I'm always supprised at these statements "overload ??"
Of course overload is nine out of ten times the cause of these dramatic faillures.
Other interesting issue i find that the US firefighters take unnecessary risks with live electrical equipment.
In NZ the fireservice, if lives are not at risk, stays clear of live power cables untill isolated by the local power authority.
Did anybody else find these statements weird?
"The initial fire started in a 240-volt underground cable below a busy corridor near Los Angeles International Airport..."
"The high-voltage copper cable in a conduit made of lead was degraded..."
High voltage 240V line??????
Was this really a 240KV line?
This is AP, not NEC. 120V and 240V are "high voltage" to 99% of americans.
[quote]Of course overload is nine out of ten times the cause of these dramatic failures[quote]
Do you have stats to back this statement. In my expierence the majority of electrical arc faults are, water, loose connections leading to excessive heat and a break down of the insulating material to the point where it is a conductor. Then there is human interference, dropping tools, covers ect.
While I am no lineman I doubt 50 year old lead sheated cable in a downtown would be 240KV. I would think the voltage level thing was just a typical lack of knowledge regarding the subject matter by the reporter
"I would think the voltage level thing was just a typical lack of knowledge regarding the subject matter by the reporter" <--Gee that would hardly be a first. My question is what explosive gasses- combustible by an unspecified "power saw" could have built up in there? Heat+Lead+Copper doesn't create any explosive substance I have ever heard of.
Another cryptic sentence: "Smoke from the fire built pressure which led to an explosion that blew a manhole cover near an office supply store, Miller said. Witnesses reported seeing the cover fly more than 20 feet."
Forwarding this story to my brother who is a fireman... maybe he can shed some light on this strange story filled with loose ends and seemingly contradictory statements..
Trollog,
Speaking for myself; I would welcome some REAL information about this.
I have a hard time believing that anyone would run underground lead shielded cable for a 240V circuit.
Remember that some of this story may have been written by the same folks who wrote "Shuttle was travelling 18 times the speed of light" when Columbia broke apart on re-entry and wrote "Osama Bin Laden almost certainly either dead or alive" (and yes...I DID actually see this one on TV).
Ghost:
There was BXL, armor cable with individual conductors lead shielded (encased). This was used for direct burial prior to UF. Which I would bet money is not the case here.
Took a man and an apprentice to carry a 250' roll of 10-2 BXL.
Some explanation on the explosion part at least... talked to my brother today about it. Seems this story is starting to make the rounds in the fire service although the investigation is still not comlete. According to him, smoke is simply airborn unburned fuel and cutting a door off its hinges with a chopsaw is enough to ingnite the fine particulate matter in smoke with results similar to a grain silo explosion. It can be quite violent. More information to follow, as it becomes available, although I am not sure fire departments are as concerned with the electrical angle vs the firefighting/safet angle on episodes like this, but still something of interest to us here might come out of it.