Abstract
When designing earthing，its earthing resistance which is an index of the rise electric potentia1 must be known. The accurate analytic of solution of the earthing resistance excepted for the electrode of the special form such as a rotating ellipsoid electrode can not obtained. There are method of earthing simulation such as the water tank method or Laplace numerical analysis equation method (for example，the Finite Element Method)used to estimate the earthing resistance of any shaped earthing electrode without analytic answer. The calculating equation of earthing resistance for hemisphere electrode can divide three factors，earth resistivity，electrode size，coefficient of 1/2π. 1/2πis a coefficient specific to a shape of hemisphere electrode. The author named this coefficient shape factor. The earthing resistance of any shaped earthing electrode can be defined utilizing shape factor (K)，earth resistivity(ρ) and typical electrode size (L) as fo11ows.R＝Kρ／LThis paper discusses the shape factor method which focuses on the any shape of the earthing electrode to calculate the earthing resistance.
