GROUNDING TRANSFORMERS: 3X SINGLE PHASE UNITS vs 3-PHASE PADMOUNT

[OhioAviator]

Hello all,

I hope this isn't a silly question, but I just can't seem to noodle this out in my head.
I need to derive a system neutral for a 4,160 Volt Delta industrial power system. The derived neutral will then connect to ground via a neutral grounding resistor. I know that I can use a zig-zag transformer or 3 single-phase transformers, appropriately connected, to derive the system neutral. My question is this... can I also use a conventional three-phase padmount transformer (wye primary, delta secondary) to derive the system neutral? I don't have three single-phase transformers on hand, but I have a three-phase padmount on hand that's the right size physically and electrically? Thanks in advance for the help.

 

[rcw retired EE]

I might be overlooking some nuance,but I believe it will work as long as the neutral point of the 4.16/2.3 kV wye winding can be isolated from ground and connected to the grounding resistor. The delta winding provides a path for zero sequence current flow.

Make sure the transformer neutral is suitable for full 4.16 kV.

 

[DTR2011]

This is done all of the time on wind farm substations for a similar purpose. A solidly grounded Wye (HV 34.5/19.2) and an un loaded Delta (LV 480)

 

[OhioAviator]

@rcwilson & smallgreek...
Thank you for your advice. I thought a padmount transformer would be okay, but I just couldn't noodle out the vector sums and the effects of all thee phases on the same core.

@smallgreek... you mentioned an unloaded Delta, however, the Delta side of the transformer can be used to supply power. I've done so in the past, for lighting and small motor loads, with no adverse effects and the ground fault relaying worked just fine and within specs.

Thanks!

 

[jghrist]

Finding a wye-delta padmount with an H0 bushing might be a problem.

 

[OhioAviator]

@jghrist... Nope, I've already got one. The wye neutral point of the primary winding is insulated from ground and the H0 bushing is insulated for full primary voltage. It seems to be a perfect match. That's the reason for my original post. I'm cheap and didn't want to spend money on single-phase cans if I didn't have to.