Transpower fears even bigger blackout for city

By energy reporter, James Gardiner

A bigger disaster than last summer's power crisis hangs over electricity supplies to all of Auckland and Northland.

A single event hitting the national grid between Huntly and Otahuhu, such as a plane crash or earthquake, would black out all areas north of that line, according to the national grid company, Transpower.

The chief executive, Bob Thomson, said yesterday that either a big power station must be built north of the Auckland Harbour Bridge or the national grid high-voltage power lines would have to be partly duplicated through the Auckland isthmus.

He said Transpower, Mercury Energy, Power NZ, Northpower and Top Energy had already begun planning how and when to upgrade the system.

Based on projected load growth, the new lines or new power station would be needed within about five years.

Asked who wanted to build a power station now, he said: "No one."

The Auckland City Council raised its fears for future security of supply in submissions to the power crisis inquiry that reported this week. It said the city's power supply was too reliant on the one sub-station, Transpower's facility at Penrose.

The inquiry, in its findings on network distribution planning, said it was "critical" that a struggle for control of the isthmus transmission not become a barrier to necessary reinforcement.

Mr Thomson yesterday acknowledged the potential weakness as demand grows for electricity north of Penrose.

The Deputy Mayor of Auckland, David Hay, agreed that the supply security issues went beyond Mercury's network. He promised full council support for every effort Mercury made to improve its supply lines to the central city.

Further detail is expected soon on Mercury's new $20 million 110kV cable planned to run between the Mt Roskill substation and the city. A cable buried under Sandringham Rd is tipped.
Mr Hay said the council would seek guarantees of supply from Mercury.

The Government has also asked Mercury for a written assurance within a fortnight that it will implement the inquiry recommendations. These include having enough back-up available for the central business district by December. At present, the city remains at risk of a 96-hour black-out if there is a further cable fault.

Mr Thomson said the Mt Roskill sub-station, although linked to Penrose, was fed directly from lines to both Otahuhu and Huntly.