Monday Photos (Spot the Violations)

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chevyx92 said:
You got it. 3 phase in and 3 phase out.
Click to expand...

now i understand a little better. i just dont understand the actual grounding issue if there is a fault. i cant see how the breaker will trip if theres a ground fault. since the A phase is the same potential as ground i dont understand how the breaker will offer protection
 
Ah Haa!

Ah Haa!

I know the violation for the transformer.

480 v corner ground systems, 480 v 3ph (phase to phase), you do not use Brown/Orange/Yellow.

You use white or grey for identifying the corner grounded phase conductor.


I'll dig through the book and find the article
 
i tried to look up corner grounded delta in the electricians handbook and its not there. just straight delta to delta. now if electricity is trying to find a way back to its source, the transformer, if theres a fault on the grounded phase wont that put voltage on all metal parts? what if someone grabs the machine that has the ground fault wont they get blasted? if theres a fault to the ground on the A or C phase it will trip the breaker. please correct me if im wrong
 
208 3ph 3w wye - Step Up to 480 Corner Grounded Delta

208 3ph 3w wye - Step Up to 480 Corner Grounded Delta

IMM_Doctor said:
I know the violation for the transformer.

480 v corner ground systems, 480 v 3ph (phase to phase), you do not use Brown/Orange/Yellow.

You use white or grey for identifying the corner grounded phase conductor.


I'll dig through the book and find the article
Click to expand...


I think the installation is somewhat common. If you have a building with only 208 wye 3-phase available, and a piece of equipment requires 480vac 3 phase, then you would reverse feed an "off-the-shelf" transformer.

"Off-the-shelf" transformers will only have H1, H2, H3 for the higher voltage 480v winding, and X1, X2, X3 , X0 at the 208v lower voltage winding. When making these reverse feed installations, NEVER bond XO. The 208 volt supply to the reverse fed xfmr is already referenced to ground at the source, and MAJOR problems will occur if you install a bond at XO.

Now that you have a new 480 3phase seperatley derived system, ground referencing is required. See 250.26 (4) Condctors to be Grounded, Multi-phase, where one phase is Grounded

Now see 220.6 Identification of a Grounded Conductor
 
if anybody here is the installer of that transformer, if there is no code violations and is indeed a corner grounded system sorry for the idiot comment :) i guess im the idiot now :D
 
IMM_Doctor said:
I think the installation is somewhat common. If you have a building with only 208 wye 3-phase available, and a piece of equipment requires 480vac 3 phase, then you would reverse feed an "off-the-shelf" transformer.

"Off-the-shelf" transformers will only have H1, H2, H3 for the higher voltage 480v winding, and X1, X2, X3 , X0 at the 208v lower voltage winding. When making these reverse feed installations, NEVER bond XO. The 208 volt supply to the reverse fed xfmr is already referenced to ground at the source, and MAJOR problems will occur if you install a bond at XO.

Now that you have a new 480 3phase seperatley derived system, ground referencing is required. See 250.26 (4) Condctors to be Grounded, Multi-phase, where one phase is Grounded

Now see 220.6 Identification of a Grounded Conductor
Click to expand...
if somebody connects XO to ground on that transformer what kind of problems would there be?
 
Last Caveat of Step Up to 480 v 3ph Corner Ground

Last Caveat of Step Up to 480 v 3ph Corner Ground

You would also need to ensure any downstream equipment is rated for 480volts or higher (each pole). There will be (2) phase conductors where there is 480 volts to ground, and (1) phase conductor at 0 volts to ground.

A multiple-pole 480v/277v device is only listed and approved to be in use where any of the phase voltages are only 277v to ground.
 
electricalperson said:
i tried to look up corner grounded delta in the electricians handbook and its not there. just straight delta to delta. now if electricity is trying to find a way back to its source, the transformer, if theres a fault on the grounded phase wont that put voltage on all metal parts? what if someone grabs the machine that has the ground fault wont they get blasted? if theres a fault to the ground on the A or C phase it will trip the breaker. please correct me if im wrong
Click to expand...
The grounded phase is no different than the neutral on a more common voltage system. The only voltage to ground on the grounded conductor is the voltage drop on that conductor between the point where you are measuring it and the main bonding jumper. A fault on the grounded phase of a corner grounded system just puts the EGC in parallel with the grounded conductor.
 
IMM_Doctor said:
I know the violation for the transformer.

480 v corner ground systems, 480 v 3ph (phase to phase), you do not use Brown/Orange/Yellow.

You use white or grey for identifying the corner grounded phase conductor.


I'll dig through the book and find the article
Click to expand...

I totally missed that one.:rolleyes:
 
Oops typo (need glasses?)

Oops typo (need glasses?)

IMM_Doctor said:
I think the installation is somewhat common. If you have a building with only 208 wye 3-phase available, and a piece of equipment requires 480vac 3 phase, then you would reverse feed an "off-the-shelf" transformer.

"Off-the-shelf" transformers will only have H1, H2, H3 for the higher voltage 480v winding, and X1, X2, X3 , X0 at the 208v lower voltage winding. When making these reverse feed installations, NEVER bond XO. The 208 volt supply to the reverse fed xfmr is already referenced to ground at the source, and MAJOR problems will occur if you install a bond at XO.

Now that you have a new 480 3phase seperatley derived system, ground referencing is required. See 250.26 (4) Condctors to be Grounded, Multi-phase, where one phase is Grounded

Now see 220.6 Identification of a Grounded Conductor
Click to expand...

DOH! 200.6 Means of Identifying Grounded Conductors. (Not 220.6)
 
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