Electric Field Evaluation and Optimization of Connecting Electrodes in Full-Scale Indoor VSC-HVDC Converter Station

In order to evaluate corona-free performance of the key HV connecting electrodes in one ±320kV VSC-HVDC indoor converter station, the equivalent 3-D models of different electrode types for electric field simulation were built with finite-element method (FEM) according to the preliminary designs. Considering the influence of devices nearby, full-scale models of all the indoor parts of the converter station were established as the boundary conditions for electric field calculation, including the indoor arm reactor yard, valve hall and DC yard. The potential and electric field distribution of the full-scale models were calculated. The maximum electric field strength of each connecting electrode was obtained and an optimization design was proposed for the electrodes whose surface field strength exceeded the critical value for evaluation. The results show that the full-scale simulation models of indoor converter station could reflect the difference of electric field distribution of the connecting electrodes with the same shape and various installation positions. For the preliminary electrode designs, serious electric field distortion occurred at the surfaces of some busbar connectors and terminal electrodes under operating condition. After optimization, the maximum field strength could decrease from 43.6kV/cm to 21.5kV/cm and the corona-free performance could be predicted. The optimized design scheme passed the corona tests and the research method could provide references for the development of connecting electrodes design and corona-free performance evaluation for VSC-HVDC or other indoor station.