Impact of mechanical deformation on space charge in XLPE

In this paper we report the effect of mechanical deformation on space charge dynamics in crosslinked polyethylene. Thin films were peeled from a 66 kV commercial XLPE cable. Space charge measurements under dc electric fields have been monitored using the pulsed electroacoustic (PEA) technique. It has been found that charge dynamics in deformed XLPE are different from that from undeformed XLPE at lower voltages. At low applied electric field, space charge is dominated by heterocharge in the deformed XLPE while homocharge governs charge formation in undeformed XLPE. However, at high electric field, there is no significant difference between them. Space charge is dominated by homocharge in both deformed and undeformed XLPE. The results indicated that through deformation, molecular chains rearrange so small molecules such as crosslinking by-products, initially being trapped, can be released. Under the influence of the applied electric field they can be ionised to form heterocharge in the sample.