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 trans-former(MF)differential protection,and the differences in current sensitivity excited by faults with various types,loca-tions,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 pro-tection,and thereby results in unaffected sensitivity of relevant protections.
small resistance earthing systemzero-sequence current balancing of main transformer differential protectionprotection sensitivityproject investment comparison
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