Knee point voltage:
This is the voltage at which a CT becomes saturated. When a CT becomes saturated it can no longer transform current. An example of this rating would be C200, C800 etc... This means that the CT will saturate near 200 Volts or 800 Volts respectively. A protection CT operates linearly between its ankle voltage and knee voltage(Voltage vs. Current graph).
Note:
A protection CT operates between this linear range, while a measuring CT operates correctly around its ankle voltage. A measuring CT is designed to measure current accurately upto 120% of its rated value.
This is the voltage at which a CT becomes saturated. When a CT becomes saturated it can no longer transform current. An example of this rating would be C200, C800 etc... This means that the CT will saturate near 200 Volts or 800 Volts respectively. A protection CT operates linearly between its ankle voltage and knee voltage(Voltage vs. Current graph).
Note:
A protection CT operates between this linear range, while a measuring CT operates correctly around its ankle voltage. A measuring CT is designed to measure current accurately upto 120% of its rated value.