Hamilton deviation relocation project
Location: Hamilton
Start date: October 2022
Completion date: May 2023
Project partners: Transpower, Groundline
Key people involved: Project Manager – Nick Gouge
Construction Manager – Gareth Hoskin
Project Supervisor – Andrew O’Neill
Senior Engineer – Stephen Horn
Cadet Engineer – Seff Curle
Expansion and deviation
With the expansion of the Tainui Inland Port, a deviation in the Hamilton Deviation Transmission Line (HAM-DEV A) was required. The project was managed by Transpower and designed by Groundline. Northpower’s Transmission Lines team were engaged to provide a constructability report evaluating the feasibility of the work to be carried out.
The complex project involved constructing two 50m double circuit duplex towers and two 47m monopoles to accommodate the deviation. Upgrades were also required for the concrete foundations of existing towers and changes to attachment points.
Planning and coordination
Adverse weather conditions, including heavy rainfall, posed challenges for our team during foundation installation. Keen to keep the project moving, our crews tackled this issue by putting large pumps in place to manage the accumulation of water during the construction of pad and pedestal type foundations.
Given the critical nature of the 220kV circuits feeding the central Waikato region, de-energising the lines required incredibly meticulous planning and coordination with transmission stations and maintenance teams, as the line circuits could only be de-energised one at a time and only for short periods.
Our solutions
We utilised a number of surveys and strategies, including use of thermal cameras, drone scoping and even the cutting of trees due to the increased sag caused by higher load that would be put on the remaining in-service circuits. Extensive safety precautions were taken to mitigate the increased sag caused by higher load that would be put on the remaining in-service circuits.
Once these surveys were completed, our transmission lines team were able to take their first outage, to put in the tong guys. These were installed to splay the conductors apart and to allow room to construct the tower 504A between the two circuits.
To complete stringing of the duplex goat conductor, Tesmec puller tensioners were used, and a helicopter was engaged to fly out Dynema pull ropes for each sub-conductor. The conductor was then held on the ground until the outages for the cut over were complete, before being transferred up the towers.
Our team worked quickly during outages to minimise disruptions and impact on the national grid. This required the development of a comprehensive methodology and programme, including hybrid phasing to quickly restore power in case of circuit trips.
Removal of old towers to accommodate new construction was also a complex undertaking within such a high risk environment and involved in-depth strategic planning and project management. Due to poor ground conditions, a 34T excavator was used to safely pull down the towers, ensuring the safety of all the teams on the job site and surrounding areas.
This complex transmission project required detailed management, planning and delivery to minimise disruptions and ensure the reliability and integrity of the transmission line network, while keeping everyone safe. We achieved success in all areas and played a pivotal role in ensuring the successful completion of the deviation project, enabling expansion of the Tainui Inland Port.
