The behavior of water in XLPE and EPR cables and its influence on the electric characteristics of insulation

This paper presen?s the latest resdts of con!inuous investigations of cable insulations degradation of crosslinked polyethylene (.XLPE) and ethylene-propylene with rubber based fomulation IEPR) when subjected to electric stress and heating in the presence of water or water vapour (this work is part 2, part I is (I}). The paper deals with water absorption and diffusion in two kinds of crosslinked polyethylene insulations - drycured arid stem-cured, and stem:-cured EPR insulation. The aim of this invedgation Is to present the resxlts of the influetice of chariging of water or water vapour pressure in the conductors of XPE and EPR cables in different service conditions on the electric clhasacteristics of ,=PE and EPR insulations - breakdown voltage {AC BDʹC7), dissipation factor (tri,&$) and rata of partial discharge (RPD). In this paper, RPD is defined as, the max. electrical fjeld ~7henth e beginning parrial discharge in the cable insulation and partial discharge were mea.sured in acc. to IEC standard, This paper also shows the relation between AC BDV aid water contentt: and AC BDV arid trig8 in 2YLPE and EPR insulations. In this testing, tlie tap water was put in the cable conductors and the ends were properly closed by tentiitial boxes (1). The re,sults Indicate that the combined affects of water cx water vapour, pressure, moisture, electric field and temperature will greatly accelerate deterioration of XLPE and EPR insulations.