Study On Relay Protection Not Matching Problem And Optimization Scheme Of220kV System In Ji’nan Electric Power Grid

Protection relays are the basic of safeguarding modern large scale power grid. When the protected power system faults, element of main protection devices should send breaking commands to the distance element quickly and accurately, in order to isolate the fault element from the power system timely. In this way, the protection relays can minimize losses to the least, and can reduce the effect on power system security power supply.Backup relays’ function are operating in a very short time when main relays fail to operate. Backup relays should be seted in accordance with the sequential matching requirements, in order to satisfy action selectivity. With the rapid development of network, the network capacity, the network structure and layout characteristics are different form the past. And because of protection relay technology, especially the rapid development and application of computer protection relay, highstandards of protection relays become basic aquiements in EHV power grid. So the importance of backup relay is greatly reduced. Therefore, setting of protection relay in EHV and UHV power grid should be strengthened in main protection, and be simplified in backup protection.Ji’nan power grid has intensive loads, and the lines between220kV substations are short. It resultes to a short-term, intensive, multi-layer ring network structure. So protection relay setting in Ji’nan area is extremely complex.220kV line protection backup protection section cannot be realized step by step, which leads to the fault line adjacent one or several steps line all trip, even to make a number of220kV substation in around area break down.This paper made a summery of development history and status of protection relay in Ji’nan power grid. On this basis this paper analyses the problems of protection relay in Ji’nan power grid. It tries to find reasonable independent operation points in this area in order to optimize the backup relay protection. In this way, it can solve not matching problems of backup relay protection.