The role of thermal relaxations and semicrystalline microstructure in charging currents of XLPE

Today’s extruded high-voltage direct-current (HVDC) cable insulation is based on either crosslinked polyethylene (XLPE) or thermoplastic. Although XLPE has a simple chemical structure, its complex semicrystalline microstructure could result in different DC conductivity behavior during thermal cycling. Monitoring the charge mobility as related to microstructure with direct observations could be complex and difficult. However, there are some indirect and facile methods to assess the microstructure, and therefore the correlation between the microstructure and charge transport properties could be easily investigated. This methodology not only provides more insight into the source of different trends for the DC conductivity as a function of time and temperature but also helps with better sample preparation/design and material selection.