变压器中性点运行方式分析

Operational mode analysis of transformer neutral point

通过对景性点不接地系统防止系统过电压措施、景性点接地对电力系统的影响进行分析,特别对操作、断线、单相接地、雷击等不同情况下景性点处出现的过电压进行分析,同时结合零序通路问题,总结出变压器景性点接地方式的选择应考虑系统零序阻抗、零序电流的分布、N-1对系统运行方式的影响等因素,做到不使接地点数目过多,以避免零序网络过于复杂、零序保护的定值不好整定、零序保护的各段保护之间不易配合,也不能因为接地点太少而使电网接地不可靠。

Combined with zero sequence channel problems, this paper analyzes the influence of neutral point ungrounded system over-voltage method and neutral point earthing towards the electric power system, especially the over-voltage in the neutral point area in different circumstances such as operation, disconnection, single-phase earthing and lightning strike, etc. And it reaches the conclusion that in the selection of transformer neutral point earthing method, some factors should be taken into consideration such as system zero sequence impedance, distribution of zero-sequence current and the influence of N-1 to the system operational mode. These can avoid the overabundance of earthing point, the excessive complication of zero-sequence internet, the hard set of zero-sequence protection point, the hard coordination of each-sectional protection of zero-sequence protection and the unreliability of grid earthing for the reason of too few earthing points.