This paper provides recommendations for the dielectric testing of HVDC GIS cable connection assemblies by comparing the dielectric strength applied as a result of cable system and GIS tests. Multiphysics simulations were performed by OEMs for their designs according to a common modelling and simulation guideline to determine the dielectric strength. A selected set of test scenarios representing the worst-case dielectric strength for the tests described in the cable system and GIS technical brochures each, was considered for simulation and subsequently compared. An open-source HVDC GIS cable connection assembly model was used to determine the uncertainty range by studying the sensitivity of the dielectric strength to various factors such as ambient temperature, test equipment tolerances, the duration and magnitude of DC-prestress, geometries, and material characteristics. The simulation results indicated that the GIS test requirements result in slightly higher stresses than cable system test requirements, but well within the uncertainty range. It was noted that the DC pre-stress duration required by the cable system standards is potentially insufficient to reach the required steady state conditions for impulse testing.
The paper is the result of the work of CIGRE joint working group B1/B3/D1.79 “Dielectric testing recommendations for gas-insulated HVDC cable connection assemblies”. It is a summary of the technical brochure which will be published in 2024. The working group was made up of 19 members representing HVDC cable system, accessory and GIS manufacturers, TSOs, developers, testing laboratories and consultants from Asia, Europe and North America.