A Research On The Wide Area Backup Protection Of The High Voltage Transmission Line

With power grid interconnecting widely, a higher demand to the stability of the power system has been put forward. It is desired that not only faults can be isolated fast, accurately and dependably, but also system can preserve steady operation while greater disturbances take place. Studies of significant power system incidents indicate that protection relays are involved in most of the major disturbances. Conventional protection relays based on their locally measured inputs generally take actions to protect an electric component without considering the impact on the whole system. With the recent advances in communication, the wide area protection has been proposed as an integrated approach to both component and system protection. Different from conventional protection relays, wide area protection systems have wide view of the power grid based on their wide measured inputs. They can offer more accurate and dependable faults isolation, and at the same time, they consider the influence on the system operation and prevent disturbances from protection actions. In this dissertation, the background and research situation of the wide area protection are introduced, and various wide area protection systems proposed at present are summarized. The characteristics, function making up and system structures are discussed, and a practical wide area transmission line backup protection scheme is proposed in this dissertation. The scope of the research includes the protection primary principle, the fault location strategy, the overall structure of the protection system and the design of hardware and software. The distance protection, directional protection and differential current protection, which are used extensively in high voltage transmission line protection, are analyzed detailedly in action characteristic and special problem. Conventional directional relays are adopted in this wide area protection and used in a flexible way. The principle and characteristics of the low voltage distance directional relay, phase distance directional relay and earth distance directional relay are analyzed concretely. The wide area backup protection proposed in this dissertation consists of the protection master system and the protection slave system. The structure and function of master system and slave system are detailedly discussed. The hardware used in the protection equipment, which includes CompactPCI bus based industrial computer and TMS320VC33 digital signal processor, is introduced. A detail design of the protection software including the software framework and program flow is presented, especially the fault treatment procedure.