6Jiansheng Yuan,Huina Yang,Liping Zhang.Simulation of sub- station grounding grids with unequal-potential[Jl.IEEE Trans on Magn ,2000,36(4) : 1468-1471.
7L Huang.Study of unequally spaced grounding grids [J]. IEEE Transaction on Power Delivery, 1995,10(2) :716-722.