Method for obtaining impulse impedance of grounding device through low lightning current impulse test

Abstract

The invention discloses a method for obtaining the impulse impedance of a grounding device through low lightning current impulse test, comprising the steps as follows: (1) using a low-current lightning impulse current generator to carry out impulse test of a grounding device, measuring the grounding resistance of the grounding device when the output current peak is 1KA and the lightning impulse waveform is 8 / 20muS, and taking the grounding resistance as the power-frequency grounding resistance R3 containing an inductive effect; (2) acquiring the spark correction coefficient K1; and (3) calculating the impulse impedance R1 of the grounding device based on the formula R1=K1*R3. According to the invention, an impulse coefficient is decomposed into a spark effect correction coefficient and an inductive effect correction coefficient through spark effect and inductive effect decoupling, the spark effect correction coefficient is obtained by related standard querying or field testing, the inductive effect correction coefficient is obtained by field low lightning current impulse test, and therefore, the impulse impedance of the grounding device under the action of actual high lightning current impulse is obtained.

Description

【Technical field】 [0001] The invention belongs to the research field of power system grounding technology, and relates to a method for obtaining the impact impedance of a grounding device by using a small lightning current impact test. 【Background technique】 [0002] A qualified grounding device is the fundamental guarantee for the safe and stable operation of the power system. Over the years, due to the inability to accurately test and evaluate the impact impedance of the grounding device of my country's line towers, coupled with the influence of soil environmental conditions and restrictions on test conditions, the current accurate evaluation of the grounding impact impedance of poles and towers cannot be carried out, which has become a threat to power. A major hidden danger to the safe operation of the system. When a lightning strike accident occurs on the transmission line, the grounding system may inject high-frequency large impulse current. The lightning impulse charac...

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Problems solved by technology

[0014] 1. Due to the inductance effect at high frequency, the impact resistance value of the ground electrode will be higher than the power frequency value

Moreover, due to the inductance effect, the wave head time of the impulse current and the size of the grounding device have a great influence on the impulse grounding resistance

[0015] 2. Due to the spark effect under high amplitude current, the impact resistance value of the ground electrode will be lower than the power frequency value

However, after several on-site actual tests by Tsinghua University and Zhejiang Electric Power Research Institute, it was confirmed that the conversion error from power frequency grounding impedance to impact impedance using the existing calibration formula is relatively large

[0022] At present, the method of using a specific value of concentrated parameter resistance to simulate the grounding device for lightning protection analysis of transmission lines is one of the main reasons for the large difference between the lightning protection analysis results and the actual operating statistics.

To sum up, the most direct and effective way to obtain the lightning impulse withstand level of the grounding device of the transmission line is to conduct field tests. And the on-site impact test is a high-frequency, high-voltage, high-current test, and the risk is relatively high. Therefore, it is urgent to use a lightning current generator that can be used for portable grounding device impact impedance testing, so as to optimize the design of the transmission line grounding device and ensure safe operation. It is of great significance to reduce line maintenance costs

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