Switching poles

[Cj24]

Hi cud u help, I was just wondering when you have for instance a 3phase isoltor it's classed as a 3pole sw am I right as in it sw's the 3 phases but why do u not sw the N therefore it being a 4 pole sw and y do we not sw the N and in other isolators we do sw the N

 

[Risteard]

Hi cud u help, I was just wondering when you have for instance a 3phase isoltor it's classed as a 3pole sw am I right as in it sw's the 3 phases but why do u not sw the N therefore it being a 4 pole sw and y do we not sw the N and in other isolators we do sw the N

In a TT installation you would have to break all live conductors or where they can't be regarded as having a sufficiently low impedance to earth.

 

[Cj24]

Yes but why do we not isolete the N in most isolators but sometimes we do

 

[Risteard]

Like I said in TN systems the neutral is reliably connected to earth.

Therefore in TT all live conductors must be broken. In TN all line (phase) conductors must be broken.