Cross-linking byproducts are suspected to be the main contributing factor in space charge formation observed in XLPE. To investigate the mechanism behind this phenomenon, low density polyethylene was soaked into three main crosslinking byproducts, acetophenone, -methylstyrene and cumyl alcohol, and space charge measurements were performed using the Pulse Electroacoustic technique (PEA). It has been found that soaking LDPE in cumyl alcohol introduces more charges into the system, with homocharges and heterocharges accumulating within the sample compared to the additive free sample. In contrast, -methylstyrene and acetophenone reduce the amount of accumulated charges. In terms of charge decay, all three byproducts enhance the decay process in the insulator. Further investigations were conducted in conditions where two byproducts are present in a sample. The results shows that acetophenone is a dominant byproduct in determining the charge density patter built up during the charging process, whilst the rate of charge decay is observed to be high in the presence of -methylstyrene in the sample.

Abstract-In this report the pulsed elcetroacoustic (PEA) technique was employed to examine the space charge pattern in acetophenone and alpha-methylstyrene soaked low-density polyethylene (LDPE) samples. The samples were stressed at three different voltages; 5kV, 8kV and 10kV, and the charge patterns in the sample bulk were compared with that obtained from the clean LDPE. These chemicals are observed to assist the transportation of the charges in the sample bulk. Each of these chemicals is in favour of different charge polarity. It seems that acetophenone assists the transportation of negative charges meanwhile the transportation of positive charges is assisted by the alphamethylstyrene. It is proposed that the chemicals provide shallow traps that aid the movement of the charges.

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