Time-Dependent Electric Field Distribution during Load Cycle Test for HVDC MI Cable

A pure resistive field distribution in DC steady state is entirely determined by an electrical conductivity of insulating material. However, in the case of transient state such as load cycle test, an influence of both the electrical conductivity and the dielectric permittivity should be essentially considered to obtain an accurate time-dependent field distribution. Therefore, in this paper, in order to evaluate this phenomenon, the characteristics of intermediate field were investigated by performing numerical analysis in load cycle test. In addition, an electric field analysis according to a temperature dependency coefficient was carried out to compare time-varying field distributions. From the result, it is found that the maximum field intensity at cooling cycle was rather higher than heating cycle. It is because both conduction current and polarization current are the significant factors in determination of the intermediate field distribution during load cycle test. It was confirmed that the time point at which the maximum electric field intensity occurred was delayed according to temperature dependence coefficient became smaller.