Megger MTO210, Инструкция по эксплуатации

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AVTMMTO210 Rev 7 Sept 2013
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5
Transformer Testing
F
WARNING
When testing a transformer or regulator, make sure that a good
ground is placed on the test specimen as shown on all
connection diagrams.
Winding Resistance Testing
Winding resistance measurements in transformers are of fundamental
importance for the following purposes:
Calculations of the I2R component of conductor losses.
Calculation of winding temperature at the end of a temperature test cycle.
As a diagnostic tool for assessing possible damage in the field.
Transformers are subject to vibration. Problems or faults occur due to poor
design, assembly, handing, poor environments, overloading or poor
maintenance. Measuring the resistance of the windings assures that the
connections are correct and the resistance measurements indicate that there are
no severe mismatches or opens. Many transformers have taps built into them.
These taps allow ratio to be increased or decreased by fractions of a percent. Any
of the ratio changes involve a mechanical movement of a contact from one
position to another. These tap changes should also be checked during a winding
resistance test.
Regardless of the configuration, either star or delta, the measurements are
normally made phase-to-phase and comparisons are made to determine if the
readings are comparable. If all readings are within one percent of each other,
then they are acceptable. Keep in mind that the purpose of the test is to check
for gross differences between the windings and for opens in the connections.
The tests are not made to duplicate the readings of the manufactured device
which was tested in the factory under controlled conditions and perhaps at other
temperatures.
Transformer winding resistances are measured in the in order to check for
abnormalities due to loose connections, broken strands, and high-contact
resistance in tap changers. Interpretation of results is usually based on a
comparison of measurements made separately on each phase in the case of a