JP2012037483A - Method for determining partial discharge generation void class - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for determining the class of a void in which partial discharge occurs, without depending on a deterioration state of a measurement target.SOLUTION: A measurement target is installed within a device such as a constant-temperature/constant-humidity tub in which a temperature/humidity can be controlled and under a condition through a step of generating bedewing on a surface of the measurement target and a step of canceling bedewing, a partial discharge initiation voltage with a monopolar pulse voltage as a test voltage is measured. A characteristic where a behavior of the partial discharge initiation voltage in the bedewing canceling step is different in accordance with the class of a void in which partial discharge occurs, is utilized to determine the partial discharge occurrence void class.

Description

  The present invention relates to a test method for determining the type of a void in which partial discharge has occurred when measuring partial discharge characteristics of an electric device such as a transformer or rotating machine that has been molded or impregnated with a resin.

  If there is a defect that causes local electric field concentration inside or on the surface of the insulating material due to application of a high voltage, local discharge (partial discharge) may occur in that portion. When an organic insulating material is exposed to a partial discharge, the material is physically and chemically deteriorated by the discharge, and in the worst case, the entire path may be destroyed. Therefore, it is necessary to carry out a partial discharge test for electrical equipment at the initial stage after manufacturing and at the time of diagnosis after a certain period of operation to diagnose initial defects and aging deterioration.

  The partial discharge measurement method using a sinusoidal alternating voltage has been studied for a long time, and various measurement methods have been established (for example, Non-Patent Document 1). In addition, in order to cope with inverter surges, which have become a problem in recent years in the insulation of inverter drive systems, studies are also being conducted on partial discharge measurement methods for voltage waveforms with sharp rises. It has been proposed (for example, Non-Patent Document 2 and Patent Document 1).

  By the way, the partial discharge includes a discharge generated inside the insulating layer (sealed void) and a discharge generated outside (open void), and can be classified into two types depending on the void form. In general, voids generated in the early stage of deterioration are sealed voids, and when the deterioration progresses, the voids progress to open voids. In other words, the progress of deterioration can be estimated by determining the void form in which partial discharge has occurred. In addition, regarding the partial discharge failure during manufacturing, it is possible to estimate the cause such as insufficient penetration of the impregnated resin into the coil if internal discharge, and dripping of resin in the heat curing process if external discharge. Thus, the identification of the partial discharge generation void form is a useful index for diagnosis of the insulation system and examination of countermeasures in case of failure.

  With respect to the method for discriminating this partial discharge generation void, the discharge occurs by using the feature that the slope of the qmax-V characteristic is larger in the external discharge from the relationship between the maximum discharge charge amount qmax and the applied voltage V. A method for discriminating whether a void is a closed system or an open system has been proposed (Non-Patent Document 3).

JP 2006-38471 A

"Partial discharge deterioration", IEEJ Technical Report (Part II) No.164 "Influence of inverter surge on insulation system", IEEJ Technical Report No. 739 "Special high-voltage rotating machine / insulation deterioration diagnosis technology for cables", IEEJ Technical Report (Part II) No. 267

  However, in this method, when the deterioration of the measurement target is progressing, the partial discharge start voltage decreases with the deterioration, and the slope of the qmax-V characteristic becomes small even with external discharge. On the other hand, when the deterioration is small, the partial discharge start voltage becomes high, so that the inclination becomes large even in the internal discharge, and it becomes difficult to determine the void form.

  In addition, when a test is performed by applying a steep impulse voltage, it is difficult to accurately measure the discharge charge amount, so that this method is also difficult to apply in this case.

  An object of this invention is to provide the measuring method for discriminating the void form which has produced partial discharge irrespective of the degradation state of a measuring object.

  According to the first aspect of the present invention, the object to be measured is placed in a thermo-hygrostat capable of controlling temperature and humidity, the partial discharge start voltage is measured under conditions involving condensation, and the insulation resistance value / static An insulation test method comprising measuring any one of a capacitance value and a tan δ value, or a combination thereof. The measurement target is placed in a constant temperature and humidity chamber where temperature and humidity can be controlled, and the partial discharge start voltage is measured under conditions with condensation. In addition, the insulation resistance value, capacitance value, tanδ value (dielectric loss tangent) ) Etc., and the characteristics that can confirm the dew condensation / moisture absorption state of the measurement object are measured.

  According to a second aspect of the present invention, there is provided an insulation test method for determining a void type of a discharge generation source in the measurement object from a measurement result using the test method of the first aspect. Based on the measurement results using the test method of claim 1, utilizing the fact that the influence of the dew condensation state on the insulator surface on the partial discharge behavior differs depending on whether the void that becomes the partial discharge generation source is an open system or a closed system. The void type of the discharge generation source is determined.

  The present invention provides a unipolar pulse voltage in an environment in which condensation is formed on the surface of a measurement object by setting the measurement object in an environment where the temperature and humidity can be controlled, such as a constant temperature and humidity chamber, and raising the temperature at a certain speed. The partial discharge start voltage is measured using the test voltage as a test voltage. The behavior of the partial discharge start voltage in the decondensation elimination process can determine the partial discharge occurrence void type regardless of the degradation state of the measurement object by using characteristics that differ depending on the type of void that generates the partial discharge.

  When measuring the partial discharge start voltage, it is desirable to use a unipolar pulse voltage with a pulse rise time of about 10 μs or less as the test voltage. When bipolar pulse voltage is used, the effect of residual charge has a complicated effect, and measurement results tend to vary. When commercial frequency AC voltage is used, absolute humidity is increased. This is because the effect of increasing the partial discharge starting voltage is exhibited beyond a certain point.If the rise of the pulse is dull, only the open voids when the present invention is implemented are used. This is because the resulting unique behavior is less likely to appear.

  The partial discharge detection method at the time of measuring the partial discharge start voltage is a measurement using a somewhat steep pulse voltage as a test power supply. Therefore, a conventional partial discharge measurement device using a sinusoidal alternating current cannot be used. It is possible to measure using a simple device such as FIG. 1 shows an example of a measuring apparatus. A measuring object of 2 is installed in a constant temperature and humidity chamber of 1, and a pulse voltage is applied to 2 by a high voltage pulse power source of 3. When a partial discharge occurs at 2 at a constant speed, a partial discharge current flowing at that time is detected by 4 high-frequency CT, and a waveform that eliminates noise components through 5 high-pass filters is detected by 6 digital oscilloscopes. To do.

  The purpose of controlling the temperature and humidity is to cause sufficient condensation on the surface of the measurement object. Specifically, it is necessary to control the temperature to be measured to be equal to or lower than the dew point temperature with respect to the temperature and humidity in the constant temperature and humidity chamber. FIG. 2 (a) shows the dew point temperature for each temperature and humidity, and FIG. 2 (b) shows the temperature difference necessary for condensation. It is necessary to control the temperature and humidity with this as a guideline, and to produce a sufficient difference between the temperature in the constant temperature and humidity chamber and the temperature to be measured by a relatively high set temperature and a fast temperature rise rate.

  Condensation that occurs when the temperature rise of the measurement target is delayed from the temperature rise in the temperature and humidity chamber is that the temperature in the temperature and humidity chamber reaches the set temperature, and then the temperature of the measurement target also reaches the set temperature. It turns into cancellation. Through this process, the partial discharge start voltage is measured by applying a unipolar pulse voltage. In particular, the type of the partial discharge occurrence void is determined using the fact that the partial discharge start voltage shows different behavior depending on whether the void where the partial discharge is generated is a closed system or an open system in the vicinity where the condensation starts to disappear. When the partial discharge generation void is a closed system, the partial discharge start voltage is sufficiently reduced at the stage of condensation, and is not affected when condensation is eliminated. However, when the partial discharge generation void is an open system, a phenomenon occurs in which the partial discharge start voltage further decreases in the vicinity where the condensation is eliminated. By distinguishing this difference, it becomes possible to classify the partial discharge generation voids. The condensation on the surface to be measured or the moisture absorption state of the insulating layer can be grasped by measuring the capacitance / tan δ or the insulation resistance together with the measurement of the partial discharge start voltage.

  According to the present invention, it is possible to determine the type of the partial discharge occurrence void regardless of the deterioration state of the measurement target.

It is the schematic which showed an example of the partial discharge start voltage measuring apparatus. It is the figure which showed the dew point temperature used as the conditions which produce dew condensation about each temperature and humidity. It is explanatory drawing of temperature and humidity control at the time of void type determination method implementation. Example 1 It is explanatory drawing which showed the implementation method of void type determination. Example 1

  By implementing partial discharge start voltage measurement using the unipolar pulse voltage as the test voltage through the process of condensation once the measurement object has been eliminated, a method for determining the type of the partial discharge occurrence void has been realized.

  The partial discharge start voltage is measured with a measuring apparatus using the high-frequency CT method shown in FIG.

  FIG. 3 shows an example of temperature / humidity control by a thermo-hygrostat performed to cause the process of condensation and the process of eliminating condensation on the surface to be measured. FIG. 4 is controlled as shown in FIG. Measurement results of partial discharge start voltage and tan δ (dielectric loss tangent) data measured together to determine the dew condensation state for each of the closed void sample and open void sample It is.

  Condensation occurs on the surface of the object to be measured by raising the temperature to a high temperature range with a certain temperature gradient as shown in FIG. As the degree of condensation can be confirmed by the data of tan δ in FIG. 4, it gradually proceeds from the start of the test, reaches a peak near the maximum value of tan δ, and then turns to cancellation.

  Looking at the measurement results of the closed system sample in FIG. 4A, the partial discharge start voltage decreases due to the moisture absorption of the insulating layer that occurs along with the surface condensation from the start of measurement. From the rapid decline trend until the transition to the stable region, it is hardly affected by the process of eliminating condensation.

  On the other hand, when the measurement result of the open type void sample in FIG. 4B is seen, the decrease of the partial discharge start voltage in the process of dew condensation is the same as in the closed type void sample, but it is sealed in the process of elimination from the peak of dew condensation. It shows characteristics that are very different from system voids. The partial discharge that occurs in the open void on the surface of the insulator is directly affected by the change in the surface conductivity of the insulator due to the progress and elimination of condensation. Can be confirmed.

  Thus, by distinguishing the characteristic behavior of the partial discharge start voltage in the condensation elimination process, it is possible to determine whether the partial discharge generation void is a closed system or an open system.

  When a partial discharge failure is detected in an insulation characteristic test performed at the time of manufacturing or when aging deterioration is diagnosed, the method of the present invention can be used to determine the type of void in which partial discharge occurs regardless of the degree of deterioration of the measurement target. It is possible to obtain an index that is greatly useful for studying countermeasures thereafter.

1 Constant temperature and humidity chamber 2 Measurement object 3 High voltage pulse power supply 4 High frequency CT
5 High-pass filter 6 Digital oscilloscope

Claims (2)

  Install the object to be measured in a constant temperature and humidity chamber that can control temperature and humidity, measure the partial discharge start voltage under conditions with condensation, and select either insulation resistance value, capacitance value, or tanδ value. An insulation test method characterized by measuring one or a combination thereof.   An insulation test method, comprising: determining a void type of a discharge generation source in the measurement target from a measurement result using the test method according to claim 1.

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