South Australia has a modest amount of wind power, at around 1.5 GW nameplate capacity, but it also has a modest demand for electricity, and there are times when wind power can meet or exceed total demand. The state has also just lost its last coal-fired power station, and its current generator mix is one towards which many other grids are moving.
The high penetration of variable wind power, and the recent exit of local coal power makes grid stability and control an important issue. To begin to investigate this issue I decided to look at the electricity data for the morning of 28th April 2016, when there was a power outage during rush hour on an electric train system in Adelaide; was this a problem purely with the railway system, or was it triggered by a grid instability?
The following two figures show data for electricity generation and import/export at 5-minute intervals for the morning of 28th April (a Thursday), and for some immediately preceding and subsequent working days. The upper figure shows total consumption in SA, the sum over all local generation, plus net import/export. The lower figure shows data for the separate generation types and for the individual interconnectors.
The upper figure shows an unusual drop in total consumption at 7:30 am, matching press reports of the time of the power outage of the railway. The size of the drop (around 100 MW) suggests to the author that it might have been a lot more than just the loss of the MW being used at the time by the railway, i.e. there might have been a sudden but temporary drop in supply which tripped the railway electrics.
The lower figure shows that wind power was almost totally absent at 7:30 am, thermal generation supply was falling, and the interconnectors were in a period of anti-phase oscillation, with a very substantial drop of over 200 MW in import via the Heywood interconnector between 7:20 and 7:30 am.
There is not enough data available to the public to determine what caused the power outage at the Adelaide railway on 28th April 2016, but the data shown above suggests to the author the distinct possibility that a sudden and large drop in supply was involved.
See the NEM ELECTRICITY DATA page above for links to the archive data used, the interconnector data shown is METEREDMWFLOW from DispatchIS files, and the generator data shown is the sum of SCADAVALUE figures from DispatchSCADA files.