Local police said they were investigating an act of premeditated vandalism targeting the technical infrastructure of a power substation near the western city of Bergheim at about 4 p.m. on Tuesday.
A police spokesperson declined to specify the damage but said the region's power supply was not affected, the Reuters news agency reported.
Electricity grid operator Amprion said external interference was likely to have caused the incident and that power supply and grid stability had been maintained throughout.
Germany's largest power producer RWE, which is a majority owner of Amprion, said in a separate statement that the incident had caused five lignite-fired power plant units, with a combined capacity of 4,200 megawatts, to go offline, according to Reuters.
In a separate incident early on Wednesday, an unknown object exploded near a train station in the southern city of Augsburg, German police said, adding that two passersby, aged 17 and 18, suffered minor injuries.
The blast occurred in a passageway of a station building, officers said, adding that the injured individuals were Ukrainian nationals.
Hours later, Augsburg's main train station was closed after another suspicious object was found there, but rail operations resumed later in the morning.
German news outlet Bild reported that a hand grenade exploded in front of a jewellery store and that the train station itself was apparently not the target.
A police spokesperson said details of the explosive device remained unclear, Reuters reported.
It said the incidents come at a time when the far-right Alternative for Germany (AfD), which favours closer ties with Moscow, leads polls ahead of a state election this weekend and Germany facing a growing threat from hybrid warfare.
The German government said on Tuesday that Russia was behind an attempted drone attack on a Ukrainian cargo plane at Leipzig/Halle Airport last month—an incident that European Union foreign policy chief Kaja Kallas said bore all the hallmarks of state-sponsored terrorism.
Also on Tuesday, devices containing conductive material damaged power lines at one of the most critical high-voltage nodes in the eastern state of Brandenburg near the Polish border.
Brandenburg's interior minister, Jan Redmann, said there appeared to be parallels between the incidents but that the investigations were at a very early stage, Reuters reported.
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Source: Reuters, IAR/PAP