‘Cause unknown’: Basslink fault investigation sheds little light on outage

An investigation by Cable Consulting International into the outage of the Basslink interconnector has not been able to identify the cause of the fault.

Basslink connects Tasmania to the mainland, providing power transmission and telecommunications services.

The cable suffered a fault in December 2015, with many Tasmanians taking a bandwidth hit as a result. The interconnector was brought back online in June.

The six-month CCI investigation into the fault has returned a verdict of “cause unknown”.

“CCI determined that the fault had occurred within the cable; the fault was not at a location of a joint, or a lead sheath to armour bond,” a statement issued today by Basslink said.

“There was no evidence of any pre-existing mechanical damage to the cable. The point of initiation within the fault path and the direction of propagation of the electrical failure could not be determined due to the severity of the fault damage.

“The operating conditions at, and preceding, the time of failure were no different to those of the year of 2015 and the cable was within its thermal rating. The insulation adjacent to the failure site was sound and showed no evidence of thermal ageing. A sample of cable remote from the fault site was in sound condition.”

“Despite best efforts, the CCI investigation has concluded that it is not possible to determine the cause of the fault,” Basslink CEO Malcolm Eccles said.

“It is not uncommon that the cause of the fault remains unknown based on other past incidences of submarine cable outages.”