What are the tests that must be made ​​to the current transformer before the introduction of current transformers in service?

Excitation curve and parameters test

turns ratio test

Ratio and phase error test

Polarity mark check

winding resistance test

There are Many Tests Like wise:

1.  Mechanical & Visual Check
2. Insulation resistance Test
3. Polarity Test
4. Resistance Test
5. Magnetization Curve Test
6. Turns Ratio Test
7. Primary Injection Test
8. High Voltage Test
9. Commissioning Test

CT magnetization curve - knee point, Polarity , Insulation resistance, Winding resistance, and ratio test. Lead resistance also need to measure.