Research On Intelligent Wide Area Backup Protection System

With the establishment of alternating and direct current UHV transmission project andsmart grid, power industry has developed rapidly. But at the same time power systemsecurity issues have become more and more prominent. So called ‘the first line of defensein power system’, relay protection has emerged much inadaptation in the process of powergrid upgrade. It is meaningful to find a new relay protection algorithm and design ideas tomake up for those shortages in traditional protection.This paper analysed shortages in traditional protection and designed an intelligentwide area backup differential protection system which could match up with traditional mainprotection. Substation centralization structures ensure speed in signal transmission andsimplifie structures of communication system. Graph theory based algorithm divides andupdates three protection zones of each protection unit in real time. Multi differentialcalculations constitute comprehensive criterion which locates and cuts faults accurately.When one protection IED appears operating malfunction or rejection, the system will judgethe error situation and block corresponding protection units. Even under the circumstanceof one protection IED out of running or breaker failure, the system won’t enlarge power cutrange.Simulation is based on Yueyang grid in Hunan province. The results indicated: widearea backup protection system located faults speedily and accurately when one or multifaults occurred in the grid; it blocked failure protection IEDs and cut faults correctlywithout enlarge power cut range; corresponding breakers operated and isolated faults whenbreaker was failure. The system owns high protection operation speed, reliability andfault-tolerant ability. It can protect power grid’s operation securely and reliably.