Several Problems Of Research In Relay Protection Based On Wide Area Information

Relaying protection in power system has a vital role when the system is in the faultstates or the abnormal operation states. The safe and stable operation of power system isclosely related with the national economy and people’s livelihood. With the continuousexpansion of power system and the interconnection of major regional power grids, thecomplexity of power system topology has been enormously increased and changed, whichhas also brought a series of new problems. With the increasing stability problems occur in thepower system, the relay protection especially the backup protection confronts withtremendous challenges. In addition, in the process of constructing a strong smart grid, theintegration of the distributed generation such as wind energy and solar energy and theintroduction of the micro-grid concept may probably lead to a more flexible operation of thepower system. Traditional backup protections, adopting the mode of off-line settingcalculation, ensure the selection through the setting coordination of the operating values andtimes. It is difficult to satisfy the selectivity and sensitivity of protection at same time becauseof the complex topology structure and flexible operating conditions of power network. Inrecent years, the wide area backup protection based on substation centralized has beenfocused by many scholars and a large amount of research projects have been established,which indicates a new opportunity.Firstly, after investigating the issues that have been studied by the domestic and theforeign researchers, this paper mainly discusses the wide area backup protection schemesbased on substation centralized which realizes the backup protection area online maintenance,quickly identifies the abnormal operational status and clears the faults. Then this papermainly studies the overall structure of wide area protection, the characteristics of thecommunication system, the fast fault location algorithms for the wide area backup protectionbased on the wide-area information. The system realizes the backup protection area onlinemaintenance by applying the graph theory and the matrix operation. And this paperelaborately presents the tripping strategies of the relay protection. At last, the blackoutaccidents that have happened in recent years abroad have been analyzed and concluded. Theprocess of the cascading failures which were initiated by the power flow transfer has been carefully studied. The Zone3of distance relays operating characteristic curve correction hasbeen conducted in condition that over-load currents may influence the Zone3of distanceprotection in the process of fault recognition and power flow transfer. Those improvementsmay avoid the misoperation of protection devices.