How do you check current transformer is ok or faulty?

To check if a current transformer (CT) is functioning properly, you can perform a visual inspection for any physical damage, such as cracks or corrosion. Additionally, use a multimeter to measure the secondary winding resistance; it should typically be low and consistent with the manufacturer's specifications. Finally, if possible, apply a known primary current and measure the secondary output to ensure it matches the expected transformation ratio. If any of these checks indicate abnormalities, the CT may be faulty.