3 phase wye/delta pole mount transformer. XO bonded to ground internally?

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dman504

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Performing quick resistance checks on a 13.8kV-347/600V pole mounted liquid filled transformer. Readings on high side phase to ground and High side to low side very high as expected. Low side windings to ground basically short. (with strap disconnected) Is XO grounded internally?
 
Very common to my knowledge.

Wouldn't 347/600 be a wye secondary? Your thread title says wye/delta.
 
Ingenieur said:
You are measuring sec ph to Xo
or
sec ph to case?

I assume delta-wye not wye-delta
Click to expand...

You are correct, delta-wye. I am measuring secondar windings to the case and the external ground strap is diconnected yet still get dead short. So figuring XO is connected to case internally?
 
dman504 said:
You are correct, delta-wye. I am measuring secondar windings to the case and the external ground strap is diconnected yet still get dead short. So figuring XO is connected to case internally?
Click to expand...

Either that or there is an insulation fault in the secondary winding somewhere. Are you getting equal no-load voltages from each ungrounded line to ground?
If you can measure it accurately, is the disconnected and deenergized resistance from each phase line to ground and to the X0 identical? How low a resistance is the "dead short" from X0 to ground?
 
GoldDigger said:
Either that or there is an insulation fault in the secondary winding somewhere. Are you getting equal no-load voltages from each ungrounded line to ground?
If you can measure it accurately, is the disconnected and deenergized resistance from each phase line to ground and to the X0 identical? How low a resistance is the "dead short" from X0 to ground?
Click to expand...

I am only using a multimeter and it shows "OL"
 
GoldDigger said:
A multimeter on ohms function will typically show OL (OverLoad) on an open circuit or higher than the largest ohm number it can display. Not a short circuit.

Sent from my XT1585 using Tapatalk
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Agreed because "OL" actually means open load not overload, so it means there is zero resistance between the two.
 
MattS87 said:
Agreed because "OL" actually means open load not overload, so it means there is zero resistance between the two.
Click to expand...
So on voltage ranges OL means OverLoad and on resistance range it means Open Load? OK.
In any case open means infinite resistance not zero resistance.
No resistor could be interpreted as either open or shorted while zero resistance is unambiguous and would correspond to a meter reading of zero.

Sent from my XT1585 using Tapatalk
 
GoldDigger said:
So on voltage ranges OL means OverLoad and on resistance range it means Open Load? OK.
In any case open means infinite resistance not zero resistance.
No resistor could be interpreted as either open or shorted while zero resistance is unambiguous and would correspond to a meter reading of zero.

Sent from my XT1585 using Tapatalk
Click to expand...

Sorry I meant no resistance not zero ohms resistance.
 
GoldDigger said:
So on voltage ranges OL means OverLoad and on resistance range it means Open Load? OK.
In any case open means infinite resistance not zero resistance.
No resistor could be interpreted as either open or shorted while zero resistance is unambiguous and would correspond to a meter reading of zero.

Sent from my XT1585 using Tapatalk
Click to expand...

Not sure if this link works, but I use a t5-1000 and the manual shows an "open circuit" reading "OL" on the ohms setting.
http://media.fluke.com/documents/T5______iceng0300.pdf
 
Link works and confirms that, like nearly all digital multimeters, 'OL' means 'open circuit'. All that aside, a photo of the transformer nameplate would likely resolve the question.
 
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