Current Transformer's Primary Current

Primary current is a function of secondary current, which is a function of the applied load. Vary that, and the primary current varies with it.

If I am understanding properly what you wrote, you have a multi-ratio current transformer with primary taps from 50 to 4000 amps (to whatever the rated secondary current, 5A or 1A). The full ratio is 4000:x, and there are multiple taps off the primary that give you a lower number of turns so that you can choose the ratio for best operation of your protective relays.

Are these values you give for one CT, or for various ones in the station? Based on the numbers, I find it doubtful that these are for one CT with 4000A full ratio and 50, 150, 200, 300, 400, 600, 800, 1500, and 2000A taps. Usually you can find pairs of taps that easily add up to the full ratio (such as a 1600A and a 2400A tap which add up to 4000 amps).