Study on electric field distribution along V-string composite insulator in compact transmission line
Ruichen Zhang, Liming Wang, and Fanghui Yin
Shenzhen International Graduate School
Tsinghua University
AndyYinEE@gmail.com
Purpose/Aim
Electric field distribution may be worse on the compact transmission line than the traditional transmission line because of reduced air gap. Strong electric field strength may cause partial discharge, audible noise, and premature degradation of insulating materials especially under harsh environmental circumstances. Therefore, it is necessary to simulate and analyze the electric field distribution along V-string composite insulator in compact transmission line. In this paper, the influence of sheds, tower, conductor, inclined angles, string structure, grading ring on the electric field distribution are taken into consideration, respectively. The results of this paper can provide a reference for the numerical calculation and design of compact transmission lines.
Experimental/Modeling methods
In this paper, a full-scale 3D modelling of 500kV AC compact transmission line is built. The finite element simulation method and software are used. In the model, the dielectric constant of air, silicone rubber, and fibre reinforced plastic core are 1, 4.3, and 6.5, respectively. The air domain of 50m*50m*50m is used for calculation.
Results/discussion
According to the simulation results, the trend of electric field distribution curve along the composite insulator is consistent with the existing theory. If considering the tower and sheds, the maximum value of electric field strength will increase by over 20%. However, the presence of conductor can decrease the maximum electric field strength by 15%. Moreover, the inclined angle of V-string, single or double strings have a weak influence, and the difference of electric field values is within 10%. After replacing the conventional corona ring with optimized corona ring designed in this paper, the maximum electric field value decreases from 5.5 kV_p/cm to 4.1 kV_p/cm.
Conclusions
If high accuracy is required, the tower, conductor, and sheds should not be ignored in the calculation of electric field along the string. However, the influence of inclined angle of V-string, single or double string on electric field distribution is insignificant. To improve the electric field distribution along the string, optimized corona ring is designed and the maximum can be reduced by 25%.
 

insulator,electric field distribution,transmission line