Hi,
As you seem to be in an idustrial environment from your login handle, you may get (almost) exactly what you want off the shelf if you Google "trip amplifiers". Various companies make them in rugged packages which have standard mounting formats such as DIN rail, etc. You may have to rectify/smooth your a.c. signal to d.c. for an input signal though.
If you really must build this as a home grown circuit you should realise it's failry complex topic and could get difficult to discuss here from first principles. Start by Googling for operational amplifier comparator circuits. There are various ways you can use one or more op-amps with hysteresis to trigger or trip at a certain voltage. You can build a "window detector" with two comparator circuits, which covers the voltage range you want, programmed with different value resistors.