Research and Experiment Verification of the Shielding Effect of a 1000 kV Equipotential Shielding Capacitor Voltage Transformer in Consideration of Surface Leakage Current

The non-uniform distribution of the surface contamination on insulation bushings of a traditional capacitor voltage transformer (Tra-CVT) will impact the electric potential distribution along the axis of the capacitor voltage divider (CVD), and causes variation of voltage dividing ratio of the CVT. An increased phase angel difference between primary and secondary voltage will be another consequence. The equipotential shielding CVT (EPS-CVT), with its unique double layer structure, is able to significantly reduce the additional measurement error (AME) caused by surface leakage current (SLC) flowing on the bushing surface. In this work the AME caused by SLC for both types of CVTs are evaluated by an implementation of newly developed equivalent simulation circuit models of both CVTs accounting SLC. A shielding effect evaluation test method is proposed and successfully demonstrated on an UHV EPS-CVT prototype to verify the effectiveness of the AME shielding function of an EPS-CVT.