitrogen gas concentration of oil-filled electrical equipment has a temperature dependency on the temperature of the insulating oil (hereinafter referred to as oil temperature), so the oil temperature rises due to heat generation due to an increase in the outside air temperature or an increase in the load on the transformer In this case, the nitrogen gas concentration in the insulating oil increases accordingly. Therefore, it cannot be accurately determined whether the increase in the nitrogen gas concentration is due to the deterioration of the insulating oil or the increase in the oil temperature. Evaluation of the amount of oxygen entering the insulating oil was also unclear.

  The method of Patent Document 1 is a technique based on the premise that there is a qualitative relationship between the nitrogen gas concentration in the insulating oil and the amount of oxygen consumed in the insulating oil. The method for quantitatively evaluating the amount of oxygen consumed in the water is not solved. Accordingly, the present invention has been made to solve the above-mentioned problems, and by using the deterioration multiplication factor of the nitrogen gas permeability coefficient, the amount of oxygen consumed by the insulating oil is quantitatively evaluated, thereby insulating the material. It is an object of the present invention to provide a deterioration diagnosis method for oil-filled electrical equipment capable of predicting and diagnosing oil deterioration and performing highly accurate deterioration diagnosis on oil-filled electrical equipment.

  The oil-filled electrical device deterioration diagnosis method according to the present invention includes an oil-filled electrical device having a conservator having a diaphragm and containing insulating oil therein, the nitrogen concentration of the insulating oil in the oil, and the insulating oil Using the nitrogen gas permeability coefficient in the undegraded diaphragm given as a function of the oil temperature, the amount of nitrogen gas entering through the undegraded diaphragm and entering the insulating oil is calculated. The amount of nitrogen gas intruding into the insulating oil actually calculated from the product of the amount of change in nitrogen concentration in the oil and the volume of the insulating oil, and nitrogen gas entering the insulating oil through the undegraded diaphragm While calculating the nitrogen gas amount evaluation coefficient calculated from the ratio to the intrusion amount, the amount of oxygen consumed for oxidation in the insulating oil within a predetermined period is changed from the nitrogen gas amount evaluation coefficient to the undegraded amount. Before passing through the diaphragm A value obtained from the product of the amount of oxygen that actually penetrates into the insulating oil and the product of the oxygen concentration dissolved in the insulating oil and the volume of the insulating oil, which is obtained from the penetration rate of oxygen that penetrates into the insulating oil. It is characterized by obtaining from the difference.

  According to the present invention, the deterioration of the insulating oil is predicted and diagnosed by quantitatively evaluating the amount of oxygen consumed by the insulating oil by using the deterioration multiplication coefficient of the nitrogen gas permeability coefficient, and the accuracy of the oil-filled electrical equipment is improved. High degradation diagnosis can be performed.

(Example)
Hereinafter, a case where an embodiment of the present invention is applied to an oil-filled transformer as an example of an oil-filled electrical device will be described with reference to the drawings.

  A schematic diagram of the oil-filled transformer 1 is shown in FIG. In FIG. 1, an oil-filled transformer tank 2 contains a transformer body (not shown) and is filled with insulating oil 10. A conservator 3 is installed above the transformer tank 2 and connected to each other by a communication pipe 4. Inside the conservator 3, a diaphragm 5 using oil-resistant rubber such as nitrile rubber is fixedly installed with a flange 6.

  Further, the diaphragm 5 communicates with a pipe 7 provided outside the conservator 3 via a flange 6, and communicates with outside air via a breather 8 attached to the pipe 7. And it has the role which prevents deterioration of the insulating oil 10 by interrupting air gas (henceforth air) 9, such as the air in the diaphragm 5, and other gas, from the insulating oil 10 in the conservator 3. FIG. The pressure of the air 9 in the diaphragm 5 is atmospheric pressure, and a desiccant such as silica gel is loaded in the breather 8 in order to prevent moisture in the outside air from entering the diaphragm 5. Yes.

  The conservator 3 of the oil-filled transformer 1 illustrated in FIG. 1 is a conservator of a type in which the diaphragm 5 is formed in a bag shape and filled with air, but the conservator 3 is formed by a sheet-shaped diaphragm 5. It may be a conservator of a type arranged so that the inside of the tank is vertically divided for 2 minutes (the upper side is filled with air).

  Here, the function of the conservator 3 will be described.

  The oil temperature of the insulating oil 10 of the oil-filled transformer 1 is constantly changed by fluctuations in the outside air temperature and heat generation caused by load loss, and its volume depends on the change in the oil temperature. For this reason, in the oil-filled transformer 1, when the transformer tank 2 is completely sealed, when the volume of the insulating oil increases, the pressure of the transformer tank 2 increases and the transformer tank 2 is damaged. The insulating oil 10 may leak. In particular, when air enters the transformer tank 2 due to oil leakage, the insulating oil 10 in contact with the air generates a degradation product such as sludge, thereby reducing the insulating performance and cooling performance of the insulating oil 10. Therefore, in the oil-filled transformer 1, a pipe 7 communicating with the outside air is provided in the transformer tank 2 to balance the pressure of the outside air (atmospheric pressure) and the inside pressure of the transformer tank 2, and the oil volume in the conservator 3 is reduced. By changing, the volume fluctuation of the insulating oil 10 of the transformer is buffered.

  That is, the conservator 3 converts the volume change of the insulating oil 10 into the volume change of the diaphragm 5 so that the pressure in the transformer tank 2 is kept constant without the insulating oil 10 being exposed to the air 9. 2 and the insulating oil 10 is prevented from overflowing from the tank to the outside.

The rubber material used for the diaphragm 5 of the conservator 3 is generally based on a nitrile rubber having excellent gas barrier performance and oil resistance, but the air 9 in the diaphragm 5 is completely insulated. It cannot be cut off from oil. Even if there is no defect such as a hole in the diaphragm 5, the gas molecules of the air 9 permeate the rubber material of the diaphragm 5 and diffuse to the inside, and the diffused gas molecules reach the oil side and are released to be insulated oil. 10 is contacted. In general, the air permeability of the oil-resistant nitrile rubber diaphragm used for Conservator 3 is 10 when measured by the method described in ASTM (American Society for Testing and Materials) D1434. It is a value on the order of ⁻⁶ cm ³ / cm ² · min · atm.

  Oil-filled transformers for electric power are expected to have a life of 20 years or longer. For this reason, even if the air permeability of the diaphragm 5 is very small during long-term use, if the amount of air entering the oil-filled transformer 1 during the operation period is integrated, the amount cannot be ignored. In particular, the intrusion of oxygen in the air 9 greatly affects the deterioration of the insulating oil 10 in the oil-filled transformer 1 and thereby the life of the oil-filled transformer 1.

  Therefore, in order to predict the deterioration of the insulating oil 10, it is very important to know the amount of oxygen that enters the oil-filled transformer 1 that causes oxidation deterioration, that is, the amount of oxygen that enters the insulating oil. As described with reference to FIG. 1, the transformer tank 2 is filled with the insulating oil 10, and the diaphragm 5 is in direct contact with the insulating oil 10. The description of “invading into 1” or “intruding into the transformer tank 2” is “to enter into the insulating oil 10 in the transformer 1” or “to the insulating oil 10 in the transformer tank 2”. It is defined that it means “invading”.

  Hereinafter, using the nitrogen gas amount evaluation coefficient A <N2>, the penetration speed when oxygen in the air 9 penetrates the diaphragm 5 and enters the oil-filled transformer tank 2 and the insulating oil 10 of the penetrated oxygen A method for diagnosing deterioration of the insulating oil 10 by evaluating the consumption amount of oil will be described.

  First, the nitrogen gas permeability coefficient k <N2 new> of the diaphragm 5 is calculated. The nitrogen gas permeability coefficient k <N2 new> is a gas permeability coefficient when the diaphragm 5 is not deteriorated. Here, the state which has not deteriorated means the state in which neither a hole nor a damage | wound has arisen in the diaphragm, and it does not ask | require whether it is unused.

  The surface area of the diaphragm 5 in contact with the air in the conservator 3 is S, and the thickness of the diaphragm 5 is d. The penetration amount of nitrogen gas in the air per unit time with respect to the oil-filled transformer 1, that is, the nitrogen penetration rate (F <N2>) is expressed as follows.

F <N2> = k <N2 new>. S / d. (P <N2 air> -P <N2 oil>) (1)
Here, P <N2 air> and P <N2 oil> are gas partial pressures of nitrogen in the air (1 atm = 101, 325 Pa) and oil, respectively, and P <N2 air> can be regarded as a constant. Moreover, the nitrogen gas partial pressure P <N2 oil> in oil is proportional to the nitrogen concentration in oil [N2 oil], the Ostwald absorption coefficient of nitrogen in the insulating oil is C <N2>, and the nitrogen concentration in the air (1 atm) Is represented as [N2 air] (constant), respectively.

P <N2 oil> = (P <N2 air> / C <N2>). ([N2 oil] / [N2 air] air) (2)
As for the Ostwald absorption coefficient C <N2> of the insulating oil 10, values for nitrogen and oxygen gas are formulated as a function of temperature in, for example, ASTM D2779-92 (2002), and this may be used. Substituting the nitrogen gas partial pressure P <N2 oil> in the oil into the formula of the nitrogen penetration rate F <N2>, it is expressed as follows.
F <N2> = S / d.P <N2 air> .k <N2 new>. [1- [N2 oil] / (C <N2>. [N2 air])] ... (3)
Thus, the nitrogen gas permeability coefficient k <N2 new>, the Ostwald absorption coefficient C <N2>, and the nitrogen concentration in oil [N2 oil] are variables. As described above, the nitrogen gas permeability coefficient k <N2> and the Ostwald absorption coefficient C <N2> are obtained as a function of the oil temperature. For example, in ASTM, the value for nitrogen is formulated as a function of the temperature. Use it. The nitrogen concentration in oil [N2 oil] is obtained by gas analysis of the actual insulating oil 10.

The nitrogen gas penetration amount Q <N2> into the transformer may be obtained by integrating the nitrogen penetration speed F <N2> over time. Q <N2> = ∫F <N2> dt (4)
Is required. The nitrogen gas penetration amount Q <N2> and the nitrogen penetration speed F <N2> are values of the state in which the diaphragm 5 is not deteriorated because the nitrogen gas permeability coefficient k <N2 new> used for derivation is These are the nitrogen gas intrusion speed and the amount of intrusion when entering the transformer through the undegraded diaphragm 5.

  Here, the nitrogen gas intrusion amount into the transformer in a certain period can be obtained by performing time integration of the period for the expression (4).

  In addition, for the actual nitrogen gas intrusion amount Q <N2 actual>, the increase amount Δ ([N2 oil]) of the nitrogen concentration in oil during that period is measured, and this is compared with the oil volume V of the oil-filled transformer. By taking the product, we can find

Q <N2 actual> = Δ ([N2 oil]) · V (5)
The ratio of the actual nitrogen gas intrusion amount Q <N2 actual> to the nitrogen gas intrusion amount Q <N2> is represented as A <N2>.

A <N2> = Q <N2 actual> / Q <N2> = M · α <N2> (6)
Let A <N2> be the nitrogen gas amount evaluation coefficient. Here, m is a coefficient relating to measurement error and evaluation error such as nitrogen concentration in oil [N2 oil] and oil volume V, and is treated as a constant in the same transformer, and in an ideal case with no error, m = 1

α <N2> is the multiplication factor of the nitrogen gas permeability coefficient due to deterioration of the conservator diaphragm,
α <N2> = K <N2 inferior> / k <N2 new> (7)
It becomes.

  Next, when considering the oxygen gas penetration rate F <O2> and the penetration amount Q <O2> into the oil-filled transformer 1, the items relating to nitrogen gas in the equations (1), (3), and (4) should be replaced with oxygen gas. Well represented by:

F <O2> = k <O2 new> .S / d. (P <O2 air> -P <O2 oil>)
= S / d · P <O2 air> · k <O2 new> · [1- [O2 oil] / (C <O2> · [O2 air])] (8)
Q <O2> = ∫F <O2> dt (9)
Here, P <O2 air> and P <O2 oil> are oxygen gas partial pressures in the air (1 atm = 101, 325 Pa) and oil, and P <O2 air> is a constant. C <O2> is an Ostwald absorption coefficient of oxygen in the insulating oil 10. For example, a value for oxygen gas is formulated as a function of temperature in ASTM, and this may be used. [O2 air] and [O2 oil] are oxygen concentrations in air and insulating oil, respectively. k <O2 new> is the oxygen gas permeation coefficient of the diaphragm 5 which has not deteriorated, and the value depends on the temperature. Therefore, data on the temperature dependence of the oil temperature range assumed in the transformer is acquired in advance. . Here, S is the surface area of the diaphragm 5 in contact with the air in the conservator 3, and d is the thickness of the diaphragm 5.

  As the oxygen gas permeability coefficient k <O2> in the equations (8) and (9), a value in a state where the diaphragm 5 is not deteriorated is used. Here, when the diaphragm 5 is deteriorated, assuming that the multiplication factor of the nitrogen gas permeability coefficient does not change between the case of nitrogen gas and the case of oxygen gas, the nitrogen gas amount evaluation coefficient A <N2 in the equation (6) >, The actual oxygen gas penetration speed F <O2 actual> and the intrusion amount Q <O2 actual> into the transformer in consideration of the deterioration of the diaphragm 5 are expressed as follows.

F <O2 actual> = A <N2> · F <O2> (10)
Q <O2 actual> = ∫F <O2 actual> dt = ∫ (A <N2> · F <O2>) dt ··· (11)
The amount of oxygen E <O2> consumed by oxidation in the insulating oil in a certain period is obtained by integrating the expression (11) over time during that period, and the amount of change Δ ([O2 oil] in the transformer oxygen concentration during that period. )
E <O2> = Q <O2 actual> -Δ ([O2 oil]) · V (12)
Can be evaluated as Here, V is the oil volume of the insulating oil 10 in the oil-filled transformer 1.

  Next, the diagnosis method of the present embodiment will be described specifically using a flowchart showing a transformer oil deterioration diagnosis method using oxygen consumption. First, before the diagnosis is started, the oxygen gas intrusion speed F <O2> and the oxygen gas intrusion amount Q <O2> of the diaphragm 5 that has not deteriorated are measured in advance.

  Measurement is started (step S50), and first, a nitrogen gas amount evaluation coefficient A <N2> is calculated (step S51). Thereafter, the actual oxygen gas penetration rate F <O2 actual> (step S52) based on the equation (10), and the actual oxygen gas penetration amount Q <O2 actual> (step S53) based on the equation (11). Is calculated. By substituting these values into equation (12), the oxygen consumption E <O2> is calculated (step S54).

  By observing the temporal change of the calculation result, it is determined whether or not the oxygen consumption E <O2> has increased at a certain time (step S55). If the oxygen consumption E <O2> has not increased, it is determined that the insulating oil 10 is not deteriorated (step S56). On the other hand, if the oxygen consumption E <O2> has increased in a certain period, it is determined that the insulating oil 10 has deteriorated (step S57). It is also possible to predict the future oxygen consumption E <O2> of the insulating oil 10 by extrapolating the relationship between the obtained oxygen consumption and time.

  Furthermore, it is also possible to determine the life of the oil-filled transformer 1 based on whether or not the increased oxygen consumption E <O2> exceeds a management value determined based on data obtained in advance through tests or the like ( Step S58). That is, when the oxygen consumption E <O2> does not exceed the control value, it is determined that the insulating oil of the oil-filled transformer 1 has not reached the end of its life and can be used continuously (step S59). When the oxygen consumption E <O2> exceeds the control value, it is determined that the insulating oil has reached the end of life (step S60).

  From the above steps, the deterioration diagnosis of the insulating oil 10 using the oxygen consumption amount E <O2> is completed (step S61).

  In the present embodiment, the following operational effects are produced.

The deterioration degree of the insulating oil 10 of the oil-filled transformer 1 is determined by the actual oxygen gas penetration rate F <O2 actual>, the intrusion amount Q <O2 actual> into _the insulating oil 10, and the oxygen consumption E in the insulating oil 10. <O2> is the oil temperature dependence of [O2 oil], oil temperature T and nitrogen gas amount evaluation coefficient A <N2> time-lapse data, and oxygen gas permeability coefficient k <O2 new> of the diaphragm 5 that has not deteriorated. If it is understood, it will be possible to evaluate. It is also possible to predict the amount of oxygen permeation and consumption into the transformer in the future by observing changes in oxygen gas penetration Q <O2 actual> and oxygen consumption E <O2> _O2 over time. is there.

  In parallel with the above-described evaluation of the amount of oxygen, the temporal change in the relationship between the various characteristics (volume resistivity, dielectric loss tangent, viscosity, charge degree) of the insulating oil 10 and the oxygen consumption E <O2> is pre-heated. By acquiring data through a deterioration test or the like, it is possible to predict the future trend of changes in the oil characteristics of the oil-filled transformer 1. This makes it possible to provide management values for various oil characteristics and to perform life diagnosis thereof.

  The insulating oil 10 used when acquiring the temporal change in the relationship between the oxygen consumption E <O2> and various characteristics of the insulating oil 10 in advance by a heat deterioration test or the like is the same type as the oil-filled transformer to be diagnosed. Of course, if it is an aged oil collected from the target transformer, the deterioration test of the insulating oil is more realistic, and a highly accurate diagnosis can be performed.

  Although the oil temperature and oxygen gas concentration [O2 oil] are measured, the derivation of the equations (7) to (11) is a phenomenon related to oxygen gas permeation in the conservator 3. It is desirable to set the oil temperature and the oxygen concentration in the oil in the transformer tank 2. On the other hand, regarding the change amount Δ ([O2 oil]) of the oxygen concentration of the transformer in the equation (12), the oxygen concentration in the oil in the transformer tank 2 or the transformer tank 2, the conservator 3, etc. It is preferable to use a volume average value in consideration of the oil volume of the part.

  As described above, the deterioration of the insulating oil 10 can be predicted and diagnosed by quantitatively evaluating the amount of oxygen consumed in the insulating oil 10 of the oil-filled electrical device by using the deterioration multiplication coefficient of the nitrogen gas permeability coefficient. This makes it possible to perform highly accurate deterioration prediction diagnosis for oil-filled electrical equipment.

The figure which shows the oil-filled transformer which concerns on embodiment of this invention. The flowchart which showed the deterioration diagnosis method of the transformer oil using oxygen consumption.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Oil-filled transformer 2 ... Transformer tank 3 ... Conservator 4 ... Communication pipe 5 ... Diaphragm 6 ... Flange 7 ... Piping 8 .... Breather 9 ... Air 10 ... Insulating oil

Claims (6)

In an oil-filled electrical device having a conservator with a diaphragm and storing insulating oil therein,
Nitrogen that permeates through the undegraded diaphragm and enters the insulating oil using the nitrogen concentration in the oil of the insulating oil and the nitrogen gas permeability coefficient in the undegraded diaphragm given as a function of the oil temperature of the insulating oil Calculate the amount of gas intrusion,
The nitrogen gas intrusion amount actually infiltrated into the insulating oil calculated from the product of the amount of change in the nitrogen concentration in the oil and the volume of the insulating oil in a predetermined period, and the permeation through the undegraded diaphragm While calculating the nitrogen gas amount evaluation coefficient calculated from the ratio with the nitrogen gas intrusion amount that penetrates into the insulating oil,
The amount of oxygen consumed for oxidation in the insulating oil within a predetermined period is actually determined from the nitrogen gas amount evaluation coefficient and the penetration rate of oxygen penetrating into the insulating oil through the undegraded diaphragm. An oil-filled electrical device characterized in that it is obtained from the difference between the amount of oxygen that has penetrated into the insulating oil and the value obtained from the product of the concentration of oxygen dissolved in the insulating oil and the volume of the insulating oil. Degradation diagnosis method. The amount of oxygen that has actually penetrated into the insulating oil is calculated by time-integrating the penetration rate of oxygen that actually penetrates into the insulating oil over a predetermined period,
The penetration rate of oxygen that actually penetrates into the insulating oil is calculated by the product of the nitrogen gas amount evaluation coefficient and the penetration rate of oxygen that penetrates the undegraded diaphragm and penetrates into the insulating oil. The deterioration diagnosis method for oil-filled electrical equipment according to claim 1.   Oxygen gas permeation through the undegraded diaphragm given the rate of oxygen permeation through the undegraded diaphragm and into the insulating oil as a function of the oxygen concentration in the oil of the insulating oil and the oil temperature of the insulating oil The deterioration diagnosis method for oil-filled electrical equipment according to claim 1, wherein the deterioration diagnosis method is calculated using a coefficient.   4. The deterioration diagnosis method for oil-filled electrical equipment according to claim 3, wherein when the value of the amount of oxygen consumed for oxidation in the insulating oil increases, the insulating oil is deteriorated.   5. The life of the oil-filled electrical device when the value of the amount of oxygen consumed for oxidation in the insulating oil exceeds a predetermined control value obtained in advance through experiments. Degradation diagnosis method for oil-filled transformer as described.   Using the amount of oxygen that has actually penetrated into the insulating oil, the amount of oxygen consumed for oxidation in the insulating oil, and the time-lapse data of the deterioration characteristics of the insulating oil with respect to these oxygen amounts in advance through a heat deterioration test The deterioration diagnosis method for an oil-filled transformer according to claim 5, wherein deterioration of the oil-filled electrical device is predicted.

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