Ohau A, and B power stations are the uppermost Meridian assets on the Waitaki river chain and are fed via canals from lakes Pukaki and Ohau.

The stations were commissioned across the 1980s and each contain four generating units.

Various electrical systems have reached end of life and are required to be upgraded to address performance and obsolescence issues and meet Electricity Industry Participation Code compliance requirements, including the 220kV Circuit Breakers located at Ohau A & B.

Both Ohau A and B Power Stations consists of four 61 MVA hydro-generator units. The generation is stepped up to 220 kV and exported via four 220 kV circuits at respective switchyards at each power station. This switchyard is shared with Transpower.

Meridian owns eight, three-pole, SF6, live tank, 220 kV circuit breakers (CBs) across the two switchyards.

The existing CBs are approaching 50 years old and are nearing end of life. All eight CBs are to be replaced with new units.

Meridian is seeking a reliable SF6 breaker, however, please advise if there is suitable SF6-free technology that could also be considered.