Underground electrical explosion in savannah

[brantmacga]

SAVANNAH, Ga. (AP) ? An explosion in underground electrical cables blew off manhole covers and started several fires in downtown Savannah Monday morning, prompting police to evacuate several stores and restaurants, many of which were without power. No injuries were immediately reported, police said.

In August, an underground electrical fire just blocks away also spewed smoke through manhole covers and cut off power downtown. That problem, Seiler said, was caused by a fault in the underground network system.

Georgia Power was in the second year of a five-year upgrade in the underground power network downtown, Seiler said.

story link

 

[mdshunk]

They've put in a fair amount of circuit breakers in the network vaults in the town I mostly work in the past few years. Funny thing is that many of them are completely underwater! What a waste. Maybe they're submarine breakers? :grin:

 

[charlie]

A major downtown or central business district has an extremely stiff network, most with 100 kA to 150 kA available and sometimes approaching 300 kA. Manhole covers weigh close to 300# and there are only cables in the manholes. It is only fault current that is vaporizing copper cable that is causing the arc blast that is blowing the covers off of the manholes.

I would appreciate you remembering the above paragraph the next time you are working around high amounts of available fault current. In other words, the best "moon suit" would not be enough to protect you in some cases where you are working on energized service equipment even in the outlying areas.

 

[brantmacga]

so charlie, what you're saying is, walk around the manhole cover?

 

[nakulak]

so charlie, what you're saying is, walk around the manhole cover?

and don't stand underneath them if they are flying around

 

[charlie]

. . . walk around the manhole cover?

Only when there is a faulted cable situation. Normally, manhole covers are in the street. :smile:

 

[richxtlc]

They've put in a fair amount of circuit breakers in the network vaults in the town I mostly work in the past few years. Funny thing is that many of them are completely underwater! What a waste. Maybe they're submarine breakers? :grin:

They do make a submersible network transformer with an attached network protector. These units have a nitrogen seal in the protector unit.

 

[brantmacga]

so charlie, how do they do these upgrades?

is there a network of conduit under the streets that they simply pull new cables through? or do they have to use a horizontal drill under the streets?

 

[brantmacga]

more information in paper today

Story Link


Wow, this looks old

 

[charlie]

. . . Wow, this looks old. . .

Actually, this looks quite good. :smile:

 

[aja21]

Actually, this looks quite good. :smile:

Yes, this looks like absolute top notch stuff compared to the 40s era stuff in our subs.

 

[mdshunk]

so charlie, how do they do these upgrades?

is there a network of conduit under the streets that they simply pull new cables through? or do they have to use a horizontal drill under the streets?

No, no boring required. They put a great deal of expense into the duct bank and vault construction, in hopes that it will last a couple hundred years without doing any more digging.

 

[don_resqcapt19]

Actually, this looks quite good. :smile:

It looks like a number of violations of the OSHA confined space rules to me.