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Line pre-acceleration protection scheme of DC distribution network

The future power supply system of the city will be the AC/DC hybrid distribution network. By introducing the DC distribution network on the existing mature AC distribution network resources, its advantages will be added to the urban power supply system. At present, the AC/DC hybrid distribution network is still in the research stage, and there is no mature regional AC/DC hybrid distribution network. AC/DC hybrid distribution network uses voltage source converter (VSC) to realize AC and DC interconnection, and the operation safety of network depends largely on the reliability of relay protection. Within milliseconds of a DC line failure, the fault current can rise to ten times the steady-state current. The network puts forward new requirements for the rapidity of relay protection, so this paper presents a pre-acceleration protection scheme. There are two requirements for the use of pre-acceleration protection in DC distribution network: the first is the pre-acceleration protection scheme can cannot hinder the normal operation of the system; the second is the pre-acceleration protection should have a beneficial effect on the system, and the worst is to maintain the original protection. The pre-acceleration protection proposed can effectively correct errors by using communication and DC circuit breaker, and can improve the time of fault isolation compared with the scheme without pre-acceleration protection.