On Monday evening, there was a power outage at a substation in Bergheim in the Rhineland in western Germany.
"We do not believe it is due to a technical fault but to an intentional act," a police spokesperson told Westdeutscher Rundfunk.
Cables had been laid on top of the power lines to cause a short circuit, North Rhine-Westphalia Interior Minister Herbert Reul said, according to the Kölner Stadt-Anzeiger newspaper.
This affected operations at two connected coal-fired power plants, but it reportedly did not lead to any power outages.
On Tuesday, a similar incident occurred on the other side of the country. Several explosive devices were found at a substation in the eastern state of Brandenburg. The station is connected to Jänschwalde, one of Germany's largest coal-fired power plants.
On Wednesday, German police announced that it was being investigated as a possible terrorist crime.
On Monday, the German government accused Russia of being behind sabotage plans in which explosive-laden drones were found at Leipzig/Halle airport earlier in August. There, and in many other countries in Europe, there have been alarms about an escalation in Russian hybrid warfare alongside the war in Ukraine.
In January of this year, there was sabotage against the electricity grid in Berlin, cutting power to around 45,000 households. A left-wing extremist group claimed responsibility.
