SU966584A1 - Method of determining resistance of film and sheet dielectrics to effect of partial discharge - Google Patents

Description

(54) METHOD FOR DETERMINING THE STABILITY OF FILM AND SHEET DIELECTRICS TO THE ACTION OF PARTIAL DISCHARGES

one.

The invention relates to electrical measuring equipment and can be used to create devices for testing solid dielectrics.

A known method for determining the resistance of film and sheet dielectrics to partial discharges is based on placing the test specimen in a cell between two cylindrical electrodes and creating an electric field 1.

The disadvantage of this method is the need to create a field strength that is much higher than the working one, which leads to reproduction errors typical for working conditions, the impossibility of comparing materials differing in thickness and dielectric constant and poor reproducibility of test results due to the dependence of the intensity of partial discharges. from the shape of the electrodes.

The closest to the proposed technical essence is a method based on measuring the intensity of partial discharges by means of a needle-density electrode system when the test sample is placed near the needle electrode 2.

The disadvantage of this method is the low accuracy and limited functionality that does not provide the possibility of obtaining true information about Q bone of materials to the action of partial discharges due to large field strengths during testing, destroying the sample long before its complete destruction by partial discharges, and Impossibility to compare durability of dissimilar materials.

The purpose of the invention is to improve the accuracy and expansion of functionality. The goal is achieved by the fact that according to the method for determining the resistance of film and sheet

Claims (2)

20 dielectrics to the action of partial discharges, based on the measurement of intensity, partial discharges by means of a needle-plane electrode system when the test sample is placed near the needle electrode, a foil is placed between the test sample and the flat electrode. A beef electrode with a diameter of 3-4 mm and a dielectric layer, whose thickness and dielectric permeability is chosen from the condition bi T / S – d - OX and where f) (j 2 and the dielectric constant, respectively, of the test sample; the dielectric layer and; dy dfi thickness of the test sample and the dielectric layer, respectively, measure the breakdown voltage and establish the test voltage, the value of which is chosen from the condition .n where Ux.np. is the breakdown voltage, and determine the resistance of the test sample to partial discharges by value : conv The initial destruction rate, which is determined by the formula Vy. ZHEp where TGU is the time of complete destruction of the test sample, the measured intensity of partial discharges under the chosen experimental conditions. The drawing shows the test cell circuit that implements the measurements according to the proposed method. test sample 1 made of solid sheet or film material, mounted near the needle electrode 2, made in the form of a thin rod, and a flat electrode 3. A layer is placed on the flat electrode 3 the dielectric of the substrate 4 is resistant to partial discharges, for example, from a mica-containing material. A thin foil electrode 5 with a diameter of 3-4 mm is placed between the sample and the substrate. The test cell is equipped with a device 6 for measuring chart bits (a high-frequency filter) and output 7 to the circuit for recording partial discharges and shutting down the unit during breakdown. The measurement process is as follows. In advance, for each sample, which is different in the substrate thickness and test voltage, the average partial discharge current is determined. Jp. The substrate is taken from the mica-containing material, the dielectric permeability of which is 4.0. Sample 1 is installed in a cell consisting of a needle electrode 2 with a diameter of 0.2 (VKontakte or with a gap of 0.1-0.3 mm) and a flat electrode 3 cooled by water. Between the electrodes under the sample with a thickness dj (foil electrode 5 is installed in series with a diameter of 3.0 mm and a substrate with a thickness of 2.0 mm or 4.0 mm. Applying a voltage between the electrodes, depending on the sample material and its thickness, 5 10 kV The time of the TGu to the sample sample, which is determined by the instant of a sharp change in the readings of the gauge of partial discharges 6 connected to the needle electrode, is fixed. Eisg, V ..: where Vjj is conditional the destruction rate. The presence of an additional intermediate electrode 5 makes it possible to determine the breakdown of the sample. At this point, intense discharges arise around the perimeter of the auxiliary electrode, the registration circuit of partial discharges 7 detects an increase in the average discharge current, and the installation is triggered The diameter of the intermediate electrode 5 of a size of 3–4 mm ensures that there is no distortion of the electric:; treating floor in the electrode system. The use of the proposed method for determining the resistance of film and sheet materials provides. the possibility of comparing materials with different dielectric constants and thicknesses with a reduced electric field strength; possible determination of absolute indicators of materials resistance to partial discharges -. the rate of destruction of the material and the dependence of the durability of the material on the intensity of partial discharges. The application of the method for the comparative assessment of the durability of some polymer films (polyethylene, fluoroplast and polyamide) makes it possible to choose the optimal insulation design for the stator windings of machines operating under the conditions of the surface corona. DETAILED DESCRIPTION A method for determining the resistance of film and sheet dielectrics to partial discharges based on measuring the intensity of partial discharges by means of a needle-plane electrode system 59 when placing a test sample near a needle electrode, so as to improve accuracy and expansion between the test sample and the flat electrode, there is a foil electrode with a diameter of 3-4 mm and a dielectric layer, thickness and dielectric constant whose value is chosen from the conditions ai, where gy is the dielectric permeability, respectively, of the test sample and the dielectric layer; , is the thickness of the test sample and the dielectric layer, respectively,. measure the breakdown voltage and. set the test voltage, the magnitude of KOTO is chosen from the condition Uv, cn50, T.c / a1 where and X pr is the breakdown voltage, and determine the resistance of the test sample to partial discharges by the magnitude of the conditional destruction rate, which is determined by where j is the time of complete destruction of the test specimen, measured, intensity; partial discharges at Bbi6pam4ix experimental conditions. Sources of information taken into account in the examination 1. A collection of US standards for the use of electrical insulating materials. M., Energy; , 1979, p. 227-231. 2. New electrodes for pactial discharde endurance tests, JEEE Trans, an. El. Jus v. E1-13, 1978, N ° 6, p. 448-450 (prototype).