Impala Canada – 310 Substation Transformer Tap Changer Repairs and Testing

Project Summary

Our team executed detailed servicing and testing of a 120 kV power transformer to restore operational integrity and ensure long-term reliability. This involved proper transformer oil handling, damaged component replacement, moisture mitigation, and comprehensive electrical testing to confirm tap changer functionality and overall transformer health. The scope of work included:

• Drained oil from the 120 kV transformer tap changer compartment and stored it in clean, sealed totes.
• Drained the transformer main tank into a designated oil tanker and filled the transformer air space with extra dry air to prevent moisture ingress.
• Removed the main tank tap changer connection access cover access cover and disconnected the tap changer leads at the rear of the epoxy mouldings.
• Replaced the damaged center-phase tap changer epoxy moulding.
• Reconnected all tap changer connections and reinstalled all access plate covers.
• Conducted a pressure test using extra dry air to verify the integrity of all sealed compartments.
• Performed transformer turns ratio (TTR) testing across all high-voltage winding tap positions to confirm the integrity of internal connections and operation of the tap changer.
• Executed a 24-hour vacuum hold on the main tank and tap changer compartment to remove residual moisture.
• Carried out oil degasification on the previously removed transformer oil
• Refilled the transformer with the processed oil after achieving and holding a vacuum level below 1 mmHg for 24 hours.
• Completed comprehensive post-filling transformer testing to confirm readiness for return to service.