Conductor Color - 480v HRG?

[newtonwb]

What would the color requirement be for the conductor the connects from X0 to the HRG?
Note: Transformer secondary is 480v wye and feeding an MCC with HRG.

 

[don_resqcapt19]

It is not a grounded conductor and it is not a grounding conductor, so it can't be white or green.

 

[infinity]

HRG?

 

[winnie]

High Resistance Ground.

OP is using HRG to mean the grounding resistor in an HRG system.

 

[mayanees]

I don't know why more companies don't install HRG systems on substations. I used to work for P&G and every substation transformer they use was equipped with HRG. Having an HRG system allows you to tolerate the first line-to-ground fault, and it's said that 95% of all arc flash incidents start as line-to-ground faults. So therefore, the majority of arc-flash incidents never occur. Granted, you don't have access to the 277 Volts, and in order to do that you'd have to set another transformer with a solidly grounded secondary.

 

[winnie]

HRG systems are not permitted to serve L-N loads, presumably because the N conductor could be at elevated voltage (277V) for an extended period of time. IMHO this is why a white wire is _not_ an answer to the OP's question.

However, I've thought for a while that HRG systems rigged with suitable ground fault breakers should be permitted to serve L-N loads. In this case a ground fault would shut down the faulted circuit and the N conductor would not be at elevated voltage. This would mean that the HRG system does not provide continuity of service, but instead provides significantly reduced L-G fault currents. In such a system (not currently code compliant), IMHO white would be the answer to the OP's question.

 

[jim dungar]

However, I've thought for a while that HRG systems rigged with suitable ground fault breakers should be permitted to serve L-N loads. In this case a ground fault would shut down the faulted circuit and the N conductor would not be at elevated voltage.

Would you L-N loads be connected before the HRG or after?
If after the HRG would need to be large enough to carry the L-N load thereby reducing its effectiveness while creating a large constant heating loss.
If the connection is before the HRG, a N-G fault would bypass the HRG thus negating its effectiveness.
Except for lighting ballasts, what loads benefit from a L-N of 277V?

 

[winnie]

Except for lighting ballasts, what loads benefit from a L-N of 277V?

Good point on which loads actually benefit from 277V.

Might be more relevant for 416/240V systems. Those are specifically intended for 240V L-N IT system loads.