| The normal relay protection can't select fault-phase when occur cross-circuits faults for the one tower with double-circuit transmission line, and one side protection will trip 3-phase line. Losing double transmission line at the same time may affect the safety operation of power system . So relay protection must have ability of correct select fault phase when transmission line occur cross-circuit faults . It must ensure only faulted poles tripped and re-closed depend on the fault type. When the transient fault take place, the transmission line will reclose successful, so the level of the security and stability of network will be improved.This thesis studies principle of the relay protection select fault-phase and multi pole reclosing for one tower with double-circuit transmission line for new relay protection devices to suit for houg-long double circuit one tower. Using the exist channel of microwave mixed with optical fiber and digital interface connect the relay protection, hong-long double circuit one tower accomplish the transport of information of the relay. The thesis mainly concerns the following aspects: the relay protection and its trip-close circuit of two circuits transmission-lines are stand alone. The device has the ability of phase-trip that is owns transmission line single phase , 2 or 3phases fault only fault phase tripped.so as to making the power system contact as close as possible. The function of reclosing distribute into relay protection of line and breaker, so it is easy to get no-serious fault information of line protection and realize self-adapted multi pole reclosing. The breaker reclosing depend on the state of owns breaker andthe adjacent breaker. The criterion of serious fault and the sequence reclosing is simple and useful. It can reduce the influence to the power system when the permanent fault take place.The analyse and amount of dynamic analog tests, RTDA tests show that the scheme is effective.
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