Ralph Craven: Upgrading grid key to powering ahead

COMMENT

The cascade failure in North America was an event of major significance for the international electricity industry and a timely reminder to New Zealand of the need for investment in the national grid to provide secure power system operation into the future.

The blackout cut power to about 50 million people across the American northeast, stretching from Michigan to New England, clobbering such major cities as Detroit, Cleveland, New York, Toronto and Ottawa. 61,800MW (megawatts) of electricity load was lost.

That's roughly 10 times the peak winter demand for all of New Zealand.

It could take some time to determine exactly what went wrong. After the huge 1965 blackout - which occurred in roughly the same area - the subsequent inquiry took three years to deliver its findings.

The National Energy Reliability Council was set up following the 1965 blackout and is now conducting a thorough investigation. The council is warning that there were probably over 10,000 discrete system events that need to be examined before any definitive conclusions can be drawn about the root causes of this outage.

What is clear - with terrorism and computer viruses quickly ruled out - is that something went terribly wrong with the transmission system.

So could the same thing happen in New Zealand? The short answer is no.

The first point to note is the different nature of our electricity grid. The east coast of the US and Canada has a vast interconnected power system. This has benefits and risks.

Generally, interconnected power systems provide for more efficient market outcomes and therefore lower costs to electricity users. In New Zealand, the North and South Island transmission networks are interconnected to form one national grid.

But our grid is obviously not as interconnected as in the US and Canada, and in a geographic sense is long and stringy, running the length of New Zealand.

Transpower operates the grid in such a manner that a single major event is unlikely to lead to cascade failure and tripping of other lines or generators, as appears to have happened in America. Rather, the "stringy" nature of the grid means the risk from a single event is more of losing supply to a region.

In the event that multiple failures occurred, control systems have been put in place so that:

* The high-voltage direct current (HVDC) link between the South and North Island would shut down so only one island should be affected.

* An automatic load-shedding scheme would cut in to disconnect blocks of load, immediately reducing demand on the system to avoid a total blackout.

New Zealand has the advantage of having a lot of hydro generation that can be restarted quickly after a blackout and used to start other power stations and begin restoring supply to consumers within a few hours.

Hydro generators are also very robust compared to other types of generation and are unlikely to suffer damage from a blackout.

In the Northeast US, generation is mainly from fossil fuelled and nuclear stations, that once tripped off need power restored to them so they can restart and then take some time to get up and running.

The last time New Zealand faced a major power system failure was in March 1996. Twenty per cent of North Island consumers were automatically shed to avoid a total blackout after the HVDC link tripped. Similar events happened twice in 1993 when 20 to 40 per cent of the North Island load was shed.

On Waitangi Day in 1987 the North Island north of Taupo was blacked out due to a fault at a major substation. Changes have since been made at substations to prevent any recurrence of this type of failure.

As transmission grids get pushed harder throughout the world there is a greater reliance on technology to keep grids stable and yet deliver more power, without building more lines.

Here in New Zealand, Transpower has put in place special systems and operating procedures to enhance the grid, so more power can be transmitted under certain conditions.

However, at some point a prudent grid owner needs to invest in more lines and upgrade existing ones if the integrity and stability of the grid is to be preserved.

Commentators and politicians in the US are bemoaning the lack of grid investment and see it as a factor in the big blackout.

So what needs to be done in New Zealand?

The national grid is currently doing a good job. It is reliable and has sufficient capacity to meet the country's current requirements.

But demand continues to grow and there is only so much patching-up that can be done to lines and towers that are in some cases more than 50 years old.

Most of NZ's national grid was built in the 1950s and 60s. There comes a time when the focus needs to shift from maintenance of old equipment, to building new infrastructure. For Transpower, that time has now arrived.

Making new transmission investment a reality is a key focus for both myself and Transpower as a whole.

New investment of in excess of $1 billion is needed over the next 10 to 15 years. Given the long lead-in time for getting core national infrastructure through the consent process and built, the next few years are crucial.

The big blackout in North America has reminded us all that a reliable electricity supply is at the heart of a vibrant modern economy.

There is a need for substantial new transmission investment here - both to maintain a high level of security of supply, and to meet the ever-increasing demand for electricity that economic growth brings.

* Dr Ralph Craven is chief executive of Transpower.