AWARDS FINALIST: Transpower – HVDC Pole 2 life-extension programme
In an impressive engineering achievement, Transpower has successfully completed a five-year, $63 million programme to extend the life of Pole – one of the two converter poles in the high-voltage direct current link – by 20 years.
This has not only secured the reliability of critical national infrastructure, but has also delivered a significant saving for consumers by deferring almost $1 billion in replacement costs.
Pole 2, originally designed with a 30-year lifespan, was approaching midlife. Rather than replace it, Transpower embarked on a pioneering refurbishment programme – something never before attempted at this scale around the globe.
Resilience
The goal was to extend the pole's life to 50 years while maintaining high reliability, minimising outages, and improving long-term seismic resilience.
The programme involved more than 30 interlinked projects, ranging from seismic strengthening and control system upgrades to the replacement or refurbishment of critical components like transformers, bushings, and harmonic filters.
One standout innovation was the replacement of oil-impregnated porcelain bushings with custom-designed resin-impregnated composite bushings. These not only eliminated fire and explosion risks, but also enhanced seismic performance – essential in a country prone to earthquakes.
Seismic upgrades were extensive, bringing Pole 2's infrastructure up to the same standard as the newer Pole 3. This included strengthening converter buildings and cable terminal stations using fibre-reinforced polymer technology and advanced bracing systems.
Planning
Transpower says the programme required meticulous planning to coordinate resources and complete work in often constrained physical spaces in and around live assets.
Given the 613-kilometre HVDC link's critical role, outages had to be minimised and carefully coordinated.
For example, spreading low-voltage switchboard replacements at Haywards and Benmore across two outages allowed lessons learned from the first to be applied to the second, reducing overall downtime and improving efficiency.
Despite the challenges - including a global pandemic and the diversion of resources to Hawke's Bay following Cyclone Gabrielle in 2023 - the programme is on schedule and under budget.
Transpower says the project has also provided significant non-commercial benefits, including professional development of staff and enhanced industry capability.
The annual Energy Excellence Awards will be held in Wellington on 13 August. The Energy Project of the Year Award is sponsored by Bluecurrent.