JPH07174812A - Withstand voltage testing method for insulator - Google Patents

Abstract

PURPOSE:To detect partial discharge in an insulator which cannot be detected due to the generation of partial discharge in air in an electrode on high voltage side at the time when partial discharge in the insulator as a sheet-like sample is detected in a withstand voltage test for the sample. CONSTITUTION:An epoxy electrode 22 which is produced by molding unitedly an epoxy insulator 13 and a high voltage electrode 14 made of a metal is set on a rubber electrode 23 which is produced by molding unitedly a rubber sheet 11 and a semiconductive rubber electrode 16, a sample sheet 21 is put between the rubber electrode 23 and an earthed electrode 15, and a withstand voltage test is carried out by a leader stroke method while the sample sheet 21 being pressed between the electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage application test method for detecting defects in an insulator such as a power cable.

[0002]

2. Description of the Related Art CV (cross-linked polyethylene) cables, which are dry insulation, are widely used due to their ease of maintenance and management, and are used for high voltage of 500 kV class. The electrical performance of cross-linked polyethylene, which is the insulator of CV cables, is very excellent, but defects such as foreign matter, voids, and semiconductive layer protrusions have hindered the original performance of the insulator. It has been found that when the insulator is destroyed, an electrical tree is generated and a partial discharge is generated. As a conventional technique, in a coaxial cable such as a high voltage cable, a partial discharge generated at a defective portion is detected, and the defect is detected by a method of cutting off the applied voltage at the same time as the detection. This method was announced under the title of "Various CV cable insulation by pre-breaking method" in 1380, 12-31 of the Institute of Electrical Engineers of Japan "National Conference of the Institute of Electrical Engineers of Japan" 1380, 12-31. This precursor cutoff method is a method in which a minute partial discharge occurs immediately before the destruction of the DUT, so this is detected by the partial discharge measuring instrument and at the same time the applied voltage is instantaneously removed. The cause of the defect causing the minute partial discharge is analyzed with almost no loss. Further, Japanese Patent Application Laid-Open No. 4-109180 discloses a device that cuts off an applied voltage by using a GTO when a partial discharge is generated by the generated signal.

[0003]

The defect detection method by the precursor cutoff method described above is applicable only to coaxial cables, but the shape of various defects in the test sheet,
It was difficult to apply to the detection of position, quantity, and type. Conventionally, in the withstand voltage test of the test sheet, when measuring partial discharge, partial discharge in the air occurs at the electrode on the high voltage side, and when the applied voltage becomes high, the partial discharge caused by defects in the insulator can be detected. There wasn't.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is a test sample including a semiconductive rubber electrode, an insulating rubber sheet, a compression jig, a ground electrode and the like. A sheet holder is used to reduce the high-pressure part in the air as much as possible, and at the same time, mechanical pressure is applied between the semi-conductive electrode and the test sheet to increase the degree of adhesion, thereby generating in the high-voltage electrode part. A voltage application test is performed by the above-described precursor cutoff method so as to prevent partial discharge in the air.

First, a test sheet holder 1 provided with electrodes used in the present invention will be described with reference to FIG.
A metal high-voltage electrode 14 is formed integrally with the epoxy insulator 13 to form an epoxy electrode 22. Further, the semiconductive rubber electrode 16 forms a rubber electrode 23 integrally molded with the rubber sheet 11. 15 is a conductive ground electrode, for which
12 is a pressing plate for compression, 19 is a support rod, and this support rod 19
Is laid on the peripheral portion of the ground electrode 15 to support the compression holding plate 12 at the upper end of the support rod. Presser plate for compression 12
For example, the spring 20 is arranged between the pressing plate 12 and the ground electrode 15, and the pressing plate 12 is always pulled toward the ground electrode plate 15. The semiconductive rubber electrode 16 is made by containing carbon, and the high voltage electrode 14 and the semiconductive rubber electrode
16 is required to be in electrical contact with each other, and the high voltage electrode 14 and the semiconductive rubber electrode 16 have a structure in which the centers of the epoxy electrode 22 and the rubber electrode 23 are aligned and the two electrodes can be joined together. The tip of the semi-conductive rubber electrode 16 of the high-voltage electrode is lowered against the elasticity of the insulating rubber sheet 11 by the operation of the pressing plate 12 and comes close to the test insulating sheet 21, and the test insulating sheet 21 is epoxy. The end face 17 of the electrode 22 is compressed by the semiconductive rubber electrode 16.
In this state, the test based on the precursor shutoff method can be started. In the above example, the pressing plate and the spring 20 are used to perform the compression between the electrode and the sample sheet 21, but another method, for example, tightening with a screw can be used.

Next, the voltage application test circuit will be described with reference to FIG.
In the figure, 4 is a test transformer, the primary side of which is a power supply 6
To each of the anti-parallel connection thyristor switches 9, and the thyristor switch 9 cuts off the electric path by a signal from the partial discharge measuring instrument 5 described later. An antiparallel connection thyristor switch 8 is connected in parallel to the primary winding between the both thyristor switches 9 and the primary winding of the transformer 4, and the primary winding is short-circuited by the signal from the partial discharge measuring instrument 5. I shall. On the secondary side of the transformer 4, the sample sheet holder 1 provided with the electrodes described in FIG. 1 is arranged and connected to the high voltage electrode 14, and the ground side thereof is grounded via the partial discharge detector 2. In addition, a coupling capacitor 7 is connected in parallel with the sample sheet holder 1,
The partial discharge detector 2 is connected to the ground side and grounded, the output signals from both the partial discharge detectors 2 are input to the noise discriminator 3, and the output signals are input to the partial discharge measuring instrument 5, The output signal from the partial discharge measuring instrument 5 is input to the control units of the thyristor switches 8 and 9 as described above.
Incidentally, 10 is a protective impedance.

[0007]

[Operation] Power is supplied from the power supply 6 through the transformer 4 to the coupling capacitor 7 in parallel with the test sheet holder 1 having electrodes. As described with reference to FIG. 1, the surface of the sample sheet 21 in the sample sheet holder 1 is covered with the epoxy electrode 22.
Then, the test sheet 21 is placed in a pressure-contact state via the rubber electrode 23, and the pulse phase of the control pole of the thyristor switch 9 is controlled to sequentially increase the test voltage (AC). In this way, when a voltage is applied to the test sheet, a partial discharge occurs, which is regarded as a signal induced in the two partial discharge detectors 2, and the polarities of these are compared. The partial discharge and the external noise are discriminated, and the signal discriminated as the partial discharge passes through the optical fiber line 22 as an optical signal by the E / O converter attached to the partial discharge measuring instrument 5, and each thyristor switch controller. (Not shown)
After being O / E converted, the thyristor switch 9 stops the pulse to the control pole, and the thyristor switch 8 generates a control pulse to short-circuit the primary winding and consume the energy in the circuit. As a result, the voltage application to the test sheet can be instantaneously interrupted when the partial discharge occurs, and the test sheet is not damaged so much. The determination as to whether partial discharge has occurred due to a defect has conventionally been made by determining that the partial discharge gradually increases, but according to this method, the voltage value generated in the transformer 4 is constantly detected and the noise discriminator 3 is detected. It is possible to confirm that an electrical tree has occurred by examining the voltage when it is determined that the partial discharge is generated and by examining the degree of the decrease.

[0008]

According to the present invention, in the insulation property test of the test sheet, the test sheet holder provided with the electrode is used, and the high voltage electrode and the semiconductive rubber electrode are covered with the epoxy resin and the rubber sheet, respectively. , But the surface of the test sheet is covered with the rubber electrode, and the rubber electrode and the test sheet can be mechanically applied to increase the degree of adhesion. The partial discharge in the air that occurs in 2) disappears, and this allows the partial discharge to be detected in the test sheet even when a high voltage is applied.

[Brief description of drawings]

FIG. 1 shows an example of a sample sheet holder provided with an electrode used in the present invention.

FIG. 2 shows a voltage application circuit embodying the present invention.

[Explanation of symbols]

 1 Test sheet holder equipped with electrode 2 Partial discharge detector 3 Noise discriminator 4 Transformer 5 Partial discharge measuring instrument 8, 9 Thyristor antiparallel connection switch 10 Protective impedance 11 Rubber sheet 12 Holding plate 14 High voltage electrode 15 Ground electrode 16 Semi-conductive rubber electrode 17 Insulator end face 18 Flange 19 Support rod 20 Spring 21 Test sheet 22 Epoxy electrode 23 Rubber electrode

Claims (1)

[Claims] 1. An epoxy insulator and a metal high voltage electrode are integrally formed on a rubber electrode integrally formed with a rubber sheet and a semiconductive rubber electrode so that the high voltage electrode and the semiconductive rubber electrode are in electrical contact with each other. The epoxy electrode is installed, the test sheet is placed between the rubber electrode and the ground electrode, the sheet is compressed by pressing the epoxy electrode and the rubber electrode, and the semiconductor rubber electrode and the ground electrode. A test method for charging an insulator, characterized in that a voltage is applied by a pre-cutoff method between the two.