Research On Logic Protection Of Urban Distribution Network

With the rapid development of society and the improvement of people’s living standards, the power supply reliability of users has become increasingly demanding. However, the traditional protection schemes only use a single terminal electrical to judge fault section which due to a series of shortcomings such as a long fault clearing time, cooperation difficulty and an expanded scope of fault. To solve above problem, this paper presents a logic protection scheme which uses multi-terminal electrical quantities to judge fault section. The details are as follows:(1) Considering the difference of required basic information sources, the existing protection scheme can be divided into point protection and side protection, and three prerequisites of side protection scheme is analyzed. The distribution network analysis model is established to make analysis easy. On the above basis, the undirected graph is used to analyze fault which happens in the open-loop mode, and the protection criterions under open-loop mode are proposed. Similarly, the directed graph is used to analyze fault which happens in the closed-loop mode, and the protection criterions under closed-loop mode are proposed.(2) The fault overcurrent information of the switch and the switch’s adjacent switch is collected by FTU in distribution network. The above information is used to establish the network adjacency state table, by which the criterion vectors of different types of switches are obtained. The fault section is determined quickly by comparing the criterion vector and action set, so the fault can be removed quickly. The effectiveness of the logic protection scheme is proved by the fault simulation analysis to example system. The hierarchical backup protection program is proposed, and each action sequence is provided. Finally, some applications of the logical protection scheme such as in overhead lines, cable lines and substation are analyzed.(3) According to the characteristics of distribution network logic protection schemes, the peer–to-peer communication is selected as the communication scheme of logic protection. Several of peer-to-peer network protocols are compared and analyzed, and the CAN bus is selected as network protocols of the logic protection scheme. Finally, the principle and function of CAN bus is analyzed and the whole logic protection design is completed.