High Resistance Ground

[RUWired]

When installing a HRG to a 3-phase 4-wire wye transformer (existing transformer) would it be correct to say that the system is not a solidily grounded system, thereby requiring the existing grounded conductors be removed?

Rick

[jim dungar]

Originally Posted by RUWired

When installing a HRG to a 3-phase 4-wire wye transformer (existing transformer) would it be correct to say that the system is not a solidily grounded system, thereby requiring the existing grounded conductors be removed?

Rick

You need to provide more details.

An HRG can supply a delta primary of a transformer.
The wye secondary is a separately derived system which can be solidly grounded and supply L-N loads, it does not impact the primary side HRG.

[SG-1]

You likely will need to move the grounded conductors to the correct side of the resistor or what ever impedance you are using, not remove them.

[winnie]

HRG systems are not permitted to serve line-to-neutral loads. So you should only have phase conductors and EGCs for any feeders and branch circuits supplied by a HRG system, and in particular there should be no _grounded_ circuit conductors (no neutrals).

-Jon

[jim dungar]

After rereading your OP, I am now under the impression that you are converting an existing 4-wire secondary into a 3-wire HRG. Yes, you are creating a system that is no longer solidly grounded.

Jon is correct, you must remove all existing L-N loads. Personally, I would 'safe off' any existing grounded conductors, so that they are not mistaken as being still in service.

[SG-1]

I agree with winnie, except you still need the grounded conductor ( neutral ) at the transformer ( X0 ) to connect to the HRG.

[RUWired]

Originally Posted by jim dungar

After rereading your OP, I am now under the impression that you are converting an existing 4-wire secondary into a 3-wire HRG. Yes, you are creating a system that is no longer solidly grounded.

Jon is correct, you must remove all existing L-N loads. Personally, I would 'safe off' any existing grounded conductors, so that they are not mistaken as being still in service.

Thanks for all the replies. I am installing a HRG on the secondary of an existing 3-phase 4-wire wye secondary transformer with existing grounded conductors going out with each feeder. I need to identify all the single phase 277 volt loads on each feeder and deal with them. Most are lighting panels that will get a new 3-wire to 4-wire transformer. The existing grounded conductors with each feeder i will reidentify them as equipment grounding conductors and move them to the ground bar and reidentify the equipment as 3-wire.

The HRG line load conductors are going to be installed where the main bonding jumper was.

Rick

[benaround]

Do the grounding impedance's have a line/load for lack of the proper terminoligy, or can

they be connected to either/or end. In other words can they be flipped 180deg and still

work as they should. Thank You.

[jim dungar]

Originally Posted by benaround

Do the grounding impedance's have a line/load for lack of the proper terminoligy, or can they be connected to either/or end. In other words can they be flipped 180deg and still work as they should. Thank You.

Technically there is no reason for them to have any specific line-load, practically, however, most commercially available ones do. This is probably because of ancillary components like current sensors and pulsing contactors.

[benaround]

Thanks Jim, By the way has anyone told you lately that you are a pretty good guy to

have hanging around this Forum ?