Electric aging of polyethylene in pulsed electric field

It is known that electric aging of polymer insulation in high pulse fields is a very intensive process which produces many problems. The breakdown after many pulse acts may be due to electric field modification because of the space charge storage or structure modification. Both reasons are discussed in this work for the case of pulse duration less than 1 ms. Space charge formation was studied using the pulse acoustic pressure method and the proton beam method. The results of measurements showed that the electric field modification because of space charge storage was not the main reason of short life time of polyethylene insulation. Electrons and holes injection from electrodes and their generation in volume of insulator are the reasons of structure aging, and, as a result, the breakdown voltage decreases. This conclusion is confirmed by the results of treeing formation at various voltage polarities and pulse duration.