Electric cable and Multi mode fiber optic cable - separation distance required?

[therunningbruce]

Apologies if this has been asked before for different levels of voltage is Medium 415 V, 11KV etc.. is there a minimum separation distance from mult-mode fibre optic cable?

or a design code which should be followed to design too. For a mixture of overheads cable racks and ducted cable runs. I'm looking to install a few 1000's of meters of cable on an existing unit and wanting to understand the design codes we should follow.

> Are the codes aimed at consequences of failure e.g. if the electric cable fails it would also take out the fiber cables ?
> are the separation distances aimed at actual impact on the signal ? (how can they be) as one is electric and one is light?
> are the separation distances aimed at reliability and long term wear from the impact of being too close to the electrical cable will eventually cause the fiber to fail? or do I need a certain type of fiber one less prone to damage ?

Thanks in advance

 

[waross]

When there are two different voltage ratings on cables, separation, either mechanical or by distance, is to avoid an insulation breakdown of the higher rated cable from breaking down the insulation and entering the lower voltage system.
Other than that you haven't provided much information, given the many types of fibre and the many possible installation methods.

I encountered one installation where the fibre cable was installed in a 4" diameter, schedule 40 conduit, for mechanical protection.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[FacEngrPE]

You can order 4160 volt mining and shovel cable with fiber optic communications in the assembly.

I am not aware of a code listed fiber cable type specifically intended for installation in a cable tray next to MV cable. I recommend discussing with your AHJ before ordering.

My opinion is that it is possible to select a non conductive fiber optic cable with material of construction construction similar to type TC (or whatever your existing cables are). Separation should not be required, unless the fiber is required to survive and stay in service following a major arcing cable fault.

You should advise your potential suppliers of your intended use. There are many types of cable constructions, some are more likely to serve the life of your facility than others. Also consider pulling more fiber than you need now. The adder for a few more cores is small relative to the other costs.

 

[cuky2000]

Fiber optic is not impacted by the proximity with the power cable. There is no clearance required for this application.

The example below shows a 200 kVdc for a duple submarine cable with fiber optic embedded in the center

 

[waross]

On the other hand, when fibre is run with a transmission line with towers, it may be prudent to use the same spacing as for grounded parts.
The fibre surface may become conductive due to atmospheric contamination and be at risk of flash-over if spaced to closely to the energized conductors.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[catserveng]

Have you looked at using Innerduct? This is becoming quite a common practice on many sites I work on, recent expansion project had our fiber cable running in the same conduit as the 12kV conductors with properly rated and installed innerduct. Have seen it used in conduit, duct banks and cable racks. We have a project coming up where the aerial version will be used.

Take a look here,

https://www.innerduct.com/hdpe-innerduct

There are multiple suppliers of this product, at least in the US.

MikeL.

 

[therunningbruce]

thanks for the input , (I'm a process background engineer).

We are putting fiber on existing racks. Some of the racks and cables date back before I was bore (and I'm old !!!).. so its hard to tell what it is its a black thick cable.

so from what I've read i think you can get fiber cables and put them next to HV cables as long as the fiber cables are the right type.

 

[cranky108]

Maybe fiber optic cable with kevelor strength member.

We use fiber in trenway, but with the fiber in what we call smerf tube on the side of the tray.
But most of our trenway is control cable, and a few low voltage power cables.

We also sometimes use fiber in shield wire (steel cable) for overhead applications.

 

[jghrist]

The NESC has clearance requirements for fiber optic cable from power conductors on overhead lines.

 

[cranky108]

Really? Then why can I purchase power conductors with fiber optic inside?
But NESC does not apply to electric utilities.

 

[cuky2000]

Jghris: please clarify what part of the NESC (IEEE Std C2) apply to clearance for FO cable.
[sub]Please advise application impact on OPGW, FO wrap up, FO in the power cable, ADSS, and insulated cable.[/sub]

Waross: FO in OPGW and embedded in phase conductors are forced to follow the established electrical clearances. However, underbuilt FO, using ADSS FO cable installation will usually follow the underbuilt rules of the NESC and may require an intermedia pole to avoid excessive sag.
[sub]For insulated cable, the FO usually is next to the phase conductors. IF Distributed Temperature Sensing (DTS)with fiber optic is desired, the FO must be attached to the power cable[/sub]

Cranky108: the NESC applies to all utilities, and many parts of the NESC are adopted by OSHA. [sub]However, electrical utilities are exempt from complying with the NEC (NFPA70). To minimize liability, most consulting firms follow the NEC and comply with the State building code that adopted the NEC.[/sub].

In general, the FO is immune to EMF, EMI, and is not a conductive as metallic cables. The only concern that we should be aware of is an application for plenum-rated fiber optic in commercial installation and for HV use, the excess heat generated by SC can damage the FO.

For HV substation application, it is a common practice using innerduct to run FO cable in trench and cable tray as mentioned by catserveng.

For a commercial and industrial application under the NEC jurisdiction, the enclosed Linkmay be helpful.

 

[bacon4life]

Also not precisely an NEC/NESC design code issue, you should also consider OSHA requirements for worker safety near energized equipment. I assume only a small portion of fiber optic installers an also qualified low voltage electricians, and even fewer are qualified to work near equipment more than 600 V.

From a long term asset management perspective, some utilities only allow fiber optic to be co-located with power conductors if the fiber is directly related to the power grid (i.e. tele-protection or SCADA). Sharing a vault or duct with telecom companies often results in a nightmare when it comes time coordinate maintenance replacement. And even at utilities that have a telecom branch, there is risk that the telecom assets will eventually spit off to a separate company.

 

[cranky108]

On utility poles, telecom and cable are allowed with the ground wire, below the phases. But the utility will ask for a fee for using there pole and equipment (this does add weight to the pole, and requires some calculations for strength).

 

[therunningbruce]

thanks for the response.

Sorry if this a daft question can you get non-conductive armored cable ?

From the information I have is that our company policy is such that we cannot use conductive armored cables.

so. hence can you get armored cable which is conductive one assumes this is every expensive? if available

 

[Palletjack]

Aerial?
Use ADSS and get on with it.
It’s allowed in the live space.

https://overheadtransmission.southw...5/Appendix-P-Examples-for-AFL-ADSS-Cables.pdf