A New Method for Surface Charge Measurement of HVDC GIL: Ring-Shaped Multipoint Potential Method

In this article, a new method for surface charge measurement of the dc GIL insulator is proposed, that is, the ring-shaped multipoint potential (RMP) method. The basic principle of the RMP method is introduced in detail. Meanwhile, a corresponding experimental platform is built, and the surface charge distribution results obtained by the RMP method are compared with those obtained by the traditional multipoint measurement (TMM) method. The results show that for the ring-shaped measuring points’ set in this article, the RMP method can detect the surface charge accumulation on about 1/3 area of the insulator surface, and the surface charge density value obtained by the RMP method is approximately equal to the sum of the surface charge density contribution value on the subelement in this region (which is equal to the surface charge density multiplied by the contribution coefficient ratio). In addition, the square root of peak mean square error (PMSE) for the RMP method performed best at 24 measuring points, with a mean error of 11.7%. This study can provide a reference for the surface charge measurement technology of dc GIL insulators.