Temperature Rise (Heat Run) test

Heat run test or temperature rise test is one of the type tests on the power transformer. This test’s results are really important for the operational economy to show the performance of the transformer in the fields.

The mean purpose of this test is to check whether the oil and winding temperatures of the transformer meet the values specified in the standard and technical projects.

HOW DO WE PERFORM HEAT RUN TEST?

Heat run test or temperature rise test is performed by applying a rated voltage and frequency to the primary side of the transformer under test, and a short-circuit winding in the secondary, for the aim of circulating rated current in the latter. The circulation of the rated current during the test makes the winding temperature rise with time.

The temperature rise test is maintained until the windings and the oil in the tank reach a constant and stable temperature and must be within the permissible limits defined by the designer.

The time taken to reach the final temperature gives an idea about the thermal time constant of the transformer, and the final temperature gives the full load temperature rise of the transformer.

HIGHTEST DEVICE USED TO MAKE HEAT RUN TEST

WinRes-20 is designed by advanced engineering technology to measure the winding resistance of transformers and the full load resistance R_o during heat run test by applying up to 20A DC.

The smart design of WinRes-20 and its advanced software provide highly detailed conclusion about the performed measurements automatically.

After the Heating phase is finished and the transformer is ready for testing, the operator should respect the following instructions:

1. Set test and device parameters.
2. Disconnect the transformer.
3. Connect the test device (WinRes-20).
4. In less than 10 minutes run the temperature rise test.

During the test, WinRes-20 keeps measuring the winding resistance to be tested continuously during the preset test duration entered by the user in Test Settings.

When the test is finished does not immediately gives you the results. To see the final result save it first and go to the test records, select the perspective result and press calculator, set R Cold and T Cold, material temperature, and heat-run calculation to get the R0 which is the value of the measured winding resistance at a real working temperature of the tested transformer. we get the results as shown in the curve below.

Using the numerical analysis methods (Linear or Exponential) configured by the device’s user, WinRes-20 can easily calculate the full load resistance R_o, which represents the resistance at the real operation temperature T_o