A squirrel did it.

The problem that knocked out power across the entire grid for an hour or longer this morning was caused by a squirrel meandering through the substation next to Mountainview Drive.

Jay Massie, superintendent of operations for Yukon Electrical Co. Ltd., said as the squirrel moved around the top of the substation, it provided the connection between an energized conductor and ground, causing a short.

And for a brief, but turbulent second or two, there would have been what they refer to in the business as a fireball, Massie said.

"They say when electricity arcs, it arcs at about 3,000 degrees Celsius," he explained. "So once this fireball starts, basically it creates a big fault.

"That fireball really does ionize the air, and really does not go out until some upstream breaker realizes basically there is more power than there should be."

Massie said it would have happened quickly, but the system would have been feeding the fireball with additional juice for the bat of an eyelash, though long enough to rock the entire grid and do substantial damage to the substation.

Yukon Electrical is estimating repair to the breaker at $10,000, including partial replacement of the damaged breaker and labour, he said.

Power for the entire Whitehorse-Aishihik-Faro grid went out at 8:58, and was first restored 32 minutes later to a small area downtown. Communities with back-up generators, like Teslin and Ross River, would have come on in about five minutes.

"Between 9:30 and 10:08, everybody else was back on except the Mayo Road," he said.

Massie said the once electricity was restored, the breaker guarding the Mayo Road opened up, as breakers sometimes do when there's a rush of power.

The squirrel would have died instantly, and was found at foot of the breaker, he said.

There were pieces of the porcelain insulator up to six metres away.

Massie said having the problem occur in the substation is the worst place it could happen.

The breakers, he said, are designed to detect and shut down trouble spots.

Massie said the fireball would have lost its kick when another breaker on the system killed the power.

The Mountainview substation has three breakers protecting three different areas.

The breaker damaged this morning was tied the system feeding the section of Porter Creek across from Porter Creek Secondary School, the Mountain View Golf Course and Northland Mobile Home Park.

The load has been switched temporarily to the Holly Street substation until repairs can be made, which Massie expects will completed next week.

The Minto Mine was switched to the back-up diesel generators on site, but for a short period before the power was restored.