When cable glands are used to terminate SWA (Steel Wire Armour) cables, the gland must be able to provide earth continuity from the termination of the armour through to the body of the equipment, either via the enclosure itself (if it is metallic), via a gland plate or through an external earth path with the use of an earth tag.
Direct To Ground Earthing
Typically when earthing an armoured cable, a number of direct-to-ground external earth link cables are used and connected to the cable gland through an earth tag. As a minimum requirement, the cable will be earthed at least one of its two ends, meaning in the event of a fault or short-circuit the most direct route to ground will be achieved.
‘Daisy Chain’ Earthing
If multiple cable entries are required in a non-metallic equipment enclosures, a ‘daisy-chain’ earthing method can be adopted. Wherein an external earth cable is connected to an earth tag within each cable gland, with at least one earth tag used to connect the earthing cable directly to ground, typically via an earth bar.
Earth Tags or CIEL Glands?
The above methods of earthing SWA cables via cable glands, can be achieved by adding the relevant aluminium or brass slip-on earth tags to the required gland assembly, this method would be suitable where lower levels of short-circuit protection are required. If higher levels of short-circuit protection are needed, in Medium Voltage installations for example, cable glands with a heavy duty Cast Integral Earth Lugs can be supplied. These CWCIEL glands are suitable for MV installations between 11kV – 33kV and are also available in both brass and aluminium variants.
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