An evaluation method for power supply capacity of distribution system

As the key-ligament between the customer and the generation & transmission system, distribution system plays a very important role in ensuring the continuous power supply for customers in safety and in high reliability. Therefore, the scientific evaluation on the power supply capacity of urban distribution network is of enormous social and economical significance. To improve the insufficiency of traditional method based on the load supply capacity referring from the transmission, this paper proposes a simple and practical method to evaluate the power supply capacity of distribution network. Firstly, the basic definition of the power supply capacity based on the N-l guideline is presented, which is composed of tow parts: one is the power supply capacity of substations, and the other is the transfer capacity of network. Secondly, according to the definition stated above, general formulas about power supply capacity of substations and network transfer capacity are deduced, and the relationship between the power supply capacity of substations and the transfer capacity of network is studied, in which the optimal transfer capacity is concluded consequently. Finally, the theories are summed up and a flow chart of power supply capacity analysis is drawn up. Through application in a district of Shanghai, China, the effectiveness and the accuracy of the proposed model are demonstrated. To summary, the method proposed in this paper under the N-l guideline is a simple and practical method to evaluate the power capacity of a distribution system; besides, the conclusions about network optimal transfer capacity based on power supply capacity can provide effective references for urban distribution network planning.