| This paper is mainly focus research on EHV 750 KV busbar protection. It is a key project [2002 ] 23 SHCH-04," Research on 750 KV Relay and Stable Facilities and its Substation Automation", proposed by State-grid Northwest Power Electric Co. Guodian Nanjing Automation Co. ,etc. is a partner research of this project.The main mal-operation problems on the 750KV busbar relay are caused by external transmission line faults. With the voltage level upgraded to a higher level in power system more complex electromagnetic transient procedure, larger short capacity, long-time DC-decaying period and easier TA saturation make relay led to mal function easily.Considering difficulty and complexity of 750kV power system and currently busbar protection application weaknesses in many countries, the thesis analyzed electric parameters impact on the busbar protection. It developed a new ct anti-saturation mechanism that can satisfy all level line from 110KV to 750KV. It also developed a prototype on an embedded developing platform. The proposed busbar protection technique can greatly solve exiting problems in and under 750KV busbar after fully dynamic experiments and tests.This paper also highlights some auxiliary protection functions, such as Busbar-tie dead-zone protection,TA secondary cable-broken, adaptive duo-buses operation, etc. The paper puts forward some new discrimination methods better than the traditional method. For example, the principle based on two sets of TA can solve problem tripping more than one busbar when faults occuring in Busbar-tie dead-zone. It proposed branch-current method combining differential current to deal with cable-broken TA location. It also developed an adaptive duplicated mechanism detecting switch-input and switch-backup trip which can decrease busbar relay judge risks because of switch error.. |
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