Ballarat CIU Detective Senior Sergeant Tim Argall said they believed two people, captured on CCTV, cut locks and entered the plant about 1.50am.

"The equipment at the sub-station arced, the offenders have done something that has caused a fairly big flash-over or explosion and there is the possibility the offenders have been burnt," he said

"We are checking in the hospitals in Ballarat, the region and Geelong and are really keen to hear from anyone who may know something about some unexplained burns," Detective Senior Sergeant Argall said.

He said police had ruled out terrorism as a motive and said a dark coloured wagon or SUV did not appear equipped for the theft of equipment including copper wiring.

"They have gone there for whatever reason, it could be people out there with nothing better to do, and through a fairly stupid simple action have caused $60,000 worth of damage to some vital infrastructure that could have been much worse."

He also emphasised the high risks to anybody entering the terminal station.

"These places have cables with thousands and thousands of volts running through them, they are secured for a reason and that is because they are very dangerous places to be," Detective Senior Sergeant Argall said.

Due to this even attending police were not able to enter the site until SP Ausnet technical crews were available, he said.

SP Ausnet which runs the facility did not rely to questions by deadline about he impact of the explosion on its wider network.

But Powercor, which supplies Ballarat's domestic and business electricity, confirmed no customers were impacted by the event.

Anyone with information is urged to phone Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au.

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