No one was injured in the incident which was reported from the 220 KV sub-station located near Crowne Plaza Hotel in Okhla at around 2:40 PM.
Officials said 12-15 fire tenders have been rushed to the spot to douse the flames.
The cause of fire is yet to be established.
Power supply to some areas like Kalkaji and Okhla was hit due to the incident.
