Influence of Repeated Electric-Stress Application on Space-Charge Profiles and Time-Dependent Currents in Silicone Rubber

Space-charge measurements are an important tool when evaluating HVDC cable-system insulation materials. The results can be used to feed numerical models and to evaluate the suitability of specific compounds. When determining the space-charge characteristics, operational conditions must be considered to correctly evaluate the effect of space charges on electric-field distribution and thus on the reliability of HVDC cable systems in service. Here, the effect of multiple electrical-stress application on space charges and time-dependent currents in different siliconerubber compounds is investigated and evaluated. Space-charge profiles and time-dependent currents reveal a clear “memory effect”. It is found that the effects are not influenced by relaxation periods between consecutive electric-stress applications.