For those who want a quick response to a sustained voltage rise ( a surge) , a relay ( or better, a regular power 'contactor' ) will take typically 20 mS or so to operate. ( That is about one cycle of the mains voltage ). This also depends on the delay in the trigger circuitry ! In most cases this should be OK for our electronic equipment. The relay or contactor will switch out ( off) the power line. Power contactors have superior contacts and current carrying capacity than ordinary relays.
To get faster operation one could use a solid state relay, but it is probably not really required. It would also be a more complex and more expensive solution.
You also don't want the mains to be cut off if there are only a few cycles of raised voltage.
The 'spike busters' are only meant to clamp transient voltages on the power line to a safer level and are of very short duration ( under 2 mS usually ). This will not help with usual mains voltage fluctuations which is the power line voltage going up or down at a relatively slower rate.
Good ( fast reacting ) servo stabilisers can be quite effective if the voltage is within it's operating range. Beyond that it would need to cut off. But if the mains jumps from 230 V to 300 V suddenly a quick acting cut out might be required .
You might need to keep some lighting circuits working even if all the other critical equipment is shut off. Shouldn't be difficult to make a few emergency lights ( using LED's ) that can handle 300 Vmains. That way you wouldn't be suddenly plunged into darkness !
Many stabilisers do have a high voltage cutout. So they would automatically take care of the refrigerator and / or other devices connected to it. I would use something separate to protect the music system and the TV rather than use just one device at the mains to protect everything in the house.
