Work on upgrading the electricity link between the South and North Islands will start about the middle of next month, with work on the Benmore substation forming part of a $300 million contract awarded in October last year to Siemens.
Transpower's HVDC (high voltage direct current) inter-island link starts at the Benmore substation, near Otematata, and ends at Haywards, near Wellington.
The contract is part of the $672 million, Pole 3 project to increase the capacity of the link to 1000MW in 2012 and 1200MW in 2014, replacing the 44-year-old Pole 1.
Next month, construction will start on critical electrical systems and buildings at Benmore and Haywards.
Civil and seismic strengthening work, including piling and earthworks, started in January and is now nearly complete.
The next step consists of building new convertor stations at Benmore and Haywards and installing modern thyristor technology.
Transpower's grid projects general manager, Mike Carter, said the Pole 3 project was a major part of a wide investment plan to reinforce the grid.
The link was critical for carrying renewable generation to the North Island and for supporting the South Island in dry periods.
"This next phase will involve constructing new convertor stations at each end of the link, expanding the 220kV switchyards at both substations and building new voltage support equipment at Haywards," he said.
The majority of the work was confined within the Benmore and Haywards substations, but there would be an increase in activity, including transporting large equipment into and out of both substations.
Motorists should be aware of that increase in traffic, Mr Carter said.
