Partial Discharge Monitoring of Single-Phase Shell-Type 500 KV GSU Transformers in Salto Grande Hydro Power Plant

Abstract

In this paper, the challenges in the condition assessment of bushing and winding insulation in single-phase shell type 500 kV, 100 MVA GSU transformers in Salto Grande Hydropower Plant are described. Since after some years of service, dissolved gas analysis recorded elevated levels of hydrogen and methane within several transformer units, measurements of partial discharge (PD) activity were introduced. It was determined that PD measurements using the conventional method at the bushing taps alone was not sensitive enough because of high external noise, so PD measurements using the ultra-high frequency method were additionally proposed for the new, recently commissioned transformer units. The advantages provided by both methods were combined into one PD monitoring system to better identify and localize the source of PD. This modern PD monitoring system employs advanced techniques of multi-channel PD source and noise separation. The modular design and user-friendly management of the system are also described.