Case Study: A Time-Critical Power Bypass – OHW-TEE


Transpower is a state-owned enterprise with 800 employees, responsible for electrical power transmission throughout New Zealand. Transpower is the owner of New Zealand’s national grid, providing the infrastructure for electric power transmission and the system operator, ensuring real-time operation of the nation's grid and the electricity market.

Their transmission network consists of 170 substations, 25,000 transmission towers, and more than 11,000 kilometers (6,800 miles) of lines.


Transpower identified the need to undertake urgent maintenance to an underground cable near Auckland, New Zealand.

Due to the criticality of this cable a by-pass transmission line was required to allow the cable to be de-energized for maintenance to be carried out.

Due to the upcoming high network demand during the summer months, the repair work was deemed urgent and needed to be completed in a short time frame. Transpower needed a partner with expertise in the design and construction of overhead lines to ensure a temporary bypass could be completed in a fast-tracked timeline.

Groundline was selected based on our expertise in design and construction, but more importantly, our experience in time-critical design and construction projects.


Completing a project of this scale in approximately half the normal time was a big challenge.

We knew it was only possible if we had stringent project management processes to ensure control over design QA/QC and allow seamless incorporation of safety in design and constructability inputs. Crucial to the success of this was a well-executed communication plan to ensure information flow between stakeholders. This was key throughout the entire process.

A fully integrated team was assigned that mixed expert design knowledge with years of construction knowledge. This integrated team enabled de-limiting of project risk and allowed our team to quickly assess several options and enable critical information to be passed onto procurement and planning swiftly.

This approach also allowed early line route spotting to verify the design assumptions, and it enabled early engagement of contractors, meaning their input was then able to be incorporated into the design and was crucial to secure easement of the temporary line route.

The design faced several other challenges too, including inclement weather - typical New Zealand, ‘four seasons in one day’!  A period of heavy rain could have caused significant delays, but our team used the weather to assist in identifying potential no-go areas in the line route that were not obvious initially.

The temporary line bypass was close to other circuits competing for space and connection to the substation. The limitations put in place by other circuit locations were considered throughout the design and construction process to avoid causing more issues and disruption.


A project of this scale would normally take more than 12-18 months to complete.  

By utilizing Groundline’s expertise in design, construction, spotting, surveying, and project management this project was completed and handed over to the contractors in just seven months and is due for commissioning mid-September 2023. This will mean a project duration of 9-10 months and without disruption to customers’ power supply.  

Transpower said:

“The Groundline team have been great to work with on the OHW Temporary Tee project. They have been delivering all the outputs on time and to the required level of quality.

This is a fast-track project and
their performance to date has been commendable.

They have been fast and extremely responsive to the project needs and timelines”.

Bad weather and flooding
Other circuits close by

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