Simulation Test Of Soil Resistivity In Frozen Soil Area And Study On Safety Of Grounding System

China is the third largest permafrost country in the world,and the permafrost area accounts for more than half of the national area.The safety problems brought by permafrost to the normal operation of substations can’t be ignored.Affected by freezing,the resistivity of soil increases obviously.Higher soil resistivity leads to higher grounding resistance.When current enters the ground,it will cause higher ground potential rise,and at the same time,the contact voltage and step voltage exceed the safety limit standard,resulting in equipment damage and even endangering personal safety.Therefore,it is necessary to study the resistivity change of frozen soil and its influence on substation grounding system,so as to further ensure the normal operation of substation and the safety of staff.Firstly,the soil structure model is established,the conductive principle of soil and the influence of water content on soil conductive ability are studied,the conductive models of different conductive modes are proposed,and the corresponding soil resistance is calculated.At the same time,the concept of soil resistivity is introduced,and the influencing factors of soil resistivity are analyzed.Then,this paper designs the frozen soil simulation test of soil res istivity affected by freezing in frozen soil area,analyzes the principle and characteristics of different soil resistivity measurement methods,and chooses the best laboratory measurement method.A test platform was set up,and the change law of soil resistivity of samples with different soil quality and water content during freezing was measured and analyzed.Finally,the grounding grid model of substation in permafrost region is established by CDEGS software,and the influence of permafrost depth on grounding resistance,contact voltage and step voltage is simulated and calculated.The influence of permafrost on safety limit of grounding parameters is analyzed,and the resistance reduction mode suitable for substation is put forward.The research content of this paper can provide the corresponding basis for the design of substation grounding system in frozen soil area,and is of great significance to ensure the safe operation of substation.