变电站小电阻接地方式的选择以及对主变保护的影响

Mode Selection of Substation Small Resistance Earthing and Its Impact on Main Transformer Protection

分析了小电阻接地方式中,三种小电阻设置方式对主变差动保护消零的不同需求,以及对于不同故障类型、不同故障地点、不同电源点的故障电流灵敏度的差异。针对多分支母线的接线形式,提出了在每个分支母线设置独立的接地变及接地电阻的方案。该方案虽然增配了部分设备,但系统运行的可靠性得到了提升,且主变差动保护在低压侧无需消零处理,相关保护灵敏度不受影响。

Focusing on transforming substations′ small resistance earthing systems,this essay analyzes,among the three modes of small resistance arrangement,the differences in requirement on zero-sequence current balancing for main transformer(MF) differential protection,and the differences in current sensitivity excited by faults with various types,locations,and source points.With respect to the wiring of multiple branch buses,it puts forward a new scheme which deploys independent earthing resistances for all the branch buses.This scheme,though requires additional equipment investment,facilitates system reliability improvement,waives the necessity of zero-sequence current balancing for MF differential protection,and thereby results in unaffected sensitivity of relevant protections.