The state-owned energy company stopped paying facility fees in September as it disagreed with Basslink’s argument that the outage was a “force majeure” or unavoidable event.

The investigation was conducted by Cable Consulting International in laboratories in Italy and the United Kingdom over six months.

It determined that the fault had occurred within the cable and that there was was no evidence of any pre-existing mechanical damage to the cable.

But the point of initiation within the fault path and the direction of the electrical failure could not be determined due to the extent of the damage.

The investigation found that operating conditions up to the failure were no different to the year before and that the cable was within its thermal rating 

No evidence of thermal ageing was revealed.

Basslink chief executive Malcolm Eccles said the report, which had been provided to Hydro Tasmania and the state government, provided sufficient evidence that the fault was unforeseen and unavoidable.

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

“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.”