Research On 35kV Power Network Neutral Grounding Of Wind Farm

It is an important technical problem to neutral grounding mode of the electric power system which associates with voltage level, network structure, insulation level, reliability of power supply, protective relaying, electromagnetic interference, and personal safety. Grounding mode of power system is one of the foundations of security. In recent years, wind farm size are becoming larger day by day, the proportion of wind-electricity in power system is increasing. while providing short circuit current to the system is also growing. So the original neutral grounding has become unable to meet the requirements for the development of grid-connected wind power system. Therefore, it is essential to fundamentally research better neutral grounded mode in order to further enhance the security and economic operation of the network.This paper studied on how to select the neutral grounding mode of wind farm 35kV network, the grounding principles and basic characteristics of all kinds of grounded mode used in medium voltage network are analyzed in detail. And then wind speed, wind generators and wind farm are modeled. Wind generator model includes wind turbine model, transferring structure model and asynchronous generator model. Xiwuqi wind farm of 35kV power network was used for research object. The Matlab/Simulink are used to simulate the frequency voltage and intermittently arc grounded over voltage to make quantitative analysis and comparison to the basic characteristics of different grounded modes .Taking account of the ground point of transition resistance, neutral grounding resistor or the coil volume, it simulate the over voltage level and the grounding point short current value of the network the neutral point under various operation, in addition, this paper discussed the problem of restrained arc over voltage. The results showed that: grounding via Peterson coil is a more satisfactory way in wind farm, the use of excessive compensation ( v = ? 15%) cases, non-fault phase frequency overvoltage maximum is 1.912 p. u . , fault current is 10.56A;The biggest Non-fault phase voltage amplitude values for 3.12 p. u ., fault current is 11.25A. The over-voltage is within the limit of insulation coordination, and fault current is good to extinguish for arc, because on the one hand the way can reduce the fault current, it is easy for arc to go out. On the other hand also reduce the recovery initial velocity voltage of fault phase, and extended recovery time, limits recovery voltage amplitude. So that it is difficult for the arc extinction to rekindle.According to the practical situation of Xiwuqi wind, grounding via Peterson coil is selected and associated equipment were calculated, and reasonable selection has been made to finally realize automatic tracing compensation for arc suppressing coil grounding mode.