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Hi Marmite, A DGA sample has been taken, upon visual inspection, copper balls where isentified throughout the unit and damaged, deformed copper bars where seen. A Black residue was coated along the leading edge of white phase and red phase copper conductors. The unit had taken a pretty bad...

Hi, I have been asked to test a transformer (33kV:11 kV 22.5 MVA star-delta unit) which recently suffered a fault condition. the unit has had its oil removed, another party has performed visual inspections. I am wondering what tests are recommended to avoid on a transformer with no oil. Tests to...

Hi Scottf and Latango, yes i believe my collegue measured incorrectly but its hard to inform some people they may have made a mistake :) 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...

Hi smallgreek, Ratio values were spot on. didn't do excitation result as was not in scope unfortunately. Cannot find manufacturers specifications (or previous test report) in relation to expected winding resistance. Trench Germany GmbH SVS 123/3 VT.

just to clarify: milli (not mega)ohms reading vs kilo ohms 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...

Correct the four wire method was used. Omicron CPC 100 was test set. when measured with multi meter, reading was 11 or so KOhm, Omicron unit can only sense to 1000 Ohms, and reading was outside this. Currents on outside, voltage on inside, good connection. Magnetic VT no Capacitive. My thinking...

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...