New Telecommunications Cable For Cook Strait

An unfamiliar ship will be in Wellington Harbour soon as part of work to install a new telecommunications cable across the Cook Strait.

The cable ship Reliance will be undertaking the work for National Grid owner and operator Transpower who will use the cable as part of managing New Zealand’s high voltage transmission network.

The new cable will replace others that have come to the end or nearing their end of life.

As well as deploying the new telecommunications cable, the Reliance which operates out of Noumea is also being contracted to recover the out-of-service telecommunications cables.

The new fibre optic cable to be laid from early March will connect at Transpower’s facilities at Oteranga Bay in the North Island and Fighting Bay in the South Island. Like the High Voltage Direct Current (HVDC) interisland cabling, the deployment will be within the protected area of the Cook Strait Cable Protection Zone.

Cook Strait is a rough stretch of water, and time and tide eventually take their toll on whatever gets laid there. To counter the strong tidal movement of the Cook Strait, the new cabling will be heavier and tougher than standard submarine telecommunications cabling used previously. Transpower’s IST General Manager Cobus Nel explains:

“We have spent some time modelling the impact of the Cook Strait tide and movement on our cabling. Typically, the lighter telecommunications cabling is more prone to movement on the seafloor than the heavier electricity cables. Movement equates to friction and friction over time leads to damage and potential failure.

“So it became a case of finding the sweet spot in terms of optimal size and weight to reduce movement in the Strait, while still being cost effective as a telecommunications cable. We think we’ve got there with the size chosen which is nearly three times heavier than earlier standard cables – but still able to be manufactured and deployed as a telecommunications cable.”

The Reliance is expected to arrive in Wellington around 28 February from Samoa (where the new cable will be loaded) before commencing work. While the exercise could take as long as a month the project team are hopeful that Wellington weather will play its part.

“We do need relatively calm conditions for cable laying which is why we have timed it for this time of the year when the Strait tends to be more settled,” said Mr Nel.

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