All right, I'll have to explain how the circuit works.
The relay is activated when the voltage on Cf is greater than 2.5V.
UA1 forms a non-inverting precision rectifier with a gain determined by R1 and R2.
[latex]Av = 1+ \frac{R1}{R2}[/latex]
The output voltage from your current transformer is equal to the current multiplied by 0.1V.
V = 0.1×I
The peak voltage will be √2 times the RMS value.
The voltage across Cf is equal to the following formula:
V = I√2×0.1×Av
For 30A I'd probably increase the voltage reference to 5V which would mean using the LM336-5
At 30A the peak voltage from the transformer will be 0.1×30√2 = 4.2V.
I'd probably make the gain of U1A equal to 1.2 which would mean replacing R1 and R2 with 3k and 15k respectively making the gain equal to 1.2.
Now when the current is 30A the voltage across Cf will be 5.1V
The relay will then turn on at