特高压GIL绝缘击穿时暂态电压时频特征分析

Time and Frequency Domain Characteristics of Transient Voltage Excited by Insulation Breakdown in UHV GIL

为研究特高压气体绝缘金属封闭输电线路(gas insulated metal-enclosed transmission line,GIL)在交接耐压试验和运行时绝缘击穿激发的暂态电压特征,利用在1100 kV苏通GIL综合管廊工程安装的超宽频暂态电压监测系统,准确测量了GIL在耐压试验和运行时绝缘击穿所产生的暂态电压。分析了GIL在不同工况下典型绝缘击穿所产生暂态电压时域波形的持续时间、变化陡度以及幅值衰减特征。通过傅里叶变化分析了暂态波形的频域特征,发现特征频率与故障位置紧密相关。最后通过连续小波变换分析了暂态电压的时频特征,发现陡变电压的瞬时频率均超过了3 MHz,可通过暂态电压的时频分布图准确判断GIL是否发生次生放电。通过对暂态电压时域和频域特征分析,有助于弄清GIL绝缘故障时暂态电压行波激发及传播特征,准确评估暂态电压对GIL的绝缘危害,提高特高压GIL运行的可靠性。

In order to study the characteristics of transient voltage excited by insulation breakdown during the resonance voltage withstand test and the operation of ultra-high voltage(UHV)gas insulated metal-enclosed transmission line(GIL),this paper uses the broadband transient voltage monitoring system installed in 1100 kV Sutong GIL utility tunnel project to accurately measure the transient voltage generated by insulation breakdown.The duration,the change steepness and the amplitude attenuation of the transient voltage waveform generated by typical GIL fault under different conditions are analyzed firstly.The frequency characteristics of transient waveform are analyzed in Fourier transform,and it is found that the characteristic frequency is closely related to the fault location.Finally the time-frequency characteristics of transient voltage are analyzed in the continuous wavelet transform.It is discovered that the instantaneous frequency of the steep voltage exceeds 3 MHz.It can accurately estimate whether the GIL has secondary discharge through the time-frequency distribution of the transient voltage.By analyzing the time and frequency domain characteristics of the transient voltage,it is helpful to understand the generation and propagation characteristics of the transient traveling voltage in GIL,accurately evaluate the damage of the transient voltage to the insulation of GIL,and improve the operation reliability of UHV GIL.