Method of Non-contacted Electric Field Measurement on HV Generator Stator Bar Based SiC Grading Coating Electroluminescence

In order to study the performances of electric field (or electric potential gradient) distribution along the stator end-winding stress grading system of the high voltage (HV) machines, a newly setup was firstly designed to measure the electroluminescent performances of silicon carbide (SiC) based stress grading coating (SGT) normally used in HV electric machine in this paper. Two kinds of test specimens were prepared, which consisted of simulated stator bars and standard correcting bars. The simulated stator bar was made to simulate the end-winding insulation system of actual large generator stator bar, and the standard correcting bar was used to obtain the relationship between the electroluminescent performance and electric stress on SiC grading coating or tape as a correcting reference. The fitting curve between the electroluminescent intensity per unit length (or area) of each SGT with the applied voltage gradient was measured by using a photomultiplier (PMT) probe (or sensor). Under the applied AC voltage, the non-contact scanning measurements of electroluminescent intensities along the SGT of simulated stator bar were carried out. This newly proposed non-contact method of electric field measurement in paper should be adequate to optimize end-winding stress grading system of the HV machines.