Nearly 23,000 customers lost electricity Sunday night for about an hour after an owl somehow climbed into an electrical transmission substation, officials said.

The bird tripped the high-voltage line at 10:20 p.m. and immediately shut down the substation. An additional three substations went down as well.

"The system has a lot of protective devices," said Margaret Oler, spokesperson for Rocky Mountain Power. "Our equipment operated exactly as it should have and did not allow the damage to go further."

Oler said field personnel responded to the problem immediately and were able to clear the damage and restore power. She said residents had their power restored in chunks, to help stabilize the system. The power was restored to the 22,800 customers on the south side of town at 11:25 p.m., Oler said.

She said the owl did not survive the 69,000-volt shock.

"Anytime an animal comes in contact with electrical facilities, it's nearly always fatal," she said.

Oler said power outages happen occasionally, but she has not seen an outage of this size in her 25 years in the business.

"Thankfully, the outage occurred on a Sunday night when there weren't many people on the roads," said Casper police Sgt. Brad Wnuk.

Wnuk said law enforcement officials hurried to respond to some of the busier intersections to help control traffic.

"The safety of motorists is always a top concern," he said. "Any time you encounter an uncontrolled intersection, you should always treat it as a four-way stop. The first person to get to the intersection gets to go first."

Wnuk said the sheer size of the outage caused some confusion, but Casper motorists were patient and courteous, helping to prevent any major accidents while the power was out.

He said a few building security alarms went off after the power came back on, but he wasn't aware of any burglaries as a result of the outage.

Power did not go out at the Wyoming Medical Center. Mike Phillips, spokesman for the hospital, said in case of an outage, the hospital has two diesel generators that will come on 9.2 seconds after the power goes out, restoring electricity to all the critical life support systems.

Phillips said the hospital has enough diesel fuel to run for seven days in the event of a long-term power outage.

Reporter John Morgan can be reached at (307) 266-0614 or john.morgan@casperstartribune.net.