LV Underground TVSS

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llmay

Member
After installing approx. 100' of u/g data cable (unshielded) in pvc conduit between bldgs., the VoIP
phone and NJ100 network jack on one end seem to be very susceptible to damage from lightning strikes. The VoIP switch on the other end is protected and is OK. Where can I get good information on protecting the equipment on the one end if we're getting some sort of resistive coupling on the u/g cable from nearby lightning strikes??
 

hurk27

Senior Member
Re: LV Underground TVSS

This will be very hard to totaly protect as lightning can magnetly coulple to these cables and cause damage. Running them in RMC would have been a better choice, Running a EGC with them will limit the damage some and TVSS will help. But to say it will protect them would be a very long call. Maybe derrec could give you some insite on how to go with fiber. As isolation is the only true way to prevent voltage gradents in the network.
 

bob

Senior Member
Location
Alabama
Re: LV Underground TVSS

I have had this problem before. The only solution IMO is to use fiber optic cable.
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: LV Underground TVSS

Optical isolation modem, and/or optical cable is the most effective and ecconimical. You can try cable protectors, but results are less than ideal.
 

rudolph8

Member
Location
Ohio
Re: LV Underground TVSS

Standard practice for underground LV applications dictates that a shielded cable be used and protected at BOTH ends with primary protection. If you look at how telcos install telephone cable this is in fact what they use. This is actually stated in section 800.30 of the NEC. A TVSS may also be added for additional piece of mind. Of course a OFN would be a better choice if one could justify the costs associated with the fiber, terms and electronics associated. There is always a trade off between performance and cost.
 

tom baker

First Chief Moderator
Staff member
Re: LV Underground TVSS

Go with OF. Fiber modems are not expensive if the distance is short, FO cable is not expensive esp in the short distances you have. You can buy the fiber cut to length.
 

dereckbc

Moderator
Staff member
Location
Plano, TX
Re: LV Underground TVSS

Optical isolation modems run around $100 a pop. You can use the cable you already have. You only need one per circuit to achieve isolation. It really comes down to how many circuits you are running, and how valuble the service is.
 
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