but there must be some guys who in the old times used earthed phase conductors as PEN conductor. Just give me a good guess . This is explicitly written in my countries code that in special cases it can be possible, but in modern times this is not allowed as per IEC standarts. So what I can not understand is, say we earth a delta phase conductor, then how can we say do not use what I connected to earth as a PEN conductor. If it had said : do not use the earthing conductor which connects the phase conductor to earth as a PEN conductor it would have made sense, but I can not understand how a phase= winding = high voltage part of the installation can be used as only "conductor". I know this is very difficult to explain to me but I cant understand what my good friends explain ...
if neutral point is missing...
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See the second para of my last post. For the corner grounded delta, the risk mentioned therein exists or so do I think.
PEN is grounded at multiple points along its route if it is bare .....
mbrooke
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Using any current carrying conductor as a earth wire is stupid and dangerous. If the PEN breaks the current will be placed over the current carrying metal and anything in contact with ground. An appliance like a toaster or Hob/cooker will have full voltage on its shell if the PEN breaks. Here in America older dryers and ovens used the neutral as an earth wire. Even if the PEN does not break because its grounded at many points current will divide between the PEN and earth/water pipes/soil. This creates EMFs, possible electrical gradients (person could be shocked) and RCD applications are impossible.
In a wye system with balanced loads, a broken PEN is less a danger because the PEN is only carrying load imbalance which is usually only a small part of load, so both voltage and current are small. If a phase is used as a PEN, Full voltage and current will be seen over the break making it more dangerous. The correct way to do this if one chooses to ground a phase is to earth the phase to the PE only at the source and then treat the earthed phase the way you would treat a neutral wire in an TN-S system.
Hope I cleared it up a bit more
This is an example statement that leads to confusion. You cannot treat a grounded phase conductor as a neutral... much like you can't treat the "neutral" of a 120/208 1? 3W system exactly the same as a "true" neutral... i.e. it is unrealistic to think there will be 0A "neutral" conductor current while there is any current on the other circuit conductors under nominal conditions.
mbrooke
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Sorry, I should have included that because its carrying full current it cant be reduced in size. The correct terminology should have been "grounded conductor" I was thinking more along the lines of grounding then current cancellation. My bad. My point was that once a phase is grounded it has to be fully insulated (bonded to ground only at the origin), it cant be switched independently or fused and it will read close to ground potential.
I have seen many corner grounded Delta systems where someone goofed fusing or switching the grounded phase.
mbrooke
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no, no a current carrying conductor can not be used as pe , the conductor which connects the earth to a phase conductor by the end or middle can be used as earth. If I am not wrong
I understand your first statement, but the description is confuseing me, not so much familiar of the exact terminology. Do you think you could draw a picture to help me understand?
BIGPOWERMAN
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if neutral point is missing...
Hi All, I think what this guy is doing is asking for some clarification of IEC362. The translation is not bad but is a little confusing.The wording is really compacted but is accurate. It is similar to our NEC250 rules. It is talking about one or more separately derived power sources. In a "normal" case you must ground the neutral of a WYE connected transformer with a non-current carrying protective earthing wire (ground bonding wire), In the case of a DELTA connected secondary, there is no neutral terminal on the transformer. In this case the transformer must be "corner grounded" with a non-current carrying protective earthing conductor to the ground bond. As standards have been harmonizing in the EU, this soon may no longer be allowed but electricians still have to be aware that many old installations exist and are grandfathered in. Here in the US there are many "HIGH LEG DELTA installations around also. While they are no longer allowed in some jurisdictions, there are many original installations still in service today
Hi All, I think what this guy is doing is asking for some clarification of IEC362. The translation is not bad but is a little confusing.The wording is really compacted but is accurate. It is similar to our NEC250 rules. It is talking about one or more separately derived power sources. In a "normal" case you must ground the neutral of a WYE connected transformer with a non-current carrying protective earthing wire (ground bonding wire), In the case of a DELTA connected secondary, there is no neutral terminal on the transformer. In this case the transformer must be "corner grounded" with a non-current carrying protective earthing conductor to the ground bond. As standards have been harmonizing in the EU, this soon may no longer be allowed but electricians still have to be aware that many old installations exist and are grandfathered in. Here in the US there are many "HIGH LEG DELTA installations around also. While they are no longer allowed in some jurisdictions, there are many original installations still in service today
Well apparently no picture shall ensue :lol:
Basically PE is the IEC equivalent of an NEC EGC. You can find a lot of info on the 'net... search on "IEC earthing systems".
A fairly good assessment IMO. Those only familiar with IEC earthing systems are a bit lost when it comes to earthing of delta secondaries. In all the IEC earthing systems info I have seen, which isn't a lot BTW, none of the systems originate from a delta secondary.
PS: Welcome to the forum :thumbsup:
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