Over voltage protection circuit
So i was making one of those water level indicator circuit:
I found the construction to be fairly easy for a newbie for me. I modified the circuit according to my needs, and have successfully constructed it. There is a small issue though. The place i live is susceptible to over voltages often and our fuse system is presently out, so my family has discouraged me from implementing the circuit at home in my main water tank. They want me to add a over voltage protection circuit so that they can feel safe. So anyone has any idea on how to construct an overload protection circuit(The circuit should be simple and understandable for a newbie like me)? My supply mains are 230v AC. It can either be before or after the transformer stage.