Unit Auxiliary Transformer LV wdg brought out with two neutrals

[elecpl123]

Hi Guys,

Unit Auxiliary T/F 13.8Kv/6.6Kv Dyn1 Vector group.In this LV Wdg brought Out with 2 neutrals,One neutral is directly grounded and another one is grounded via NGR,What may be the reason for providing 2 neutrals?

 

[NCTHAI]

This is doubt ful.. silly question... but is second one is neutral earthing or body earthing or core earthing??

I am sure you must have verified but worth to check again.

If one winding only and two neutral connected -one with NGR and one without, what purpose does NGR servces?

Am I missing something?

 

[rbulsara]

ncthai is right.

Ask the mfr. as to what they are.

 

[jghrist]

What is the source of the two neutrals? If there is only one wye winding, there is only one neutral. If there are two conductors connected to this one neutral, one solidly grounded and one grounded through a resistor, then the solidly grounded conductor shorts out the resistor. Something is missing in this scenario.

 

[edison123]

I agree with NCTHAI. The solid grounding must be for the tank/core. Ask the OEM.

 

[edison123]

Check if there is continuity between each of these neutrals to the secondary LV winding. I am sure only one (with NGR) will have the continuity.

 

[elecpl123]

hi Guys Thanks to all,

For your response when i contact manufacturer he has given reply ie two neutrals provided one is exposed to environment and another one is in the cable box.we have been using cable from neutral to NGR.Depending upon type of termination kits using we have to choose the neutral.If we are using Outdoor termination kit we have to take neutral from the Bushing ann indoor termination kit we have to take it from the box.

 

[rbulsara]

You should be using only one of the neutrals.
Keep the one that connected to NGR. Disconnect the one that is directly bonded to the ground, according to your original post, because that one will simply bypass (short out) the NGR!