20hp pump cutoff circuit

I am working with a 20hp water pump for which I need a circuit that cuts off the power supply when the current goes over a cutoff value. The maximum current is 30A.

The problem is that the value of current is also an important issue.
The pump keeps on functioning for a longer time if the current is only a bit greater than 30A but if the current is much larger than 30A, then the pump sustains itself for a comparatively shorter time.

Can anybody provide me with some text pertaining to this issue or the cutoff circuits...?

The common system is a thermal overload protection device. They are an industry standard item. Most starter contractor systems for larger motors have them built in.

Put a 30A motor starter in the circuit with 30A over loads. Available at any industrial electrical supply store. You can buy them online too at WW Grainger and Mc Master Carr and other places.

I have a box full of used motor starters. You can probably find a used one for sale on Ebay.