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Basic knowledge of partial discharge detection

time:2021/9/17   source:华天电力  reading:258 time

Introduction to the basic knowledge of partial discharge detection system


I. Overview:


Partial discharge test is the main test item for the insulation of power equipment. It is a partial discharge detection system developed according to the latest international technological progress. It integrates computer control, digital sampling, display and printing technology. The partial discharge map information is displayed with brand-new two-dimensional and three-dimensional graphics. The system can be single-channel or dual-channel input signals. The pilot-holding dual-channel input mode enables it to have the functions of balanced loop detection and pulse polarity discrimination detection.


Pure program control working mode; full Chinese character menu prompt; arbitrary storage and printing; automatic generation of test reports; two-dimensional and three-dimensional partial discharge graph display; digital windowing technology, strong anti-interference ability; dual-channel measurement and digital differential technology, Simultaneously measure the partial discharge signals of two samples or two measurement points of one sample, which can easily analyze the source of the partial discharge signals.


Partial Discharge Detector.png


2. System principle:


The detection method adopted by the system is the direct method, the bridge balance method, and the current pulse method which are most widely used in the world. The basic principle: when the sample produces a partial discharge, an instantaneous voltage change ΔU occurs at both ends of the sample Cx. A coupling capacitor Ck is coupled to the detection impedance Zm, a pulse current I will be generated in the loop. This pulse current I is sampled, amplified and displayed by the pulse voltage generated by the detection impedance Zm, and the apparent discharge volume of the partial discharge can be measured. And other parameters. The pulse current method mainly uses the lower frequency part of the partial discharge signal spectrum to avoid radio interference.


The system is equipped with RLC-type detection impedance, which measures the pulse signal generated by partial discharge and suppresses the power frequency and other low-frequency interference signals of the experimental power supply.


The system is a pulse peak indicator test system, with computer program-controlled filtering, amplification, sampling, storage and display functions. Data collection and test voltage are carried out synchronously. Can use direct method, bridge balance method, complex rate n, average discharge current I, square rate D, can make various maps: qn, q-ф, q-ф-t, etc., the whole measuring system can detect less than 1000pC Ultrasonic signal of partial discharge volume. The software has the function of partial discharge fault automatic identification based on the statistical evaluation of test results and partial discharge data, and automatically generates reports; the virtual oscilloscope has linear and elliptical 2-dimensional and 3-dimensional graphical display modes.


The device is suitable for partial discharge test of GIS, cables, 110KV and above power transformers, 35KV and above power transformers, bushings, arresters, coupling capacitors and other power equipment.


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