North Island users tap into emergency power supply

A Canterbury bushfire forced North Island electricity users to be switched to supplies from a station built to help out in a dry-year power crisis.

Smoke from a fire in Balmoral Forest, North Canterbury, caused the high-voltage, direct current (HVDC) line to short-circuit, cutting the supply of cheap hydro electricity to North Island consumers.

A spokesman for Transpower, which runs the national power grid, said the link was cut for more than four hours on Sunday afternoon, prompting the dry-year reserve station at Whirinaki in the Hawkes Bay to be used.

Power was restored without any damage to the grid.

The Whirinaki station opened last year and is designed to provide generation back-up when lake levels in the South Island fall dangerously low. It is only the second time it has been used to plug an emergency gap in power supply.

Contact Energy, which runs the station, built it on behalf of the Government at a cost of about $150 million.

The 155MW plant can also be turned on in case of generation or transmission breakdowns.

Whirinaki has three oil-fired turbines which can be started quickly to fill any supply gap caused by emergency shutdowns.

Other thermal power stations, that use cheaper gas or coal as fuel often take a while to come into full production, giving the Whirinaki plant an advantage in emergencies.

The HVDC line line runs from the Benmore dam to Wellington, running along the Cook Strait sea bed. It is designed to carry the cheap hydro electricity from the South Island to the North Island.

It can also carry electricity the other way and during recent dry years was used to supply the South Island with power generated in the North Island.