How much measurement error can someone expect from various degrees of CT saturation?

Current transformer saturation is normal occurrence in the field. The system often has been reconfigured or strengthened since the current transformer was put into place. This often results in higher available fault current, which can lead to CT saturation during faults. Usually, the degree of saturation due to AC and DC fault current is not enough to cause the system to misoperate, but is enough to introduce measurement error to the relay. Other times, it causes the relaying to trip/malfunction. Replacing CTs that occasionally saturate during faults often times is impractical and unnecessary.