SU866508A1 - Method of measuring intensity of partial discharges in pores of dielectrics - Google Patents

Description

(54) METHOD OF MEASURING THE INTENSITY OF PARTIAL

DISCHARGES IN PORES OF DIELECTRICS

I

This invention relates to the metrology of high-voltage electrically insulating materials and products and can be used to obtain quantitative characteristics of partial discharges in insulation.

A known method is based on measuring the number of partial bits above a certain level at half the variable voltage.

At the same time, the partial-bit signals are subject to amplitude selection using level discriminators, counted by counters, the states of which are used to calculate the average repetition rate of bits Ы.

However, the described method, the proposed complex implementation in the form of logic and digital circuits, allows for the distortion of information in the case of action in conjunction with the discharges of extraneous impulsive noise, which are mixed as separate normal signals even with a significant,

phase shifts relative to pulsed discharges. In addition, it assumes a loss of information, since it takes into account only the number of bits per half period of alternating voltage without analyzing the width of the interval occupied by these bits, although in reality it is one and. The same number of bits can occupy different time intervals in accordance with the difference in voltage drops between the ignition and gas levels.

The purpose of the invention is to improve the measurement accuracy.

The goal is achieved by the fact that

Claims (1)

The ts measurements of the intensity of partial discharges into porhl dielectrics, which consist in influencing the object of measurement of high ac voltage, recording and analyzing the signal parameter of partial discharges in half the period of high ac voltage, convert the signal of partial discharges into radio pulses and calibrate the radio pulses in duration and amplitude, pulse width demodulation of calibrated pulses and measurement of the average value of the demodulated voltage, proportional to the duration of the signal of partial bits, and the average value of the demodulated voltage is chosen as the parameter of the signal of partial bits. Impulse noise, acting inside the bit intervals and close in phase to the partial bit signal, has less effect on the measurement result, as they act on either the excited resonant filter or the unexcited resonant filter, which should be excited from the next normal signal. Impulse noise, operating outside of the intervals of bits with their small number, does not give a significant increase in the average voltage after demodulation. Here, inertia plays a positive role, inherent in resonant systems and demodulators. By choosing a certain goodness of the filter, it is possible to get a certain amount of damped oscillations from each signal of partial bits, i.e. multiply the number of received pulses by a factor of | 5 (a limited number of times. At the same time, the time constant of the demodulator is also matched with the alternating voltage period. Thus, the implementation of the method involves a sequential circuit of blocks: high alternating voltage source, band-wired selective voltage - L Itel, an amplifying threshold device that passes signals above a certain threshold (level of noise or permissible level of discharges) and limits them in amplitude, pulse-width demodulator, meter the average value of the voltage. The drawing shows time diagrams showing the conversion of the partial discharge signal according to the proposed method (a — radio pulses framed on the trick of a band-pass selective amplifier from partial discharge signals; b — packs of single-field pulses calibrated in amplitude amplifying threshold device BQMJ in - voltage at shdokha pulse width demodulator, which has e time constant matched to the period of high ac voltage). The average value of this voltage contains information on the number of frequency bits per half of the alternating voltage period and on the width of the time interval occupied by the partial bits. The method can be combined with the study of the ionization voltage or the voltage of occurrence of partial tests. It has been shown that by choosing a sufficiently noticeable intensity threshold (and several bits per half-period), it is possible to ensure good noise immunity of the equipment used, since in this case even large single impulse noise have little effect on the measurement result of the average voltage. The proposed method can significantly improve the efficiency of monitoring high-voltage insulation of not only cables, but also other electrical insulating products, such as transformers, capacitors, insulators, etc. Claims The method of measuring the intensity of partial discharges in the pores of dielectrics, which consists in affecting the object of measurement of a high alternating voltage, recording and analyzing the signal parameter of the partial discharges during a half period of a high alternating voltage, characterized in that , they convert the partial discharge signal into radio pulses, calibrate radio pulses in duration and amplitude, and generate 41-pulse demodulation of calibrated pulses and measure The average value of the demodulated voltage is proportional to the duration of the partial discharge signal, and the average value of the demodulated voltage is chosen as the parameter of the partial discharge signal. Sources of information taken into account in the examination of i.Uenef q; ia eCettricci, vol. 46, NS i, 1969, p. 783-790.