22 February, 2017
Courtesy of the Australian
The closure of more conventional power stations is likely to increase fluctuations in frequency in the electricity market, posing a risk to the security of the system, the operator of a NSW electricity generator has warned.
Delta Electricity, which operates the 1970s-built Vales Point coal-fired power station, said it had seen increasing numbers of deviations to frequency over the last three years. Delta told a landmark inquiry by the Australian Energy Market Commission that this “raises concerns about the ongoing security” of the national electricity market.
“As the number of events continues to increase, it is possible that the underlying cause could become a threat to system security,” Delta said in a submission to the commission.
Traditionally, conventional spinning generators fuelled by coal, gas or hydro are synchronised to the frequency of the grid of about 50 Hertz and provide “inertia” to allow the system to cope with frequency changes, the AEMC said in its interim report in December. By contrast, wind and solar have low inertia.
Delta told the AEMC that the increase in the changes in frequency observed at Vales Point, at Lake Macquarie, could be caused by the greater reliance on intermittent generation, along with other factors. Wind farms and rooftop solar are considered intermittent because they only work when the sun is shining or wind blowing.
“It is likely that further withdrawal of conventional synchronous plant from the market will increase frequency deviations which could pose a threat to system security,” the submission says.
A slew of coal-fired generators have been decommissioned in the last few years. Victoria’s Hazelwood brown-coal power plant is due to close by the end of next month. South Australia’s Northern power plant was closed last year, while other closures have included NSW’s Munmorah and Wallerawang and Queensland’s Swanbank B.
Delta has also raised concerns that the centrally-managed scheme where the energy market operator handles minor deviations in frequency is becoming “less stable”.
There is growing debate about how to keep the system in a secure state as the mix of generation sources changes.
The Clean Energy Council has told the commission that “inertia is not the only consideration” and that grids in North America and UK impose tighter frequency controls on synchronous electricity generators.
“The current arrangements are not delivering a secure power system in the long-term interests of consumers and should be revisited,” the council’s submission says.