Backup power question...

[Fulthrotl]

i have a client who wants an emergency power strategy.

normally, when things go poo, a backup genset is delivered,
the 2000 amp 480 main is opened and locked out, cam locks
are drug out in parallell across the production floor,
and it's temped in.

what i'm looking at doing is making something a little more
organized, and i'm looking to see if anyone would fault this:

parameters:

main distribution room has nothing other than the metering
gear and main circuit breaker inside. room is uniquely keyed,
and access is limited to qualified personnel only. key control in
place.

what i want to do is come off the load side of the main with
conductors in parallell suitable for the load, going to a cabinet
with cam locks, contained within this room, so access control
is maintained.

the bottom of this cabinet will have holes cored thru a concrete
wall, to another locked cabinet on the outside of the building.

scenario is, power goes out, cat power gets called, the main is
opened and locked out, the camlock cabinet and the outer cabinet
are opened, cam locks are plugged in and ran to the genset in the
parking lot, and we are off and running.

as all of the equipment involved has access control, and the only
thing that is being done is bringing leads off the load side of the
main, is this code compliant?

is there a better solution anyone has implemented?

thanks for any feedback....


randy

 

[fmtjfw]

702.5 Transfer Equipment. Transfer equipment shall be suitable for the intended use and designed and installed so as to prevent the inadvertent interconnection of normal and alternate sources of supply in any operation of the transfer equipment. Transfer equipment and electric power production systems installed to permit operation in parallel with the normal source shall meet the requirements of Article 705.
Transfer equipment, located on the load side of branch circuit protection, shall be permitted to contain supplemental
overcurrent protection having an interrupting rating sufficient for the available fault current that the generator can
deliver. The supplementary overcurrent protection devices shall be part of a listed transfer equipment.
Transfer equipment shall be required for all standby systems subject to the provisions of this article and for which an
electric utility supply is either the normal or standby source.

Exception: Temporary connection of a portable generator without transfer equipment shall be permitted where conditions of maintenance and supervision ensure that only qualified persons service the installation and where the normal supply is physically isolated by a lockable disconnecting means or by disconnection of the normal supply conductors.

The Power Company is not bound by the NEC and may have more requirements than 702.5.

Then again the Power Company is more likely to understand interlocking locks.

The locking scheme you describe does not appear to enforce the red text of 705.2 It appears you could open the service main. Take the key out of the service main. Open the generator connection cabinet with the key. Connect the generator cables. Close the generator cable cabinet. Take the key out of the generator connection cabinet. Use the key to close the service main.

However the red text in the Exception may allow what you want to do.

 

[iceworm]

i have a client who wants an emergency power strategy.

normally, when things go poo, a backup genset is delivered,
the 2000 amp 480 main is opened and locked out, cam locks
are drug out in parallell across the production floor,
and it's temped in. ...

Disclaimer: The following is pure opinion. Disregard at your leisure. Design by internet gossip is worth what you paid for it.

My first concern is not if the proposed mod meets code. It would be, "Is this good design practice?" The way the OP reads, you are the "engineer of record".

The current plan for backup power is a temporary 590 connection. Utility isolation is by a work permit and LOTO. Aparently the utility and AHJ are okay with this arrangement. I agree, it is fine method for a temporary installation of backup power.

Now you are looking at installing a convenient connection point for the backup power. I'm wondering, why's that? It can't be the time. The customer is waiting on Cat to deliver, and who knows - Cat may not have a gen sitting there. If it was time there would already be a gen sitting there - probably connected.

So, I'm guessing it is a case of wanting to be less intrusive on the main power installation and getting the cables off the production floor. So now I'm wondering: How often does this happen? How long is each occurance?

I've been involved with a few backup power installations in the 2MW range. The norm for the installations I've seen, have a CB in the backup feed that is electrically interlocked with the main. We're are using the backups 5 - 10 times per year. All have an installed generator. But the design constrainsts are different than yours. It could take a week to get a gen. And that is assuming there was one just laying around. And at -40 we got maybe a couple of hours.

After your proposed modification, the connection is still per 590, and the utility isolation is still by WP and LOTO. I don't think you have a code problem. (I did not do any research, so I could be wrong on this.) The regulatory issues will be with the utility and the fire marshal. Once the mod is done the temp connection is much easier (less intrusive) and I can easily see the utility squawking and insisting on isolation by design as opposed to by procedure.

Welcome to being the engineer of record. Get prepared to whip out your design philosophy to show that you have met all of the interested parties concerns. If the only concern is, "Does this meet code?", I'd say the job is pre-fubared. A 2000A temporary power gen connection is way past code minimum requirements.

Just a suggestion: I would never call this "emergency" in discussion with the AHJ, firemarshal, or utility. Unfortunately 590 calls this connection "Emergency" - sigh.


good luck - I'll be interested in how it comes out.

ice

 

[charlie b]

Here is a suggestion on adding another level of control.

• Put the camlocks in the outside cabinet.
• That makes the inside cabinet nothing more than a junction box or pull box. So it can be secured by bolted panel covers, with no accessible door. That way, this cabinet is not involved in the power transfer process.
• Install a kirk key system on the main breaker and the door to the outer box. One key, two locks.
• When normal power is lost, and while the generator is being brought to the site, you open the main breaker, and do your LOTO process. That process should include removing the kirk key from the main breaker.
• Once the LOTO process is completed, you take the kirk key to the outer cabinet and open its door.
• This prevents closure of the main breaker while the outer cabinet is open and being used to connect the generator. It is not that I would not trust the LOTO process, but this provides a better control then a LOTO alone.
• When normal power is available, you won't be able to reclose the main breaker until you close the outer cabinet door and remove the kirk key from that door. That, of course, requires you to disconnect the portable generator cables.

 

[zbang]

[*]Install a kirk key system on the main breaker and the door to the outer box. One key, two locks.

Kirk-key was my thought, also. I'd be a bit more comfortable with a unfused switch of some kind between the camloks and the bus and a KK on that, but I'm not the one paying for it. Or, put the camloks in a separate cabinet in the main distro room so they're within sight of the main breaker. I don't like having the locked cabinet outside. You'd still the the KK setup Charlie describes with the added protection of the room around it.


fmtjfw- I think the point of the cabinet is that you can't close/lock it with the cables in place. This is easy to implement if the door closes to within an inch of the camloks (assuming panel-mount).

 

[fmtjfw]

Aha!

Aha!

Kirk-key was my thought, also. I'd be a bit more comfortable with a unfused switch of some kind between the camloks and the bus and a KK on that, but I'm not the one paying for it. Or, put the camloks in a separate cabinet in the main distro room so they're within sight of the main breaker. I don't like having the locked cabinet outside. You'd still the the KK setup Charlie describes with the added protection of the room around it.


fmtjfw- I think the point of the cabinet is that you can't close/lock it with the cables in place. This is easy to implement if the door closes to within an inch of the camloks (assuming panel-mount).

I get it now.

 

[Fulthrotl]

Exception: Temporary connection of a portable generator without transfer equipment shall be permitted where conditions of maintenance and supervision ensure that only qualified persons service the installation and where the normal supply is physically isolated by a lockable disconnecting means or by disconnection of the normal supply conductors.
However the red text in the Exception may allow what you want to do.

the exception was where i was hanging my hat.

the kirk key is a most excellent idea, gentlemen.

however, the main can have a shunt trip on it.... what if....
you had a limit switch on the outside cabinet, that operated
the shunt trip if the outer cabinet door was opened, and
the inside cabinet door had one as well? set it up in such
a way that they couldn't be defeated, and when either door
is open, the breaker opens and won't reclose?

i was reluctant to put the camlocks outside the building
wall, as tampering might occur. if you open the outside
cabinet, there would be pass throughs cored and sleeved,
so you could pass the cam locks in thru them and plug
them in inside.

all of this is due diligence for a professional accreditation
that they want to have, somewhat of an ISO 9000 for the
food packing industry, and they need a backup power
strategy.

i believe they have only needed to bring in a genset once.

this will get blessed by my EE before it gets to the spending
money stage. thank you for taking the time to reply.

 

[hillbilly1]

The problem with the LOTO is more than one person has a key, even though they are qualified personnel, it does not meet OSHA regs because of the multiple keys. That being said, the Kirk key set up with the door would not work because you cannot leave the door open with the cables connected, and if you close it, the key could be removed, and re-inserted in the main and the main could be re-closed with the generator connected. A single key LOTO would be the cheapest way to go, but the right way would be adding the Kirk key set up with an external molded case switch.

 

[zbang]

That being said, the Kirk key set up with the door would not work because you cannot leave the door open with the cables connected, and if you close it, the key could be removed, and re-inserted in the main and the main could be re-closed with the generator connected.

The whole point is that you can't close the connector cabinet door with the cables connected (why is that a problem?), so you can't remove the key, so you can't use the key to enable closing the main. By placing the connector cabinet in the locked electrical room, you limit access to those connections.

 

[hillbilly1]

The whole point is that you can't close the connector cabinet door with the cables connected (why is that a problem?), so you can't remove the key, so you can't use the key to enable closing the main. By placing the connector cabinet in the locked electrical room, you limit access to those connections.

The problem is, being outside, with the unsecured door, unless you can secure that area with a fence of some sort, someone could access live parts because the transition from inside cable to cam locks would be exposed unless you use factory made cables with the cam locks loose in the cabinet. Just something to think about. The cabinets usually have an cable access hole in the bottom to allow the door to be closed.

 

[Fulthrotl]

The problem is, being outside, with the unsecured door, unless you can secure that area with a fence of some sort, someone could access live parts because the transition from inside cable to cam locks would be exposed unless you use factory made cables with the cam locks loose in the cabinet. Just something to think about. The cabinets usually have an cable access hole in the bottom to allow the door to be closed.

what i'm gonna suggest is a locked hoffman box outside the building, 18 x 18 x 6, covering three 6" holes
cored and sleeved thru the tilt up wall. hoffman box is for weatherproofing and mischief control. no LOTO
function beyond that.

on the inside of the building there is, right next to the switchgear closet, a 30" x 30" pocket between the
building corner and the outside of the electrical closet. i am going to run a 12" x 12" gutter up the side of
the gear, across the top of the gear, thru the wall at the end of the closet, into that 30" x 30" void. i am
then going to turn a 90 down, dropping to a 2' x 2' x 2' box mounted on the inside of the building, just
above those cored holes, with cam locks facing forward, 4' above the floor.

that 30" by 30" area will have a metal door fabricated with a kirk lock matching the one on the breaker.
behind that door will also be a limit switch, tied to the shunt trip on the main breaker.

door open = breaker shunted.

drill:

open breaker, remove kirk key.
use kirk key to open door closing
off void inside of building. limit switch
ensures shunt trip of main.

inside of door is a key opening the hoffman pass
thru box outside of building.

also inside of locked void is storage for
coiled up cam locks, tails, and assorted stuff for
connection purposes.
stored where they can't be gotten to and walk off.
you can't get to them unless the building is dead.

24/7/365 support agreement with Aggreko for a
suitable genset on 4 hours notice.

and a single line with a wet ink EE signature on it,
and a laminated instruction set both on the face
of the gear, and the inside door, giving the procedure,
and the contact number for calling for the genset.

i think thats enough dynamite, butch.

thanks for your help.. i appreciate the insight.

 

[iceworm]

i think thats enough dynamite, butch. ....

I think so. I'm impressed. The plan is past complete awsomeness (seriously). Now all that has to happen is for your customer to like it - how could they not. They want a plan for temporary power to meet their certification and you nailed it.

Just curious questions:
This gen - 1MVA? 2MVA?

What is the order of magnitude cost on the 24/7/365, available in 4 hours, gen agreement? Same price as buying one? But you don't have to keep up the maintenance?

That's 4 hours from the telcon on Christmas Eve till its sitting in your yard ready for connection? That's major impressive.

ice

 

[Fulthrotl]

I think so. I'm impressed. The plan is past complete awsomeness (seriously). Now all that has to happen is for your customer to like it - how could they not. They want a plan for temporary power to meet their certification and you nailed it.

Just curious questions:
This gen - 1MVA? 2MVA?

What is the order of magnitude cost on the 24/7/365, available in 4 hours, gen agreement? Same price as buying one? But you don't have to keep up the maintenance?

That's 4 hours from the telcon on Christmas Eve till its sitting in your yard ready for connection? That's major impressive.

ice

i haven't got it all nailed down yet, it's the weekend... and i'm taking today off.. sort of....

there are two backup strategies, light day... and maxi pad.

lite days provides enough generator to run two of the four chillers to keep the frozen food frozen,
minimal hotel load, and office space. food stays safely frozen, they can operate their office, but no production.
maxi pad is running everything, full production.

now comes the load audit.... if memory serves, last time i hooked up a 1 meg portable, it was fused at 3,000 amps
of 480.... so i'm guessing no more than a half of a meg on maxi, dunno yet on mini.....

then comes the hogswaggling on the generator... that is where i hopefully will add real value to the whole deal...
there's quite a number of commercial genset providers available in the LA area.....

the best generator rental deal i ever saw, was a long time ago, at the tulare farm show..... the rental company
provided a one meg cat genset for a week for the show for free, to be able to put their name on the side of the
genset, for the advertising... it was sitting right there all proud at the intersections of the main tents.

free sets the bar pretty high.... i'll see what the best i can do is......

 

[zbang]

and a single line with a wet ink EE signature on it,
and a laminated instruction set both on the face
of the gear, and the inside door, giving the procedure,
and the contact number for calling for the genset.

i think thats enough dynamite, butch.

Sounds all good to me, too.

 

[hillbilly1]

what i'm gonna suggest is a locked hoffman box outside the building, 18 x 18 x 6, covering three 6" holes
cored and sleeved thru the tilt up wall. hoffman box is for weatherproofing and mischief control. no LOTO
function beyond that.

on the inside of the building there is, right next to the switchgear closet, a 30" x 30" pocket between the
building corner and the outside of the electrical closet. i am going to run a 12" x 12" gutter up the side of
the gear, across the top of the gear, thru the wall at the end of the closet, into that 30" x 30" void. i am
then going to turn a 90 down, dropping to a 2' x 2' x 2' box mounted on the inside of the building, just
above those cored holes, with cam locks facing forward, 4' above the floor.

that 30" by 30" area will have a metal door fabricated with a kirk lock matching the one on the breaker.
behind that door will also be a limit switch, tied to the shunt trip on the main breaker.

door open = breaker shunted.

drill:

open breaker, remove kirk key.
use kirk key to open door closing
off void inside of building. limit switch
ensures shunt trip of main.

inside of door is a key opening the hoffman pass
thru box outside of building.

also inside of locked void is storage for
coiled up cam locks, tails, and assorted stuff for
connection purposes.
stored where they can't be gotten to and walk off.
you can't get to them unless the building is dead.

24/7/365 support agreement with Aggreko for a
suitable genset on 4 hours notice.

and a single line with a wet ink EE signature on it,
and a laminated instruction set both on the face
of the gear, and the inside door, giving the procedure,
and the contact number for calling for the genset.

i think thats enough dynamite, butch.

thanks for your help.. i appreciate the insight.

That should work! If somebody somehow gets the door open without the Kirk key, the shunt trip should de-energize the open Cam locks, though there still may be a problem of someone closing the door, removing the Kirk key, and placing it back in the main with the generator still connected. You know you have to design everything idiot proof these days! :roll:

 

[Fulthrotl]

That should work! If somebody somehow gets the door open without the Kirk key, the shunt trip should de-energize the open Cam locks, though there still may be a problem of someone closing the door, removing the Kirk key, and placing it back in the main with the generator still connected. You know you have to design everything idiot proof these days! :roll:

the cam locks will be close enough to the inside of the door that
you can't close the door on the camlocks plugged into the sockets.

so, you can't get the key out. unless you defeat the limit switch
intentionally, you can't reclose the main.

if someone is that bound and determined to win a darwin award,
they can just take off the poco pull section covers and climb in, wearing
flip flops and a wet bathing suit, ahead of the main.

you can't fix stupid.

speaking of which, i want to implement a permanent rotation meter,
so i can see which way the hamsters are running, and also that all
three phases are hot before switching back over to poco electrons.

emergency power should be simple, with everything needed at
hand.

i need to see who makes one of those....

i've seen outages where things come up turning the other way.
chillers, and hydraulic pumps love that.
it's rare, but if i had a rotation meter with a set of dry contacts,
and it would supervise all phases being there, if you lost a leg
or things were backwards, you could run that shunt trip thru
that contact as well....

oh oh.... i feel the onset of the dreaded "while you are at it"
syndrome.

 

[gadfly56]

If you've already lost power, what pops the shunt??

 

[hillbilly1]

the cam locks will be close enough to the inside of the door that
you can't close the door on the camlocks plugged into the sockets.

so, you can't get the key out. unless you defeat the limit switch
intentionally, you can't reclose the main.

if someone is that bound and determined to win a darwin award,
they can just take off the poco pull section covers and climb in, wearing
flip flops and a wet bathing suit, ahead of the main.

you can't fix stupid.

speaking of which, i want to implement a permanent rotation meter,
so i can see which way the hamsters are running, and also that all
three phases are hot before switching back over to poco electrons.

emergency power should be simple, with everything needed at
hand.

i need to see who makes one of those....

i've seen outages where things come up turning the other way.
chillers, and hydraulic pumps love that.
it's rare, but if i had a rotation meter with a set of dry contacts,
and it would supervise all phases being there, if you lost a leg
or things were backwards, you could run that shunt trip thru
that contact as well....

oh oh.... i feel the onset of the dreaded "while you are at it"
syndrome.

There is a company that makes that type of cabinet, didn't have the shunt trip or the Kirk key though, it had pilot lights on the front showing voltage available, along with pilot lights that shown rotation connected, and also a complete set of cam locks, but I don't remember the manufacture. It was made overseas, because the manufacture had screwed up some wiring on it, and they had to send the correct step down transformers. (they were powering the pilot lights from three 480 volt to 120 volt step downs, instead of three 277 volt to 120 volt, if you lost a phase, you could not tell which one, and also a possible back feed keeping all three lit.)

 

[Fulthrotl]

If you've already lost power, what pops the shunt??

tying in the shunt is more of a failsafe if someone screws with
opening the door while the panel is hot, not in a power failure
situation.

the physical design of the enclosure and the kirk keys were my safety plan,
the shunt trip was "just 'cause".....

 

[Open Neutral]

that 30" by 30" area will have a metal door fabricated with a kirk lock matching the one on the breaker.
behind that door will also be a limit switch, tied to the shunt trip on the main breaker.

door open = breaker shunted.

Dumb question: what powers the shunt trip?