Bus Duct Seperation of Normal and Emergency Power? 1

[Mbrooke]

Can an electrical fault in one duct take out others? What about separation in case of fire?

I have a scenario where normal, equipment, critical and life safety is grouped within inches of each other through out the entire building going horizontally from the basement all the way to the vertical risers piercing each floor diaphragm.

The thing is normal and essential panels, transfomer, conduit, ect are kept in separate rooms each with 2 hour fire barriers, doors and fire calk.

Here are a few examples where essential power is grouped with normal power:

https://imgur.com/a/OkdArks#m0rcDdR

https://imgur.com/ukyjjOn

Essential system horizontal bus-duct grouping:

 

[mpparent]

Well, IEEE 493 may provide some insight. Failure rates for bus duct is .0003 failures/yr.

Mike

Mike

 

[Mbrooke]

Thanks! Any important excerpts? I don't have IEEE 493 with me.

At this point I'm just running on "feelings" which is not good lol.

 

[mparenteau]

None that I recall. At this point, it's your engineering judgement, but at least you can quote from the standard.

Mike

 

[LionelHutz]

Which major airport was taken down when both normal and emergency feeds in the same tunnel burned?

 

[Mbrooke]

As I am reading NFPA 99, only the final branch circuit of the life safety system must be protected from fire and common mode failure, correct?

https://imgur.com/f0GSy3v

 

[DTR2011]

I believe the Airport was Atlanta.

 

[FacEngrPE]

Opinion - this is an engineering judgement risk evaluation question.

I would read "Life Safety Branch" to be the entire life safety distribution system from the point where it branches from the building power feed system should be protected from common mode failures. So if one bus duct fails what is the risk of it taking out the second bus duct? Will the circuit protection detect the kinds of faults that could become common mode failures? Does the busduct have a listing as a part of a fire stop system? What does the fire stopping in the structure look like?

I do not think protecting from common mode failures prohibits putting two busducts in the same chase, but it likely requires some careful design.

It was Hartsfield Jackson Atlanta international Airport

https://www.ajc.com/business/root-c...ery-for-georgia-power/FfM3v9wFF5IH1qbtzsukzJ/

I am not aware of a root cause report.

Fred

 

[Mbrooke]

The thing is I don't know how a fault in one bus duct will effect another. There are fire stops where the bus-duct goes through a floor or wall, but thats about it.

I do agree, to me the origin would be at least at the ATS, but more sensibly at the parelleling and main gear OCPD.


Regarding this:

"Competitors of the company are not required to disclose similar information and to require the company to do so would put it in an economic disadvantage,” the company said."

What a load of rubbish. There is really nothing special about most MV POCOs systems, and the tunnel along with all locked equipment is the least of any vulnerability.

The thing is tax funded material (even 1 cent) is required to be disclosed:

https://www.google.com/url?sa=t&rct...68vpAhWYg3IEHTV6D7UQFjAAegQIARAB&url=https://

http://www.vendorportal.ecms.va.gov...00002002.PDF&usg=AOvVaw0Ulgoe7p6EmOmpt4TCHqWn

https://www.google.com/url?sa=t&rct...7MvpAhWXoXIEHSgHAsYQFjABegQIARAB&url=https://

http://www.vendorportal.ecms.va.gov...00002009.pdf&usg=AOvVaw1ei1IBaKrPCrW3_SBHwBOe

 

[FacEngrPE]

Found the docket number for the Atlanta Hartsfield-Jackson Airport fire and power outage here

https://microgridknowledge.com/power-outage-atlanta-airport/

Docket No. 170858, which can be found here

https://psc.ga.gov/search/facts-document/?documentId=170858

https://psc.ga.gov/search/facts-document/?documentId=170858

The docket response is better than the newspaper indicated. The internal document explaining the maintenance procedures was provided to the PSC, but was claimed to be proprietary trade secrete, and is not included in the PSC publiclyreleased docket.

Regarding life safety circuits, this is not my specialty, so consider this an opinion. if your source was a Public Utility and you did not have in building life safety backup generation fire pumps need to have a service entrance separate from the normal service entrance. Upstream of the service entrance the POCO can feed it from what ever they want, unless other rules apply.

Not part of NFPA, sometimes local requirements are feeders from more than one utility substation, via diffident paths. This can require miles of high voltage circuit at customer expense, a local generator usually costs less.

If I was working this job I probably would review the contract directions to see if the concern is addressed, and possibly the UFC documents (

https://www.wbdg.org/ffc/dod/unified-facilities-criteria-ufc)

or applicable code. Then might present the issue as a question to the contracting agent,

Fred

 

[Mbrooke]

Thanks

Georgia Power (and some other utilities) remind me a local dealership owner who was so boastful and concerned with secrecy he believed he was the only who thought of a unique sales strategy (keep raising the price just to the point turning buyers away would not cause the raise to back-fire, offer discounts on an deliberately inflated price) when unbeknownst everyone was already doing the same thing. For example I was able to correctly guess Con Edison's transmission layout before it was disclosed in NERC's "Lessons Learned" There is also the fact the public is the ultimate authority on such matters like infrastructure.


Anyway, I will give those docs a look. I learned that they do offer fire rated busduct- I will give that a look even though I don't think it was used here.