Fiber Tracer Wire Required to be grounded/bonded

[jstpie5]

Is there any NEC / NESC or other requirement to ground/bond the tracer wire on communication wire on one end (Fiber in this case)?

Here's the scenario:

There is a 138kV transmission line near a large solar farm and a 7.62kV distribution line running parallel about 50ft away serving residential power. Direct bury fiber was installed (above ground) on the distribution line poles but the tracer was not grounded at either end.

The tracer wire has ~850Vac when measured to a good ground due to what I think is induced voltage from the 138kV transmission line. The communication company says it's the utilities (distribution line) company's fault and vise versa.

The fiber company says they don't need to ground the tracer because it's not designed to carry current. They said they are going to remove it from the pole and bury it. I'm afraid there will still be induced voltage on the fiber after they bury it (probably only going to bury 10" or so).

Please tell me there is a requirement to ground/bond the tracer...

I found this article from Corning (https://www.corning.com/catalog/coc/documents/standard-recommended-procedures/005-012.pdf) - see section 2.27

I was thinking maybe NESC rule 99 would be applicable but not totally sure.

 

[hbiss]

Well, you already have the manufacturer's recommendation.

2.27. Bonding and Grounding: In order to maintain a high degree of safety and reliability in underground plant, maintain all applicable construction standards regarding grounding. Corning Optical Communications recommends grounding of all metallic cable elements at splice points and building entrances; however, follow your company’s normal bonding and grounding specifications. NOTE: Corning Optical Communications recommends grounding the metallic cable elements as the cable is installed. In the event of a lightning strike, a cable will dissipate the added charge through a path of least resistance. If the cable is not properly grounded, this path could be through the cable sheath, causing damage in the form of pinholes. This damage can degrade the reliability of the cable.

As for NESC and rule 99, there is this: 5 Questions About Fiber Optic Bonding, Grounding, and Locating.

Then of course this situation already exists:

There is a 138kV transmission line near a large solar farm and a 7.62kV distribution line running parallel about 50ft away serving residential power. Direct bury fiber was installed (above ground) on the distribution line poles but the tracer was not grounded at either end.

The tracer wire has ~850Vac when measured to a good ground due to what I think is induced voltage from the 138kV transmission line. The communication company says it's the utilities (distribution line) company's fault and vise versa.

The fiber company says they don't need to ground the tracer because it's not designed to carry current. They said they are going to remove it from the pole and bury it. I'm afraid there will still be induced voltage on the fiber after they bury it (probably only going to bury 10" or so).

Sounds like a no brainer to me or are they going to wait until someone gets killed?

-Hal

 

[GoldDigger]

Is there any NEC / NESC or other requirement to ground/bond the tracer wire on communication wire on one end (Fiber in this case)?

Here's the scenario:

There is a 138kV transmission line near a large solar farm and a 7.62kV distribution line running parallel about 50ft away serving residential power. Direct bury fiber was installed (above ground) on the distribution line poles but the tracer was not grounded at either end.

The tracer wire has ~850Vac when measured to a good ground due to what I think is induced voltage from the 138kV transmission line. The communication company says it's the utilities (distribution line) company's fault and vise versa.

Measured with what meter impedance? 850V at any current could cause equipment damage, but to be dangerous to a person there has to be current. (The fault current available from capacitive coupling to the transmission line will be roughly proportional to the length of the cable segment.)
How many hot conductors in the distribution line? For three phase the induced capacitive current will be much lower at a given distance than from a single phase. Two out of 3 phases will be just as bad as one out of three.

 

[jstpie5]

Measured with what meter impedance?

10MOhm

How many hot conductors in the distribution line?

Turns out it's actually 115kV, but 3ph. looks to be 2/ph ~500kcmil (well probably 556.5 but I'm not going to measure it lol).

Also, I should add that the fiber technician is the one who was "shocked" to find out the tracer was hot (literally). He said it felt like an electric fence.

I took the tracer and grounded by touching to the pole ground and there was a small spark, but otherwise nothing crazy.

Do you folks think there will still be induced voltage if the line is buried (and the tracer stays floating)?

 

[jstpie5]

also found these articles. Bottom line - bond the fricken tracer wire.

One from the cable manufacturer of the exact cable installed: https://superioressexcommunications...s/2020/12/TG113-OSP-Bonding-and-Grounding.pdf



And an interpretation from NESC on rule 99: https://standards.ieee.org/wp-content/uploads/import/documents/interpretations/ir581.pdf

 

[winnie]

Have you tried measuring the available current backing up that 850V, or measured with different meter resistance? 850V into a 10 meg meter doesn't really say much about the sustained shock potential or actual hazard to equipment.

-Jon

 

[jstpie5]

Have you tried measuring the available current backing up that 850V, or measured with different meter resistance?

How would one measure the current? I only have limited tools and the meter I am using is technically only rated to measure up to 750Vac - it was beeping and screaming at me the whole time haha.

 

[jstpie5]

NEC 770.114 - "Non-current-carrying conductive members of optical fiber cables shall be bonded to a grounded equipment rack or enclosure, or grounded in accordance with the grounding methods specified by 770.100(B)(2)."

nuff said

 

[winnie]

You have your answer on requirements for bonding, so this is just to answer your metering question:

I don't know the OSHA/safety requirements for this measurement; I don't work with systems that cannot be de-energized before connecting meters.

With the wire bonded to ground use a clamp on meter to measure the current through the bond. If this current is low enough, then you use the current shunt connection of your multimeter to directly measure the current between wire and ground.

Most likely the inductive charging current on this wire is measured in the 10's of microamps. But if there is an actual conductive fault or resistive leakage path, the current to ground could measure in the mA or even A. You know there isn't a solid fault because if there was the wire voltage would be in the kV range and there would be smoke evident somewhere.

-Jon

 

[ggunn]

Apart from the NEC and measurement issues, would not grounding the tracer wire make it harder to detect when someone is looking for a buried fiber cable?

 

[hbiss]

Apart from the NEC and measurement issues, would not grounding the tracer wire make it harder to detect when someone is looking for a buried fiber cable?

I think that's explained in one of the articles linked above. No.

-Hal