Protection mechanism in tornado-hit turbines caused drop in power that led to entire system being tripped, Aemo says.

The state-wide blackout in South Australia which prompted a national political storm over energy policy was caused by extreme weather, which triggered a cascading sequence resulting in the state separating from the national energy market, according to a final assessment from the Australian Energy Market Operator.

The final report finds that the state’s windfarms rode out the grid disturbances prompted by the loss of key transmission lines during two tornadoes with wind speeds between 190 and 260 km/h – but the activation of a protection mechanism in the turbines triggered a sustained reduction in power in the state, with a drop of 456MW over a period of less than seven seconds.

The sudden reduction in wind power on the day of the blackout prompted a significant increase in imported power flowing through the Heywood interconnector, which then tripped the whole system and triggered the state-wide blackout on 28 September.

Transmission towers toppled by high winds in South Australia

The market operator says “the intermittency of the wind was not a material factor in the black system event itself” but it says the impact of the sudden drop in power due to the in-built protection mechanisms was “greater than expected”.

Curiously, the Aemo says it was “unaware of this protection feature before the black system event”.

It says it has now asked for the control settings governing windfarms to be overhauled to remove the risk of such an event happening again. It says the changes will improve its ability to forecast the impact of over-speed protection during high wind conditions.

Demand response means encouraging consumers to lower their energy consumption during periods of peak demand.

The Aemo has another pointed message for governments in its final assessment of events in South Australia last September. It says the technical challenges associated with the current change in the electricity-generation mix are best managed by both regulatory and market means.

The final report, which will trigger a fresh round of political infighting between SA and the Turnbull government, supersedes Aemo’s three previous preliminary reports on the blackout.

Source: the guardian

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