* Big power volumes dropped and added suddenly
* Germany at centre of European grid system
* Problems mastered according to plan (Adds expanded explanation of Italian power price rise)
By Vera Eckert
FRANKFURT, March 20 (Reuters) - Electrical grids in Europe succeeded in managing the unprecedented disruption to solar power from Friday's 2-1/2-hour eclipse that brought sudden, massive drops in supply.
Germany, Europe's leading economy and boasting the world's biggest solar-powered installations, was at the heart of the event.
Of 89 gigawatt (GW) of installed European solar capacity, it has 38.2 GW, which in theory is enough to meet half of its maximum demand.
The initial 15 GW drop in Germany was less than operators had feared. They were able to draw on alternative power sources including coal, gas, biogas, nuclear and hydroelectric energy pumped from storage and were helped by demand reductions from industry including four aluminium plants.
"Good preparations paid off, we were able to handle all swings in production," said Ulrike Hoerchens, spokeswoman for one of the four high-voltage grid firms, TenneT, which operates in the region with the highest share of photovoltaic units.
Solar power output has expanded sharply to 38.2 gigawatts (GW) since the region's last notable eclipse in 2003, so the country - which borders nine nations - needed to prove its power market and network handling centres could function under extraordinary conditions.
German solar output right before the eclipse totalled 21.7 GW, then dropped to a low point of 6.2 GW, followed by an addition of 15 GW again within the following hour, TenneT said.
The speed of feed-in was treble the normal maximum, which could have caused disruptions.
At Germany's national meteorological office in Offenbach near Frankfurt, some 50 people were gathered on the roof of a six-storey building equipped with home-made viewing devices - among many people across the region stepping out to see the event.
Operators across Europe had been making preparations for several months, improving communications and doubling staff levels on the day.
Europe saw a decrease in solar power of a total 17 GW and an increase afterwards by 25 GW, said Pierre Bornard, deputy chief executive of French grid RTE and chairman of grid company lobby ENTSO-E.
In Britain, the National Grid said solar output would be reduced by 850 megawatts but there would be a small drop in demand as people were expected to go outside to see the phenomenon.
In Spain, grid firm Red Electrica said reserve levels had been raised and big consumers could have been disconnected, while Italy's Terna decided to switch off 30 percent of solar capacity and make it up from other sources, which traders said raised prices.
An industry source said Italian prices were also pushed higher by reduced availability of power imports from neighbouring countries as the eclipse reduced solar output.
Norwegian, Danish and Czech grid sources said supply had been under control. (Additional reporting by Tom Kaeckenhoff, Anneli Palmen, Victoria Bryan, Jose Rodriguez, Nina Chestney, Stephen Jewkes, Nerijus Adomaitis, Geert de Clercq, Oleg Vukmanovic, Michael Kahn; Editing by Dale Hudson/Ruth Pitchford)