Sun, Sep 26, 2021

The transformer’s efficiency depends mostly on the perfection of the particular turns or the transformer’s voltage ratio. The transformer turns ratio test is, therefore, an essential type of transformer test. To prevent dangerous voltage, the voltage can only be applied in the high voltage winding. The purpose of this article, therefore, is to explain step by step procedure for the transformer turns ratio test

The ratio of the turns between the windings

The Power transformer turns ratio test is an AC low voltage test that specifies a high voltage winding ratio to all other non-load windings. The turn ratio test is performed on all the taps of each winding.

Power Transformer Turns Ratio Test

The Transformer Turns Ratio tester (TTR) is the system used to calculate the turns ratio between the windings. Voltage is added to the H-marked lead, and the test set measures the X-marked lead.

Ratio calculations are carried out at all tap locations and are determined by dividing the induced voltage reading into the applied voltage value. As ratio tests are carried out on three-phase transformers, the ratio is carried out in one phase at a time with a three-phase TTR before the three-phase transformer ratio meter calculations are completed.

Turns Ratio Monitoring Protocol Step by Step

Step 1: Isolate the equipment, add the working ground to all outgoing and incoming cables, and detach outgoing and incoming cables from the connecting transformer terminals.

Disconnected cables should have ample clearance from switchgear terminals greater than the phase spacing distance. Use nylon rope to keep cables away from incoming and outgoing terminals as needed.

Step 2: Attach the H-designated three-phase test lead to the military-style connector at one end to the mating link on the H-marked test package. Ensure that the index notch of the connector is correctly aligned.

Step 3: Attach the X designated three-phase test of the lead military-style connector to the mating link on the test set marked with an X at one end. Ensure that the index notch of the connector is correctly aligned.

Step 4: Connect the stated H1, H2, H3 test lead to the corresponding H1, H2, H3 transformer terminal/bushing. Link the H0 test lead when the H0 terminal and bushing is present.

Step 5: Link the specified X1, X2, X3 test leads to the corresponding X1, X2, X3 transformer terminals/ and bushes. Link the X0 test lead if the X0 terminal/bush is present.

Step 6: Perform rotate ratio measurements for all tap positions.

Step 7:Confirm that the assessed ratios are within 0.5% of the estimated rates.

Transformers with wire connections but do not have a neutral wire outlet shall be checked for a three-phase power supply ratio. Any inequality in the three phases’ magnetizing properties would result in a neutral change, resulting in uneven phase voltages. Where such inequality is found, the transformer turns ratio test should be modified, either to a delta or a wire connection, and the line voltages measured. When these values are equal to each other and the right values, the ratio is correct.

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