长段电缆中局部放电脉冲信号的传输特性及耦合研究

局部放电测量广泛应用于各种电力设备的绝缘状况诊断中,对于XLPE电缆,局部放电可以检测到各种绝缘缺陷,例如电缆加工、运行以及安装过程中的人为缺陷,以及绝缘层中的气隙和电树枝老化。然而,当局部放电脉冲在电缆中传播时,由于衰减的原因,脉冲波形发生了变化。因此,对于电缆局部放电测量,了解局部放电脉冲在电缆中传播时的变化规律是非常关键的,因此本文针对电缆局部放电脉冲传播时,脉冲波形的变化进行了深入分析,并且讨论的了不同耦合带宽对信号检测的影响,得出：当电缆发生局部放电时,脉冲信号幅值随着传播距离的增加迅速衰减,但脉冲视在放电量衰减幅度相对较小；同时,宽带耦合具有较高的灵敏度,但是其电荷校准曲线误差较大,并且会导致信噪比降低,缺陷检出度下降；窄带耦合虽然能够获得较为准确地电荷校准曲线,却会导致脉冲波形发生叠加,影响故障点定位；所以,在实际应用中,需要根据实际需求,确定检测带宽。

Transmission characteristics and coupling of partial discharge pulse signals in long cables

Partial discharge measurement is widely used in insulation condition diagnosis of various power equipment. For XLPE cables, partial discharge can detect various insulation defects, such as artificial defects during cable processing, operation and installation, as well as air gap and aging of electrical branches in insulation layer. However, when the partial discharge pulse propagates in the cable, the pulse waveform changes due to attenuation. Therefore, for Cable Partial Discharge measurement, it is very important to understand the change rule of partial discharge pulse when it propagates in cable. Therefore, this paper makes a thorough analysis of the change of pulse waveform when cable partial discharge pulse propagates, and discusses the influence of different coupling bandwidths on signal detection. It is concluded that when cable partial discharge occurs, the amplitude of pulse signal follows. The increase of propagation distance decreases rapidly, but the attenuation amplitude of apparent discharge is relatively small; at the same time, broadband coupling has higher sensitivity, but its charge calibration curve error is larger and it will lead to the decrease of signal-to-noise ratio; although narrowband coupling can obtain more accurate charge calibration curve, it will cause pulse waveforms to overlap, affecting fault location; therefore, in practical application, root is needed. According to the actual demand, the detection bandwidth is determined.