Winding Resistance Test

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 the connections are correct and the resistance measurements indicate 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 will also be checked during a winding resistance test.

Regardless of the configuration, the measurements are 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 the purpose of the test is to test 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 tested in the factory under controlled conditions.

Application includes: Transformers, Current and Voltage Transformers, Bushings, Generators, Motors, Switchgear (SF6).