3Core cables boding, ground continuity conductor

[Power0020]

a 22 kV solar plant, employs multi-core steel tape armored cables, should I add ground continuity conductor running parallel to it? or depend on the armor (bonded at both ends) to act as a continuity conductor?

 

[RRaghunath]

It depends on the length of the 22kV cable I guess. If both ends of the cable are within the same earth mat, then, it is safe to use armour as earth continuity conductor. In this case, there will be earth mat parallel conductors interconnecting the earth masses at the two ends of the cable.
Another consideration is estimated earth fault current magnitude in 22kV system and whether the armour is designed to carry that current safely!

Rompicherla Raghunath

 

[waross]

Some codes do not approve armour as a grounding conductor. Spirally applied armour may become a long heating element under fault conditions while not passing enough current to reliably operate the protection devices.
Grounding at both ends may allow induced current to circulate in the armour.
Ideally the ECG conductor should be in the same magnetic encirclement as the phase conductors, but this is not always the case.

Bill
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"Why not the best?"
Jimmy Carter

 

[7anoter4]

IEEE Std 575-2014 IEEE Guide for Bonding Shields and Sheaths of Single-Conductor Power Cables Rated 5 kV through 500 kV.
6.3.3 Parallel ground continuity conductor:
Accordingly, it is recommended that single-point bonded and multiple single-point bonded cable installations be provided with a parallel GCC that is grounded at both ends of the route.

 

[waross]

To answer your first question directly:
Yes you should run a parallel ground conductor, bonded at both ends.
Consider bonding your armour at one end only.
For long runs consider sectionalizing the armour and grounding each section at one end only.

Bill
--------------------
"Why not the best?"
Jimmy Carter