计及护层环流的电缆温升分析与故障定位方法研究

由于传统IEC热路法无法计算复杂工况下环流变化后电缆温度,因此,采用有限元法并结合电磁场与传热学原理,针对不同接地方式与运行工况下的三相电缆,计算与分析不同常见护层故障下环流变化后的电缆温升情况,为电缆运行状况判断提供参考。结果表明:对于护层交叉互联接地电缆,交叉互联箱进水地或护层接头故障后,故障相电缆温升高达10℃,且故障相电缆在故障点前后出现5℃的温差;对于护层单端接地电缆,发生两相护层故障后,故障点前段电缆较正常运行温升高达13℃以上,故障点前后段电缆存在10℃的温差;三相电缆温升及各相之间温差情况可为电缆温度在线监测提供参考,并根据电缆前后温差出现点对电缆故障点进行定位,尽快检修处理,从而减少后续击穿烧毁事故的发生。

Cable temperature rise analysis and fault location considering sheath circulation

Because the traditional IEC thermal circuit method can not calculate the temperature of the cable after the loop flow changes in complex working conditions,the finite element method combined with electromagnetic field and heat transfer theory was adopted to calculate and analyze the temperature rise of the cable after the loop flow changes under different common protective layer faults for three-phase cable under different grounding modes and operating conditions.Operating condition judgment provides reference.The results show that for the shield cross-connected grounding cable,the temperature of the fault phase cable rises to 10℃after the fault of the water inlet or shield joint of the cross-connected box,and the temperature difference of the fault phase cable before and after the fault point appears to be 5℃.For single-end grounded cable with sheath,the temperature of the front section of the cable at fault point rises above 13℃compared with that of the normal operation after two-phase sheath failure,and there is a temperature difference of 10℃between the front and back section of the cable at fault point;The temperature rise of three-phase cable and the temperature difference between different phases provide reference for the on-line monitoring of cable temperature.According to the temperature difference before and after the cable,the fault points of the cable can be located and repaired as soon as possible,so as to reduce the occurrence of subsequent breakdown and burnout accidents.