Temperature effect on space charge dynamics in LDPE/MgO nanocomposite under DC stress

A pulsed electro-acoustic method (PEA) of space charge measuring system was developed, which could be used to investigate space charge distribution in solid dielectric at a temperature high up to 383 K. With the measuring system, space charge dynamics in the composite of low density polyethylene (LDPE) and nano-MgO which is expected to be used as an insulation of HVDC plastic insulated cable was investigated from room temperature to 353 K in detail. It is shown that the amount of space charge decreases significantly at a higher temperature in all samples including the LDPE sample. However, it should be pointed out that the amount of space charge in samples with nano-MgO is lower than that in LDPE and the shape of space charge in the composites varies with temperature. In order to know space charge decay rate, space charge in all samples after being pre-stressed for 1800s was measured and it is found that the decay rate increases significantly as temperature increasing.