Tests and Simulation Research on Control Value of Electric Field Intensity for Valve Hall Fittings

Abstract

The design limit of surface electric field intensity of valve hall fittings is the key technical index to prevent the corona discharge of fittings during operation. This index can be obtained by the correction of the corona electric field intensity of the fittings. However, the corona electric field intensity cannot be measured directly and accurately by experiment. At present, corona test combined with finite element electric field calculation is an effective method. Corona experiments of glossy spherical electrodes with different diameters were carried out in this paper, and the dc corona voltage of 33-1000mm diameter spherical electrode samples was obtained. The finite element model for calculating the electric field intensity of spherical electrode was built, and the curves of the corona electric field corresponding to the corona inception voltage of the spherical electrodes with different diameters are obtained. Through discussion, two misunderstandings in the industry on using Peek’s law and using 3000V/mm as the corona inception criterion are clarified. In addition, the control value of electric field intensity of valve hall fittings with a certain engineering margin is proposed, that is, for fittings with an equivalent diameter of less than 200mm, the control value of electric field intensity is 2000V/mm, and for fittings with an equivalent diameter of more than 200mm, the control value of electric field intensity is 1200V/mm. The proposed control value of electric field intensity have been widely used in HVDC projects’ fitting design in China.