Research on the Optimization of Grounding Methods and Power Loss Reduction Based on AC 500kV XLPE Submarine Cable Project

Based on the Zhoushan alternating current (AC) 500kV cross-linked polyethylene (XLPE) submarine cable project, a method of metal sheath grounding via a low resistor, a low reactor, or a low resistor in parallel with a reactor at both terminals of the cable to reduce the power loss has been proposed in this paper. By numerically modeling the submarine cable system with the PSCAD/EMTDC software, the voltage and current distributions, and power loss on the sheath, armor and total submarine cable under three types of grounding impedors are calculated. The results show that with the increase of resistance value or inductance value, the sheath current decreases, and the armor current and sheath voltage increase, but the overall loss of the submarine cable decreases. When the submarine cable is operating under normal, short-circuit or transient conditions, in which the sheath voltage does not exceed the critical condition of these allowable values, the way that the sheath is grounded via a low resistor is the most beneficial to the power loss reduction. When the corresponding critical resistance value is 2.1 ohms at the start of cable and 1.3 ohms at the end respectively, it will reduce the power loss of cable for one phase 23.5% and the total power loss including resistors for one phase 14.2%, which is conducive to improving both the safety and operation economy of submarine cable.