Wye-Wye Neutral and Equipment Grounding

[ThePunisher]

I would like to obtain everyone's comments on the transformer we perceived to be grounded.

The transformer is a 10 MVA 34.5 - 0.60 kV, Wye-wye with both primary and secondary neutrals grounded effectively. The primary supply side is also connected to a secondary Wye with neutral grounded. The secondary neutral is serving line-neutral loads.

We have used a dedicated return conductor from the transformer to the primary supply side. We used Equipment Grounding conductor to interconnect the equipment as shown...I would like to obtain anyone's comment in case we forgot something.

 

[wroggent]

If I understand your drawing correctly it looks like the neutral is grounded at the transformer secondary and also in your disconnecting equipment. Don't know where you're located but I believe the NEC would prohibit this unless it's a utility owned transformer.

 

[ThePunisher]

I apologize for the confusion wroggent, the neutral is not grounded at the disconnecting means and so the slash green marks indicates deletion of the connection of the neutral to ground at the disconnecting means.

My doubt is how the SBJs (supply bonding jumpers) are connected at both primary and secondary wye points.

Thanks

 

[ThePunisher]

To add, if the primary and secondary zero sequence network of the wye(grounded)-wye(grounded) transformer are tied up and connected to the primary supply system, assuming the supply is also wye(grounded) how can we set the relays to be discriminate as to the location of the fault (primary and secondary)?

 

[Mbrooke]

Is this a utility transformer? Or customer owned under the NEC?

 

[ThePunisher]

It is customer owned

 

[ThePunisher]

I received information that the transformer is utility supplied and owned

 

[Mbrooke]

If utility owned than the neutral must be tied together and at the grounding system as well in the transformer.

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