Research on the Earth Grid Design of the Substation with Multi Circuit Transmission Line in High Soil Resistivity Area
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Abstract
By Increasing the maximum allowed earth resistance on safety premise, the high cost of reducing the earth resistance of substations in high soil resistivity area can be effectively controlled. Therefore, this paper analysis the influence of circuit number to the system fault current, split factor and ground fault current, further the maximum allowed earth resistance. It is suggested to use computer simulation instead of simple formula to calculate the split factor, so as to overcome the problem of limitation and deviation of the formula. CDEGS is employed to analysis a 220 kV substation in the southwest of China. The results show that a smaller design value of ground fault current can be obtained when the circuit changes is considered. That is effective to increase the maximum allowed earth resistance and enhance economics.
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