Study Of Arc Grounding Overvoltage Suppression Using ZnO Neutral Grounding Mode

Reasonable setting and controlling Power system neutral point grounding technology is very important to prevent system accidents.The mass usage of cable has made the increase of system capacitive current,and the arc grounding overvoltage has become increasingly prominent.The neutral isolated mode is easy to cause arc grounding overvoltage,which would last for a long time and enlarge the fault.For the neutral grounded by Peterson coil mode and neutral grounded by low-resistance mode,the problem is the automation and reliability of distribution.To solve the above problems and to get a breakthrough in operation reliability of power grid,it is an important and urgent task to develop the theory of grounding system.In this paper,the ZnO nonlinear resistance grounding mode is studied,and the method to suppress and identify arc grounding voltage is discussed.Firstly,a new method for determining voltage-current(U-I)characteristics of ZnO nonlinear resistance is proposed,and the U-I characteristics of ZnO nonlinear resistance is put forward.Then,by using discrete wavelet,the multi-resolution analysis on zero sequence current is performed.According to the high frequency component energy ratio within the time window,the identification strategy which can distinguish the permanent grounding fault and intermittent arc grounding fault is put forward.Finally,combined with the effectiveness of the ZnO nonlinear resistance and the identification strategy,the ZnO nonlinear resistance grounding mode identification method is designed.Results illustrate that the new neutral grounding mode can suppress arc grounding overvoltage,and the neutral grounded by ZnO nonlinear resistance mode possesses the advantages of ungrounded mode and low-resistance grounding mode.