The Research On Algorithm Of Wide Area Protection And Local Substation Coordination Strategy

Relay protection is an important foundation to safeguard the power system security. The traditional protection is based on the local information, the setting was complicated, the operation time was long, and it may mal-operate when flow transferring caused by overload happened. The traditional protection cannot adapt the higher requirements of the Complex large grid. Recent years, as the rapid development of computer technology and network communication technology, it aroused wide concern about novel back-up protection system based on wide area measured information. The application of wide area measured information has effect on the structure mode and implementation principle of wide area back-up protection, much theoretical problems and technical issues should be solved. Combined the National Nature and Science Foundation Project"back-up protection system coordinate centralized decision and distributed implementation", this paper mainly studied wide area protection algorithm, the protection criterion of local substation; solved the setting and coordination problems of the traditional back-up protection, avoided mal-operation when flow transferring caused by overload happened.At first, the current situation of wide area protection and the main problem exited are analyzed in this paper, on the basis represented the primary content of this paper. In the aspect of wide area back-up protection, this paper analyzed the affect of capacitive current of transmission line and TA measurement errors on wide area current differential protection, and proposed the solution. At the basis of wide area protection based on direction elements has been further studied. A new wide area direction protection based on fault direction information from multiple measured points was proposed. Fault recognition algorithm for protected zone within multiple elements has been put forward. And the operation logic of wide area direction protection is presented on the basis of the cooperation relationship among conventional direction component.Considering the wide area back-up protection affected in a big way, it required to be altitudinal reliability and Security. Using wide area back-up protection algorithms based on different principles is helpful to improve the performance of wide area back-up protection. In this paper, a novel wide area back-up protection algorithm was proposed, which based on the distribution of fault voltage. It can help to solve the setting and coordination problems of the traditional back-up protection and the mal-operation when flow transferring caused by overload happened. This algorithm used the value of fault voltage and fault current measured from one side of the line to estimate fault voltage of the other side of line. The ratio of estimated value to measured value makes up the protection criteria. It isn't affected by transition resistance, and it wouldn't misoperate when flow transferring caused by overload happened. The principle of this algorithm is simple and it requires little information. It has little request on the synchronization of the information from different sides and is convenient to implement. The simulation proved that the algorithm can successfully distinguish the faulted line under different type of faults.The information organization of local substation and the coordination of wide area back-up protection and convention back-up protection were important content of wide area protection research. According to different algorithms and improve the flexibility of information, this paper analyzed the information organization. Also, the initial criterion and fault recognition criterion were presented at the local substation. Initial criterion was made up of zero and negative sequence voltage, together with positive voltage, which was used for narrowing the fault area down, decreasing the information upload to primary substation. Fault recognition criterion can reinforce the reliability of wide area back-up protection. According to the new features of wide area back-up protection, the simplification of the setting principle of convention back-up protection and the third-zone phase distance protection criterion were proposed. At this foundation the logic of wide area back-up protection and convention back-up protection is analyzed.The application of wide area back-up protection can effectively solve the the mal-operation when flow transferring caused by overload. But it may cause line fault by seriously overload. To ensure the safe operation of transmission line, this paper analyzed the current-carrying characteristic of transmission line, and then proposed an inverse over-current protection scheme based on of transmission line. The primary principle and implementation method was introduced in this paper.At last, this paper summarized the work of research, and the further research directions are given.