Electricity department officials said no one was injured.
The fire broke out suddenly at the Thalavaipet Electrical sub-station located six km from Bhavani around 7 AM, officials said.
The fire damaged the transformer and 14,000 litres of oil inside it was also burnt.
Fire fighting tenders from nearby Bhavani, Appakudal, Gobichettipalayam and Chitode doused the fire which gutted the sub-station.
Power supply to more than 20 villages located around the sub-station was affected following the fire, officials said.
