基于拉普拉斯变换下的雷电冲击波过冲仿真分析

Simulation Analysis of Lightning Impulse Wave Overshoot Based on Laplace Transform

随着输变电技术的发展,越来越多的新型电力设备应运而生。雷电冲击全波试验是检测电力设备绝缘性能的重要指标之一,对波前时间、半峰值时间和过冲都有明确要求。对于结构简单的设备,其参数和波形通过调配波前电阻和波尾电阻可满足需求,而内部结构复杂的电力设备会出现波前时间与过冲无法同时满足试验要求的情况,虽然国标中提出了优先满足过冲,但并未明确给出有效的处理方法。为此,通过简化试验回路,根据拉普拉斯变换推导出过冲计算公式,利用Pspice软件进行仿真分析,验证过冲为5%和10%情况下公式的准确性。根据该公式,分析不同等效电容和不同等效电感下的过冲,得到以下结论:测试时确保试验接线尽可能短或采用铜箔接线方式;保证冲击高压发生器本体电容充放电特性的情况下尽量选择较少的级数,级数的增加会增加等效电感,降低放电同步率;当波前时间和过冲均不满足条件时,可通过增大电阻和减小电容的方式进行调整。

With the development of power transmission and transformation technology,more and more new power equipment emerges.The lightning impulse full-wave test is one of the important indicators for testing the insulation performance of power equipment,and there are clear requirements for wave front time,half-peak time and overshoot.For equipment with a simple structure,its parameters and waveforms can meet the requirements by adjusting wave front resistance and wave tail resistance,while for power equipment with complex internal structure,wave front time and overshoot often fail to simultaneously meet the test requirements.Although the national standard proposes to give priority to overshoot,it does not clearly give an effective treatment method.In this paper,the overshoot calculation formula is deduced by Laplace transform based on simplified test loop,and simulation analysis is carried out through the Pspice software to verify accuracy of the formula when overshoot is 5%and 10%.According to this formula,overshoot under different equivalent capacitances and different equivalent inductances is analyzed,and conclusionsare drawn as follows:Make sure that the test wiring is as short as possible or use copper foil wiring during the test;Select as few stages as possible.The increase of stages will increase equivalent inductance and reduce discharge synchronization rate.When either wave front time or overshoot do not meet the conditions,it can be adjusted by increasing resistance and decreasing capacitance.