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Basslink subsea cable returns to service

After more than six months of repairing a fault of an unknown cause, the telecommunications and energy subsea cable is being returned to service.

Basslink's subsea cable providing energy and wholesale high-speed telecommunications services to Tasmania is expected to be operational as of June 14, the company announced, with the third and final cable jointing repair having been completed last week.

The cable was reburied in the seabed over the weekend, with Basslink CEO Malcolm Eccles adding that all subsequent operational testing has been successful.

"We have been extremely satisfied with the final stages of the repair project, and all testing has shown the interconnector is ready to resume operation," Eccles said.

Basslink is still investigating the cause of the fault.

"There has been well over 100 people working incredibly hard at sea and on land to rectify the fault," Eccles said last week.

The Basslink Interconnector, the world's second-longest subsea cable, has been down since December, leaving many Tasmanians without energy and internet services.

Cable repairs were hit with months-long delays: In March, Basslink revealed that excess water damage into its cable would result in repairs not being completed until mid-June. Prior to this, Basslink had said repairs would be done by late May .

This was followed in April by Basslink saying it would require six days of consecutive clear weather to repair each of the three joints in order to complete repairs on its subsea cable.

In May, it then said it had lost more than 20 days to inclement weather since completing the first joint, with the repair timeframe pushed out to late June.

"As the jointing works take place on the deck of the vessel and are highly susceptible to weather conditions, each joint will require a window of relatively calm sea conditions and clear weather for six continuous days to allow such works to be completed safely," Basslink said.

"Bad weather or rough sea state can damage the cable, result in abortive jointing works, or pose unnecessary occupational, health, and safety risks for the repair crew. The jointing works are highly complex, and will see the three lengths of new cables (ie, the high-voltage cable, the metallic return cable, and the fibre optic cable) joined to the existing cables and bundled together, before being laid on the seabed."

The fault in the cable was discovered 90.5km from the Tasmanian coastline and removed and capped on Easter Sunday, three months after going down.

The outage has lasted so long that the Tasmanian government got involved; Minister for Information Technology and Innovation Michael Ferguson in March said the government was "very disappointed" that TPG's group of internet service providers (ISPs) had still not made provisions for the Basslink outage, "urging them to buy more capacity on the remaining Telstra cables" in order to provide customers with services.

"Our understanding is that customers of TPG, which includes iiNet, Internode, and Netspace brands, have been affected, while customers of other non-Telstra ISPs are provided for," Ferguson said at the time.

"I have spoken to TPG senior management to put forward the concerns of Tasmanian customers. I have been assured that TPG are aware of the issues and will continue to expand their use of the ample Telstra capability.

"As I stated some time ago, Telstra advised there was sufficient capacity to cater for all Tasmanian retail and wholesale customers on the two fibre bundles it owns and operates across Bass Strait."

Ferguson added that he had also "reminded" Telstra Wholesale "of the importance of constructively receiving requests for more capacity from TPG".

Telstra itself had commented that it is the duty of telcos to provide continued services for their customers despite outages, with Telstra offering capacity to allow this.

TPG thereafter negotiated for extra bandwidth over Telstra's fibre-optic cable.