Back Share Print

North Island Grid Upgrade Project (NIGUP) 400kV Transmission Line for Transpower

Delivering energy security to New Zealand’s North Island

Contract Value
Project Duration
Commenced: 2010
Estimated Completion
New Zealand

“The North Island Grid Upgrade Project has provided greater electricity supply security to the upper North Island and will ensure that as cities and communities grow our electricity infrastructure will be able to meet the increase in demand.”
—Phil Heatley, New Zealand Energy and Resources Minister

Project Overview

Transpower plans, builds, maintains and operates New Zealand’s high voltage electricity transmission network. Their vision is “to continually operate, maintain and develop New Zealand’s transmission network, to ensure they meet the ongoing electricity needs of New Zealanders.”

With the population in the upper North Island having more than tripled since the four existing transmission lines (carrying six circuits) were built over 40 years ago, the growing electricity demand required a significant upgrade.

As a result, Transpower initiated the building of a new transmission link between Whakamaru and Pakuranga. Together with a new substation and substation equipment that would increase transmission capacity, the new link will support the development of renewable energy and provide a secure supply of electricity to Auckland and the Northland.

UGL was part of a specialist and symbiotic alliance with Balfour Beatty (BBUGL) and Transpower to deliver this project from end to end, including the task of dismantling and removing the existing 100kv line.

BBUGL began work on the line in 2010, and since then has constructed 186km of new 400kV overhead line, including the erection 
of 432 new transmission towers and installation of over 7,000 tonnes of conductor. The line includes several ‘monopole’ towers designed in partnership with the local council to fit with the topography of the area, reducing impact on rural settings. Standing at 65m, these are the tallest transmission poles anywhere in New Zealand.

The Challenge

The 400kV Transmission Line Upgrade Project was a technical and environmental challenge in its entirety with the sheer size of the project meant that Transpower had to change their environmental systems to deliver the results.

In addition, the project required involvement and liaison with nine councils, over 300 directly-affected landowners, the community and multiple government agencies and regulators.

At times, there were over 50 varying work streams, over 300 kilometres of access tracks and roads on working farms being installed and the moving of 180,000m3 of earth in some of the North Island’s most challenging terrain. This provided some large environmental challenges to overcome, to minimise the environmental impact of the project, with solutions including the innovative use of helicopters to reduce the environmental footprint of heavy machinery on the ground.

The Solution

BBUGL was engaged to manage the design, supply and construction of the 400kV, 3 phase, 50Hz A.C., double circuit steel lattice structure, overhead transmission line approximately 196km long, from Whakamaru North Substation to Brownhill Cable Transition Station.

BBUGL also had the task of dismantling and removing the existing Arapuni to Pakuranga 110kV overhead transmission line.

Specifically, to successfully complete this project, BBUGL 
was contracted to:

  • Verify and finalise all design and technical criteria required for the design of the transmission line and for compliance 
to all specified standards and regulations
Manage the PLS-CADD line model for the 400kV overhead line for selection and verification of the suitability of the structure locations, structure types and heights
  • Design, manufacture, prototype and sample test all materials necessary for the transmission line including:
Conductor, earthwire, Optical Ground Wire (OPGW), insulator sets and insulator and conductor fittings, including vibration control devices
Supporting structures complete with all fittings and including body and leg extensions and structure foundations
Erection of terminal span from the transmission line terminal structures to the gantry at Brownhill Cable Transition Station
Optical fibre joint boxes on structures (5,429) and on each gantry structure and terminate the OPGW as specified
Structure earthing and all other equipment required for the mitigation of potential electrical effects from the transmission line on landowner and third party facilities
Fabrication of welded structural cages for tower leg foundations.  Approximately 3,000 x 1 metre diameter, 
8 metre long cages - 1500T of steel in total.
Construct all access tracks for the line construction and clearance of the line route as specified
Coordination of the works, with associated but separate construction contracts
Modifications, as required to the four 110kV overhead transmission lines crossed by the 400kV line
Provide sufficient design and construction information for others to secure approvals for construction and/or reinforcement of bridges, road access and temporary facilities for camps, site works
Provision of a complete set of the design and as-built records, including final PLS-CADD line model including models for all the towers
Site reinstatement
Stakeholder management
Final inspection


Key Outcomes and Benefits

BBUGL won a Transpower STAR award for this project. The judges felt the Alliance team (UGL, Balfour Beatty and Transpower) demonstrated outstanding innovation across every aspect of the NIGUP project, which presented a significant range of issues. As a result, the team established an excellent safety culture which delivered outstanding safety performances throughout the project.

Some of the highlights of this power upgrade project included:

  • Compliance with Health, Safety and Environmental Standards
  • 993,455 man hours
  • Compliance with Quality Standards
  • Two monthly internal audits
  • Six monthly Telarc audits
  • No issues highlighted
  • Completed on time and on budget

The Transpower Alliance also won the Deloitte Energy Award for Environmental Excellence for its work on the North Island Grid Upgrade Project (NIGUP).

back to top