Transformer grounding

hhsting

Senior Member
In the attached Exhibit below on the secondary side wire from center of wye winding to terminal bar is it neutral, System bonding jumper, supply side bonding jumper? Which one and if not none then what is it? Does anyone know?

a234bb69e021714acac330b00f774096.jpg



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augie47

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I believe that's the same question you asked here:


and it was answered.
 

ActionDave

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Huh? The question is black wire from center of wye to terminal bar what is that? Neutral, supply side bonding jumper, supply side bonding jumper?
It's not a black wire, it is a line on an picture illustrating the way the transformer is internally wired and where that particular point of the transformer is used. Standard delta/wye transformer secondary is labeled X1, X2, X3, and X0. X1, X2, X3 are line one, two, and three and X0 is the neutral or grounded conductor.

The picture you posted shows the XO bonded in the transformer, there is another illustration in the same spot in the handbook that shows the XO bonded in the first disconnect.
 

hhsting

Senior Member
It's not a black wire, it is a line on an picture illustrating the way the transformer is internally wired and where that particular point of the transformer is used. Standard delta/wye transformer secondary is labeled X1, X2, X3, and X0. X1, X2, X3 are line one, two, and three and X0 is the neutral or grounded conductor.

The picture you posted shows the XO bonded in the transformer, there is another illustration in the same spot in the handbook that shows the XO bonded in the first disconnect.

So then the black line is internal wiring of transformer? Others are saying that the black line is neutral???
 

don_resqcapt19

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So then the black line is internal wiring of transformer? Others are saying that the black line is neutral???
That black line is the connection to XO. XO is the neutral point of the transformer and by definition the conductor connected to it is a neutral conductor.
However, why would it make any difference what it is called?
 

hhsting

Senior Member
That black line is the connection to XO. XO is the neutral point of the transformer and by definition the conductor connected to it is a neutral conductor.
However, why would it make any difference what it is called?

I have plans that say black line is SBJ or neutral and they call out size of the black line. When i looked at exhibit it didnt call out anything. I was wondering how to size it and what it actually is? Its still confusing the X0 as you see transformer is it terminal bar or the center point wye in pic?
 
Last edited:

infinity

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Alright is the terminal bar inside the transformer X0 point or the wye center point the X0 point?
The transformer will have some common point usually a piece of bus that is for the connection of the field neutral conductor and it is the point where the one side of each coil terminates. Look at this photo and see if it makes sense. The X0 bus is at the bottom.
3 Phase Transformer.jpg
 

hhsting

Senior Member
The transformer will have some common point usually a piece of bus that is for the connection of the field neutral conductor and it is the point where the one side of each coil terminates. Look at this photo and see if it makes sense. The X0 bus is at the bottom.
View attachment 2557800

Ok but What is that X0 point in the exhibit post #1 the terminal bar in transformer or the center point of wye?


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infinity

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Ok but What is that X0 point in the exhibit post #1 the terminal bar in transformer or the center point of wye?
It's just a representation of how it's internally connected not the actual way manufacturers wire them. What is shown in the photo in post #13 is typically how they are constructed. Here's another one with the X0 on top.
3 Phase Transformer 001.jpg
 

ActionDave

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I have plans that say black line is SBJ or neutral and they call out size of the black line. When i looked at exhibit it didnt call out anything. I was wondering how to size it and what it actually is? Its still confusing the X0 as you see transformer is it terminal bar or the center point wye in pic?
The whole point of the illustration is to show where you put your grounding electrode conductor and system bonding jumper are placed. Don't size anything off of that illustration. Don't look for any information off of it beyond what it is intended for.
 

don_resqcapt19

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Alright is the terminal bar inside the transformer X0 point or the wye center point the X0 point?
The center point of the transformer is the neutral point. The terminal bar is just that....a terminal bar.

The center point or XO is where the current has to return to and that conductor must be sized as a neutral. In cases where there is only a very small neutral load, the neutral sizing rules tell you that in no case can the neutral be smaller than what is required for the supply side bonding jumper, but it is still the white conductor.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
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Electrical Contractor
I don't agree. The conductor from the XO point on the transformer to the terminal block is the neutral. The neutral does not start at the terminal block,
I agree with this. If the wire from X-0 to the neutral bus isn't white, it's because the transformer maker put it in and didn't use a white wire.
 
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