Armored Fiber Optic Cable and Lightning

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Seandb

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South Africa
Hi all, I am a fiber optic technician (feel free to ask me about that stuff) and I am in a situation where we have an existing installed Corrugated steel tape (CST) fiber optic cable. The area experiences high levels of lightning damage, and this is clearly due to the previous installer NOT grounding or bonding any of the cable anywhere! Scary, but anyway, I am here to resolve the issue. I am familiar with NEC770:100 and we have implemented the bonding process already using 6AWG to bond the cables to each other. My question I need assistance with is the ends of the cables:

  1. Do we ground to the buildings grounding arrangement?
  2. If not, is there a formula or calculation I need to use to design the grounding arrangement?
  3. The soil resistivity varies from 42ohm.m to 6000ohm.m


SECONDLY, at which point do I resort to installing an additional shielding cable above and parralel to the fiber, and do I gound that seperatley to the fiber or onto the fiber?

Please do not use acronyms in order for me to research the terminology easier.
 
Ragin Cajun said:
Are you getting damaging currents over the armor? Is armored FO cable REALLY needed?

RC
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Hi RC, Thanks for the reply. Yes, the lightning is causing chaos, every place where the cable ends, whether it be a joint box, and even in the customer premise it has shorted and burnt. The cable itself is damaged at the point of strike, sometimes direct strike and sometimes from nearby trees.

That was my point, the armored cable is not needed, but to replace now would have enormous financial repercussions, so we have to get what is in the ground, earthed and bonded.
 
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