Today's San Francisco explosion

Mostly Cajun writes about the explosion in downtown San Francisco.

News story on Foxnews about an explosion near a San Francisco mall.

"All of a sudden there was a big, big, big boom and the lights flickered off," said Ellen, who joined other workers in a smoky stairwell as she made her way to the street from the 28th floor above the Ralph Lauren store. She wouldn�t give her last name, but said she worked for Charles Schwab.

"I thought it was a bomb," she said. "It was very scary."

The blast came from a vault that houses four Pacific Gas & Electric Co. transformers fed by a 34,000-volt electrical cable, said company spokesman Paul Moreno.

Ah! Explosion in a transformer vault. Be still my throbbing heart. This is the stuff dreams are made of!

The cause could not immediately be determined because a bomb squad was investigating, but Moreno said there have been vault explosions in the past.

No sh*t, Sherlock! We don�t like �em, but they ARE a fact of electrical life. We do all sorts of testing and predicting, and we can, with a well-engineered and properly maintained system, reduce the number of these explosions, but they DO happen.

No utility workers were present when the explosion buckled a sidewalk and shot a manhole cover 25 feet across the street, according to Fire Chief Joanne Hayes-White.

We generally aren�t. Silly us! If we think the d*mned thing is getting ready to blow up, we haul major butt and shut it off!

Okay! Okay! I know THIS ONE!

Electrical disasters are both my hobby and my profession. Allow me a few points here.

34,000 volt cable. That�s a decent voltage level. Above that level, insulated cables get REALLY expensive and interesting to deal with. That�s also a huge amount of power. A cable with copper as thick as your thumb can carry multiple thousands of horsepower under perfectly normal conditions. That "normal conditions" presupposes that all the insulation in every component in the system is in good shape.

He then goes on to talk a bit about how these happen and why as well as give a few examples of personal experiences. He is a fun writer so it's worth visiting to read for yourself. Go and read: Oops