Transformer xo

[jkrauss]

Over the years I've see transformers xo termination done different ways . I install my grounding electrode conductor from effectively grounded building steel and cold water ground to xo
Termination on the transformer then go from xo to bond the transformer if a bonding strap is not provided . I have also seen some installations when the grounding electrode conductor is not
Terminated on xo first but is landed on bonding lug then a small jumper or bonding strap is
Is installed to xo. my question is dose the grounding electrodes have to go to xo first?

 

[LEO2854]

Over the years I've see transformers xo termination done different ways . I install my grounding electrode conductor from effectively grounded building steel and cold water ground to xo
Termination on the transformer then go from xo to bond the transformer if a bonding strap is not provided . I have also seen some installations when the grounding electrode conductor is not
Terminated on xo first but is landed on bonding lug then a small jumper or bonding strap is
Is installed to xo. my question is dose the grounding electrodes have to go to xo first?

I don't think it really matters because it is still connected..

 

[Dennis Alwon]

I am posting to bump the thread as Leo said it didn't. That happens at times.

 

[infinity]

Over the years I've see transformers xo termination done different ways . I install my grounding electrode conductor from effectively grounded building steel and cold water ground to xo
Termination on the transformer then go from xo to bond the transformer if a bonding strap is not provided . I have also seen some installations when the grounding electrode conductor is not
Terminated on xo first but is landed on bonding lug then a small jumper or bonding strap is
Is installed to xo. my question is dose the grounding electrodes have to go to xo first?

IMO the bold part is only permitted when the GEC lands on the same terminal as the bonding jumper.

250.30(A)(5) Grounding Electrode Conductor, Single Separately
Derived System. A grounding electrode conductor for a
single separately derived system shall be sized in accor-
dance with 250.66 for the derived ungrounded conductors.
It shall be used to connect the grounded conductor of the
derived system to the grounding electrode as specified in
250.30(A)(4). This connection shall be made at the same
point on the separately derived system where the system
bonding jumper is connected.
Exception No. 1: If the system bonding jumper specified in
250.30(A)(1) is a wire or busbar, it shall be permitted to
connect the grounding electrode conductor to the equip-
ment grounding terminal, bar, or bus, provided the equip-
ment grounding terminal, bar, or bus is of suffıcient size for
the separately derived system.

 

[ramonb.usaraga]

Transformer Xo

Transformer Xo

My opinion is, it should be directly connected to Xo. Xo is the neutral point of the transformer where if connected to ground either solidly grounded or via NGR, stabilizes the voltage. For curiousity, its seldom touched by a maintenance personnel during repair and we assurred its electrical connection at all times once it is torqued and contact resistance tested. For other part of the grounding system if it is to be connected, it might be loosen for sometimes and the integrity may not be the same as it was. Sometimes, some personnel usually neglect this, because its only a grounding. Grounding is very essential to electrical system and should not be taken for granted especially on Xo side.

 

[Smart $]

My opinion is, it should be directly connected to Xo. Xo is the neutral point of the transformer where if connected to ground either solidly grounded or via NGR, stabilizes the voltage. ...

You WOULD NOT connect a GEC to X0 on an NGR system. X0 (neutral) connects to one side of resistor, grounding to other side.

 

[jumper]

You WOULD NOT connect a GEC to X0 on an NGR system. X0 (neutral) connects to one side of resistor, grounding to other side.

I am guessing that this NGR system is that High Impedance type in 250.36, no?

 

[brian john]

I am guessing that this NGR system is that High Impedance type in 250.36, no?

Neutral Grounding Resistor=NGR

For other part of the grounding system if it is to be connected, it might be loosen for sometimes and the integrity may not be the same as it was. Sometimes, some personnel usually neglect this, because its only a grounding. Grounding is very essential to electrical system and should not be taken for granted especially on Xo side

It is just as likely to get loose in one location as another, there may be justifications for your thought process, but this one holds no electrons.

 

[Smart $]

I am guessing that this NGR system is that High Impedance type in 250.36, no?

Yes, 250.36 High-Impedance Grounded Neutral Systems.