Purpose of the measurement
The resistance between all pairs of phase terminals of each transformer winding are measured using direct current. Furthermore the corresponding winding temperature is measured.
The measured resistances are needed in connection with the load loss measurement when the load losses are corrected to correspond to the reference temperature. The resistance measurement will also show whether the winding joints are in order and the windings correctly connected.
Apparatus and basic measuring circuit
The measurement is performed by TETTEX 2285 transformer test system.
This device is an automatic winding analyzer, optimized for three phase power and distribution transformer measurements.
Where:
- T1Ā – transformer under test,
- A – Ammeter,
- U – Voltmeter
- B – DC supply,
- ThĀ – Thermometer
The principle of the measurement is as follows:
The voltage drop Udc caused by the direct current Idc an by the resistance RAB, RAC and RBC is measured.The resistances are then calculated from Udc and Idc using correction for the error caused by the internal resistance of the voltage measuring equipment.
The temperature is measured from oil filled thermometer pockets situated in the transformer cover by means of an electronic thermometer connected to the computer.
Test report
The resistance values and the average temperature are calculated. In the report theĀ terminals, between which the resistances are measured, the connection, the tappingĀ position and the average temperature of the windings during the measurement areĀ stated.
Reference: Testing of power transformers – ABB
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Edvard Csanyi
Hi, I'm an electrical engineer, programmer and founder of EEP - Electrical Engineering Portal. I worked twelve years at Schneider Electric in the position of technical support for low- and medium-voltage projects and the design of busbar trunking systems.I'm highly specialized in the design of LV/MV switchgear and low-voltage, high-power busbar trunking (<6300A) in substations, commercial buildings and industry facilities. I'm also a professional in AutoCAD programming.
Profile: Edvard Csanyi
its very best site for information thank you very much
Hi dear Edvard
I have a big problem while testing a zigzag transformer. I don’t know how to test vector group of zigzag transformer. I know how to normal power transformer like YNd11 or other groups by using Autocad, but I face problem with zigzag transformer. Could you please tell me how to test it? Thank you so much.
Regards
Oye
Dear Oye,
What kind of test you want to perform? Ratio? Phase shift? Using the winding anaylser 2293 a lot of test can performed without problem.
see also http://www.haefely.com/pdf/2293_DS_1409_SG-.pdf
Best regards,
Robin
this blog is very cool for knowledge sharing.Good job!
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thanks
I am M.Tech in Power Systems and a PMP working on Solar & Substations projects interested in Transformer, Breakers, Designing and Project Management articles.
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