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Doble Supports NB Power Subsea Cable Replacement Project

By in General, Cables, Service | November 5, 2019

Over the past six months Doble has been supporting New Brunswick Power (NB Power) with the Fundy Isles subsea cable replacement project. Deer, Campobello, and Grand Manan islands off the coast of New Brunswick in the Bay of Fundy have been connected to the mainland power grid by 69 kV submarine gas compression cables since 1978. NB Power had already started to plan the replacement of these cables but following damage to the cables in 2018 the replacement programme was quickly accelerated to ensure reliable power was maintained to the communities on these islands.

NB Power placed a turn key contract with a European cable maker to manufacture and install the cables. The replacement cables were made at two locations in Europe:

  1. The 69 kV 300 mm2 XLPE cable cores with a lead sheath and semiconducting jacket were manufactured in France. These cables were transported to Germany on drums each holding approximately 3.5 km of cable.
  2. At the German factory the three cable cores were laid-up (twisted together) with a fibre optic cable (to improve data services to the islands) and fillers. The laid-up cable bundle was finished with a covering of steel wire armour to protect the cables in service. The finished cable weighs approximately 74 kg per metre and is 186 mm in diameter.

Throughout the manufacturing at the two sites Doble conducted factory audits and inspections for NB Power. During one of these audits a significant processing problem was identified with a number of the cables. Wendi Wright, NB Power Project Manager, said, “because of Doble’s deep understanding of what is important in making an XLPE cable, these non-conformances were caught before they could have caused significant issues and delays later in the project”. She added, “ultimately these lengths of cable had to be re-manufactured to within specification”.

Doble also witnessed the FAT testing of the cable cores and the three finished armoured subsea cables; passage cable (3.5 km), channel cable (15 km) and a spare (0.7 km). Only the longest cable contains factory made joints and Doble was there to witness the construction of these along with the subsequent x-raying and PD testing.

Doble was also present on the cable laying vessel in Canada to witness the installation of the cables. The route starts on Deer Island, crosses to Campobello where it goes overhead across the island before the longer of the two sections (15 km) under the channel, to Grand Manan. Each end of the cable was pulled through directionally drilled ducts from the Cable Riser Stations onshore to 3m below the low tide mark.

The Bay of Fundy has the highest tidal range in the World. Simon Sutton, Doble Technical Solutions Director for EMEA, who monitored the installation from on board the cable laying vessel said, “the high currents experienced throughout the installation phase of the project restricted cable laying to the period around slack tide when the Remote Operated Vehicle (ROV) could monitor the laying of the cable on the seabed”. He continued, “the currents also made the cable pull-ins to shore challenging and on one occasion the video monitoring system at the entrance to the duct was swept away more than once”.

The cables are now installed and will be operational following commissioning testing. The new cables are designed to provide forty years of service. “The acceleration of the project schedule following the damage suffered by the Passage cable has proved to be challenging. It’s been a huge team effort to get the cables replaced so quickly. NB Power team are very grateful for Doble’s support and flexibility throughout the project”, said Wendi Wright.

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Doble Engineering Company

Doble Engineering Company