XLPE绝缘老化中的单次放电波形统计分析

为了研究绝缘中发生局部放电的物理机制,对交联聚乙烯(XLPE)绝缘试样进行了加速电老化试验,使用超宽频带局部放电检测系统(频带10 MHz～3 GHz)测量了试样的放电信号,并通过统计分析超宽频带放电的单次脉冲信号探讨了XLPE绝缘老化过程中的放电机理。研究表明,XLPE绝缘电老化过程中单次放电波形的下降沿、脉冲幅值都有显著变化:下降沿从老化前的近15 ns上升到老化50 h的约90 ns,单次放电波形幅值在老化前约1 000 mV,老化15 h后维持在约200 mV,老化到30 h时上升到近500 mV,老化50 h时上升到约600 mV。由单次放电信号的波形特征推断XLPE绝缘老化过程中放电从流注型放电转化为汤姆逊放电的变化过程。

Statistical Analysis of PD Pulse Occurring in XLPE Insulation During Its Electrical Aging

In order to understand the physical mechanisms of partial discharge(PD) in insulation,the accelerated electrical aging tests of XLPE specimens were performed and an ultra-wideband(UWB) PD measurement system was adopted to study the characteristics and mechanisms of PD in XLPE during electrical aging.The bandwidth of the UWB PD measurement system spans the frequency range from 10MHz to 3GHz.The UWB PD pulses were analyzed by a statistical method,by which the shape parameters of the PD pulses,the parameters of rise times,fall times,and amplitudes were analyzed.These shape parameters were helpful to evaluating the PD mechanisms and the aging status.The results showed that the single waveform parameters changed greatly in the different aging stages,such as fall time and pulse amplitude.The rise time varied slightly during aging,while the fall time changed greatly,increasing from about 15ns before aging to about 90 ns after aging for 50 hours.The PD pulse amplitude was about 1000 mV when the specimens were in the virgin stage.It fell down after aging for several hours,and it decreased at the value about 200 mV after aging for 15 hours.And then,it increased if it was further aging and was about 500 mV after aging for 30 hours,about 600 mV for 50 hours.The rising edge was steep and the fall time was short before aging,so it was supposed that the streamer discharges took place.And the fall time was long when aging severely,therefore the PD mechanism was supposed to be Townsend discharges.