Investigation of an HVDC Submarine Cable Fast Discharge Strategy Based on Electric and Thermal Field Analysis

High-voltage direct current (HVDC) submarine cables should be discharged to efficiently reduce the cable voltage after the withstand voltage test in the substation. This article proposes a fast discharge optimization strategy to minimize the time duration from the test voltage to the ground voltage. The discharge process is under the constraints of the maximum power and thermal duration of the resistors and can be divided into two stages. The first stage is the process when the discharge device moves close to the cable terminal before the physical connection. The device structure is optimized to reduce the arc length around the cable terminal. The second stage optimizes the resistor bridging process after the connection to accelerate the discharge process. Compared to the traditional constant resistance discharge method, the proposed structure of the discharge resistors shortens the average arc length by 36.2%, and the discharge time is reduced from 31.5 to 13.2 min. The optimized strategy reduces the potential threat of the arc to the equipment in the substation and the probability of cable damage due to overvoltage.