Study On Grounding Characteristics And Application Of Deep Well DC Grounding Electrode Considering Soil Electrothermal Coupling

With the maturity of HVDC transmission technology,in order to reduce the operating cost of the ground electrode and improve the utilization efficiency of the ground electrode,a common ground electrode technology has emerged in recent years,so higher requirements have been placed on the choice of the ground electrode pole;deep well The grounding technology has the advantages of small footprint and low pole site requirements.It has great advantages in areas with tight land resources,but the deep well grounding end effect is obvious,and the temperature rise problem is serious,which restricts its development,so it is necessary.Accurate analysis of the factors affecting the temperature rise of the deep-well grounding electrode provides a theoretical reference for the design of deep-well DC grounding.In this paper,the numerical algorithm of deep well DC ground electrode considering the electric and thermal coupling of soil is established.The dynamic change of soil electrical and thermal parameters with temperature is introduced into the calculation process of current field and temperature field.At the same time,the method of "thin shell theory" is adopted to solve The problem of singularity is analyzed;first,the effect of soil thermal parameters on the maximum temperature rise of the ground electrode is studied,and then the structural parameters of a single ground electrode and the different layout types of multiple electrodes in parallel on the temperature rise and ground characteristics of the deep well ground electrode are calculated.The results show that the thermal conductivity has a more obvious effect on the maximum temperature rise of the ground electrode;increasing the length of the ground electrode and the coke cross-section can reduce the current density of the electrode,and the cooling effect is very obvious;when the soil resistivity is large,it is found that with the commissioning The length of the grounding resistance and the surface potential are no longer fixed,and the temperature rise is higher;increasing the burial depth reduces the surface heat dissipation at the first end,the temperature rise slightly increases,and the choice of burial depth is more affected by the horizontal layering structure of the soil;With the increase of the number of injection points,the number of segments,the length of the number of segments,and the number of parallel ground electrodes,the maximum temperature of the ground electrode when running for 180 days There is a certain decrease in the rise,and the increase in the number of injection points reduces the accumulation of current at the end,and the temperature rise is significantly improved;the increase in the number of parallel roots increases the maximum operating time of the ground electrode;finally,considering the complex soil structure The influence of the temperature rise of mountains,oceans and lakes was calculated,and the results showed that the temperature rise of mountains and oceans changed significantly with the distance from the ground electrode.The temperature rise of the lake was almost unchanged due to the small area;considering the grounding The influence of the pole on the underground metal pipeline is analyzed,and the change rule of the minimum protective distance of the metal pipeline under the horizontal layered soil structure is analyzed.The results show that the influence of the first and second layers of soil resistivity on the minimum protective distance is related to the thickness of the upper soil.The greater the thickness of the soil layer,the more obvious the effect of the change in resistivity on it;the effect of the upper soil thickness on the metal protection distance is related to the ratio of the soil resistivity.The larger the ratio,the greater the minimum protection distance that the upper soil thickness increases The greater the impact;finally,the temperature rise simulation software was built through the Comsol Multiphysics software platform,grounded according to the actual Based on the soil structure of the pole site,the influence of different schemes on the temperature rise of the ground electrode is analyzed.