Method of measuring secondary cable transfer impedance caused by ground net impact current

Abstract

The invention discloses a method of measuring secondary cable transfer impedance caused by ground net impact current, comprising accessing an impulse t voltage generator in a transformer station ground net, laying a secondary cable, and using standard impact voltage and current waveforms to inject current into the current ground entry point of the ground net, and to extract current at a current discharge point; employing an oscilloscope to measure the output current waveform of the impulse voltage generator; employing the oscilloscope to measure the potential difference between core wires at any end of the laid secondary cable, and the potential difference between the core wires at the end and the ground net; respectively using 2 to divide the two measured potential differences; and respectively comparing the peak values of the two obtained potential differences with the output current peak values of the impulse voltage generator. The measurement method of the invention can obtain the transfer impedance between core wires of the secondary cable, and the transfer impedance between the core wires and the ground net to be used for assessing grounding system impact characteristics, and guiding grounding engineer construction.

Description

technical field [0001] The invention relates to the field of high-voltage technology, in particular to a method for measuring the transfer impedance of a secondary cable caused by an impact current of a grounding grid, which is used to evaluate the impact of the grounding grid on a secondary cable when it is struck by lightning. Background technique [0002] In order to meet the needs of work and safety in the power system, it is often necessary to connect some parts of the power system and its electrical equipment to the earth, which is grounding. Power system grounding can be divided into three types: working grounding, lightning protection grounding and protective grounding in terms of its purpose. Among them, lightning protection grounding is to avoid the harm of lightning. Lightning protection equipment such as lightning rods, lightning conductors and arresters must be equipped with corresponding grounding devices to guide lightning current into the earth. The groundin...

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Problems solved by technology

Due to the large grounding grid, this method requires a very long lead wire, and at the same time, due to the large grounding resistance of the current electrode, the output capability of the key equipment in the experiment - the impulse voltage generator (or impulse current generator) is severely limited , causing the output waveform to be distorted and the output voltage to decrease, which cannot meet the actual measurement requirements.

The previous method to solve this problem is usually to develop a higher-grade current generator, and the experimental cost is very high

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