Torroidal transformer design help needed
The thing is with Rogowski Coils is that the design is very easy. If you do not care about high accuracy. The more windings the higher the output the better you can measure it. It will not saturate because there is no iron core. Take a plastic loop in the shape of a donut. It would be best if the donut has a small hole and a large outside diameter. Wire insulated copper around it in windings. The more turns you will make the higher the output signal. The two ends of the wire you hook up to an integrator circuit for integration of the signal and amplification. When complete put the to be measured wire/cable through the donut.
Count the number of turns you make the formula for calculating the current is:
$$
v_{(t)}={\frac{-AN\mu _{0}}{l}}{\frac {dI(t)}{dt}}
$$
found here:
https://en.wikipedia.org/wiki/Rogowski_coil#Formulae
It may be a lot of work and the accuracy is probably low but certainly possible.