Rolling blackout

A rolling blackout, also referred to as rotational load shedding or feeder rotation, is an intentionally engineered electrical power shutdown where electricity delivery is stopped for non-overlapping periods of time over different parts of the distribution region. Rolling blackouts are a last-resort measure used by an electric utility company to avoid a total blackout of the power system. They are a type of demand response for a situation where the demand for electricity exceeds the power supply capability of the network. Rolling blackouts may be localised to a specific part of the electricity network or may be more widespread and affect entire countries and continents. Rolling blackouts generally result from two causes: insufficient generation capacity or inadequate transmission infrastructure to deliver sufficient power to the area where it is needed.

Rolling blackouts are a common or even a normal daily event in many developing countries where electricity generation capacity is underfunded or infrastructure is poorly managed. Rolling blackouts in developed countries are rare because demand is accurately forecasted, adequate infrastructure investment is scheduled and networks are well managed; such events are considered an unacceptable failure of planning and can cause significant political damage to responsible governments. In well managed under-capacity systems, blackouts are scheduled in advance and advertised to allow people to work around them, but in most cases they happen without warning, typically whenever the transmission frequency falls below the 'safe' limit. Rolling blackouts are also used as a response strategy to cope with reduced output beyond reserve capacity from power stations taken offline unexpectedly such as through an extreme weather event.

In South Australia, in February 2017, following heatwave conditions, SA Power Networks used load shedding to cope with demand for 30 minutes. The Australian Energy Market Operator (AEMO) had instructed SA Power Networks to commence 100 MW rotational load-shedding via a government-agreed list due to lack of available generation supply in South Australia.

The Heywood Interconnector between South Australia and Victoria was recently expanded to allow greater power capacity (600 MW) to avoid lack of capacity, however an increased proportion of that generation is from intermittent renewable sources like wind and solar. In 2016, South Australia closed its only coal-fired power plant located at Port Augusta.

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