Transformer Delta to Y

Status
Not open for further replies.
B

brother

Senior Member
Location
"I have learned, in whatsoever STATE I am, therewi
I was talking with a buddy and he was telling me that at a project hes working on, they discovered why a breaker (main) kept tripping. He said these guys (engineers) had a 'Y-Y' transformer, but it was a 'Delta' system that was supplying the area. He asked me about it and I could give much info on it, I just know that they always ordered the right one the projects I worked on, and Im used to seeing a 'Delta-Y' transformer. So im not sure if the Y-Y transformer was causing their issues. He says it going to be an 'expensive' fix with this transformer.

Its a 750 kva and its gonna have to be changed. OUCH!! I feel for the ones who have to pay for it. So what do you think?? would this really cause the issues (breaker tripping) that they have??
 
480 Wye to 208Y120 Wye format ?


I am not sure but heard few stories about the Y-Y transformer if you have three cores it will have ferreiosit { sp } issue if used single core it will be not to bad but some issue with other items myself I havent have much experince with Y-Y format which I uselly don't run into not often I know Jim Dunger and few other may know more details with this set up.

so just hang on tight someone will chime in pretty fast with this one.

Merci,Marc
 
The type of transformer primary, wye or delta, and the type of supply have very little in common with each other. On those few situations where it may be a concern, I would not expect the problem to cause a breaker to trip.
 
jim dungar said:
The type of transformer primary, wye or delta, and the type of supply have very little in common with each other. On those few situations where it may be a concern, I would not expect the problem to cause a breaker to trip.
Click to expand...

unless they hooked up the XO on the primary.
brother, if the hooked up the XO, tell them to disconenct it, see if that stops the problem and I'll send them a bill.
:D
 
If the transformer is a wye wye you do indeed connect the primary neutral to HO and the secondary to XO.

If they where back feeding a delta / wye then you would not connect to the primary neutral to XO.
 
I thought the OP state it was being delta fed. (and my reference should have been HO)
 
In distribution what are the advantages of wye wye if any over delta wye?

Is the neutral connected on the primary in a wye wye?

Is there a phase shift in wye wye?
 
If you have a Y-Y service transformer the H0 and X0 bushings are usually bonded together and therefore bonded to ground via the secondary.

There are advantages and disadvantages to having the primary circuit neutral conductor bonded to the H0 bushing, and therefore no standard practice that I have seen.

Generator systems are a different beast than utility distribution system and usually follow different standard practices.
 
weressl said:
The sytem is already grounded. No double grounding is necessary OR (should be) permitted.

When I refered to supply transformer I was writing about the trasnformer that supplies the Y/Y unit.
Click to expand...

My point was that grounding is a a quite different matter to voltage balance.
 
Besoeker said:
My point was that grounding is a a quite different matter to voltage balance.
Click to expand...

Chinese whisper.

My orignal comment was to Larry's comment that you need to ground to maintain voltage stability. I answered to Larry that it is assured by the grounding of the supply transformer.

You should have commented on Larry's post, unless you are saying that grounding of the neutral has nothing to do with voltage stability.
 
Call me confused, it seems to me that if neutral of the transformer primary is not connected to the neutral of the primary supply system, you would see voltages on the secondary side that would be similar to having an open neutral on the secondary side.

1) If you have a system feeding a wye _load_, and there is no neutral brought to the common point of the load, then the 'phase to common' voltage at the load depends upon the balance of the load. This is the common 'open neutral' scenario that we argue about with MWBCs.

2) If the load described above were three entirely independent single phase transformers, then the voltage shift associated with the open neutral would clearly be unchanged; the various 'phase to common' voltages would depend upon the balance of the single phase loads.

3) If the one terminal of the secondaries of the single phase transformers are then tied together (forming a wye system), then the voltage shift is still unchanged; the load on each secondary phase is reflected as the load on the respective primary, and if these loads are not balanced, then you will get a shift in the various phase to common voltages.

IMHO if you have three single phase transformers, connected in a wye-wye bank, then you have to connect the primary neutral to the primary supply system, or you will see secondary voltages that look like an open neutral situation.

4) But what happens in the situation where the three transformers are wound on the three legs of a common three phase core? In this case, the flux threading each leg is caused by all three primary coils. I cannot quickly visualize if this common coupling will act to prevent the shift of the neutral voltage.

-Jon
 
Status
Not open for further replies.
Top