Selection Method of Neutral Point Overvoltage Protection for 220kV Transformer

Through the 220kV main transformer under the lightning overvoltage, the neutral point gap breakdown, the zero sequence protection jumps off the main transformer accident, indicating that the discharge dispersion of the gap is very large, and the 220kV neutral point is not grounded, its protection must be The arrester is shared after the parallel gap. The voltage distribution of the neutral point in the transformer during the wave process is discussed. The two-phase incoming wave or three-phase incoming wave is the main reason for the protection device action. Deeply demonstrate the problem of insulation coordination between the neutral point of the transformer and the protection device. To reduce the dispersion of the breakdown discharge of the gap, the simplest and most effective way is to place a special transparent insulation cover over the gap.