"Since everything worked properly once power was restored, and since we have not had any further disruptions, a geomagnetic disruption is the likeliest explanation," Sydkraft operations engineer Sven-Aake Andersson told Swedish news agency TT on Friday.
A second powerful solar flare in just three days hit the Earth on Thursday, as the planet was recovering from a similar, earlier geomagnetic storm that snarled telecommunications and sparked a burst of the Northern Lights.
The storms also created some interference with the North American power grid.
A solar flare is a magnetic storm on the sun that appears as a very bright spot, and sends gas from the sun's surface into space.
The solar eruption will continue to affect the Earth's magnetic field for the next two weeks, experts say.
The first storm erupted from the surface of the sun around 1100 GMT Tuesday, firing a giant cloud of charged ions straight towards the Earth. It was the third most powerful solar eruption ever observed.
The second eruption was observed Wednesday at 2048 GMT, and the geomagnetic storm it created hit the Earth around 1500 GMT Thursday, according to the US National Oceanic and Atmospheric Administration's Space Environment Center.
NOAA space weather officials classified the geomagnetic storm as a G-5 or "extreme" on a scale that runs 1 to 5. In terms of frequency, this level of storm occurs only once, if at all, during the 11-year solar activity cycle, officials said.