高压直流接地极入地电流对临近输电线路杆塔接地体的干扰

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

建立了高压直流输电系统的接地系统,计算了高压直流接地极单极运行对流经邻近输电线路避雷线的干扰电流以及杆塔接地体射线(电极)吸收或释放的电流密度;评估了不同单极运行模式下,入地电流为3 000A时杆塔接地体射线末端的腐蚀深度。结果表明:接地极阳极放电,靠近接地极3km区域内的避雷线吸收杆塔接地体的净电流,阴极运行情况下则反之;接地极附近12.5km的范围内避雷线的电流变化较大。阳极运行时,杆塔上靠近直流接地极的射线吸收电流,远离的射线释放电流,阴极运行情况下则反之;射线末端的电流密度最大。阴极运行的概率越大,杆塔射线末端的腐蚀深度就越大,靠近接地极的10km范围内射线末端均是重点防护区域。

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.