Separation Between Electrical and Instrumentation Ducts

Our practice [ in power station design] is to put the instrument cables in the upper most row in steel [grounded] ducts and keeping 10 inches [center line to center line] distance between rows, in pvc ducts, low voltage and control cables and in lowermost row medium voltage cables. In manhole the instrument cable are in close top solid bottom cable tray. The steel ducts and cable trays are grounded in manhole.

According to the commentary, the arrangement is done in man holes that look big. Right now, we are inspecting an installation were the cables run together in the same tray holes, according to the project engineering drawings, the average tray holes is 1x1x1.6 meters. It was one misunderstand of specification ("instrumentation underground raceways shall be done by electrical discipline"), In order of that we recommended split electricity and instrumentation.

I do not believe that you are qualified to, "inspect an installation".

I also believe that your practice is unethical and should be stopped!

You should immediately refund the commission your were paid, and leave the site.

Recommend to the customer who hired you that they should hire a QUALIFIED inspection organization that does not rely on total strangers whose qualifications are unknown and have no obligation to provide correct answers to questions such as yours.

I only comment what is found, and only look for specific code or norm that support, separate installation.

You want the forum to do the work for which you are being paid.

THAT IS UNETHICAL!!!!

I do not believe there is a real code standard on this because of the occasional ambiguity of what is considered electrical and instrumentation cables. Is a one microsecond wide 2kV 400 ampere pulse four times a day considered electrical or instrumentation?

look at the drawings and the specs on them. if it isn't clear then pick up he phone and call the person who drew them. is that so hard?

I agree with redfred, actually no standard is available. But - if it is possible- I shall run this cable in separate steel duct-from instrument or communication cables.

However, NESC [ANSI C2] /2007 requires 3 inches [clearance] concrete between supply and communication conduit system [Rule 320 B(2)].

Redfred is right.

Where I used to work, we had high voltage and low voltage (control) lines running in the same conduit in some of our process equipment. Because that's how they always did it with no problems they claimed.

And until we started to get erratic results, only then did it come down that we could do one of (2) things.

1. The first is to make sure the control and feed back lines were shielded.
2. Run separate conduit for High Voltage and control lines, (lines were still shielded).