Overvoltage of 110kV, 220kV Transformer Neutral Point and Its Protection Analysis

In most of the 110kV and 220kV power grid, the neutral point insulation of the ungrounded transformer is vulnerable to be damaged. So the arrester and nod gap in paralleled are generally used in protecting the insulation. But there is some shortage of this protection method. In this paper, a simulation was done research the over voltage on neutral point, by using ATP, and the reason why the shortage exists was proposed. An improvement method to solve that problem was also referred, which is increasing the distance of rod gap and the rated voltage of MOA.