地铁直流电缆放电在线检测中干扰信号的研究

Research of Interference in On-line Discharge Detection in 1500 V Subway Direct Current Cable

为解决地铁直流电缆电气接线的特殊性而导致其放电检测中存在的大量干扰信号,实验研究了整流装置产生的整流脉冲、机车启动制动产生的电流脉冲、随机性脉冲信号及其它电子设备产生的窄带信号等干扰信号的特征。研究表明,并联的被测电缆上均存在很好的整流脉冲干扰周期性和规律性;窄带干扰和机车反馈电流脉冲干扰幅值大但其频谱较低(<2MHz);随机脉冲干扰信号虽具有不确定性,但其重复率与电缆放电的重复率存在数量级差别。根据干扰信号特征提出了可行的抗干扰措施,为检测地铁直流电缆放电奠定了基础。

The 1500V DC feeder cable is one of the key devices for the safety operation of subway system, and its insulation status directly affects the security of electricity supply of rail traffic. Result of study shows that using online detecting discharge method to assess its insulating status is feasible, but interference suppression is one key parts of partial discharge detection. Therefore, this paper discusses and studies the potential interference signal in detecting discharge for the direct current cable. The electric wiring of the subway direct current cable is very special, which determine that there are many interference signals in discharge detection signal for the subway direct current cable. The results of laboratory simulation and field measurement shows that the main interferences involves discharge pulse generated by other equipments of the traction substation, white noise, rectifying pulse generated by the rectifying equipments, current pulse generated by the braking of the locomotive, stochastic pulse signal, and narrow-band signal generated by electric equipment. The characteristic of last four kinds of aforementioned signals is mainly investigated in the text. The research results showed that rectifying pulse had good periodicity and synchronously appeared in all parallel cables; narrow-band interference signal and current pulse generated by the braking of the locomotive has big amplitude, but theirs spectrum does not exceed 2MHz; stochastic pulse signal is uncertain, however, its repetition is more lower than the repetition of the discharge signal of the DC feeder cable. Because the discharge recurrence rate is high and the frequency spectrum of discharge is wide, therefore, the FFT, wavelet, time-windows and statistics methods should be synthetically used to suppress interference. Finally, the anti-interference steps are proposed and the effect is given. The work provides a reference for anti-interference for on-line discharge detection for 1500V subway DC cable.