Armor Grounding - If not used as earthing conductor

[m.qasim]

Hi,

for a low voltage, single core three phase plus neutral system:
If the armor of the cable is not used as the earth conductor, (instead a separate conductor is connecting load and source panel to the earth grid),

What is the IEC requirement about grounding the armor (when it is not used as earthing conductor)?

My opinion is to ground the armor on one side, but I don't have any backup. I have searched online but could not find a specific answer.
While the opposite opinion is to insulate the armor at both sides as there is no need to ground it.

Is there any IEC requirement to ground the cable armor regardless of its being used as earth conductor or not!!

the cable is CU/XLPE/AWA/PVC


Thanks in advance.

 

[sreid]

Just an opinion. If a hot wire shorts to the armor (say a nail is driven thru the cable)and the armor is not grounded, you have a Hot armor.

 

[waross]

The armor may be considered a raceway and a raceway must be grounded at the source end.
Normal practice is to ground the armor at the supply end.
For single conductor ground the armor at the supply end and isolate at the load end.
This is to prevent induced current flowing in the armor.
For multi-conductor cable both ends may be grounded but there must be a grounding conductor included in the cable and it must be grounded.
For spiral armor that has been in service for awhile, a fault current in the armor will tend to flow around the spiral rather than passing from wrap to wrap.
In such a case there are two possibilities.
1. The armor may act as a spiral heating element.
2. The resistance and the impedance or the spiral may be too high to trip the over-current protection and may even be too high to trip the overload protection.

Bill
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