The magnetic balance test is a most commonly used proactive test is performed only on three-phase transformers to detect the faults in the core and to verify the imbalance in the magnetic circuit also to identify inter-turn faults in the transformer at the early stage of manufacturing work.
HOW DO WE TEST TRANSFORMER MAGNETIC BALANCE?
Transformer Magnetic Balance Test Procedures:
1. Keep the transformer Tap Changer in an ordinary position.
2. Apply a single-phase AC voltage on one of the terminals of the HV winding.
3. Measure the voltage between the two other HV terminals.
4. Repeat the test for each of the three phases.
|Left side phase||Central phase|| Right side phase|
|Voltage applied at left side phase||100%||60 – 90 %||10 – 40 %|
|Voltage applied at central phase||50%||100%||50%|
|Voltage applied at right side phase||10 – 40 %||60 – 90 %||100%|
Table.1. Transformer Magnetic Balance Test
Based on the results shown in the table above, if the voltage applied at one side is equal the sum of the voltages obtained at the two other sides, this indicates that the transformer is magnetically balanced. But If there is any short circuit between turns, the sum of the two voltages may not be equal to the applied voltage.
The results shown in the table indicate that the Magnetic balance test is only an indicative test for the transformer. The results obtained by the distribution of the voltage in the core of the transformer are not absolute, therefore, this test should be used in conjunction with other tests to give more effective results.
HIGHTEST DEVICE USED TO TEST TRANSFORMER MAGNETIC BALANCE
The HighTest Products ”TURA-03” and ”TURA-X” can make Magnetic Balance test easily, but to perform it using ”TURA-01”, you have to connect it with ”TPA-03” adapter and then choose ‘Magnetic Balance Test’ menu. You can choose the connection type as ‘Phase to Phase (LL)’. You can assign the test voltage.
The result page will appear as follows.