Applied Research On Short Circuit Current Limit By Installation Of Small Reactor On Neutral-point Of 500kV Transformer At 500kV Jilantai Substation

Inner Mongolia Power Grid(the West The West Inner Mongolia Power Grid) is located in the northern part of the North China Power Grid; it is part of the North China Power Grid and it is the main transportation channel of power. The main grid of The West Inner Mongolia Power Grid includes two parts; they are internal 500 kV main grids and outward transportation channel.The short-circuit current of The West Inner Mongolia Power Grid rises rapidly in recent years; the short-circuit current level of the 220 kV side of power grid is rising; and some 500 kV substation single-phase short circuit current levels of the 220 kV side are high, approaching or exceeding the rated breaking capacity of equipment, and there is some margin in three-phase short-circuit current level. The cause of excessive current are: firstly, 500 kV power grid is planning and constructing,and at the same time 220 kV power grid failed to sort out and zoning; secondly, a lot of power access 220 kV system, the short-circuit capacity of 500 kV network cannot take advantage; again, part of the power access node is too concentrated by the impact of the power distribution; in addition, there are many ground system in the system and the lack of optimization grounding, resulting in a large number of substations single-phase three-phase short-circuit current is higher than the short-circuit current.Currently, autotransformer of the West The West Inner Mongolia Power Grid 500 kV are widely used, the neutral point of the transformer directly ground, the zero-sequence reactance of system is smaller, and it results in 220 kV single-phase short-circuit current value exceeding the value of the three-phase short-circuit current, part of substation closes to rated breaking current, and it affects the safe and stable operation of the power grid. In the operation of 21 500 kV substations, the problem of the short-circuit current of 500 kV Jilantai substation is the most serious, the three-phase short-circuit of 220 kV bus station in the Jilantai substation is 41.3 kA, while the single-phase ground fault current value 48.73 kA, and the rated breaking current close to 220 kV switch is 50 kA.In 2014, after synchronizing and closing the new units of Alashan grid,it will produces single-phase short circuit,and the current exceeds 50 kA, more than the problems of breaker breaking current. The question of single-phase short circuit current is too big,and it became one of the main factors of limiting the development of grid operation and it takes quick and effective way to reduce the level of single-phase short-circuit current.This paper based on the research of short-circuit current limitation technology at home and abroad, and combined with the actual of 500 kV Jilantai substation; from the viewpoint of safety and economic benefits of 500 kV main transformer, the main transformer neutral point grounding becomes the best small reactors program.This paper mainly analyzed the impact of small reactance grounding of the limiting short-circuit current to main transformer neutral point by a small electrical resistance of different anti-ground, it determines the resistance of small reactors. Meanwhile, after carrying out in-depth research of the installation of small reactors with over-voltage and insulation, wiring form, select the device parameters, layout and other issues.This project is the first case to install a small neutral point reactance way to limit the level of the single-phase short-circuit current case in the West Inner Mongolia Power Grid, the implementation of this project will play a role model for the design and operation, and it can accumulated many experience, it is important for the widely adopted within the next grid.