Experimental Study On Surface Charge Distribution Of Insulating Dielectric Under The HVDC Test Wire

The economic development and resource distribution is not balanced in China. The development of High Voltage Direct Current (HVDC) system can help to optimize the supply and configuration of energy. And many HVDC projects have been built in latest several years in China. With the rapid construction of HVDC transmission projects, more and more HVDC transmission lines may pass over the farmland with greenhouses. However, the total electric field of the ground when the presence of greenhouses is seldom studied. It is urgent to study the influence of the dielectric surface charges to the total electric field when the greenhouse models exist underneath the transmission lines, and provide a reference for practical engineering.Due to the greenhouse film has good insulation, compared with the condition of the buildings and human under the transmission line, the boundary condition is more complex, and now the electric field near the insulating dielectric can not be predicted accurately. This paper pays close attention to the accumulation of the charges on the dielectric surface and the influence of the surface charges to the total electric field when the greenhouse models exist underneath the DC test wire. A set of single conductor experiments are performed in the laboratory, and the Faraday cage method is used to measure the insulating dielectric surface charge. Through the qualitative analysis and discussion of the experimental results, the distribution of surface charge on the plastic film at different voltages and different positions is obtained. The accumulation and dissipation characteristics of the plastic film, shade net and fabric are also compared. On this basis, the paper analyzes the relationship between the surface charge density on the three dielectrics and the ground-level electric field strength.Through a lot of experiments, the paper not only analyzes the distribution characteristics of the dielectric surface charge, but also gets the relationship between dielectric surface charge and the electric field of ground level. Conclusions of this paper lay the foundation for the experimental study on the real HVDC transmission lines.