In seasonal frozen soil area

the soil resistivity increases rapidly after freezing

which leads to several times of increase in the grounding resistance

and the change of fault current flowing into grounding grid in the condition of short circuit in substation. In this paper

the influence of the depth of frozen soil on the shunt coefficient of the grid is studied. Firstly

a soil structure model of seasonal frozen soil region is established

and the distribution law of short circuit current of substation grounding grid is obtained under different conditions by changing the structure and resistivity of the soil according to its freezing law. The results show that: 1)the grounding electrode depth of tower is smaller than the burial depth of the grounding grid

so the frozen soil has a greater impact on grounding device

resulting in a sharp increase in the shunt coefficient of grounding grid

even more than 50%

and the original design of grounding grid cannot meet the safety standards anymore;2)only adding vertical grounding electrodes to grounding grid will increase its shunt coefficient;and 3)the grounding device of 6-7 tower near the substation is the main factor affecting the shunt coefficient

so adding vertical grounding electrodes to the device and increasing the buried depth can reduce the shunt coefficient of grounding grid

and consequently improve the safety performance of grounding grid in seasonal frozen soil region.