Influence of DC pre-stress of initiation characteristics on electrical tree in XLPE under DC- impulse voltage

Cross-linked polyethylene (XLPE) DC cables may be affected by the impulse voltage during operation, resulting in the generation of electrical trees. In order to investigate the influence of DC pre-stress time and amplitude on the characteristics of electrical tree initiation under DC superimposed impulse voltage, -50 kV lightning impulse voltage is superimposed under DC bias voltage. The DC voltage amplitude is 0kv, 10kV, 30KV, and the pre-stress time is 1min, 10min, 60min respectively. It is shown that the electrical tree initiation length increases with increasing DC pre-stress time and becomes saturated after a certain period of pre-stress time; When the polarity of DC voltage and impulse voltage is opposite, DC voltage may be restrain the electrical tree initiation length in a certain range of amplitude; The electrical tree initiation length is related to the depth of space charge distribution.