VT Earthing

[HMDJRG]

Please kindly explain the difference between “Y pahse earthing in and “N earthing in VT secondary winding. (Voltage level is 33kV or above).

Regards

HMDJRG

 

[waross]

Y phase?? Do you mean wye point earthing?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[RRaghunath]

3-phase Y/Y connected VTs have 3-phase, 4-wire secondary distribution. Now, there is option to earth the 4th or star point of the VT secondaries or to earth one of the phases.
While it is standard practice to earth the star point, in some cases, specifically in case of unit connected generators, it is preferred to earth the Y-phase rather than the Star point.
The advantage with this is that the earth fault protection in the generator system can be set without any fear of it maloperating for a phase-to-ground fault in VT secondary circuits.
IEEE C57.13.3 Grounding of Instrument Transformer Secondary Circuits is a good reference.

 

[davidbeach]

But what is the "Y-phase"? I've often seen B-phase grounded in these applications, and could imagine an S-phase grounded in areas that refer to phases as R-S-T, but Y?

 

[rbulsara]

Y equates to B in R-Y-B systems (Red- Yellow-Blue) in many Asian systems.

 

[davidbeach]

So, A-B-C, 1-2-3, and R-S-T aren't enough naming conventions, there has to be more?

One color scheme for all voltage levels? Sounds like a prescription for trouble.

 

[RRaghunath]

Davidbeach,
Incidentally I pickedup the "Y-phase" from the referred IEEE.
It is true too many naming conventions! A-B-C, 1-2-3 and R-S-T that you mentioned I can add u-v-w (IEC countries!!).