Y Y Connected VT Grounding
Y Y Connected VT Grounding
(OP)
I am installing (3) 2400/120V VT's which will be Y connected, for metering, and have a concern about grounding. Is it good practice to ground the Y point of both high and low voltage windings? Is their a concern of an alternate zero sequence path with the HV grounded? Will leaving the HV Y point float present any problems - metering/relaying? I have seen both configurations used. The system is on an IPP generator (Delta Connected Induction) with a Y-Y step up transformer.






RE: Y Y Connected VT Grounding
If you connect the secondaries in Y, then you should ground that point as well....and only in one point.
I've never heard about a concern for zero-sequence path by ground HV side of VTs connected in Y. If the VTs are single-bushing units, they must be grounded.
RE: Y Y Connected VT Grounding
The primary wyepoint should be solidly grounded to limit core saturation/overvoltage on the primary windings from secondary-burden imbalance (for a 4160V bus.) ANSI Std C57.13 §7 is an applicable reference.
RE: Y Y Connected VT Grounding
I think the zero-sequence path would only be a problem if the secondaries were delta connected. pintalo implies grounded-wye secondaries, correct?
RE: Y Y Connected VT Grounding
For IEEE recommended practice for harmonic control you may check STD519.
Now, the circulation of harmonics in this application is usually not a concern because metering and relaying equipment will not import nor produce harmonics; unless that you are are in a harmonic rich environment (With distortion factors >20%). Or some distortion and using induction type meters.
See Chapter 6 of STD 519.
In power system you may have to evaluate wye-grd versus ungrounded to diminish the circulation of triple harmonics or to reduce short circuit levels, but that is discussion for another Post. Have a good weekend.
RE: Y Y Connected VT Grounding
RE: Y Y Connected VT Grounding
RE: Y Y Connected VT Grounding
Good luck
http://www.beckwithelectric.com/lc/protection/vtcongnd/summary.htm
RE: Y Y Connected VT Grounding
GRW