Answer / Sharad Pal

Protection Current Transformer (CT) testing using a primary injection kit involves the following steps:
1. Disconnect the CT from the circuit and isolate it.
2. Connect the primary winding of the CT to the primary injection unit.
3. Apply a known current to the primary injection unit, which is then transferred to the secondary winding of the CT.
4. Measure the output voltage on the secondary side using a voltmeter and compare it with the rated value of the CT.
5. Calculate the percentage ratio error (PRE) using the formula: PRE = [(measured secondary voltage / rated secondary voltage) - 1] * 100%. The acceptable limit for PRE is typically less than 2%.
6. Repeat steps 4 and 5 for various current levels to ensure accurate performance over a wide range of operating conditions.

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