The incident comes as authorities hunt a suspected militant climate activist accused of a string of attacks on substations across Germany last week that sought to cut supplies from coal-fired power plants.
In the Berlin incident, emergency services were alerted to the blaze in the Moabit area in the early hours.
"A construction site and part of the substation were burning and were damaged by the fire," police said, adding there was no disruption to supply.
They were investigating with the help of the grid operator whether the fire was arson or caused by a technical fault.
Attacks on substations took place last week in the states of North Rhine-Westphalia, in the west, and Brandenburg in the east, which did not cause major blackouts but led to temporary shutdowns of some equipment at power plants.
Police are hunting a 48-year-old who has sent letters claiming responsibility for the acts as a protest against the fossil-fuel industry.
Germany has been hit by a number of attacks on the power grid in recent months, with far-left militants claiming responsibility in some cases.
Authorities are also on alert for Russia-linked sabotage plots.
READ ALSO: 'Daily target' - What we know so far about intensifying hybrid attacks on Germany
Comments