1994 Volume 114 Issue 7-8 Pages 723-731
In Japan, electric power systems are developing with economical growth. Especially, the recent demand of electrical power in mertropolitan area becomes 2.6 times as much as in 1973 when 500kV system was first applied. It is expected that trends of increasing power demands may continue in future. To safisfy this demand, Utilities developed new transmission lines to make networks so substantial and aimed stable and efficient operation of the power system. However, this countermeasure caused extremely large fault currents at the substations where large power sources are concentrated. Problems such as large fault current beyond interrupting capacity of circuit breaker or electromagnetic interference now become very sever. To solve these difficulties, Tokyo Electric Power Company is going to develop 1, 000kV networks. Those increase the capacity of transmitted power and suppresses the fault current level by splitting the 500kV system in several parts. Considering the associated difficulties to 1, 000kV networks such as increasing capacitive current on transmission line, prolonged D. C. time constans due to large diameter of conductors and other electrical characteristics of 1, 000kV networks, we examine the applications of the reliable protection system. The results are summarized as follows. 1) To adopt multiple phase autoreclosing with high speed grounding switches to suppress secondary arcing on faulted phases 2) To adopt air core type CT for 1, 000kV busbar protection as a countermeasure against CT saturation 3) To adopt the current comparison scheme to realize sensitive protection for paralleled transformer bank. New protection system would be tested in field from 1995.