Power: Mowbray Underground Transmission Line
Underground Transmission Cable
Client: Transend
Location: Launceston, Tasmania

Zinfra was contracted by Transend, through open tender, to install Tasmania’s longest section of underground 110kV cable.

In a Tasmanian first, specialised high voltage cable with fibre optics, capable of monitoring the temperature of the cable, was used.

The large project was complex and stakeholder management was paramount for the project, as the cable was installed under a railway, parks, urban areas, farms, swamp land, environmentally sensitive areas and Aboriginal heritage sites.

The project formed part of the Great Launceston area supply upgrade program which saw the construction of a new substation at St Leonards (completed under a separate contract by Zinfra) and the linking of the existing Mowbray and Norwood substations - forming a ring around Greater Launceston.

The project works included:
• Procure and install 12km  of 110kV underground  800mm2 copper cable, including jointing, testing and commissioning
• Design for the project was completed by AECOM NZ, who have underground cable expertise
• Trenching, directional drilling, civil works
• Fibre optics, Distributed Temperature Sensing
• Revegetation to stakeholder standards.

The single core 800mm2 cable was procured from LS Cables in Korea.  A delegation of supervisors from the manufacturer was required on site to validate the warranty on the product.

As such, a team of LS Cable employees assisted and supervised the installation and jointing aspects of the work. 

The jointing required joint bays measuring 13 x 3m each to be constructed, in which a sterile, temperature controlled environment was required to ensure the electrical integrity of the joint.

The final joint in the substation yard, had to be completed several meters above ground, in a tarpaulin-enclosed space, to provide a suitable environment to join the cables. 

The project encountered and overcame many hurdles.  The cable was required to be installed below:
• Public places, such as parks and pedestrian areas
• A railway line
• Private land
• Council land
• Aboriginal heritage sites
• Environmentally sensitive locations
• Endangered species of fauna
• Swamp areas.

Another major challenge was the presence of acid sulphate in some areas.  The highly corrosive, dangerous substance required planning, work methodologies and a manual to be created.  Correct handling of acid sulphate soil was critical to avoid harm to workers and animals and to prevent its spread in waterways.

This project was critical to Launceston’s electrical network and presented technical “firsts” for Tasmania.  The challenges faced - technical, logistical and stakeholder - were professionally managed by Zinfra to deliver a successful project for Transend.

The brownfield project was completed in 2012 and delivered in budget, with zero LTIs or MTIs.