JPH07218480A - Method for measuring insulation characteristics of electrically insulated coil - Google Patents

Abstract

(57) [Abstract] [Purpose] Regarding a method for measuring insulation characteristics of a coil, it is possible to easily measure a partial discharge generated in the coil in a short time without using a dedicated measuring instrument. [Composition] Partial discharge generated from the coil insulation layer is detected as an AE wave by an AE sensor attached to a coil iron core,
This is a method of amplifying the AE signal and then transmitting the signal to an RMS voltmeter and an AE analyzer to measure two types of insulation characteristic values of the RMS voltage and the maximum amplitude value of the AE wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the insulation characteristics of an electric insulating coil (coil) used in electric equipment by using an acoustic emission (hereinafter abbreviated as AE) method.

[0002]

2. Description of the Related Art Generally, a coil used in electric equipment has a different insulation method depending on the conditions and environment in which it is used. A good mica tape is wound around a conductor and the space between them is hardened with resin. Due to long-term operation of the insulating layer of this coil, if voids are created in the insulating layer due to heat deterioration, etc., partial discharge will occur inside and outside the insulating layer, and the insulating material will be decomposed and eroded, resulting in reduced insulation performance. In the end, however, discharge deterioration may become noticeable and a dielectric breakdown accident may occur. Therefore, it is important for maintenance management to detect insulation deterioration (partial discharge) and repair or update the insulation before dielectric breakdown.

Conventionally, for this purpose, a mega test, a DC voltage test, a dielectric loss tangent test, an AC current test, a partial discharge test and the like have been carried out as a test method for detecting the deterioration of the insulation characteristic. Of these, the test power source that uses DC voltage (mega test, DC voltage test) is mainly intended for measuring insulation resistance. In addition, the method using AC voltage (dielectric loss tangent test, AC current test, partial discharge test) is intended to measure the change in characteristic value based on partial discharge. As a test method for examining the insulation characteristics in detail, the AC voltage test is generally used rather than the DC voltage test whose main purpose is to measure the insulation resistance, and the dielectric loss tangent test (tan δ test) is applied to the insulator with the AC voltage. Value, tanδ-voltage characteristic (existence of partial discharge, checking the average value of partial discharge starting voltage and partial discharge generation amount), and tanδ-temperature characteristic (change in material of insulator) It is a test to check the insulation properties such as moisture absorption, dryness, fouling, and voids, or the degree of deterioration.

The AC current test is a test method for examining the property of insulation from the relationship between the current and the voltage flowing when an AC voltage is applied to an insulator. This test method is a simple test method that combines both the tan δ test and the partial discharge test, and is characterized in that the device and its handling are simple. However, the information obtained in the test and its accuracy are inferior to those in the tan δ test and the partial discharge test. In the partial discharge test, AC voltage is applied to the insulator to measure the discharge charge, the number of discharge pulses,
Discharge starting voltage at which a certain discharge charge is generated, maximum discharge charge,
This is a method of grasping the deterioration status of an insulator from the amount of information such as discharge energy. Partial discharge is a local defect in insulation,
For example, it is generated due to voids, cracks, inclusion of foreign matter, etc. and is closely related to dielectric breakdown, so it is currently used in various fields, and various new measurement methods are being studied.

[0005]

As a conventional method for detecting deterioration, the tan δ test is used in order to investigate the average value of the partial discharge generation amount in the AC voltage test, and the local defect or damage in the insulation is investigated. Therefore, it was necessary to carry out the partial discharge tests separately. However, for the tan δ test, it is necessary to prepare special equipment such as a standard capacitor and a measurement circuit unit (sharing bridge) as a test device, and it takes time to balance the bridge in the measurement operation of the shaling bridge. So
Measurement of tan δ-voltage characteristic It took a long time to measure the voltage finely. Also, in the partial discharge test, as in the case of the tan δ test, a dedicated measuring device is required, and the measurement operation is likely to cause individual differences and the measurement time is long. The present invention was devised in order to solve these drawbacks, and its object is a method for measuring the insulation characteristics of a coil without using a dedicated measuring instrument for the partial discharge generated in the coil. It is to provide a test method that can be easily measured in a short time.

[0006]

The AE method is a method of detecting partial discharge other than the electrical test method. When a partial discharge is generated in the coil insulation layer of an electric device, a shock wave including ultrasonic waves is generated by the discharge, and the shock wave at this time becomes an AE wave and propagates to the iron core and the frame of the electric device. Can be detected by an AE sensor attached to the sensor, and by this sensor, the A generated by the partial discharge generated from the electrically insulated coil to which the voltage is applied.
After detecting the E wave and amplifying the AE signal, it is possible to simultaneously measure the effective voltage and the maximum amplitude value of the AE signal.

[0007]

Next, the operation will be described. Due to the long-term operation of the insulating layer of the electric device coil, when a void is generated in the insulating layer, a partial discharge is generated therein. It is considered that this discharge causes the air in the void to instantaneously expand to form a shock wave, which compresses the inner wall of the void and causes an AE wave in the insulating layer. An AE sensor attached to the iron core that houses the coil examined the relationship between the partial discharge charge amount generated from the coil and the maximum amplitude value of the AE parameter. It was found that and the maximum amplitude value of the AE wave have a proportional relationship.

Further, as the applied voltage increases, the number of partial discharges increases and the maximum discharge charge amount also increases. Along with this, the number of AE waves generated also increases and the maximum amplitude value of AE waves also increases. To do. As the insulation deterioration of the coil progresses, the number of voids also increases, but this increases the partial discharge, which also increases the AE wave. In this way, if the AE wave generated by the partial discharge is detected by the AE sensor, and the signal is amplified and then measured by the RMS voltmeter, the presence or absence of the partial discharge and the start voltage of the partial discharge are measured as in the tan δ test. Also, the average value of the partial discharge generation amount can be known. At the same time, if the maximum amplitude value of the AE wave is measured, a local defect in the insulator can be found as in the partial discharge test. Then, the deterioration of the insulation characteristic of the coil can be detected by examining the change of the value of the effective value voltage or the maximum amplitude value of the AE wave with time.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram for measuring the insulation characteristic of the present invention. In FIG. 1, a model coil 1 as an electrically insulating coil is housed in a slot of a model iron core 2.
In order to detect the partial discharge generated from the model coil 1, the AE sensor 3 is attached in close contact with the surface of the model iron core 2. The output signal of the AE sensor is amplified by the preamplifier 4 by 40 dB and then input to the RMS voltmeter 5 and the AE analyzer 6. The signal amplified by 40 dB by the preamplifier 4 is converted into an effective value (RMS) voltage by an effective value voltmeter 5 (3400A manufactured by YHP) and displayed on the meter. At the same time, AE analyzer 6 (LOCAL-manufactured by PAC)
The signal input to AT) is set in the AE analyzer so that the maximum amplitude value of the AE wave is displayed.

For the measurement, an AC high voltage is applied to the model coil 1 from the withstand voltage tester 7, the meter of the rms value voltmeter 5 at that time is read, and the maximum amplitude value of the AE wave displayed on the AE analyzer 6 is measured. It is easy to read because it does not require any measurement time and no special measurement operation is required. "RMS voltage-voltage characteristics" when the model coil 1 is degraded in voltage
A characteristic diagram of the change with time of is shown in FIG. Among them, indicates the characteristics before voltage deterioration, is the initial voltage deterioration, is the middle voltage deterioration period, and is the final voltage deterioration period (after that, dielectric breakdown occurs immediately after the voltage deterioration).

According to this, the RMS voltage starts to increase from around 4 kV regardless of the timing of voltage deterioration, but there is a tendency that the RMS voltage increases as the deterioration progresses. FIG. 3 is a characteristic diagram of the change with time of the “maximum amplitude value of AE-applied voltage characteristic” measured simultaneously with the “RMS voltage-applied voltage characteristic”. Since the maximum amplitude value of AE is displayed in logarithm, near the partial discharge inception voltage 4kV
The front and rear rise is emphasized. It can be seen that as the deterioration progresses, the rising of the maximum amplitude value moves to the low voltage side and the maximum amplitude value also increases.

FIG. 5 shows "tan δ-applied voltage characteristics" measured at the same time as the former two. 2 to 3 are measured at the same time as in FIGS. 2 and 3, and it can be seen that the deterioration tendencies are almost the same. Further, even if the AE analyzer is not used, as shown in FIG. 6, instead of the preamplifier 4 and the AE analyzer 6, the AE tester 8 (950 circuit manufactured by NF Circuit Design Block Co., Ltd.) is used.
1), pulse voltmeter 9 (PPV-8 manufactured by Fuji Precision Electric Co., Ltd.)
The same measurement can be performed using. In this way, the deterioration of the insulation characteristics of the coil can be detected from the change with time of the “RMS voltage-applied voltage characteristic” or the “maximum amplitude value-applied voltage characteristic”. Here, "RMS voltage-in the model coil
The method for detecting the insulation deterioration of the coil is described based on the temporal changes in the "applied voltage characteristic" and the "maximum amplitude value-applied voltage characteristic". However, the insulation deterioration can be detected in the same manner as in the actual coil.

[0013]

According to the present invention, the partial discharge generated in the coil can be easily measured in a short time without using a dedicated measuring instrument, and the deterioration of the insulation characteristic of the coil due to the operation of the electric device can be prevented by the "RMS voltage". A method of detecting from the change with time of “applied voltage characteristic” and “maximum amplitude value-applied voltage characteristic” was obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram for measuring insulation characteristics according to the present invention.

FIG. 2 is a characteristic diagram showing a change with time of “RMS voltage-applied voltage characteristic of AE wave”.

FIG. 3 is a characteristic diagram showing changes with time of the maximum amplitude value of AE wave-applied voltage characteristic.

FIG. 4 is a characteristic diagram showing a relationship between a maximum discharge charge amount of partial discharge generated from a coil and a maximum amplitude value of an AE parameter.

FIG. 5 is a characteristic diagram showing changes with time of tan δ-applied voltage characteristics.

FIG. 6 is another configuration diagram showing a method for measuring an insulation characteristic according to the present invention.

[Explanation of symbols]

 1 Model coil 2 Model iron core 3 AE sensor 4 Preamplifier 5 RMS voltmeter 6 AE analyzer 7 Withstand voltage tester 8 AE tester 9 Pulse voltmeter

Claims (1)

[Claims] 1. A method for measuring the insulation characteristics of an electrically insulated coil used in an electric device, comprising: an acoustic emission attached to an iron core containing the electrically insulated coil or a frame in contact with the iron core ( AE)
Acoustic waves caused by the partial discharge generated from the electrically insulated coil to which voltage is applied by the sensor
A method for measuring an insulation characteristic of an electrically insulating coil, comprising detecting an emission (AE) wave, amplifying the AE signal, and then simultaneously measuring the effective value voltage and the maximum amplitude value of the AE signal.