Development of Nonlinear Field Grading Material for Controlling Electric Field in DC Connectors

In HVDC cable system, DC connectors e.g. joints and terminations are critical and vulnerable components. This is because of the non-uniform electric field distribution in DC connectors which can enhance the electric field at triple points and lead to degradation and failure in the long time. As a result, for a reliable HVDC cable system, accurate design of the DC connectors plays a vital role. To improve the uniformity of field distribution under all operating conditions especially at the interface of connector and cable insulation, nonlinear field grading material (NLFGM) stems as a viable solution. This study focuses on the development and test of SiR/SiC as NFLGM material for electric field grading in DC cable connectors. To investigate the performance of developed material, an electro-thermal model for 80kV DC cable joint under different thermal gradient conditions was used. The electric field distribution in the joint and across the interface of cable insulation and SiR as the joint insulation with and without NLFGM were simulated. The results show significant change in distribution of electric potential and decrease in amplitude of electric field in presence of NLFGM.