To improve accuracy of fault diagnosis of substation grounding grid

we have designed and customized a random form grounding grid model of a 35 k V substation based on dimensional similarity principle. According to the calculation results of the surface potential and magnetic induction intensity of the grounding grid

the test results of typical faults diagnosis of grounding grid based on surface potential and magnetic induction intensity are compared by simulating typical faults. The change rules of surface potential and magnetic induction intensity when grounding grid has typical faults are also summarized. A judging rule of grounding grid state is proposed based on the grey relational degree theory according to the change rules. The results show that the surface potential of conductors’ nodes is higher

and the surface potential of mesh is lower. The magnetic induction intensity is larger

and the magnetic induction intensity of the current injection point is the largest. The proposed judging rule can be used to diagnose the grounding grid’s fault type and location accurately.