Does a fault in ground of three-phase do more damage to home appliance than a fault in ground of single phase? and why?
In a home with three phase input and single phase loads, fault in the ground damages all connected appliances (circuit breaker didn't move!). While in home with single phase input and single phase loads, a fault in ground was protected by the home circuit breaker.
Best Answer
Three phase is exactly the same voltage to earth as single phase. In fact, what comes to our homes is usually one phase out of the three. There are various methods of distributing and sharing all 3 phases in a road, street or small area to give a semblance of balance to the grid but the earth remains the same and there is no single earth fault on single phase that is somehow different on three phases.
If my house developed a ground fault (of some type) I wouldn't expect my neighbours house to have their appliances damaged - is this any different to a house with all three phases distributed amongst the rooms? I might expect that if there were two neutral faults this could happen; (a) neutral becomes disconnected at source and (b) a single line shorts to neutral - this would apply line voltage (\$\sqrt3\$ x phase voltage) to be applied to appliances on the other two phases - sure this would cause damage BUT it's a long way different from some form of ground/earth fault.