Repair of the Basslink cable linking Tasmania across the Bass strait to mainland Australia has been delayed, and it may not now be available until early May, according to revised estimates from the operator. On 21 December last the 500 MW interconnector was disconnected owing to a line fault. The fault was found in due course to be located 98 km off the Tasmanian coast. Basslink originally announced the cable would be repaired and returned to service by 19 March, but in the light of the difficulty of the repair the cable is unlikely to be back in use before early May.
The power and communications cable had been used to import 30% of the island's electricity from coal-fired power in Australia, with hydroelectric power going the other way.
But the drought has severely diminished levels in Tasmania's hydropower dams, leaving the government with no option but to boost supplies by reopening a gas-fired power plant and bringing in 200 diesel generators from the mainland.
Reservoir levels are continuing to fall, from 15.5% capacity in early March, and heading towards a record 14% low.
The government is also investigating whether dam levels have been driven down by Tasmania's selling clean power to the mainland, with hydroelectric energy being exported right up until the Basslink cable breakage.
The Siemens/Prysmian built Basslink is an HVDC monopolar configuration with metallic return operating at a nominal voltage of 400 kV and a rated DC current of 1250 A. It consists of a 290 km long submarine power cable from Loy Yang substation in Victoria to Four Mile Bluff above George Town in Tasmania.
The nominal rating of the link is 500 MW continuous, in either direction, although it is capable of transmitting 630 MW between its substations for up to 4 hours.
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