Characterization of XLPE cable insulation by dynamic mechanical thermal analyzer (DMTA)

Polymeric insulated cables and accessories are becoming widely used at voltages over 120 kV, even up to 500 kV. Although high electrical stress presents the greatest challenge, some attention should be given to the fact that the polymeric insulation is also subjected to mechanical stress which can affect the electrical performance of the high-voltage cable system. Thus, the mechanical response to an AC stress induced by oscillating electrostatic forces could be an important factor with regard to long-term degradation of polymeric insulation. This paper presents preliminary mechanical relaxation measurements on XLPE and LDPE specimens taken from unaged transmission type cables. Dynamic mechanical relaxation showing radial profiles of the mechanical loss tangent and tensile modulus E' are presented in a temperature range of 40 to 120/spl deg/C.