Today is...
Sunday, May 20, 2018
Welcome to, the global online
community of automation professionals.
Featured Video...
Featured Video
EtherCAT with CTC’s master lets your multivendor network play well together...
Our Advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive
Communication cable and power cable segregation
I have a doubt regarding laying of power cables and communication cables together...
By Hitesh B. Kakadiya on 30 June, 2005 - 9:20 pm

Hi all,

I have a doubt regarding laying of power cables and communication cables together. I beleive that they can travel together parellaly but should not be allowed to cross( to avoid interference). Whereas one of my senior believes otherwise. Can anyone guide ? Also , if they are to be laid together, what should be the ideal separation?

Please send me a mail.

Thanks all in advance


By Anonymous on 2 July, 2005 - 4:32 pm

There are a couple issues here. One is electrical noise, the other is code.

For noise issues, segregation is important, and if they must cross, it should be at right angles.

if your installation is in the US, it will need to follow NEC guidelines (at least outside the cabinets it will). You cannot install certain types of communication cables in the same raceways as power cables. The rules on this are probably the most confusing of all the rules in the NEC.

Also, any cable you install in a raceway has to have an insulation rating exceeding the highest voltage found in any conductor in the raceway.

By Dick Caro on 2 July, 2005 - 4:23 pm

Trust your senior! Data cables should not be run in parallel with alternating current (AC) power cables since they will pick up the 50/60 Hz alternating current by inductive coupling. If you must run these cables in parallel, keep the distances as short as possible. The data cable should use twisted pair wiring so that any AC coupled to the data cable will be balanced on each wire and will cancel itself in the receiving circuit. Such noise pickup is called common-mode and most receiving circuits offer high common-mode noise rejection.

Data cables may safely cross AC power cables at right angles, since this minimizes coupling. The greater the distance between data and AC power cables, the less the coupling. Obviously, direct current (DC) power cables can be run in parallel with data cables without adverse effect.

Dick Caro
Richard H. Caro, CEO
CMC Associates
2 Beth Circle, Acton, MA 01720
Tel: +1.978.635.9449 Mobile: +.978.764.4728
Fax: +1.978.246.1270

By Phil Corso, PE on 4 July, 2005 - 12:54 pm
1 out of 1 members thought this post was helpful...

Responding to Dick Caro's comments . . . we don't often disagree but your comment that DC cables have no adverse effect on data cables is incorrect.

Even DC cables are sources of hi-current transients. Refer to my May 1 and May 2 responses to thread "1026209342" covering coupling of control, power, and data circuits.

My paper "Probabilistic Risk Assessment of Equipment Safety Systems" provides DOs and DON'Ts that specifically addresses false-alarms and unwarranted-trips caused by inductive and capacitive coupling of different circuits.

Phil Corso, PE {Boca Raton, FL, USA}
[] (

By Dick Caro on 6 July, 2005 - 4:25 pm

Phil, I stand corrected. DC power cables to switching devices can indeed have transients that can be coupled to low power signal lines. I was thinking more about the 12/24 volt DC lines often used to power remote multiplexers and RTUs where there hopefully are no significant transients. Thanks for keeping me honest Phil.

Dick Caro
Richard H. Caro, CEO
CMC Associates
2 Beth Circle, Acton, MA 01720
Tel: +1.978.635.9449 Mobile: +.978.764.4728
Fax: +1.978.246.1270

By Mohammad Ali Mukhtar on 1 February, 2011 - 7:56 am

Are there is any standard which defines the segregation distance between the cables (data & power) when they run parallelly in same cable raceway as well as when in different raceway which runs parallelly at different level vertically?

By bob peterson on 1 February, 2011 - 12:28 pm

I guess it depends on just what you are talking about and where youmight be located in the world.

In the US, the electrical code often (but not always) prohibits running them in the same raceway, although you can run them in the same cable tray if it has a divider.


1 out of 1 members thought this post was helpful...

Mohammad... I suggest you search the Control.Com Archives for the following Thread #:

1026209342, "480 Vac EMI to 24V DI Signals"

Regards, Phil Corso

By Bill Schwarz on 2 February, 2011 - 1:10 pm

I have some guidelines developed by Hitachi related to industrial plant cable installation practices. Contact me off-list and I'll send you what I have.

bills [at]

By Steve Myres on 4 July, 2005 - 12:51 pm

Long parallel runs are the most likely to cause crosstalk. If the runs must pass each other, do so perpendicular and at a decent minimum distance, say 6". Your senior is correct.

For what it's worth . . .
(take out any spaces the forum inserts in the URL)


10.01.00 All cables assigned to a particular duct/conduit shall be grouped and pulled in simultaneously using cable grips and suitable lubricants. Cables removed from one duct/conduit shall not be reused without approval of Employer.

10.02.00 Cables shall be segregated as per IEEE Std.-422 and IEEE 524 (1992) In vertically stacked
trays, the higher voltage cable shall be in higher position and instrumentation cable shall be in bottom tier of the tray stack. The distance between instrumentation cables and those of other system shall be as follows:

From 11 kV/6.6 kV/3.3 kV tray system - 914 mm
From 415V tray system - 610 mm
From control cable tray system - 305 mm

thanks your answer.....

> (take out any spaces the forum inserts in the URL)

---- snip ----

Hi all,

Can anyone point me to standards that specify the minimum separation between directly buried high voltage power cable (carrying 10's and 100's of kilovolts) and telecoms copper plant (carrying services such as DSL)?

As far as i know interference will comes into picture as we lay both the control and power cable together. Power cable which carries a large power when compared to control cable. Interference depends on the voltage it is carrying.

The whole issue of transfer of energy from power circuits to telecommunications cable is confusing. Why would a collapsing magnetic field finds its way into data cable when it has a much lower resistance path from the cpc that's runs with all power circuits.