The Applied Study Of Regional Protection In Distribution Network With Distributed Generation

As traditional energy is draining away, distributed generation is becoming an important direction to the sustainable development of power industry, because of it can make use of renewable energy well. However, it would change the structure of distribution network when access to the system, which may take some bad influence to the coordinate relationship of current protection and automatic reclosing, then causes the difficulties such as the coordination of current protection, the detection of fault characteristics, the coordination of fuse, and may take non-synchronous closing or the persisting of arc.Firstly, the paper reviews study status of the small capacity distributed generation high penetrated of distribution network protection in the world; then, the paper analysis the influence brought by small capacity distributed generation to distribution network relay protection; finally, the paper advances regional relay protection scheme based agents and communications technologies combining predecessors experiences. The protection scheme is the following aspects:â‘ Structure and function of regional relay protection. The scheme set agent unit in the high voltage side of the distribution transformer to administer all small capacity distributed generation accessed to the distribution network system.The main task of agent unit is responsible for notifying all small capacity distributed generation of the branch open or close its breaker; then, take the branch agent and trunk agent as a protection area,and set a protection host computer for collecting all fault message calculated by agent to judge fault element, which can remove fault quickly;â‘¡Structure and function of agent unit. The paper takes circuit breaker, agent, protection algorithm and action logic as an agent unit that is used to send message to the protection host computer or carry out the action command of the host computer in the regional relay protection;â‘¢Algorithm and action flow of regional relay protection. The protection host computer can confirm fault element according to the fault associated matrix when receive the message of agent unit, and then notify all agent unit to action. In addition, the paper gives reference solutions to some special problems may arise. â‘£The paper build a micro-power and a constant power simulation model according to the different output of small capacity distributed generation by PSCAD/EMTDC software, and then check the algorithm. The simulation analysis result shows that the regional relay protection can judge fault element even if the short circuit fault is different in locations and types. In addition, because of the regional relay protection needing a strong communications system, so the paper also established LAN model between agent unit and host computer, and calculates the communication network flow. Then the paper analyses the communication delay and flow by OPNET software. The results show that the network did not produce communication congestion, and the delay is also within the acceptable range, which can meet requirements of relay protection.