Hydro Tasmania ramps up diesel units as Basslink outage extended

Hydro Tasmania will be forced to use diesel power generators for longer because the Basslink power cable to Victoria will not be fixed until well into the winter.

The first 24 megawatts of an emergency 100 megawatts of diesel capacity have been installed at Hydro's Meadowbank hydroelectric power plant in Tasmania's Central Highlands region as part of the state's Energy Supply Plan intended to prevent blackouts until the winter rains arrive and fill dams.

The owner of the 290-kilometre Basslink interconnector, the world's second-longest undersea electricity cable, advised this week that the damaged line would likely not return to service until mid-June, about two weeks later than previously forecast.

The 500-megawatt cable, which has been out of action since December, typically delivers electricity generated by Victoria's brown coal generators to Tasmania in drier weather. When prices in Victoria are high enough, Tasmania's hydropower plants can export excess energy across the Bass Strait.

Basslink chief executive Malcolm Eccles said the fault had been found some 90.5 kilometres off the Tasmanian coast, and preparations are under way for repair.

More than 1 kilometre of the cable has been cut and will be replaced, with the ends to be connected to the cut ends lying on the sea bed. Water damage in the cable will require a third joint, and each joint requires continous clear weather to be completed.

The cable has been unusable since tripping on December 20 when it was importing energy into Tasmania at close to full capacity. Tasmania had been importing up to 40 per cent of its energy needs across the cable prior to the outage, although it also exported some power to Victoria in December at a time when wholesale prices peaked at $1626 per megawatt-hour, about 30 times normal levels.

The Basslink venture, owned by Singapore's Keppel Infrastructure Trust, originally estimated the outage would last about 60 days but it has taken longer to pinpoint the fault than anticipated.
Risk of brown-outs

A drought in Tasmania has heightened the risks of brown-outs in the state.

Hydro Tasmania chief executive Steve Davy said water inflows to storage dams had been only about half of average levels over the past three months. If they continued at that rate, storage levels were expected to drop to only about 12 per cent. Total storage as of this Monday was 13.9 per cent.

The company has been relying on gas generation at the Tamar Valley power station, diesel plant and reduced demand from customers to help replace the lost capacity from Basslink.

Major energy users such as Rio Tinto's Bell Bay aluminium smelter and the Norske Skog paper mill have been affected and have had to cut back use.

Mr Davy said that even with a relatively dry late autumn and early winter, Tasmania typically receives reasonable inflows in May and June.

"It always rains in our catchments in winter and there is no reason to believe this winter will be any different," he said. "However, if the rainfall through to June is even lower than half the historical average, the Energy Supply Plan will provide a response as the situation unfolds."

The state's energy supply plan involves installing up to 200 megawatts of temporary diesel generation, at Meadowbank and other sites, the return of the Trent gas unit after repairs in Abu Dhabi, and other measures to assist with storage.

If the cable outage continues past June 30, a second phase of the supply plan would kick in, including the potential running of diesel/gas dual fuel units at Bell Bay.

The Sydney Morning Herald