SU847234A1 - Method of determining electric strength of electro-insulation materials - Google Patents

Description

The invention relates to electrical engineering, in particular to the field of testing for the breakdown of electrical insulation materials, mainly thin "and ultrathin films, and can be used in the development of methods and devices for the breakdown of electrical insulation films.

A known method for determining the electrical strength of insulating materials, which consists in a stepwise rise of high voltage supplied to the electrodes, between which a sample of the test material is placed. The breakdown voltage is determined according to the testimony of a voltmeter connected in parallel with the electrodes. At the moment of breakdown of the sample, the overcurrent relay is activated by the action of the breakdown current. This method is characterized by a single breakdown of a “nonreducing character as a result of the loss of electrical strength” by the sample [1]. 25

The disadvantage of this method lies in the impossibility of determining the voltage of the first breakdown in the case of the existence of self-healing breakdowns, as well as in the difficulty of reproducing and low productivity of the test process.

It is known that the breakdown of thin electrical insulating films in many cases occurs with self-healing, when at the time of breakdown the foil electrodes at the breakdown point move away from the film and the sample does not close, so that conditions arise for subsequent breakdowns at the same place [2].

Closest to the proposed technical solution is a method of breakdown of thin films, which consists in applying a linearly increasing voltage to the sample. In the primary circuit of a high-voltage transformer of a high voltage source (IVN), a maximum current relay is included, which turns off the IVN as a result of a sharp increase in the current in this winding during sample breakdown and shorting of the electrodes between which the sample is placed. Breakdown voltage is determined by a voltmeter connected in parallel with the electrodes [h].

The disadvantage of this method is the closure of the electrodes as a result of the loss of electrical strength by a sample. so that with self-healing breakdowns, it is impossible to determine the actual breakdown voltage.

The purpose of the invention is to improve the accuracy of measurement and simplification of the method.

This goal is achieved by the fact that they include the studied sample of electrical insulation material with electrodes as a capacitor of an integrating RC-circuit, the input of which is supplied with a constant maximum voltage, and the voltage of the first breakdown of the sample is recorded.

In this case, the time constant of the RC chain should be large enough for the recording device to clearly distinguish the first breakdown. If an electrostatic voltmeter is used as a recording device, then the time constant should be at least 3-5 s.

The drawing shows a structural diagram of a device that implements the proposed method.

The device contains an IVN 1 with a constant value and sign of the output voltage, a resistor 2, test electrodes 3, between which a sample 4 is installed. A recording device 5 is connected in parallel with the sample.

An example of the method.

A sample of electrical insulating material is placed between the electrodes, a circuit is made up of an IVN, a sample with electrodes and a resistor, the value of which is determined by the given time of voltage rise on the sample and the high voltage is turned on, while the capacitor formed by the electrodes with the sample begins to be charged from the IVN.

With the loss of the electrical strength of the sample, its instantaneous discharge occurs, and the voltage across the sample decreases to zero. In the case of self-healing breakdowns, sample shorting does not occur, so that the voltage on the sample again slowly increases. This allows you to clearly record the moment of the first breakdown by the recording device and count the value of the breakdown voltage.

The proposed method for determining the electrical strength of electrical insulating materials has the following advantages compared to known methods:

the ability to clearly fix the first breakdown from a series of self-healing breakdowns and thereby improve the accuracy of determining the electrical strength of the films;

the simplicity of the method and the possibility of its automation due to the replacement of a long operation of linearly increasing the voltage across the sample with a short-term operation of switching on a high voltage.

Claims (1)

Claim A method for determining the electric strength of electrical insulating materials, mainly film, consisting in the influence of a monotonically increasing voltage on the test sample, characterized in that, in order to improve the measurement accuracy and simplify the method, include the test sample with electrodes as a capacitor of an integrating RC circuit, at the input which serves a constant maximum voltage, and fix the voltage of the first breakdown of the sample.