Influence of temperature and frequency on leakage current of XLPE cable insulation

Crosslinked polyethylene (XLPE) with outstanding high temperature performance and electrical properties has been widely used as cable insulation. Leakage current of cable is the inevitable product in the process of electric energy transmission, and the gathering of leakage current is easy to cause gas combustion, explosion of the cap and other accidents. To understand the influence of temperature and frequency on the leakage current of cable, Novcontrol Broadband Dielectric Spectroscopy measurement system has been used to measure the dielectric spectroscope of XLPE samples in the temperature range from 20 °C to 200 °C and frequency range from 10
^-2
Hz to 10
⁵
Hz. In the experiments, the dependency of permittivity, conductivity and electric modulus on frequency and temperature has been conducted. By observing the dielectric spectrum, some variation rules of parameters could be found, for example, the real part of complex permittivity decrease repidly and dissipation factor decrease slowly with increasing frequency at higher temperature. The AC conductivity follows the Jonscher power law, which DC conductance region follows the Arrhenius rule. The dielectric dispersion phenomena can be also observed on the spectroscope of the electric modulus as well, the dielectric loss peak move to the higher frequency area with the increase of temperature. Finally, the mechanism and process of XLPE relaxation polarization were discussed, the contribution of relaxation polarization to leakage current and the generation of leakage current was explained. The results show that the leakage current of XLPE cable has a strong dependence on the temperature and frequency.