高寒地区车载柔性电缆终端的局部放电特性与破坏机理

Partial Discharge Characteristics and Breakdown Mechanism for Locomotive Cable Flexible Terminal in Alpine Area

为研究在高寒地区运行的车载柔性电缆终端频繁爆炸的现象,构建了能够复现现场低温环境的局部放电测试系统。研究了放电起始/熄灭电压、放电发展规律以及放电相位谱图在不同低温条件下的特征;同时利用特征参数对放电谱图正负半周不对称的特性进行了分析;此外,分析了柔性终端内部主要绝缘材料在低温下的特性变化。研究结果表明:温度在–10℃以下时,放电起始电压与熄灭电压均随着温度的降低而降低,在同一电压下温度越低放电越剧烈;当温度达到–40℃时,绝大部分柔性终端在工作电压下即会发生局部放电;低温下柔性终端在负半周放电更加剧烈,这种不对称度随着温度的降低和放电的发展而增大。此外,通过对柔性电缆终端的解剖在应力管与主绝缘之间的交界面发现放电痕迹,分析得出这是因应力管与主绝缘在低温下材料匹配性降低所产生的放电。

In order to study the frequent explosion on the flexible terminals of locomotive cable, we set up a partial discharge(PD) test system which can create the low-temperature environment. The initial/extinct voltage of PD, discharge development and phase resolved partial discharge(PRPD) spectrograms of the locomotive cable terminals at different low temperatures were studied. Meanwhile, asymmetry between positive part and negative part were analyzed by the characteristics of PRPD spectrograms. In addition, the change of material properties in locomotive cable terminal at low temperatures was analyzed. The results show that the PD initial and extinct voltages decrease with decreasing temperature when the temperature is below –10 ℃, and the discharge magnitude rises with the decrease of temperature at the same voltage. PD will happen in flexible terminals at the working voltage when the temperature falls to –40℃. The PD of flexible terminal is more severe in negative half-cycle at low temperatures, and the asymmetric degree increases with the decrease of temperature and the development of discharge. Furthermore, the discharge mark is found in the boundary between the stress control tube and main insulation by dissecting a cable terminal. It is concluded that the reason for discharge is the reduction of matching ability between stress control tube and main insulation.