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The rebuild of the national grid is underway but Transpower can’t guarantee that there won’t be further outages in the north between now and 2014 when the project is completed.
“It takes a long time to build these things and the question is – in the next three to four years can we guarantee supply – of course we can’t.” Transpower will do everything we can to avoid outages, he adds, but when they are doing this much work on the network it will be difficult to get to the early completion date in 2013 without another outage. Strange was speaking in January 2010 only days after Auckland had suffered its third outage within a two-year period – caused by a chain of events that started with a fire under the 220kV line in the Waikato. Strange went into detail about all three outages to paint a picture of what Transpower is up against in maintaining continuity of power supply to the thirsty consumers of Auckland and beyond. The outage in October 2009 that left Northland in the dark and cut power to the country’s only oil refinery was caused by a container hoist working under the 220kv line in the industrial suburb of Penrose, Auckland, close to Energy NZ’s offices. “A huge container fork hoist went too close to the overhead lines and caused a flash-over and it happened during the few days of the year when we are doing maintenance on some of the lines,” says Strange. Having power lines hit by the likes of cranes and highly loaded trucks is quite common around the country, he adds, but the over-head 220kv line between Otahuhu and Henderson, that carries all the power to Auckland’s west and onto Northland, is particularly high risk. When this line was first built in 1947, it hung over farmland. Dense industrial areas have been consented by various councils underneath the lines over the years making access difficult and the chances of a ‘flash-over’ through fire, smoke and accidental touching extremely high. The most recent outage in January was caused by a chain of events compounded by a fire under the 220kV line in the Waikato and a farmer who denied contractors maintenance access, and necessary rolling cuts from Huntly north. The Otahahu Combined Cycle generation plant had been out for three months for repairs and within half an hour on the day, Transpower lost two circuits in the Waikato. “We knew what had happened and it wasn’t a huge problem. Lines were stretched but under control.” Then they had the problem with the farmer denying access to the major 220kV line and the fire. “Land owners are difficult sometimes but we can live through that,” says Strange, who is a farmer himself. “However, we also had a problem with a storm of lightening that put the remaining lines at risk.” Transpower called for, and got, reductions from the lines companies, but nothing could stop the rolling cuts, says Strange. It was a chain of events that couldn’t be predicted. “Again, it was a call for diversity. If the 440kV line had been there we wouldn’t have known about it.” People think modern transmission technology can do away with the need for a grid, and that great pylons and lines are a thing of the past, says Strange – referring to the opposition to the $820 million, 440kV line being built through the Waikato. “A decade ago, the then leader of Transpower did just that. He believed distributor generation would sweep the world and we could stop investing in long-term upgrades and maintenance. That was the ‘glide-path’ and you know where that has left us.” The country’s dependence on electricity is increasing all the time; from traffic lights to computers to EFTPOS, power is more essential to the economy, he iterates. “You would be surprised how many calls we get about cars stuck in garages. Dependence is growing and growing.” The 440kV line is just one of a number of projects totalling $3.5 billion (the biggest spend ever in New Zealand) that are in progress to guarantee security of supply. These include an alternative power route through Auckland that cuts through the middle of the city and ducts up the Northern Motorway. This new 220kV underground cable starts from Pakuranga where the 440kv line terminates and stretches through trenches to Penrose then through a tunnel and existing ducts across the Harbour Bridge to Albany. When commissioned in 2015, Northland supply will have two alternatives routes. “When you are building such assets it takes six to seven years to build and the problem is every time we put something in, we have to take something out,” says Strange, indicating there could be more pain for Auckland and Northland over the next few years.
Energy NZ Vol.4 No.3 May-June 2010 |
Transpower chief Patrick Strange (pictured) admitted to delegates at the Power Conference earlier this year it was going to be difficult to finish the $3.5 billion plus grid upgrade without adverse effects on supply.