Current transformer (CT) test procedure
This test is considered as one of the main test, it’s aimed to test:
- Current transformer ratio.
- Current transformer polarity.
- Burden of current transformer.
- Knee point of current transformer.
- Current transformer winding resistance.
- Magnetization curve of current transformer.
- Megger test (insulation test).
Required Equipment for Current Transformer
- Current transformer (CT) analyzer.
- Megger.
Mechanical check and visual inspection of current transformer
- Check tightness of all connection.
- Check ferrules.
Current transformer analyzer connection
- CT analyzer has 4 leads, two should be connected to primary side which contains primary side of CT and other two should be connected to secondary side of CT which you want to check its ratio.Â
- After connecting CT analyzer through laptop and using CT analyzer software, test can be started and result can be printed out for CT ratio, CT polarity, CT burden, CT knee point & CT winding resistance.
- This result should be compared with current transformer factory test and be sure that result within acceptable tolerance.
- To measure the burden: Inject 1 ampere on secondary side of CT, and using multi-meter you can measure voltage calculate burden by multiply voltage and current and compare it with CT burden.
- To test insulation: Using megger by 1 kilo volt injection for 1 minute, this test should be done. between primary to secondary and secondary to secondary But for Primary to ground 5 kilo volt injection for 1 minute.
- See figure below which shows CT analyzer connection for CT TEST.