OPTIMAL PROGRAMS TO REDUCE THE RESISTANCE OF GROUNDING SYSTEMS

In this paper, some optimal programs have been proposed through the analyses of transient grounding resistance (TGR) to reduce the grounding resistance using the flnite-difierence time-domain method. First, the TGR of various electrode types, lengths and sectional programs is studied, and it is found that a ∞at bar is the most flnancially e-cient conductor to be used as grounding electrode. Enlarging grounding electrode length can reduce grounding resistance when it is shorter than the efiective length, but the reduction efiect declines as the length increases. Additionally, a series of small electrodes would lead to a much lower resistance than a single large one. Second, it is demonstrated that locally improving the soil near the grounding system is an e-cient way of reducing the grounding resistance. Improving a limited area soil surrounding the lifting line would reduce the peak resistance signiflcantly, while local enlarging electrodes surrounded soil conductivity can reduce the grounding system steady resistance obviously.