Influence of HVDC Grounding Electrode's Ground Current on the Tower Grounding Body of Adjacent Transmission Line

A grounding system of a HVDC transmission system was established, and the interference current flowing through the grounding wire and the tower grounding ray electrodes' absorption or leakage current density of the transmission line adjacent to the HVDC grounding electrode in monopolar mode were analyzed. Ray ends' corrosion depth of each tower grounding body was assessed with a grounding current of 3000 A under different unipolar operating mode conditions. The results showed that when the HVDC grounding electrode was positively discharged, the net current of each tower grounding body within 3 km around the HVDC grounding electrode flowed into the grounding wire, the net current of each tower grounding body out of the 3 km around the HVDC grounding electrode flowed out from the grounding wire. When the HVDC system was negatively discharged, the net currents' flowing direction was reversed; in the range of 12.5 km near the HVDC grounding electrode, the current flowing through the grounding wire changed greatly. When the HVDC system was positively discharged, the rays of each tower closed to the HVDC grounding electrode absorbed current, and the rays away from the HVDC grounding electrode released current, when the HVDC system was negatively discharged, the state of absorbing or releasing current was reversed. When the ray absorbed or releaseed the current, the current density of the ray end was the maximum. The greater the probability of cathode operation, the greater the corrosion depth of the tower grounding body ray end. The range within 10 km of the HVDC grounding electrode was the key protection area.