Study On Mechanism And Defend Of Chopped Wave Overvoltage Of Transformers Based On Insulator Arc-over

Chopped wave which is generated by lightning stroke on lead-in wire causing chopped wave overvoltage of transformers is proposed based on the present situation of lighting protection of transformers to the question that some lightning disturbances of transformers could not be avoided or the reason of accidents could not be judged. This problem usually is ignored. The mechanism of chopped wave overvoltage of transformers caused by insulator arc-over chopped wave after lighting stroke terminal tower by the means that theoretical analysis, establishing model and computer simulation are combined. The waveforms of chopped wave overvoltage of transformers are gained by simulate and a kind of effective proofing measure is proposed.Firstly, the harm of chopped wave overvoltage of transformers and the necessary of chopped wave test of transformers is expounded. The waveform and mathematics model of standard lightning chopped wave are described. The mechanism of chopped wave overvoltage of transformers caused by insulator arc-over chopped wave after lighting stroke terminal tower is analysis emphasize.Secondly, the mathematics models of lightning, tower, insulator arc-over and transformer are presented. The waveforms of chopped wave and chopped wave voltage of transformers are gained through simulation model which is established by MATLAB software. Three factors effecting chopped wave overvoltage are lightning magnitude, the distance between lightning stroke point and the transformer, class rating of the transformer. They are discussed in this paper.Finally, the way of buried cable used between terminal tower and the transformer is proposed. This measure could reduce the magnitude of chopped wave and the chopped wave overvoltage of transformers by the shielding tier of cable draining current. It could be concluded that the magnitude of chopped wave overvoltage is more than the rated lighting impulse withstand voltage of transformers and the chopped wave overvoltage of transformers could be defend effectively by buried cable.