Bryan Leyland: Reliable power depends on planning

COMMENT

Power supply difficulties in the north of the South Island arise from serious problems with our transmission system and the industry structure. That they have grabbed public attention shows how sensitive we have become to any threat of a power shortage.

The problem with the supply into Christchurch is that the lines are overloaded.

In a power system, there are two types of overloading. The most common is when the lines and equipment need to carry more current than they are designed for. When this happens, load must be shed within 15 minutes or so to avoid the risk of damage.

Because it is not unusual to lose a transmission line from lightning or tree contact, it is normal, and prudent, to assume a system is overloaded if it cannot carry all the load with one line out of service.

The other form of overloading is "voltage collapse". On long transmission lines, the load that can be transmitted is limited by the system's ability to maintain the voltage at the end of the line.

When the limit is reached, the voltage will suddenly drop to 20 or 30 per cent of normal. Not only will lights go dim but motors driving refrigerators and the like burn out and electronic equipment can fail.

If this happens, virtually all the load must be shed to restore the voltage. The load can be restored only in small blocks and some might not be safely restored until after the peak period.

This is the problem in the South Island - a voltage collapse from Christchurch to Golden Bay would be a disaster. It is imperative that load is shed before the system becomes at risk if one of the lines is lost.

The problem is not new - it was discussed in Transpower's 2002 System Security Forecast. What has happened since is an unexpectedly high growth in winter peak demand because of the increasing use of electric heating. Domestic heating was the main reason for a recent 10 per cent increase in peak demand from one winter to the next.

Transpower has been trying to increase the load it can transmit by installing capacitor banks at Christchurch, but this year it had problems with a recently installed bank. That, plus the promise of a severe winter, made it realise it would need to shed load on unusually cold evenings.

Before deregulation, it was easy for the Electricity Department to control load over peak demand periods by asking power board engineers - mostly department-trained - to shed water-heaters. But now Transpower cannot insist water-heaters are switched off, and not many engineers understand the transmission system (because when it was formed, the Electricity Corporation decided training them was a waste of money).

The common-sense solutions of the past become very difficult indeed.

Transpower did not want to attract attention to a problem that could be solved by asking for co-operation from the lines companies and the retailers. But those companies and retailers saw it as yet another occasion when Transpower's failure to keep the system up to scratch was inconveniencing their customers. Unsurprisingly, they went public.

It seems their differences have now been resolved. With luck, the hot water load will be shed on a few cold evenings and no one will be seriously inconvenienced. If this is not enough, there may be public appeals to switch off non-vital equipment and for some industries to shut down for a few hours.

The chances are that next year will be much the same and the year after may be even worse. The north of the South Island is not alone - the supply to Auckland has the same problem.

What we are seeing is a direct result of the beliefs of those who led deregulation. These included:

* That retailers would pay Transpower to upgrade its system. They didn't.

* Distributed generation was the way of the future, so we would never need to upgrade the transmission system. It didn't happen and we are paying the price.

* Central planning is bad and the market will provide. But our power system cannot operate or develop efficiently without co-ordination between generation and transmission.

If the Government had simply kept an eye on demand to ensure it was matched by expanded generation and transmission, we would not be in a mess.

In the absence of any long-term planning for energy resources, generation and transmission all that Transpower can do is to try to rush through a 400kV transmission system from the Waitaki to Christchurch and another from Whakamaru to Auckland, at an estimated cost of $2.5 billion. The main, and urgent, objective is to fix the most seriously overloaded parts of our system.

New Zealand, however, needs 5500MW of new generation over the next 20 years to meet load growth and replace ageing thermal power stations. In the next 20 years we have to build stations equivalent to 75 per cent of all those we have built in the past 100 years.

If we make a decision on transmission before we know where the stations are likely to be, we will probably cut ourselves off from access to our best energy reserves.

The southern half of the South Island has huge reserves of hydropower, coal and offshore gas which would easily support 3000MW of generation. But if Transpower's 400kV upgrade goes ahead, no more than 1000MW of this resource could be used.

The North Island would have to look elsewhere for its power - expensive North Island coal, imported coal, or imported liquefied natural gas.

But if we built a new DC transmission superhighway from the South Island stations to Auckland, we could deliver all this power to Auckland at about the same cost as the alternative 400kV upgrade.

If the Government's commitment to the Kyoto Protocol rules out coal, another option is to build a nuclear station on the Kaipara. The Electricity Department had plans for this 30 years ago, but they were shelved with the discovery of Maui gas.

If 2000MW were fed into Auckland from a Kaipara station, it would eliminate the need for the 400kV upgrade in the North Island. Being able to credit a saving of $1 billion to the nuclear power station, together with avoiding carbon tax, may make it look very attractive indeed.

The 400kV upgrade into Christchurch could also be replaced by increased generation. A 360MW coal-fired station at Westport connected to an existing 220kV line would have the dual benefit of backing up the transmission into the city and providing reserve capacity for the South Island hydro stations.

There are other options, but they will never see the light of day unless the Government accepts the need for long-term planning and co-ordinated development of transmission and generation.

It says the Electricity Commission will do this. However, the commission's powers are limited and it is controlled by a Minister of Energy who believes burning coal is bad.

We must ensure that power stations and the transmission system are planned, built and operated to give us a reliable supply at the lowest cost. We have learned that the existing market cannot achieve this.

It is time we considered following the example of Brazil. It flirted with a market like ours, realised it didn't work and replaced it with co-ordinated operation and competitive generation.

* Bryan Leyland, of Pt Chevalier, is a consulting engineer.