VT primary winding resistance
VT primary winding resistance
(OP)
I have recently tested a 132 kV:110 V, 50(300) VA, Class 0.5M(1M) Trench German GmbH voltage transformer. I obtained a primary winding resistance in the order of 10+ KOhms. A collegue tested an identical unit and came to a value of 40 mOhm.I have tried to locate information on calculations or past test reports to no avail. Could someone inform me of calculation used to determine primary winding resistance of a voltage transformer or supply any past experience/values.
thanks in advance (first time poster so go easy on me :)
Chris
thanks in advance (first time poster so go easy on me :)
Chris






RE: VT primary winding resistance
One would expect milli ohms, perhaps a few ohms, depending on design.
RE: VT primary winding resistance
My thinking is that due to the number of turns on the primary and low VA rating of the unit that the resistance would be much larger than say for a Power transformer (which has less turns ratio ie 110kV to 22 kV and is larger ie 50 MVA and has winding resistance of roughly 1 ohm)
My thinking is that a VT has longer run of wire and of smaller guage (due to space and size limitations) this would give a much higher resistance than that of a power transformer. is this right train of thought?
RE: VT primary winding resistance
Muthu
www.edison.co.in
RE: VT primary winding resistance
Muthu
www.edison.co.in
RE: VT primary winding resistance
measuring using 4 wire method. started with 5 Amp injection, outside measureable range of CPC (primary injection device) lowered current to increase ohm range from 20 Milli ohm-2 ohm to maximum of 1000 ohm. still outside reading.
Some previous test reports indicate reading in K ohms, but looking for calculation/formulae to verify method and answer.
thank you for your quick replies too, was expecting to wait days. this is great. thumbs up for Eng-Tips forum!
RE: VT primary winding resistance
RE: VT primary winding resistance
Cannot find manufacturers specifications (or previous test report) in relation to expected winding resistance. Trench Germany GmbH SVS 123/3 VT.
RE: VT primary winding resistance
The milli-ohm measurement was certainly not correct and should be performed again. Sounds like maybe this was a secondary winding resistance?
Did you check the test reports? We normally show the primary winding resistance factory measurements on our test reports.
For those who believe a kOhm reading is very high, remember that a 132 kV VT, probably has in the range of 25,000 to 40,000 turns of very fine wire on the primary.
RE: VT primary winding resistance
As for the 40mohm reading the collegue got, are you sure they didn't test the secondary accidently? Doesn't sound too far off for 110V secondary, but seems too low for primary of a tiny 132kV winding.
RE: VT primary winding resistance
Latango, you raise a good point, thankfully the terminals where in good condition with no evidence of corrosion/foreign debris.
as noted test report for this VT have been lost/misplaced and manufacturers info does not contain factory test reports. (unit is 15-20 years old and due to change over of business from state owned to private some things have been misplaced)
thank you to all who answered this question. I am amazed at the quick response time and would be happy to hear/read more replies/ideas on this.