高压电缆外护层绝缘降低时护层保护器的参数配置

摘要

针对高压电缆外护层绝缘电阻普遍降低的现状以及其耐压水平降低的可能性,建立了单端接地和交叉互联接地电缆的ATP-EMTP仿真模型,研究了在雷电过电压、操作过电压和短路故障的情况下,配置低伏安特性保护器后保护器是否能正确动作且不损坏保护耐压水平降低的外护层.结果表明:在雷电过电压和操作过电压情况下,降低保护器伏安特性能有效降低作用于外护层的残压,流经保护器的电流仍然低于其标称放电电流;对于单相短路情况,单端接地条件下保护器需要吸收的短路能量较大,降低保护器伏安特性会使保护器爆炸,而对于交叉互联接地情况,降低保护器伏安特性保护器是否会爆炸与短路电流的大小有关,较大的短路电流会使得保护器爆炸.最后提出了电缆外护层绝缘降低时护层保护器配置的建议.%Considering the universally decreased insulation resistance of high voltage cable sheath and the possibility of its decreased withstand voltage level, the paper studies whether the protector can act correctly without damage to protect the sheath with decreased insulation under lightning overvoltage, operation overvoltage and short circuit when configuring protectors with low voltage-current characteristics by establishing ATP-EMTP simulation models of single-ended grounding and crossbonding grounding.The results show that reducing the voltage-current characteristics of protector can reduce the residual voltage acting on the outer sheath, and the current flowing through the protector is still below its nominal discharge current;in the case of single-phase short circuit, under the condition of single-end grounding, the protector needs to absorb a large amount of short circuit energy, reducing the voltage-current characteris-tics will lead to protector explosion;under the condition of crossbonding grounding, whether the protector explode or not depends on the magnitude of short circuit current, while a larger short-circuit current will cause the protector to explode.Finally, suggestions of the protector configuration of the outer sheath with decreased insulation are proposed.