Ultimate and Comprehensive Guide of Transformer Ratio Testing

A transformer turns ratio is the test taken for the confirmation of the accuracy of the transformer. This test will help in ensuring the correct ratio of both the primary turn and the secondary turns. It can also help in finding some issues regarding the tap-changer performance, incorrect winding connections, shorted turns and open windings. As there are so many benefits in the transformer turns ratio test and it is cheap in cost, it is vital and also considered as the best to test the transformer frequently. 

Importance of ratio measurement of the transformers 

  • The transformer ratio test is extremely important for different reasons like, 
  • Assessment of the possible damages 
  • Quality verification 
  • Establishment of the condition of the transformer and trends condition 

Validation of the design specifications 

This transformer turns ration test should be completed frequently as the accuracy of the transformer is significant. In the process of testing, if the ratio results differ from the expected to the targeted value, the chance of the defect or error will be high. If there are any untargeted results, it might indicate a defect in the winding or the tap-changer as well. 

Available styles varieties of the transformer turn ratio test 

As there are different types of transformers, it is possible to observe the performance of the transformer in the different types of testing. These types of transformer turn ratio test will differ in their style and test conditions. However, most of the sets will have at least two high leads and two low leads. Here are the different styles of testing. 

Single-phase models 

These single-phase models are designed to measure the turn ratio and exciting current windings in the transformers. These models are primarily used for testing only the single-phase power that is operated with a low ratio. Now, this is used up to three-phased transformers. If it is used for the three-phase transformers, each phase has to be tested separately. 

Three-phase models

It is not like a single-phase model, but the three-phase model can be employed to test several high ratios as well. 

Steps in transformer testing 

Step 1: Disconnect and isolate the transformer from both the incoming and outgoing cables. Ensure that you apply the working ground to the incoming and outside cables prior to disconnecting from the transformer. Most importantly, the disconnected cables should have some importance of clearance from the switchgear terminals. 

Step 2: Connect the test set to the H designed to lead and ensure that the connector that is marked with H. Also, ensure to check about the index of the connector lines up precisely. 

Step 3: Repeat step 2 with the X designated lead and ensure that the connector is marked with X and check the index of the connector notch that is lined up properly. 

Step 4: While using the three-model phase model, connect H1, H2, and H3, which is designated to test leads to the corresponding terminal of the transformer. Then, connect the H0 test lead which will found there. 

Step 5: Repeat step 4 buy with the X designated test leads and connect X1, X2, and X3 to the corresponding terminals.

Step 6: When everything is connected, it is now the right time to carry out the testing and you need to measure ratios with the right calculations. 

Final thoughts 

Thus, you might have now understood about the testing of the transformer. So, make sure you are doing in the right way and ensuring the efficiency of the transformer. 

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