Fast Track Transformer Delivery to the largest hydro power station in New Zealand

1 March, 2015

WTC has recently supplied three 135MVA 220/13.8kV transformers to Manapouri Power Station, the largest hydro station in New Zealand. Two WTC units have replaced the faulty transformers plus one additional unit will be used as the station spare transformer.

Meridian Energy made a decision to replace the transformers after finding a fault within the cooling fins. In February 2014 during the HV bushing replacement, aluminium particles were found on the tank side of the HV bushings. An investigation found the source of aluminium to be the cooling fins in the heat exchanger (transformer oil cooler) – the aluminium cooling fins surrounding the copper cooling tubes had dislodged, fractured and fretted. This resulted in aluminium particles being distributed throughout the transformer. Such contamination introduced an operating risk in the underground Manapouri power house. A complete inspection of all in-service units resulted in the removal of two of the seven 135MVA transformers from service on the basis of the high levels of contamination discovered during inspection. This resulted in lost generation capacity at Manapouri power station.

Meridian Energy nominated to procure two replacement units plus one additional unit to replace the station spare.  Wilson Transformer Company had been awarded a contract to manufacture, deliver and supervise the installation of these three transformers. This project was crucial for both Meridian Energy and WTC due to the urgency of the work, technical challenges and transport constraints. Wilson Transformer Company guaranteed a fast track delivery, with the first unit being delivered in December 2014, and the other two in February 2015.