The explosion of emergency batteries at the Natanz nuclear facility destroyed the power distribution system and shut down the centrifuges.

Chairman of the Iranian Parliamentary Energy Commission:
The electrical substation at Natanz is located underground, at a depth of fifty meters.

Sabotage in the power distribution system (nuclear facility) was associated with emergency power supplies.  In a complex battery operation that resulted in an explosion (the saboteur) managed to destroy both the power distribution system and the power cable, resulting in a power outage for the centrifuges.