Connecting Loads to Outside Substation Critical Panel

[hidalgoe]

Is it considered good, contemporary design practice to connect a temporary or permanent load to an outside substation critical power panel?

The substation in question has a 12.47kV/4.16YkV,3750kVA transformer with two secondary Cutler-Hammer/Westinghouse
VCP-W vacuum CBs. This substation supplies power to a host of offices and critical 24x7 type facilities at our government installation.

A 4.16kV/120/240V, 25kVA, single phase, transformer provides power to a critical power panel (125A main CB).

This panel supplies control power to reclosing relays (79)and breaker motors and to a battery charger for the vacuum breakers tripping function.

Substation illumination is supplied from this panel also.
(This load was connected to the critical power panel before I arrived).

A contractor is suggesting that a 60A service sourced from the critical panel for an EPA Superfund load simply because it is cheap and convenient (there are no reasonably close power sources). I am proposing that a utility transformer (say 45kVA) be installed at the substation to handle miscellaneous loads such as the one being proposed. The only problem for the contractor is that this will cost more money.

 

[abeltio]

hidalgoe...
The operative word here is "critical".
Regardless of the practice... the questions I would ask myself are:
1. What if "something" happens... fingers will start to point to whomever approved the temporary connection.
2. Who is the "owner" of the critical power panel? somebody in operations must have the responsibility for that panel... my guess is that they will scream their lungs out if you propose a temporary connection to their critical power panel (and probably seriously consider you certifiable for even asking too ;-)

Summarizing:
In my plant the answer would always be a surely non-regrettable: NO WAY!!!

Also you may want to check the terms of the contract...who is responsible for supplying temporary power?
In either case the solution may be renting a portable gen-set...

Even the 45KVA transformer will require approval from your operations guys and you'll also have to consider the corresponding protection...
Grounds and shorts are not unheard of on construction sites... imagine that you have one and that you trip the substation (including of course your critical power panel)... again... in my opinion: nothing connects to the critical power panel on a temporary basis...if it is a must have (design change, modification or upgrade) then proper approval is needed from all relevant parties/agencies same as the ones obtained for the original installation.

Hope this helps.
saludos.
a.

 

[jbartos]

Suggestion: It appears the original posting is seeking an industry standard.
Visit

http://www.activeharmonicfilters.com/Procedures/Check List.doc

http://www.state.vt.us/psd/ee/appx5.PDF

etc. for more info

 

[busbar]

The term “EPA Superfund load” should have no bearing on the priority or expectation of continuity of requested electric service, particularly where that may compromise operational safety and continuity of the larger facility electrical system.

The request to serve a foreign project from existing systems was very likely not previously intended, engineered or accounted for, and should not be honored as in no way intended for the proposed application. From the listed powered components and the reliability of site operation obtained under routine or emergency conditions, this casual load could not be reasonably assured from undesirably and seriously affecting the reliability of the site electrical-system protective-relaying scheme. With typical dependence on the station loads listed, the 240V critical-power bus may perilously be affected to a high economic degree with a potentially large loss of safety and service continuity.

It sounds like the remediation contractor failed to allow for this aspect of his project. Consider carefully your obligation to furnish same. As an alternative, propose that he fund design, installation and removal at completion of a separate and wholly independent line built from off site to serve any project needs at his own expense. Project incidental electric power needs from site facilities’ electric power should have been resolved far before contract acceptance. Depending upon contractual obligations, you may want to seek recovery of the cost for effort and other facility resources expended solely for accommodating the remediation.