System strength — such as voltage control — is one of the most talked-about issues in the National Energy Market (NEM) this year. There are currently three rule changes dealing directly with system strength issues, which could have a profound impact on the electricity grid.
Cornwall Insight Australia has examined the top 100 constraints by their marginal $/MW/dispatch interval related to system strength issues across the NEM for the last four years. The research found a significant increase in Queensland’s (QLD) constraints over the past year, increasing by $420,000/MWh in 2019.
Graph note: The constraint data for 2020 is only up to June 2020 to make it comparable to previous years the value was doubled.
Ben Cerini, Principal Consultant at Cornwall Insight Australia, said:
“These constraints are at their worst over the spring, so, 2020 figures could be much larger than depicted here once the final six months of results come in. The constraint costs for SA — which have traditionally dominated the total across the NEM — are almost solely due to the wind generation limits. However, recently these have trended down.
“The large increase in constraint issues in QLD was mostly due to the constraints on Mount Emerald Wind Farm and Haughton Solar Farm resulting from system strength issues in Northern Queensland. We can expect these constraints will only continue to increase and will likely overtake the much talked about wind system strength constraints in South Australia (SA). That is until new system strength alleviation measures are installed. For example, the new synchronous condenser set to be installed at the Kaban Green Power Hub, which may slow the rapid rise in fault levels.
“The system strength issue in New South Wales (NSW) that was ramping up in 2019 was predominantly due to the constraint invoked to avoid voltage collapse in South NSW resulting from the loss of the single biggest generator in Victoria (VIC) (or Basslink). This constraint has only bound 200 hours in the first six months, or 400hrs equivalent in 2020 compared to ~2,100 in 2019. The lack of this constraint binding in 2020 may be in part due to the increase in generation in southern NSW.
“As more generation comes online in NSW, we are likely to see a new constraint bind limiting the flow of generation east through Wagga Wagga to less than 300MW. This is of course, until HumeLink comes online, which is not scheduled until at least 2025.
“Understanding the direction of system strength policy and regulation is key to ensuring participants in the market are aware of potential impacts on projects as well as being able to identify areas of the grid that need support.”