摘要
特高压直流系统共用接地极可减少极址占地面积且节省投资,但单极运行时会引起极址大地电位升高,出现跨步电压升高、土壤发热等问题,因此开展直流接地极的相关研究对提高其安全运行具有重要意义。为此,基于COMSOL有限元分析软件,建立了特高压直流输电接地极的电流场和温度场全耦合暂态分析模型,与传统的电热模型相比,该模型能有效反映土壤参数随温度变化的过程。通过某±500 kV共用接地极各种运行工况下地面跨步电压和土壤最高温升的分析计算以及与测量值的比较,验证了该模型的有效性。基于该模型分析了土壤的电阻率、热导率和比热容对接地极运行的影响规律。研究结果表明热导率的变化对土壤温升影响更显著,对于额定入地电流为3 030 A、圆环半径为360 m、埋深为3 m的接地极,当按最大入地电流运行检验该接地极参数时,为满足跨步电压要求,接地极表层土壤电阻率需低于35Ω·m。所提出的模型和研究成果可用于指导高压直流共用接地极的优化设计。
The UHVDC common grounding electrode has the advantages of reducing the covered area of site and saving investment, but it will cause related problems such as increase in step voltage, soil heating and electrode corrosion etc when monopole runs. Therefore, it is of great significance to carry out the related research of the DC grounding electrode for improving its safe operation. We set up a model of fully coupling transient current field and temperature field of DC grounding electrode based on the COMSOL finite element software. The model could effectively reflect the influence process of current filed and temperature field after soil parameters change with temperature. Moreover, the model was ap- plied to analyze and calculate the step voltage and soil highest temperature rise of a ±500 kV common grounding electrode under various operating conditions, proving the effectiveness of the model compared to the measured value. Then the influences of factors, such as soil resistivity, thermal conductivity, and specific heat capacity, on grounding elec- trode parameters were analyzed based on the model. The results show that, with the increase of resistivity, step voltage and the highest soil temperature lineal will increase;with the increase of thermal conductivity and specific heat capacity, the highest temperature approximation will lineally drop; the influence of the thermal conductivity on soil temperature is more significant compared with that of specific heat capacity. For the grounding with 3 030 A rated current, 360 m radius and 3 m depth, in order to meet the requirements of the step voltage, the surface soil resistivity of the earth should be less than 35Ω.m. The research results of this paper can be used to guide the optimization design of HVDC common groun- ding electrode.
出处
《高电压技术》
EI
CAS
CSCD
北大核心
2015年第11期3672-3678,共7页
High Voltage Engineering
基金
国家自然科学基金(51307097)~~
关键词
特高压直流
电流场
温度场
全耦合
暂态
土壤温升
热导率
比热容
UHVDC
current filed
temperature field
fully coupling
transient
soil temperature rise
thermal conductivity
specific heat capacity
