HVDC cables and cable accessories play a fundamental role within the spreading of the HVDC transmission technologies. Depending on the transmission topology of the HVDC network, the overvoltage during fault can have different shapes and amplitudes, including oscillating polarity reversal (OPR) and temporary overvoltages (TOV). Due to the reversed polarity and space charge accumulation inside insulating materials the electric field can significantly increase and might lead to failure of the insulation. The knowledge of the electric field under those type of stresses is thus mandatory to ensure a reliable design. Time dependent simulations are essential to determine the electric field distribution and they became more complicated in the case of OPR and superimposed impulse voltage (S/IMP). The aim of this paper is to propose a time decoupled simulation method to compute the electric field in case of OPR and S/IMP without losing in result accuracy. The proposed simulation method, applied in a fluid-filled cable/Gas Insulated Switchgear (GIS) termination, shows that OPR can be very critical for this accessory and might not be covered by standard tests. The results show that, due to space and surface charges accumulation, the maximum stress could occur after the first peak of the OPR.
Caterine Toigo, T. Vu, F. Jacquier, A. Girodet
Presented at ISH2021