Research On Protection Configuration And Distance Relay In The Presence Of SSSC

Static synchronous series compensator(SSSC)is one of new controllable series compensator,which has the ability to control the load flow quickly and improve the line transmission capacity as well as stability of power system.SSSC is complicated and has to withstand line current due to serial connection,thereby withstanding a large short-circuit current during system fault.As a consequence,fast and reliable protections are essential.The parameters of the AC power system is inevitably changed due to the presence of SSSC,thus having a negative impact on the protective relay of the power system,especially on distance relay that is widely used in HV or EHV transmission line.Given that it is challenging and realistic to study effect of SSSC on distance relay as well as cooperation between protection configuration of SSSC and protective relay of the power system for the demonstration project of SSSC.Research results are provided in this thesis from three aspects,which include basic operating principle,protection configuration and impact on distance protection of SSSC.(1)Based on basic operating principle of SSSC,a simplified mathematical model of equivalent voltage source is established for SSSC.Output characteristics of SSSC after line fault is analyzed,Then protection configuration of SSSC and impact on distance relay are studied.(2)Based on the H-Bridge cascaded circuit topology,the partition protection configuration is adopted in this paper for SSSC,and the overcurrent protection in the partition of VSC is in coordination with protections of other partition.In addition,it is composed of main and auxiliary current differential protection for the main protection of coupling transformer,and moreover two action stages are setted for operation characteristics of both differential protections as well as overcurrent protection in the partition of VSC.(3)Taking protection strategy of SSSC into consideration,the impact on measured impedance of impedance relay is studied for different compensation modes and level of SSSC as well as fault location.Then results of PSCAD/EMTDC simulation are given in the paper.Finally cooperation strategy between protection strategy of SSSC and distance protection as well as autoreclosure of the power system is put forward.