IEC-Armour as grounding conductor?

[ctpt]

Hi everybody,

My questions are for experts in the IEC world. I understand that as per NEC, a separate grounding conductor is run with phase conductors (as a fourth core in a three phase cable or as a separate grounding conductor) especially for grounded systems <1000V. Please correct me if I am wrong. Now, my questions are –

1. Is there any such requirement in IEC? I understand that in IEC there is no such mandatory requirement of running a fourth conductor for grounding alongside the phase conductor. I also understand that if we are using an armoured cable, IEC allows the armour to be used as a grounding conductor(PE).

2. If armour can be used as a grounding conductor, is there any IEC which tells us what should be minimum cross section of the armour and/or does it tell that armour should withstand the full ground fault current for that particular duration. If both the cases I would like to know the relevant IEC code numbers.

(I was referring to some standard cable manufacturer’s data and found that the standard armour cross section in some cases may not be able to carry the full fault current, particularly in a 400V solidly grounded system with high fault current)

You help will be much appreciated.

Thanks,

 

[fredy2005]

Dear Engineers:

The question could be resolved if you consider the neutral configuration. In the IEC indicates that for TT systems is not necessary a separate ground cable, but if the neutral system is a TN-S the separate ground cable is necessary, in order to keep the electrical facilities safe. If the armour has the capacity to accomplish with the fault current requirements in order to keep the facilities safe it could be accepted, but in my experience it doesn't accomplish with the short circuit capacity. The armours are generally used to control electrical fields but no strong short circuit currents.