Auto power off for 220 V AC cable breaks
simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Using a "remote-control over mains" transmitter and receiver to prove line integrity.

There are a range of devices using the X10 protocol for home automation. I can't recommend any particular product (and we don't do that on this site anyway) but there should be something suitable for the scheme shown in Figure 1.


On power up the RESET button is pressed. This energises RLY1 and provides power to the 220 V line.
An X10 transmitter at the far end of the line is wired for constant 'ON' 
transmit.
An X10 receiver at the feed end monitors this signal and once received it latches RLY1 on. The RESET button may now be released.
If the transmitter signal is lost the receiver should drop out and remove power from the relay coil. The line power will be disconnected.


X10 devices may be expensive - I don't know - but there are sure to be many similar systems available in various price ranges.