Study on the rational scheme of voltage levels in urban electric networks

To make a rational scheme of voltage levels is an effective way to ensure the security and reduce the losses for urban electric networks. This paper firstly studies the relationship of voltage levels with transmission capacity and short-circuit current in detail, and investigates the present situation of voltage levels of some cities in China as well as in several developed countries. Then, both economic and technical comparisons are performed in detail for a series of voltage level schemes to evaluate their adaptability and feasibility. Based on these investigations and analyses, principles for the rational scheme of the voltage levels of urban electric networks in China are identified, that is, to decreasing the transmission voltage levels and boosting the mediue voltage level. The result of this paper is of great benefit for the stragic decision making of the rational scheme of voltage levels in China. (7 pages)