Method to Determine Wave Resistance of Impulse Voltage Generator for Lightning Impulse Test

Xuan Yaowei, Le Yanjie, Zhang Nafei, Lu Zhifei
HIMALAYAL - SHANGHAI - CHINA

Abstract: In the lightning impulse test, the wave resistance (front resistance denoted by Rf and time to half-value resistance denoted by Rt ) of impulse voltage generator should be adjusted in order to make the impulse waveform comply with the standard of IEC 60060-1: the standard waveform should have a front time denoted by tf of 1.2 μs with the tolerance is ± 30% and a time to half-value denoted by tt of 50 μs with the tolerance is ± 20%. Aiming at determining the wave resistance of impulse voltage generator quickly, the equivalent discharging circuit of the impulse voltage generator was analyzed mathematically, then non-linear equations for solving Rf and Rt were established and solved by hybrid genetic algorithm. After obtaining the numerical solution of Rf and Rt , the discharge circuit was stimulated and analyzed by using Matlab. Finally, the field test was carried out in the high voltage test hall to verify the simulation results.

The results indicate that the method to determine the wave resistance is effective, and can provide theoretical guidance for field test personnel to reduce the equipment debugging time.

Key Words: lightning impulse test, impulse voltage generator, front resistance, time to half-value resistance, hybrid genetic algorithm.

Introduction
It is inevitable that high-voltage electric equipments of electric power system are subject to lightning impulse, so impulse voltage generator needs to be utilized for conducting lightning impulse test in the type test or delivery test. According to IEC 60060-1, details of standard lightning impulse waveform are as follows: a front time denoted by tf of 1.2 μs and a time to half-value denoted by tt of 50 μs with the tolerance is ± 30% and ± 20%. However, in the actual lightning impulse test, it tends to be difficult to obtain standard impulse waveform. Therefore, test personnel needs to be experienced and can correctly adjust equipment parameters based on voltage level and capacity of test objects, reducing the number of tests and damage to test objects.