Arcing of Double Ended 15 kv switchgear

[Loderunner]

I would like to have some information related to arcing of double ended 15kv switchgear . The AHJ states there is a great possiblity an arcing equivalent to 1.76 sticks of dynamite could damage the ATS which is located in front of this gear. It is approximately 5.5 ft from the face of the gear. ??? what is the possibility of an arcing to happen, and has there been a situation occur of this nature anywhere in the world. :shock:

 

[MJJBEE]

Do a google search on arc flash it's a definite possibility at that voltage

 

[zog]

We respond to emergency calls for arc flash/blast incidents from 15kV switchgear weekly, they happen often enough to be a major concern. Arc flash incident energy is measured in cal/cm2 (Joules/cm2) by conducting an arc flash analysis.

I have no idea where he got 1.76 stick of dynamite, no such calculation exists that I know of for those units, I think he just pulled that number out of you know where.

There is a video from a secutiry camera from an arc flash in WI on some 15kV switchgear that sent 3 guys to a burn center (One had to be induced into a 3 month coma).

The NEC requires arc flash labeling for that equipment (Article 210.16 I think)

 

[coulter]

Hummm -

1.76 sticks. I wonder if that is 10% stumping powder or a higher percentage.

Three significant figures says one has a lot of confidence in the calculation. I would be very interested in the source reference for the equations, calculation method.

Loderunner- Perhaps you could ask the AHJ where that comes from.

 

[coulter]

Loderunner -
NFPA 70E gives some methods to calculate incident energy and approach distances.

As to causes. Assuming the equipment is being kept relativly clean, has even minor maintenance pulled, and the fixers are keeping their wrenches out of the energized busses, I don't know what could cause it.

Zog -

You say you are responding weekly to arcflash incidents in 15kV equipment. That is 50 a year your company is responding to. What are some of the root causes? Also, maybe you could give me some examples of the worst and least incidents so I can have some idea of the magnitude of the issues. I'm thinking that it is surprising there are any companies still operating in your state. At 50 incidents a year just in your area, all the companies would be shutdown from equipment damage or OSHA violations.

The thought just occured to me that I may not understand the definition of "Flash Hazard". So I looked it up in NFPA 70E. "A dangereous condition associated the release of energy caused by an electric arc."

Using that definition, I'm going to translate to:

A backhoe sticks a bucket through a cable and the CB trips. All the CB fire is contained inside the cabinet. - Not an Arcflash Incident, A fault and a CB trip is not necessarily an arcflash incident.

A backhoe sticks a bucket through a cable and the CB trips. The CB door flies open and minimal fire from the arc chutes comes out the door. - This is an Arcflash Incident, minimal, but an incident.

In my mind, an arcflash incident means there was equipment damage that released sufficient energy for either a potential personnel hazard or to damage other equipment.

Then again, I may well not understand the definition of "arc flash/blast incidents from 15kV switchgear ".

 

[zog]

We provide emergency services for power generation, transmission, and distribution systems in the midwest. Large industrial plant built in the 1920's-1940 are common in detroit and cleveland (Steel mills and Automotive plants) that have very old 15 kV equipment that is not maintained. I am not implying at all that there are injuries associated with these failures, many are in manholes or remote substations/vaults.

I agree with your defintions of incident, but failures are common, along with equipment damage. Keep in mind all of these systems have alternate feeds so production is usually only affected for a few minutes, the damaged cable or switch is isolated, and they call us. If I knew how to upload pics I would post some examples.