I think a wye-wye with a tertiary winding could be used to reduce zero sequence impedance and it could thus be fed from a delta source? Although the OP did not state whether the 13.8 system was Delta or wye......
Key question is whether the 13.8 system has a neutral. If it does, then I would say a wye wye would be preferred.
"Wye, Wye, You Always Tie"
Ok, so I assume your neutral is available at the transformer primary and can be landed on the XO?
Then you would not want the neutral to be solidly grounded at the transformer.
That had crossed my mind, whether the OP meant "HIGH resistance grounded". If It is HRG, he could not use a transformer that was designed for a MGN system as the primary neutral would be the tank.
Medium voltage uses low resistance while 480V uses high resistance.
That seems counterintuitive.....so "low resistance grounded" is the proper term for a resistance grounded system at MV? I have never heard that term before (but I don't do much MV).
A common general term would be impedance grounded. But yes, these systems usually try to have about 5A ground current on LV using an HRG and 400A on MV using an LRG.
Ok yeah, the terms are a bit confusing. I hear "low resistance grounded" and I think "solidly grounded". I understand there are different schemes for the resistor/ground current value. Ive just got to think "low resistance impedance grounded" instead of assuming someone is trying to say solidly grounded just because they left "impedance" out
So is it fair to state that HRG is designed so that the power dissipated in the ground impedance (not necessarily resistive?) can be maintained indefinitely. Thus allowing continued operation of the system after a ground fault, with an alarm condition raised? While the LRG allows sufficient fault current that the grounding impedance will overheat and fail if the alarm condition does not immediately (duration?) shut down the circuit?Ok yeah, the terms are a bit confusing. I hear "low resistance grounded" and I think "solidly grounded". I understand there are different schemes for the resistor/ground current value. Ive just got to think "low resistance impedance grounded" instead of assuming someone is trying to say solidly grounded just because they left "impedance" out
It appears that'll high resistance grounding is used at MV but typically a only up to 5KV:
"HRG May be utilized on low voltage systems or medium voltage systems up to
5kV. IEEE Standard 141-1993 states that “high resistance grounding
should be restricted to 5kV class or lower systems with charging currents
of about 5.5A or less and should not be attempted on 15kV systems, unless
proper grounding relaying is employed”.
Yes, this is the general idea.
Do you have an example of conductor connections and components used for a LRG on MV? I'm guessing no connection to the MGN?
