Solar Generator LV/ MV Transformer

PV_Crane

New member
Can anyone tell me if there is a standard LV/MV transformer winding configuration when connecting a PV Solar Generator with a 480Vac 3 phase output to MV?

Is it 480V "Y" to MV Delta? or 480V Delta to MV Delta or ??
 

ron

Senior Member
It depends on the inverter.
Many are Y on the low side and delta on the high.
 

kingpb

Senior Member
standard delta-wye(grd) step-up in most cases, but if your connecting the MV side to utility, you need to make sure you have the correct phase connection if paralleling at all. So the standard 30 deg shift may not work, even though it's still a delta-wye.
 

don_resqcapt19

Moderator
Staff member
standard delta-wye(grd) step-up in most cases, but if your connecting the MV side to utility, you need to make sure you have the correct phase connection if paralleling at all. So the standard 30 deg shift may not work, even though it's still a delta-wye.
Why would the phase shift matter when connecting a single transformer to the utility? As long as you sync when you close the tie breaker, the phase shift in the transfomer should not matter? I know that you work with these types of issues all the time and I don't, so what am I missing?
 

kingpb

Senior Member
Generally speaking, in most cases it probably isn't going to be an issue, whereby the standard IEEE 30 deg shift with phases connected such that they reach their positive maximum in the order of a, b, c, when rotated in a counterclockwise rotation (positive sequence) are encountered. However, there are utility systems that may role the phases, such that the phases may reach their positive maximum in the order of a, c, b.

When connecting to the utility system, without generation, it is not usually an issue unless you are tying/paralleling two different feeds/systems together. Add generation in parallel and you better make sure your generation matches up, or your sync checks will never give a permissive to close. Same with two different feeders, if they go through different transformations at the point of interconnection, they could be 30, 60, 120, etc. out of phase and you need to know this BEFORE you buy the transformer, because 30 degrees out can be handles with a delta-wye, but say a 60 deg out of phase you'll need to use a delta-delta.

Best to create a 3-line phasing and connection diagram if in any doubt what so ever.

Hope that made sense.
 
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