What do you see wrong with this service?

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imaee

Member
Thanks for the help with this service to a 1000 HP motor. Original equipment had a customer-owned 2500 kVA transformer mounted to end of breaker cabinet through a bus cabinet. The main is a 3000 amp breaker that feeds both 1) a 2000 amp breaker to a 1000 HP motor and 2) a 200 amp breaker to other ancillary loads.

The equipment was moved to a new site with a utility-owned transformer (different primary voltage).This is a 480 volt wye service to the motor. About 45,000 amps available fault current at 480 volts.

The old transformer was cut loose from the end of the assembly. A new feed from utility 2500 kVA transformer was brought into the bus cabinet on the end where the old transformer bus bars used to terminate. The new feed is 8 paralleled 500 MCM cu cables per phase in 8 conduits. I do not know the ground size but you can see it in the pics.

From the transformer to main, I had the following concerns and want to know if they are valid or if there are others:

1) Were conduit bushings installed? Picture looked like wire had abrasions.

2) Is bus cabinet suitable for cables?

3) Is the part of bus previously used for bus termination/connection listed for cable termination and is it suitable for multiple and stacked terminations?

4) How is cable protected from sharp cabinet edges?

5) Is cable lashing/support being installed?

6) Is the bus rated to support cable under normal weight and during fault stress?

7) Is proper phase-phase and phase-ground spacing maintained?

8) Are cable ties suitable securing method for the varnish coated glass wrapping the terminations?

9) Does field modifying the equipment/bus void the UL listing and are field certifications required?

10) With the transformer being cut away, how is remaining thin metal and openings providing proper arc blast protection?

Pictures are: Original transformer disconnected and moved to side for shipping (you can see terminals coming from transformer and switchgear in foreground):



Another view of original transformer with switchgear in background:



Original transformer cut loose from skid and old bus jumpers laying in front:



New cable entry into bus cabinet. You can see where old transformer used to be mounted on left side where bus jumpers went through opening:



A view of cables coming in bottom of bus cabinet. Note the white rubber strip put on the cabinet frame to keep cable from rubbing on sharp edge.



Another view of cabinet and cables:



A view of the terminations with stacked lugs on each side. They used the old bus termination holes.

 

Fulthrotl

~Autocorrect is My Worst Enema.~
The old transformer was cut loose from the end of the assembly. A new feed from utility 2500 kVA transformer was brought into the bus cabinet on the end where the old transformer bus bars used to terminate. The new feed is 8 paralleled 500 MCM cu cables per phase in 8 conduits. I do not know the ground size but you can see it in the pics.

From the transformer to main, I had the following concerns and want to know if they are valid or if there are others:

3) Is the part of bus previously used for bus termination/connection listed for cable termination and is it suitable for multiple and stacked terminations?

9) Does field modifying the equipment/bus void the UL listing and are field certifications required?

that's the deal right there.
there has been a modification which most likely voids the UL listing.

everything else is workmanship.
the tie wraps on the fish paper i don't find appealing.
i'd of cut some dielectric material and put spacers in between phases, but that's just me.
did they even need anything at all? probably not. did the original bus bars have anything there?

as for the arc containment, my thought is that if you made a cover of #10 mild steel,
it's far and away stronger than most anything that was there before.

but again, this is all modifications voiding the UL listing.

services such as Intertek perform field UL listing.... i've used them,
and while not cheap, neither is an injury involving non listed equipment.

if someone is going to pay a UL listing service to issue a report on something,
it's a lot cheaper if it's you instead of a personal injury attorney buying the report.

btw-
seeing someone with a steel tape measure inside a piece of gear, causes the
little hairs on the back of my neck to stand up. i've worked in places where they
don't even allow a steel tape measure on the jobsite. a wood or fiberglass folding
tape is all that is permitted.
 

iwire

Moderator
Staff member
Location
Massachusetts
that's the deal right there.
there has been a modification which most likely voids the UL listing.

ULs position is that you cannot 'void' a listing.


You might make field modifications to listed equipment but it is still listed equipment. It is up to the AHJ to determine if the modifications are significant enough for the AHJ to require a field evaluation. In other words the AHJ can accept any modification if they so choose.

Now that said, at these current levels I would be very surprised if the AHJ did not want some engineering data about the weight of the cables on the bus and the potential need for cable bracing.
 

Ingenieur

Senior Member
Location
Earth
What does the motor drive?
1000 HP on 480 is unusual
the fault current will be huge
what is the starting type? FVNR, ss soft start, vfd, etc

as far as the installation
I would have used shorter bolts
spacers as others have mentioned
I would also check the minimum clearance between lugs but the paper may mitigate that
 

imaee

Member
Thanks for the feedback

that's the deal right there.
there has been a modification which most likely voids the UL listing.
That was a concern. It is certainly not being used the way it was originally designed to be used. The question is how bad is it? Do they need a field certification or does Siemens need to say it is ok to bolt the conductor on like that or what?

the tie wraps on the fish paper i don't find appealing.
i'd of cut some dielectric material and put spacers in between phases, but that's just me.
did they even need anything at all? probably not. did the original bus bars have anything there?
That paper is a dielectric but the securing method looks iffy to me. It is made by Bondex and is 7 mils thick with a rating of 1700v/mil. Not sure if it is intended to be used and secured that way.

The original bus bars had about a 3 inch spacing or so. This setup has less than 3/4 inch.

as for the arc containment, my thought is that if you made a cover of #10 mild steel,
it's far and away stronger than most anything that was there before.
The metal on the transformer cover was about 1/8 inch. The metal where the bus bars went through was about 1/16 inch.

but again, this is all modifications voiding the UL listing.

services such as Intertek perform field UL listing.... i've used them,
and while not cheap, neither is an injury involving non listed equipment.

if someone is going to pay a UL listing service to issue a report on something,
it's a lot cheaper if it's you instead of a personal injury attorney buying the report.
Could they just sign off that the modifications were ok or does it need to be a panelboard designer like Siemens or something?

btw-
seeing someone with a steel tape measure inside a piece of gear, causes the
little hairs on the back of my neck to stand up. i've worked in places where they
don't even allow a steel tape measure on the jobsite. a wood or fiberglass folding
tape is all that is permitted.
That was all that was handy. Nothing is energized at this point.
 

imaee

Member
ULs position is that you cannot 'void' a listing.

You might make field modifications to listed equipment but it is still listed equipment.
Would you consider that a normal modification within the intended use as approved? I'm not sure how far one can go before they throw a penalty flag.

It is up to the AHJ to determine if the modifications are significant enough for the AHJ to require a field evaluation. In other words the AHJ can accept any modification if they so choose.

Now that said, at these current levels I would be very surprised if the AHJ did not want some engineering data about the weight of the cables on the bus and the potential need for cable bracing.
The bus was probably not designed to handle that kind of cable torque and fault force loading but who makes that call: Siemens, a stamping PE, the contractor who came up with the mod?

Thanks
 

imaee

Member
What does the motor drive?
1000 HP on 480 is unusual
the fault current will be huge
Metal shredder. All motors running increase fault current about 6-8 kA above the 45 kA or so from utility.

what is the starting type? FVNR, ss soft start, vfd, etc
Not sure of the starting type but I think someone said clutch? 1500 amp running load at service, 5000 amp load at service when motor starts.

I got the sub-panel layout from the 3000A main wrong earlier, it is:
2000A panel feeds big motor (about 1200A running). 600A panel feeding two other panels: 1) 400A panel feeding about 320A of 480 volt loads and 2) 30A panel feeding about 20A of load to a 15 kVA, 208 volt transformer.

as far as the installation
I would have used shorter bolts
spacers as others have mentioned
I would also check the minimum clearance between lugs but the paper may mitigate that
I thought about 2 inches was needed for 480 volt. The paper might mitigate it, if it stays put.

Thanks
 

Ingenieur

Senior Member
Location
Earth
A rule of thumb is a motor will supply 4 times its running kva into a fault

thought it was a shredder or some kind of recycling machine
worked on one in Anchorage AK years ago

probably does have hydrostatic clutch of some sort
gotta get a lot of hammer/grinder/shearer mass spinning lol
 

iwire

Moderator
Staff member
Location
Massachusetts
The bus was probably not designed to handle that kind of cable torque and fault force loading but who makes that call: Siemens, a stamping PE, the contractor who came up with the mod?

Thanks

When the companies I have worked for have needed to make these types of changes they have gone to the maker of the equipment or if the equipment is old to a local switchboard manufacturer who can design and provide the needed parts.

As far as I know this route has satisfied the AHJ.
 

imaee

Member
A rule of thumb is a motor will supply 4 times its running kva into a fault

thought it was a shredder or some kind of recycling machine
worked on one in Anchorage AK years ago

probably does have hydrostatic clutch of some sort
gotta get a lot of hammer/grinder/shearer mass spinning lol
It has to be some kind of loud too.
 

imaee

Member
When the companies I have worked for have needed to make these types of changes they have gone to the maker of the equipment or if the equipment is old to a local switchboard manufacturer who can design and provide the needed parts.

As far as I know this route has satisfied the AHJ.
Sounds reasonable. Thanks.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The biggest issue I see is the one iwire talked about ...the short circuit bracing. I probably would have had someone, either OEM or 3rd party make a bus detail designed for cables.

I would have used heat shrink on the barrels of the connectors in place of the fish paper.
 
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