35kV交联电缆振荡过电压击穿故障分析及抑制措施

Analysis of Oscillating Over-voltage Breakdown Fault of 35 kV XLPE Power Cable with Countermeasures

近年来,北京电网出现过多起交联电缆振荡过电压击穿的事故,对电网安全造成了极大的威胁。文中深入研究了交联电缆振荡过电压击穿事故的原因,以及事故发生发展的过程,进一步认识了振荡过电压对电力设备的影响。笔者以某110 kV变电站35 kV电缆击穿故障为例,首先给出系统接线及事故概况,然后通过电缆中间接头解体检查与对故障录波数据的深入分析,指出故障原因是由于吊车碰架空导线造成瞬时单相接地,引起了局部35 kV系统的低频振荡,产生振荡过电压,造成电缆相间绝缘击穿,发生相间短路故障。最后,提出了相应的技术防范抑制措施与下一步研究工作的建议。

In recent years, several breakdown failures of XLPE power cable have happened in Beijing power grid, which have threatened the power grid security. In this paper, the cause of the oscillating over-voltage breakdown failure electric and the accident process are analyzed to further understand the impact of the oscillating over-voltage on power equipment. Taking the breakdown fault of 35 kV power cable of a transformer substation for example, the main-line diagrams of the grid and the fault description are given, disassembly inspection of the cable middle joint is conducted, and the fault recorder data are analyzed. Conclusion is drawn that the breakdown fault is caused by transient single-phase grounding due to the touch of crane and overhead wires, which activates low frequency oscillation of local 35 kV system to generate oscillating overvoltage. Moreover, corresponding countermeasures are suggested.