接地网形式对近水源区杆塔接地网外延降阻影响

Influence of Grounding Grid on Extension Resistance Reduction of Tower Grounding Grid near Water Source Area

为研究雷击电力杆塔时杆塔接地网降低接地电阻的效果,建立近水源平原和山区的单桩塔接地网和四桩塔接地网模型,计算不同土壤电阻率、电流频率下接地网形式对近水源区杆塔接地电阻的影响,并对比分析平原和山区地势条件下杆塔接地网形式的最优方案。仿真结果表明:接地网的接地电阻随着土壤电阻率和电流频率增大而升高。对于近水源的平原地区,单桩塔“米”字型接地网在单桩塔中降阻效果最显著,以单边外延接地网为比较基准,在工频和高频条件下的平均降阻效率分别为64.49%和76.15%;四桩塔方框带射线和垂直接地极型接地网在四桩塔中降阻效果最显著,以方框型接地网为比较基准,平均降阻效率在工频和高频条件下分别为56.99%和44.68%。对于近水源的山坡地区,单桩塔“米”字型接地网降阻效果在单桩塔中最显著,以单边外延为比较基准,在工频和高频条件下的平均降阻效率分别为48.11%和55.93%。四桩塔方框带射线型接地网、方框带射线和垂直接地极型接地网、方框射线末端带垂直接地极型接地网降阻效果差距不明显,以方框型接地网为比较基准,在工频条件下和高频条件下平均降阻效率分别为64%左右和71%左右。

In order to study the effect of tower grounding grid on reducing grounding resistance when lightning strikes power towers,single pile tower grounding grid and four-pile tower grounding grid models are built near water source plain and mountainous areas,and study the influence of grounding grid shape on grounding resistance under the conditions of different soil resistivity,current frequency,terrain and other influencing factors.The selection scheme of grounding grid form under different terrain conditions is put forward.The results show that the increase of soil resistivity and current frequency will lead to the increase of grounding resistance of grounding grid.For the plain area near the water source,the single-pile tower"star"-shaped grounding grid has the most significant resistance reduction effect in the single-pile tower.Taking the unilateral extension grounding grid as a comparison benchmark,the average resistance-reduction efficiency under power frequency and high frequency conditions is 64.49%and 76.15%respectively;the four-pile tower quadrilateral grounding grid with ray and vertical grounding electrode has the most significant resistance reduction effect in the four-pile tower;and taking the quadrilateral grounding grid as a comparison benchmark,the average resistance reduction efficiency is 56.99%and 44.68%under power frequency and high frequency conditions respectively.For the hillside area near the water source,the resistance reduction effect of the single-pile tower"star"-shaped grounding grid is the most significant among the single-pile towers;and taking the unilateral extension grounding grid as a comparison benchmark,the average resistance reduction efficiency under power frequency and high frequency conditions is 48.11%and 55.93%respectively.There is no obvious difference in resistance-reducing effect between the four-pile tower quadrilateral grounding grid with ray,the quadrilateral grounding grid with ray and vertical grounding electrode and the quadrilateral grounding grid with vertical grounding electrode at the end of ray.Taking the unilateral extension grounding grid as a comparison benchmark,the average resistance reduction efficiency under power frequency conditions and high frequency is about 64%and 71%respectively.