Research Of 20kV Single-Phase Power Distribution System

ABSTRACT:The development of power distribution technology is closely related with that of national economy. With the economy's fast development of our country, the phenomenon of "has a stranglehold" in the distribution network is getting more and more serious. In recent years, the state grid takes an active part in the experimental unit application study on the middle-voltage power distribution method of the 20kV voltage rate and the single-phase method of low-voltage power distribution. Combine the merits of improving power supply ability, enlarging middle-voltage power supply radius, decreasing power loss and etc in the 20kV distribution system with the advantages of small capacity, dense distribution points, short low-voltage distribution line in the low-voltage single-phase distribution technique, which can reduce distribution network loss and improve power supply reliability and voltage quality significantly, contributing to promote the development of distribution network and build community of resource-saving type. So many questions related with the new power distribution method of 20kV single-phase power distribution have become subjects to be urgently researched.In the beginning of the thesis, according to field investigation, analysis and research of the 20kV single-phase power distribution system in the domestic and abroad, summarizes the superiorities of using the 20kV voltage rate in the middle-voltage distribution network and selecting the single-phase power supply method in the low-voltage power distribution system; Based on the present situation of distribution network in our country, several kinds of middle-voltage connection mode which are suitable in the 20kV cable line and overhead line are given; According to the different characteristics of using electricity in our country resident user, the single-phase power distribution connection mode which are suitable for the different load density areas are given.To carry on the power flow analysis of the single-phase power distribution network, this article has studied the unique single-phase three-wire circuit model of transformer in the single-phase electrical power distribution system, utilizing the indication method between nodes to give the power flow computation model of the single-phase three-wire transformer, and using the forward and backward substitution method to make the power flow calculation on the distribution network. This thesis aims at a real lOkV power distribution region where the load increase massively while the power supply ability of distribution line has been close to the upper limit, carrying on the voltage-rise, designing the voltage-rise transformation plan; Aiming at a three-phase power supply plot where the low voltage line loss is large and the voltage quality is low in the original power supply region, designing the single-phase transformation plan; And making the power flow calculation on the two power distribution patterns of transformed and before, finally indicating that the model and the transformation plan the article proposed was effective and feasible, providing the theory support for the promotion and application of 20kV single-phase power distribution technology.