A partial solar eclipse that raised early concerns over European power grid stability had little ill effect on the morning of March 20, according to IEEE Spectrum.

Enrico Maria Carlini, head of Electric System Engineering for National Dispatching at Rome-based transmission system operator Terna, says the grid was more stable than normal during the event. Frequency strayed about 25 millihertz (MH) all morning, which Carlini says is roughly half of the normal variability in Europe's grid frequency.

In all, Europe lost and regained about 17 gigawatts (GW) of solar power generation during the March 20 event, according to the European Network for Transmission System Operators for Electricity in Brussels.

“Those plants were ordered to limit their output to about 30% of total capacity from 7 am to 2 pm CET," says Carlini. That action, he says, reduced the solar power deflation during the eclipse by about 500 megawatts (MW) and trimmed the post-eclipse rebound by 2 GW.

The solar electric output swings still represented the biggest power gyrations that Germany's Transmission System Operators (TSOs) have confronted, according to Bruno Burger, an expert in renewable energy integration at the Fraunhofer Institute for Solar Energy Systems in Freiburg.

Germany's solar generation was at nearly 13 GW when the eclipse began. At the peak of the eclipse, at around 10.30 CET, it had fallen to 5.4 GW. Then by noon, output had rebounded to about 20 GW. The post-eclipse surge would have soaked up about 50% more than the maximum negative power reserve capacity that Germany's TSOs had in place in 2013 and 2014.

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