Tasmania Basslink outage cause unknown, investigation finds

One year after an outage of the Basslink interconnector helped to tip Tasmania into a months-long electricity crisis, an independent investigation into the failure of the subsea electricity cable linking Tasmania to mainland Australia has returned a verdict of “cause unknown.”

Last December, Tasmania lost its power link to the mainland in one of a series of unfortunate events – including a severe hydropower shortage after record low rainfall – that saw the island state resort to diesel gen-sets, sending power prices sky high.

International cable experts charged with investigating the fault said on Monday that outage was a force majeure event, with no discernible cause revealed.

The independent investigation, completed by UK-based Cable Consulting International (CCI, spanned more than six months, encompassed forensic examinations and laboratory analysis in Italy and the UK.

CCI determined that the fault had occurred within the cable and there was no evidence of any pre-existing mechanical damage to the cable. The investigation also found that the cable was within its thermal rating at the time of failure, and that the insulation adjacent to the failure site was sound and showed no evidence of thermal ageing.

The findings are in line with the position of Basslink, which consistently maintained that the cable fault was a force majeure event. The company said it had accepted CCI’s findings and would not be undertaking any further testing of its asset.

“Despite best efforts, the CCI investigation has concluded that it is not possible to determine the cause of the fault. It is not uncommon that the cause of the fault remains unknown based on other past incidences of submarine cable outages,” said Basslink CEO Malcolm Eccles.

“We have provided the report in its entirety to Hydro Tasmania and the Tasmanian government and trust it will provide them with sufficient expert evidence to accept that the fault was a force majeure event.

“Given this, we would like Hydro Tasmania to recommence meeting its contractual obligations to Basslink immediately,” he said.

Eccles said the “silver lining” to the whole exercise was that CCI had found the other section of Basslink’s cable to be in sound condition.

“This gives us confidence in the long-term outlook of the asset,” he said.

The inconclusive findings, however, will do nothing to advance the case for a second interconnector between Tasmania and the mainland – a long-mooted proposal that took on added urgency after the Basslink outage, and in the context of the federal election campaign.

While supported by the Turnbull government, with a promise of CEFC backing, a report into adding the second interconnector suggested it would not be worth the $1 billion investment unless at least 1,000MW of new renewable energy capacity was built in Tasmania.

Meanwhile, in Western Australia, the Pilbara Development Commission is looking into the viability of adding a subsea cable to transport solar power from the Pilbara and Kimberley to Java in Indonesia.

A pre-feasibility study into the ambitious $6-$10 billion project is expected to be completed in January. Read more here.