Study On Fault Processing Methods For20kV Distribution Networks

With the rapid economic development and the people’s living standard has been being improved constantly in China, power consumption has increased fast which lead to10kV distribution networks not being able to fit for the developing situation, In order to solve this problem, plan and construction of20kV distribution networks is put forward, In China, medium voltage distribution networks are mainly composed of10kV distribution networks and methods of fault process are mainly focused on10KV distribution networks. This paper focuses on study on fault processing methods for20kV distribution networks. The main work in this paper is shown following:Connection modes of20kV distribution networks are summarized and influence on fault recovery by connection modes is analyzed.Two-phase earthing short circuit characteristics are analyzed and single-phase matrix algorithms suitable for two grounded ways are put forward.Multi-sectioned and multi-linked grids and double-source and multi-loop grids are the most complex connection modes in20kV distribution networks. Faul recovery of these two connection modes is very difficult. In order to solve the fault recovery problem of these two connection modes, a fault recovery method based on dichotomy division and balanced load distribution is put forward. This method regards the fault recovery area as a rooted tree and calculates the expected rate of part of the rooted tree above one node and part of the rooted tree below the node. If the expected rate of the part above one node and the part below the node is closest, the node is selected as the division node of the rooted tree and the rooted tree is divided into two new rooted trees. Continue to divide the new trees until every new tree has only one loop switch connected. The feeder behind the loop switch can restore the corresponding new rooted tree.A multi-fault recovery algorithm which suits for20kV distribution networks is put forward, In this paper, the fault recovery area of a multi-fault is divided into many independent fault recovery areas. Two independent fault recovery areas may be connected through a feeder which is called a public feeder. As public feeders exist, fault recovery of independent fault recovery areas may interact with each other. A public feeder is decomposed into many virtual feeders to eliminate the interactions among independent fault recovery areas. Then fault recovery plans of unaided fault recovery areas can be generated by using traditional fault recovery methods. As fault recovery plans of unaided fault recovery areas can be generated in parallel, this method can guarantee fault recovery real-time.