Protection Researches Of Distribution Network Based On The Positive Sequence Fault Components

The access of the distributed generations has brought many problems to the relaysof the distributed network. When small capacity distributed generations access to thedistribution network, it will effect the fault current which go through the relays and thecurrent protection can not work exactly. So the access of the distributed generations willbring new problems to the relays of the distributed network.Firstly, the relay researches of distributed generations in domestic and internationalare introduced. Secondly, the paper established the distributed network which containsthe distributed generations, use PSCAD to simulate the influences of the distributedgenerations to the fault currents at the relays, the sensitivity of the relays and theprotection range in the condition of different capacities, different access points ofdistributed generations. The results reflect the tridition current protection will beaffected when distributed generations access.Based on the problem above on, by the directional component of the positivesequence current and voltage fault components at the both ends to make up the directionpilot protection with sick protection supported, the paper uses the fault componentsprotection principle of direction elements to decide the fault area and control the breakerto cut the fault. The results of the simulate also reflect the protection can slove theproblems which are brought by the distributed generations, and it has some value in thesystems which contain distributed generation.The extraction method of the fault components. Is the most important to thedirection protection based on the postive sequence fault component. Because of the lackof the combine postive sequence component mothed, the paper uses the the sineapproximation to get the postive sequence fault component by sine fitting to thechanging non-sine single. Compared the two methods, the paper using the PSCAD tosimulate the correctness of positive fault component direction protection in thecondition of different capacities, the result proves the method is better, and the positivefault component direction pilot protection based on the sine approximation hasobvious advantages, it is better.