On Monday evening, there was a power outage at a substation in Bergheim in the Ruhr area of western Germany.
"We do not believe it is due to a technical fault but to an intentional act," a police spokesperson told Westdeutscher Rundfunk.
It is not clear what may have caused the disruption, but it did not lead to any outages.
The suspected sabotage follows Monday's news that several explosive devices were found at a substation near Jänschwalde, one of Germany's largest coal-fired power plants in the eastern state of Brandenburg.
On Monday, the German government directly accused Russia of being behind sabotage plans after explosive-laden drones were found at Leipzig/Halle airport earlier in August. There, and in many other countries in Europe, there have been warnings 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.
