Abstract:

The potential distribution near the Yulongling electrode site within 10 km when a grounding line in converter stations sharing a DC common grounding electrode is being maintaining while the other one is under monopolar ground-return mode, has a directly relationship to the maintenance work of Chusui ±800 kV DC transmission engineering and Xingan ±500 kV DC transmission engineering. The potential distribution near the grounding electrode site was researched by using software CDEGS and the research results were compared with the actual measurements during the system debugging. The results show that in the above operating case, the peak distribution occurs above the electrode sites inner ring and outer ring, and the ground potential above the inner ring is higher than that above the outer ring, which decays rapidly. The step voltage peak is also at the rings but less than the design value, and the contact voltage can meet the limit requirement according to the standard measures. The actual measurements and calculated results are basically consistent except that the step voltage value in some area is high due to the low soil resistivity, so the maintenance operation in this area should take appropriate protective measures.

Key words: common grounding electrode, monopolar ground-return mode, ground surface potential distribution, step voltage, contact voltage, line maintenance