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What earthing arrangement is this?
Former Community Member
The supply is from a private transformer in a four core cable 3ph + n. The cable armour is earthed and connected to the MET. However there is also a green and yellow cable connected to the neutral terminal at the main isolator going back to a the transformer casing. The transformer is only 5 or 6 metres away. I think this must have been intended to make it a tncs supply but seems to me to just create parallel neutral conductors. Or is it tn-s-c-s? I have only been able to go off visual inspection because I could not disconnect the supply..
If the neutral point is the point where the three phases' neutral-ends meet (in or on the transformer), then the conductor in question in PNB is a PEN by this definition. Here, again, this would not have been my choice when thinking about the effects of a break in this conductor with no other fault in the system.
No it's not - by any definition it would need to be carrying load or imbalance current and earth fault current
It could only be PEN conductor if the neutral was offered for earthing purposes - akin to a larger version of a PME cut out
What were are discussing is the case where the neutral is earthed at a point outside the transformer casing - which is pretty well every distribution transformer ever manufactured - the debate is that the conductor that creates that star point connection is a PEN, if it is earthed at one location after it leaves the transformer - regardless of that means of earthing being a sperate or combined earth
If the neutral point is the point where the three phases' neutral-ends meet (in or on the transformer), then the conductor in question in PNB is a PEN by this definition. Here, again, this would not have been my choice when thinking about the effects of a break in this conductor with no other fault in the system.
No it's not - by any definition it would need to be carrying load or imbalance current and earth fault current
It could only be PEN conductor if the neutral was offered for earthing purposes - akin to a larger version of a PME cut out
What were are discussing is the case where the neutral is earthed at a point outside the transformer casing - which is pretty well every distribution transformer ever manufactured - the debate is that the conductor that creates that star point connection is a PEN, if it is earthed at one location after it leaves the transformer - regardless of that means of earthing being a sperate or combined earth
