240volt Delta non grounded

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Finally got back to take readings on this transformer, I don't always get to set my own priorities...

Voltage phase to phase:
X1-X2 240v
X1-X3 240v
X2-X3 240v

Voltage phase to ground,
Main Output breaker on;
X1 135v
X2 145v
X3 135v
Main Output breaker open/Leads to breaker disconnected attransformer
X1 146v
X2 132v
X3 132v

Ohms to Ground measured with 1000v Megger
X1 13G
X2 13.5G
X3 14G

 
LarrywdH said:
Finally got back to take readings on this transformer, I don't always get to set my own priorities...

Voltage phase to phase:
X1-X2 240v
X1-X3 240v
X2-X3 240v

Voltage phase to ground,
Main Output breaker on;
X1 135v
X2 145v
X3 135v
Main Output breaker open/Leads to breaker disconnected attransformer
X1 146v
X2 132v
X3 132v

Ohms to Ground measured with 1000v Megger
X1 13G
X2 13.5G
X3 14G

Click to expand...
In your OP you said you had a ground detector lit up. What is being used for a ground detector? Is it still lit up? The numbers you gave look like an ungrounded system without a fault.
 
Looks like Delta with no corner grounding. You still don't know if there is a center tapped neutral. Can you see the service wiring? You can look at the POCO meter and the FM number will tell you what the service is. A 4W Delta with power leg will have a FM 15S meter. If it's a solid state meter, it may say 15S/16S. 16S is for 4W Wye. If it's a CT service, it'll be FM 8S/9S. Older services may use different meters, but not worth discussing. Based on the Ohms to ground, I'd say it's an ungrounded 3W Delta. That's why there's a ground detector. I've never seen a 4W Delta with an ungrounded neutral. If there's a step-down transformer between the service and you, I can't be of much help.
 
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Edit timed out....

Duh! I read your OP and I see it's a 480/240 transformer fed panel, so leave me out of the picture...I'm just a lowly POCO guy.
 
LarrywdH said:
Finally got back to take readings on this transformer, I don't always get to set my own priorities...

Voltage phase to phase:
X1-X2 240v
X1-X3 240v
X2-X3 240v

Voltage phase to ground,
Main Output breaker on;
X1 135v
X2 145v
X3 135v
Main Output breaker open/Leads to breaker disconnected attransformer
X1 146v
X2 132v
X3 132v

Ohms to Ground measured with 1000v Megger
X1 13G
X2 13.5G
X3 14G
Click to expand...

While not a transformer test expert, 13G-Ohm to ground says to me the transformer is fine.

Regarding voltage to ground, if PoCo primary loads can be unbalanced, can secondary voltages be proportionally unbalanced downstream?
 
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