When the main switch in a building is turned off or the breaker trips or the fuse burns, power to both live and neutral lines is disconnected. The earth line is never disconnected.
When the electrical feed to a building is switched off manually, both lines are turned off for safety. Either line of the alternating current is live relative to earth or ground potential and is dangerous.
When an electric breaker blows, it will cause both beakers to open their circuits because they are mechanically tied together. In the case of fuse boxes (older) if a fuse blows it cannot be accessed without disconnecting both lines due to a mechanical interlock on the box.
They look like this (North America):
The earth or ground line is a safety line that must never be disconnected. it allows a path for a dangerous short circuit of crossed wires or bare wires touching metal objects to return to the source of electricity and blow the breaker or fuse.
Breakers and fuses keep electricity safe by opening the circuit to prevent electrocution or fire. If blown, the problem down line needs to be cleared before replacement. Do not bypass a fuse!