Research Of The Neutral Point Grounding Mode In Dalian 66kV System

It is a complex and technical problem that the neutral point grounding mode selection of low voltage distribution network in our country. Because there is a great relationship between neutral point grounding mode and grid's structure, the reliability need of grid, personal safety, etc. There are three modes in the existing middle and low voltage distribution network in our country, neutral point directly grounding, neutral point grounded by resistance, neutral point grounded by extinction coil. The cable lines are increasing with the development of China's economy recently years. The operation mode existed of neutral point directly grounding fall into disuse gradually. The other two kinds of neutral point grounding mode have their own advantages, so it's controversial that the selection of neutral point operation mode in middle and low voltage distribution network existed.In Dalian 66kV distribution network structure was high-speed build changed follow the economic development of Dalian area in recent years. The proportion of cable lines increased year by year, which brings challenges to the 66kV grid mainly overhead lines. One of the biggest challenges is the occurrence of single-phase grounding fault in 66kV power distribution line. There will be a great zero-sequence current because of the cable line's capacitance current, the arc is not easy to cut off. Then expand the failure, damage the equipment insulation and other issues comes.This paper first introduces the current situation of the main neutral point grounding mode at home and abroad existing distribution network, and then analyzes the selection criteria of the neutral point grounding mode in different operating requirements and environment. Through the research on the theory of the main neutral point grounding mode in distribution network, and the characteristics of the different operational requirements, the application range of the main neutral point grounding mode is analyzed. Based on the above theoretical research and operational characteristics, the 66kV distribution network neutral point grounding mode in Dalian area is analyzed and simulated, and the existing or possible existing problems are summarized. In view of these problems, the solutions are proposed to solve the problems, and the optimization scheme is verified by theoretical calculation and data simulation analysis. The implementation of feasible optimization scheme has been verified.