Bushing CT-Based Monitoring of Internal Discharge in an UHV Shunt Reactor

Partial discharge (PD) monitoring is critical for ensuring the safe and stable operation of transformers and shunt reactors. Developing a non-invasive PD monitoring method applicable to both offline and online scenarios can significantly enhance operational safety. Conventional bushing current transformers (BCTs), primarily designed for power-frequency current measurement, exhibit topological similarities to Rogowski coils commonly used for high-frequency current sensing. The authors have verified their high-frequency current sensing capability. Diagnostic PD test data from an ultra-high-voltage shunt reactor (returned to the factory due to acetylene generation) at an ultra high voltage(UHV)substation demonstrate that bushing CTs exhibit consistent variation trends with conventional high-frequency current transformers (HFCTs) installed at the core and clamping structures. The correlation coefficient R 2 between the two exceeds 0.89, with matching phase-resolved partial discharge (PRPD) patterns and comparable signal-to-noise ratios to HFCTs. These findings validate the feasibility and advantages of utilizing BCTs for online PD monitoring in transformers and shunt reactors.