Special problems of 220 kV digital substation design

This paper introduces features of 220 kV digital substation, such as larger double protection and longitudinal differential protection, analyzes the special problems, including the loop of current and voltage, the protection tripping way, on both sides of line protection, and isolation of protection and circuit breaker, and proposes solutions. For 220 kV digital substation inconsistent with the existing order, it analyzes the provisions of the rules and explains the reasons of the problem on both sides of the line protection software version. Considering running habits, it installs srap in the protection and circuit breaker smart terminal devices respectively and proposes the way of isolation of protection and circuit breaker.