Neutral Grounding Practice for Utility Pad Mount Transformers

[rockman7892]

I was wondering what standard practice was for grounding of neutral connections on utility pad mount transformers served from and overhead distribution line that contains a neutral. Question applies 1-phase pad mount fed from OH lateral feeder but similar question also applies to 3-phase with wye-wye padmount. .

For 1-phase transformers I usually see these as single bushing transformers with that have neutral internally bonded to tank/ground. In these applications are concentric neutral cables used with the concentric neutral connection to grounding point in transformer with intent for the neutral current to flow back to the overhead line neutral via the concentric neutral? Or is this grounding point in transformer only connected to earth through ground rod or ground rings with the intended neutral path to flow via ground to the nearest pole where it finds pole ground and travels up to overhead neutral?

If concentric neutral is typical means, is transformer also typically grounded to earth through ground rod or ground ring around padmount?

Thanks

 

[stevenal]

For 1-phase transformers I usually see these as single bushing transformers with that have neutral internally bonded to tank/ground. In these applications are concentric neutral cables used with the concentric neutral connection to grounding point in transformer with intent for the neutral current to flow back to the overhead line neutral via the concentric neutral?

Yes

Or is this grounding point in transformer only connected to earth through ground rod or ground rings with the intended neutral path to flow via ground to the nearest pole where it finds pole ground and travels up to overhead neutral?

No

If concentric neutral is typical means, is transformer also typically grounded to earth through ground rod or ground ring around padmount?

Thanks

Yes, one needs to control the touch potential.

 

[wcaseyharman]

I understand my utility does exactly as you describe - neutral is tied to the transformer tank and to the vault ground, as well as the customer neutral (and by extension the customer’s ground)