What is the Practical Significance of Knee-Point Voltage in CT Design?

The knee point of a transformer or a current transformer is the voltage value from which when an increase of 10% to the voltage, an increase of 50% to the saturation curve occurs.

A simple graphic way to find this value is by means of homotety, i.e., you draw a right triangle with one side 10 and the other 50, and displace until the hypotenus reaches the tangen to the no load saturation curve.