Substation main xformer earthing?

[Ryoko]

I'm modeling a substation for a game. I would like it to be generally technically correct. Currently, I'm modeling the main xformer and I noticed they have 4 terminals on the low side. I can guess these are for phases A/B/C plus a neutral. My question is where would this 4th terminal normally be connected in a substation setting?

 

[berkeman]

I did a Google search on your thread title and got lots of good hits. Are here two of them:

https://eepower.com/technical-artic...ion-grounding-parts-of-the-grounding-system/#

https://ttesusa.com/blog/explore-th...ng-in-power-systems-for-safety-and-stability/

 

[Baluncore]

My question is where would this 4th terminal normally be connected in a substation setting?

I would expect it to be the neutral, at the centre of the three-phase star, connected to protective earth. It is there to protect the insulators from overvoltage.

It might depend on the country and national standard.

 

[Ryoko]

I did a Google search on your thread title and got lots of good hits. Are here two of them:

https://eepower.com/technical-artic...ion-grounding-parts-of-the-grounding-system/#

https://ttesusa.com/blog/explore-th...ng-in-power-systems-for-safety-and-stability/

I saw those articles. But unfortunately it was more theoretical than practical. I guess what I'm asking if I walked into a substation, what would that 4th connection look like? Is it just strapped to an earthing connection in the ground or tied to the xformer case?

 

[berkeman]

Hmm, is this article any better?

https://eepower.com/technical-artic...tion-grounding-parts-of-the-grounding-system/

 

[Ryoko]

Hmm, is this article any better?

View attachment 356767
https://eepower.com/technical-artic...tion-grounding-parts-of-the-grounding-system/

That helps a little. It seems there is an extra bus bar for grounding redundancy. (I'm probably over thinking this. It is just a game model after all. Hard to take the engineering hat off.)

 

[Baluncore]

Is it just strapped to an earthing connection in the ground or tied to the xformer case?

The floor of the sub-station will have a grid of flat copper straps on the surface, earthed through deep holes in the ground. The 4th connection, as an earthed neutral, will be connected to that grid with a strap. The chassis of the transformer will be separately bonded to the earth grid.

 

[Ivan Nikiforov]

I saw those articles. But unfortunately it was more theoretical than practical. I guess what I'm asking if I walked into a substation, what would that 4th connection look like? Is it just strapped to an earthing connection in the ground or tied to the xformer case?

Hello! The ground wire is shown with a red arrow. This connection must be made at the transformer terminal at the neutral connection point. The transformer housing is connected to the ground loop by a separate conductor. When designing, please specify the operating mode of the neutral conductor - TN-C or TN-S.

 

[Ryoko]

View attachment 356772
Hello! The ground wire is shown with a red arrow. This connection must be made at the transformer terminal at the neutral connection point. The transformer housing is connected to the ground loop by a separate conductor. When designing, please specify the operating mode of the neutral conductor - TN-C or TN-S.

Not actually designing anything. I just want the model to be reasonably accurate. Though admittedly 99.9% of people playing a game looking at it would never see anything wrong even when it is totally messed up. I've played games with power distribution as part of the modeled environment and it drives me nuts just how horribly wrong it is most of the time. But the art guys like it.