Abstract:

This article briefly states protection action and action time sequence in terms of a trip accident at the medium voltage (MV) side of the double-bus dual-subsection of 500kV intelligent substation. For complete blackout at the MV side, in-depth analysis of the behavior of bus differential protection and main transformer protection action are made, and the action conditions and mechanism of the bus at the MV side and the main transformer at the intelligent substation pointed out. Through comparison of the fault circuits between the double-bus dual-subsection at a conventional substation, mutually actuated failure thinking and action theory between the double-bus dual-subsection of the intelligent substation, and the coordination between protective and intelligent terminals are analyzed in detail, and emphasis is put on the introduction of improvement reason and method of fault links. The theory and conditions of fault intertrip circuit between the main transformer and the bus differential protection are investigated; the difference of the intelligent substation in intertrip, fault circuit and logic judgment analyzed; and the measures for improving compound-voltage blocking, overcurrent judgment and constant time lag put forward. Emphasis is put on the study of the inversion of CT polarity circuit at a new intelligent substation; CT polarity configuration scheme and protection action reason pointed out in combination of the trip accident; and reasonable improvement measures brought up according to the method of operation.

Key words: Intelligent substation, intertrip, intelligent terminals, CT polarity, compound-voltage