一起110 kV高压交流电缆外护套烧损故障原因分析

Cause Analysis on Burning Failure of the Outer Sheath of 110 kV High-voltage AC Cable

摘要:

高压单芯交流电缆在城市输电网中得到越来越广泛的应用,但当其接地系统发生异常时会产生不同程度的悬浮电位。在分析一起电缆外护套烧损故障的基础上,对电缆线路的悬浮电位情况进行了讨论研究。铝护套接地异常后产生的悬浮电位,与电缆石墨(半导电)层的接地状态有关。当直接接地断开且石墨层未有效接地时,电缆石墨层悬浮电压可能会达到相电压的90%以上。高悬浮电压必然会导致石墨层对地绝缘薄弱处高频充放电,并不断烧蚀外护套,引发火灾等严重后果。

Abstract:

High － voltage single － core cable is widely used in urban transmission network，but it will produce a different degree of floating potential when its grounding system is abnormal． Based on the cause analysis of the burning failure of the outer sheath of 110 kV high － voltage AC cable，the possible floating potential of actual cable line is discussed and studied． The floating potential after the aluminum sheath grounding disappears is proportional to the line voltage level and is related to the grounding state of the graphite ( semi － conductive) layer of the cable． When the direct grounding is disconnected and the graphite layer is not effectively grounded，the floating voltage of graphite layer of the cable may reach more than 90% of the phase voltage，and the high floating voltage will inevitably lead to the high － frequency charge and discharge of the graphite layer on the weak ground insulation，and the constantly ablation of the outer sheath，causing fire and other serious consequences．