Research on the Scheme of Shared Grounding Electrode for Four-Circuit HVDC System

  Introduction  To address the difficulty in selecting the grounding electrode location, a shared grounding electrode scheme is adopted. The shared grounding electrode can be transformed from an independent grounding electrode. It is relatively uncommon for a four-circuit DC system to share a grounding electrode, so its sharing scheme needs to be carefully studied.

  Method  Based on the actual project and the existing situation of independent grounding electrodes, three schemes of grounding electrode sharing at the electrode location were proposed. Through simulation, the step voltage and current distribution of vertical grounding electrodes and deep well grounding electrodes were studied.

  Result  When multiple grounding electrodes operate simultaneously, due to the shielding effect between conductors, their electrical characteristics differ from those of independent operation. When operating with the same polarity, regardless of whether it is a vertical grounding electrode or a deep well grounding electrode, the step potential increases compared to when it operates independently, and the electrode current distribution is more uneven.

  Conclusion  Under the three feasible schemes, the step voltage does not exceed the limit value, but the step voltage is the smallest under scheme I, and there is no significant difference in the current distribution of the vertical grounding electrode.