Transpower's secret control room

Alan Hunt keeps an eye on 16 screens that track electricity supply throughout New Zealand. Picture / Amos Chapple

On the rural outskirts of Hamilton, a 10-minute drive from the city centre, a driveway comes off a narrow country road. Twenty metres over a small rise is a low-slung, modern building surrounded by a high barbed-wire fence and security cameras.

It is not until you get through the outer perimeter and two security doors into the building that you first see the name of Transpower - the state-owned enterprise charged with running the national power grid.

Inside is one of its two national co-ordination centres, where our national electricity grid is managed. Both centres run alongside each other, sometimes with two staff in Hamilton and one in Wellington, sometimes the reverse.

Each operator sits before a bank of 16 screens. The top left monitor transmits a continuous video feed of fellow operators in the other city.

These people control the flow of energy into every home, factory and office in New Zealand; the power feeding every television, computer, dialysis machine and lightbulb.

And the tool they are using - the national power grid - is becoming older and increasingly creaky as demand for electricity soars.

The record high last year was hit in mid-August, with 1947 megawatts (MW) of energy used, while this winter's peak of 1998 MW was reached at 6pm on June 29.

Transpower and the local lines companies are planning for a winter high this year of 2060 MW. It says the maximum supply it can muster is 2130 MW.

The first day of a cold snap is always the hardest to cope with, says systems co-ordination manager Kevin Small. By day two of a cold spell, people have warmed the house, put on more clothes, or can simply cope better than the first day.

High demand is a combination of low temperature and "luminosity" - how dark the evening is. A storm front approaching sends people scurrying home to turn on every light and heater.

But there is more to managing the national grid than just ensuring enough electricity reaches all the heaters and ovens. "Voltage collapse" is the biggest fear of any grid operator.

The exact time and place of such a collapse is unknown. It can trigger a cascading failure through the system, heading like a chain of ever-larger dominoes, dumping increasing loads along the network, causing ever-larger scale blackouts.

Every grid has a voltage collapse point, where, in general terms, the voltage of the load required is greater than the voltage the generators and capacitors can supply. When this mismatch happens, voltage levels can drop to such a low level they cannot be retrieved.

A need to watch voltage stability carefully is a relatively new problem in electrical power grids, says Small.

Power stations are paid through the market to keep energy in reserve, in effect keeping a generator spinning, ready to be engaged instantly and putting power into the system. Others promise to have it available within 60 seconds, with more ready within nine minutes.

Small says 10 years ago problems with voltage stability were rare, better known among the ranks of engineering modellers and treated as an academic exercise. Now, with an ageing system, they happen all the time.

Another Transpower worker describes the risk of voltage collapse as "knowing there's an edge to the cliff, but not knowing exactly where it is", all adding up to staying a safe distance from the likely cliff-edge.

In August 2003, such a collapse swept across the Eastern United States, blacking out 35 million Americans and 10 million Canadians. Around 100 individual power plants "tripped" or were automatically shut by circuit breakers sensing voltage fluctuations.

Human error, which included operators ignoring alarms, bad communications and creaking infrastructure were eventually blamed for the blackout.

On the Wednesday evening the Herald visited, things were quiet, with the predicted load creeping up steadily as the evening wore on. Operator Alan Hunt was able to comfortably dispatch enough energy into the system to cope.

One of his 16 screens continuously runs a contingency analysis telling him all the possible implications of his actions.

With his screens are six keyboards and six mouses. "It's always the second one that's the right one," jokes Hunt.

He has two jobs, maintaining the security of supply, but also acting in the same way as the stock exchange - putting the generating power stations in touch with where the demand is.

"The only issue with us is that the electricity moves at the speed of light, so we are the ultimate 'just in time' business - we do deliver at the speed of light," says Transpower's general manager Kieran Devine.

The control room gets six-hourly updates of weather forecasts and is plugged into a sophisticated lightning detection system which uses radar to spot lightning strikes.

Things can move quickly from calm to high stress when a major line stops transmitting electricity, or a power station shuts down.

The overriding philosophy of the backup generation needed to be kept in reserve is expressed by Transpower in engineering jargon as "N -1". The minus 1 means the system can afford to lose a major component, be it a major line or power station, without anyone noticing.

But operators must be able to quickly re-configure the system, tapping into reserve-generation sources and trying to avoid blackouts.

Controllers say it is easier if a power station trips, since they can contact the company to find out what has happened and how long it may take to fix.

More trouble is a line (or circuit, as operators describe them) cutting out. While a line is shown to them as a 20cm green line on a screen, it can be many hundreds of kilometres long, with pylons heading up hillsides through bush.

Maintenance is increasingly difficult, as the stretched grid has less capacity to remove circuits when they need work.

Devine says about 8000 significant pieces of the grid are removed from service for maintenance each year. Each time this happens, the grid must be configured to make sure lights do not go out.

"To take a line out into Auckland these days requires a reasonably senior person quite a substantial period of time - we're talking days - to do the security analysis to make sure that when the line is taken out of service there is minimal risk.

"The 110 grid was started in about 1920, the 220 kv grid was started in 1960 - the first grid had a 40-year life, the 220 grid is basically coming to the end of its capability of dealing with our sized system. We actually need to step up again."

Soon, New Zealand will have a grid with 10,000 MW of installed generation, he says. No other system in the world of such a size has transmission voltages as low.

"The decision facing New Zealand is whether we can eke out with what we've got or bite the bullet and build the better grid right now."

The present call is for more "distributed generation", where power stations are built close to where the energy is needed. This would mean more stations around Auckland and fewer pylons criss-crossing the countryside.

Transpower's big plan is to build a $500 million, 440 kv power line between Otahuhu and Whakamaru. This 200km line will stretch through Waikato farmland, angering residents, who say it will damage their health and lower property values.

Devine says the beauty of a good transmission grid is that it allows some in Auckland to get access to fuel from across the nation: gas from Taranaki, coal burned in the Huntly Power Station, geothermal energy from Wairakei, and hydro generation from the South Island.

Energy Commissioner Roy Hemmingway is analysing this problem and investigating viable alternatives to Transpower's planned new Waikato 400 kv line.

But on a wet Wednesday evening, Transpower's Waikato political storm seems a long way from the quiet of its control room as Alan Hunt settles into his 12-hour shift.

With his 16 screens, six keyboards and six mouses, control of this supposedly creaking part of our national infrastructure is in his hands.