Electricity engineering consultant Bryan Leyland reviews a period in our transmission history when, in his belief, we got it so wrong.
LONG-DISTANCE TRANSMISSION in New Zealand started up in the 1930s as hydropower stations were built in locations remote from the major load centres and many 110kV lines were built in both islands over the following two decades.
In 1953 the first 220 kV line was commissioned and from then until the 1970s many new 220 kV lines were built to accommodate the Waitaki hydro system and Manapouri hydropower station in the South Island, and various schemes on the Waikato.
Between 1990 and 2010, very few transmission lines were built, even though demand was increasing steadily. At the time Bob Thomson, who was then CEO of Transpower, believed that ‘distributed generation’ was advancing rapidly and, as a result, there would be no more need to expand the national transmission system.
Bob’s reasoning was, I believe, based on the assumption that small combined heat and power units would soon become available and be widely adopted. In effect, he assumed that the best use for 100MW of gas was to turn it into about 50MW of heat (to be used some way or another) and about 30MW of electricity. He ignored the fact that if the same amount of gas was used in a modern combined cycle station it would produce about 60MW of electricity.
It also meant gas consumption would double. Where was all the extra gas coming from? This reasoning also ignored the fact that if thousands of these units were installed, it would still be necessary to have transmission and generation to back them up because, if there was a blackout, the system must be energised before the combined heat and power units could restart. On top of the expense, managing such a system would be a nightmare, and voltage and frequency extremely difficult to control.
In spite of these very obvious shortcomings in my view, Bob was able to persuade his Board – which, at that time, had Sir Colin Maiden, a distinguished engineer, as chairman – that there was no need to invest in expanding the transmission system. (In the Board’s defence, Bob allegedly told them that his senior management supported his thesis: I am reliably informed that this was not the case.) Bob Thomson once told me that he thought that Transpower would never build another transmission line. I believe that as a result of this belief Transpower did not bother to object when, under the Resource Management Act, laws and regulations were proposed that would make it extremely difficult to upgrade existing lines and even more difficult to build new ones.
Even though the country’s load was increasing and the transmission system was under stress, Transpower’s management did not waver from its belief in distributed generation.
Bob Thomson retired in 2003 and was replaced by Dr Craven from Australia who was shocked to discover that there were no long term plans for building new transmission lines to meet load growth, reduce losses and cater for new power stations being built in Taranaki and the central and southern North Island.
A necessarily hasty analysis of the options finished up recommending a new 400kV transmission line from Atiamuri to Auckland. This line was planned to initially operate at 220kV and be upgraded to 400kV between 2030 and 2040. Whether or not this was the best option is a vexed question. Some engineers were strongly of the opinion that a better option was to upgrade existing 220kV single circuit lines to carry a much higher current. This would have deferred the need to build a 400kV line and so give time for a more rational assessment of possibly attractive options such as extending the direct current (DC) link from Wellington up to Auckland by converting one of the single circuit 220kV lines to direct current.
Since the decision was made there have been major improvements in DC technology and many engineers are now convinced that long-distance high-voltage AC transmission will soon be supplanted by direct current. The recent development of the world’s first high voltage direct current circuit breaker serves to support this belief. This was a major step forward in direct current technology as it allows a fully interconnected DC system. It is now probable that the 400kV line will never operate at 400kV.
Under the electricity reforms and the market regime I believe many opportunities for improving the system and reducing costs have been ignored, because many of the people making the decisions have been economists who did not understand that power systems were not at all like the markets that they were familiar with.
The effective demise of ripple control is a case in point. Thirty years ago, all electric water heaters were controlled by local power boards (who purchased bulk power from the New Zealand Electricity Department) and the ripple control systems ensured that the load on a peak demand day was virtually steady from about 8AM to 9PM. The savings in transmission, distribution and generation were huge. Electricity reforms left these lines companies in charge of the ripple injection system with the ripple relays open to ‘competition’. Regulators also made the Transpower charges ‘pass through’ to the lines companies thus depriving them of any financial incentive for the lines companies to manage the consumers’ demand.
New Zealand demand now peaks between 7am and 8am, and then drops significantly before increasing to a maximum at around 6pm. In all probability, the system peak is between 200MW and 400MW greater than needs to be. For this, the consumer pays dearly.
An argument for ripple control
A further problem is that many influential people blindly assumed that ‘smart meters’ would supersede ripple control and take over control of hot water and other appliances. To my knowledge, this has never happened. Instead, the ripple control systems have been steadily run down and are now used much less than previously, even though the potential for the control of consumers’ water heaters and other loads that can be switched off without the consumer noticing, is enormous.
Using low-frequency radio, a new technology, it is possible to control all the water heaters in the country or any single water heater. These radio transmitters will also cost much less than conventional ripple injection systems that are much less versatile.
With a radio system, Transpower could shut down all water heaters in the event of a system emergency such as a loss of generating plant or simply to avoid having to run a large amount of spinning reserve just in case there was a short-term problem with generation or transmission.
The retailers could manage their consumers’ loads when they were purchasing on the spot market and thus reduce costs to the consumer. The lines companies could manage loads on their system or on any feeder whenever they needed to. The annual benefit to the consumer if all these were implemented would probably run into hundreds of millions of dollars.
So, in summary, we have a power system that is far from optimal because of poor decision-making in the past and because the economists who manage the market have never understood the electricity system.
No one seems to want to look at the system from the point of view of the consumer. If this had been the objective from the start, I believe we would have paid billions of dollars less for our generation and today have a system designed to deliver power efficiently and reliably at the least cost.