Analysis Of Ground Surface Potential Distribution Under Single-Pole Operation Mode Of HVDC Transmission Lines

The HVDC transmission system operates in bipole mode under normal conditions, The DC current is transmitted between the two poles on both sides.But it will operate in ground- between return status with single or both poles, when the system is in debug or if some failure occurs. On such occasions, if the ground return current of the HVDC system is large enough, it will cause the rise of the ground surface potential.Such change may have negative effects on AC power systems, so it is nessesary to study the influence of the single-pole ground-return mode operation of HVDC transmission lines. Firstly, it needs to compute the distribution of such surface potential. The image method and Laplace method are efficient for the analysis of the distribution of such surface potential.This paper illustrates the application of those methods in various soil structures and programmed the calculation with MATLAB. For the complicated electrodes and soil structures, case studies are carried out by employing the worldwide popular software CDEGS. Its functions include EMC computation, grounding analysis and so on. The MALZ module is mainly used for the computation of the grounding resistance, the ground potential rise, the ground potential distribution, touch voltage and step voltage, etc.This paper establishes the soil resistivity model of East China according to the field measurement and the related information in historical record. It also takes into account such factors as soil structure, lakes, rivers, oceans and pipes, which have some influence on the distributin of the ground potential distributions. Based on the above analysis, the characteristics of the ground surface potential distribution under DC single-pole operation mode is summarized.