Workers are putting in a total of 5000 hours a week at the Benmore substation to improve the electricity supply between the North and South Islands in a $672 million project.
Transpower is upgrading the HVDC (high-voltage direct-current) link, which includes the Cook Strait cable, between Benmore and Haywards in Wellington to increase the amount of electricity that can be transmitted between the two islands.
Pole 1 and pole 2, commissioned in 1965 and 1991 respectively, convert electricity from alternating current to direct current and then back again to AC at the end of the link.
At present, the total capacity of the HVDC link is 700MW. That will increase to 1000MW in 2012, and then to 1200MW in 2014, once pole 3 and supporting infrastructure is completed.
Site manager Alan Bulling said the civic work at the HVDC pole 3 inter-island link project at Benmore substation was "almost on programme".
Two of four transformers, weighing 250 tonnes each, were already at Prime Port, Timaru, he said.
However, a delay in the delivery of the control system required to operate the new pole, because of delays in the supply and testing in Germany, means pole 3 will likely be completed in late 2012.
Communications manager Adele Fitzpatrick attributed the "slight delay" to the New Zealand energy system being more challenging than others.
New Zealand's long, thin shape meant the system was "strong in parts and weak in others", she said.
European countries benefitted from having a "mesh-like" system, as opposed to a single link responsible for transporting electricity, she said.
Site engineer Matthew Gnad said the work was a key project that came with no shortage of complicating factors.
"Construction is hard enough, but in a live switch house it's a whole other thing," he said.
Working on a site with high-voltage lines and heavy equipment meant construction staff had to work differently from normal.
Special care was also taken to mitigate the effects of an earthquake, which was estimated to occur once every 2500 years, he said.
Pole 3 sits on 33 lead rubber bearings, which in turn sit on 50 sliding plates that enable the structure to move 600cm in any direction in a seismic event.
Ms Fitzpatrick described the project as being "vital in maintaining one electricity market in New Zealand".
The project was designed to cater for peak usage - "the highest point of consumption at a given time", she said.
Mr Gnad said ventilation specialists, plumbers, electricians, painters, gib fixers, roofers, tilers and crane operators among others had worked on the project, and about 25 houses had been rented in and around Otematata
Power play
• The HVDC (high-voltage direct-current) upgrade at the Benmore dam:Total estimated cost $672 million.
• Capacity will be increased to 1000MW in 2012 and to 1200MW in 2014.
• HVDC transmission line between Benmore and Haywards (Wellington) is 567km long.
• Length of HVDC submarine cable: 40km.
• HVDC line commissioned in 1965. - ben.guild@odt.co.nz
