Transformer config

Status
Not open for further replies.
F

Foutah

Member
Location
Texas
Occupation
Electrical Tech
Hello everyone and happy Easter. I just join this site and hope I can get advice and criticism to made me better in what I’m doing. I reside in Texas, recently Centerpoint tells us they will require all customers to configure their entrances transformers 12470V to 460v to wye to wye. We have inside the plant different configuration. We delta delta for one line and an other delta wye. My question is what will happen or what should I do when wye to wye become mandatory. I guess I’ll have changed my tap. However I still need guidance if I may ask.
Thank you
 
Foutah said:
Hello everyone and happy Easter. I just join this site and hope I can get advice and criticism to made me better in what I’m doing. I reside in Texas, recently Centerpoint tells us they will require all customers to configure their entrances transformers 12470V to 460v to wye to wye. We have inside the plant different configuration. We delta delta for one line and an other delta wye. My question is what will happen or what should I do when wye to wye become mandatory. I guess I’ll have changed my tap. However I still need guidance if I may ask.
Thank you
Click to expand...
I would look carefully at which transformers exactly that applies to, and are you sure they will require you to upgrade and this isn't just for new installations? Seems questionable they can require you to upgrade existing equipment on your side of the service point.
 
Hi there well the plant manager informed me that Centerpoint point told him they will. And in the coming months they call meeting with us to discuss the matter. The reason is in 2 days back to back one of the 200Amp at the entrance poles A leg comes out not melt.
Im not planning to change anything but I believe in this site I can have someone to inform me better or even advise what to do or not do. Because the provider will not care about the customer anyway. Therefore i need tool to let my plan manager who is not a tech guys me I already know the change can affect or the voltage or the current from secondary.
regards
 
If you have specific equipment that require the delta-delta configuration, now would be the time to start lobbying the POCO to get either clarification or exemption, explaining the negative impact of such a change. Maybe even involving the PSC. I'm with electrofelon on this as I don't see how they can make such a significant change that would potentially effect hundreds or thousands of commercial customers and force an expensive and even maybe impossible reconfiguration of the existing facility electrical system, and utilization equipment.
Now if this only pertains to new installation, that then just requires forethought in the design process.
Don't know the POCO's rationale for making such a change. Is a wye xfer cheaper than a delta as they replace and upgrade their system? Or is the demographics of the neighborhood changing to more residential and wye configuration would be more practical for the POCO with such customers?
 
Foutah said:
Hi there well the plant manager informed me that Centerpoint point told him they will. And in the coming months they call meeting with us to discuss the matter. The reason is in 2 days back to back one of the 200Amp at the entrance poles A leg comes out not melt.
Im not planning to change anything but I believe in this site I can have someone to inform me better or even advise what to do or not do. Because the provider will not care about the customer anyway. Therefore i need tool to let my plan manager who is not a tech guys me I already know the change can affect or the voltage or the current from secondary.
regards
Click to expand...
“A leg comes out not melt”
What does that mean?
Are these your transformers?
They are delta delta now?
Have you changed one out? If so are the impedances matched?
unequal loading on Delta can cause high currents to flow in the delta windings leading to voltage imbalance. The ratios and Z must be identical in a delta bank.
 
We had a situation where the POCO upgrade their MV distribution from line-line to line-neutral (effectively they went from delta to wye) as part if a planned system capacity improvement. The few customers with MV services were made aware of this planned change years in advance and were allowed to install any transformer as long as it was dual voltage.

There is one local POCO that does require Wye primaries but it is for only on voltage, roughly 35kV, once the transformed is larger than about 1500kVA. I seem to recall this has to do with ferroresonance when a single fuse operates
 
jim dungar said:
There is one local POCO that does require Wye primaries but it is for only on voltage, roughly 35kV, once the transformed is larger than about 1500kVA. I seem to recall this has to do with ferroresonance when a single fuse operates
Click to expand...

The following is from pg.9 of the CenterPoint Energy spec for primary service (last revised 4/5/2012).

CenterPoint_primary_service_spec.png
https://www.centerpointenergy.com/en-us/Documents/Primary-Service-Specification.pdf

So they are requiring a wye primary only for 35 kV as you said, Jim. The spec doesn't require 12 kV primaries to be wye, but perhaps this has changed. I think the OP should confirm that wye is now needed for 12 kV and not just for 35 kV.
 
Last edited:
Status
Not open for further replies.
Top