Power cable and control cable in the same trench

It's certainly not best engineering practice.

Have you tried bribing him?

First of all, look in the Chinese electric code to see if he's telling the truth. cnpower might have an answer to that.

In any case 10.5kV would probably require a very large separation distance from the control cables. We use three feet of separation between 440V and control cables so 10.5kV would probably require several dozen feet of separation!

Laying of control cables and power cable are not at all advisable, we have suffered a lot in Our Copper and aluminium rolling mills, we found abnormal hunting, we have checked the each and every hydraulic systems, etcc.... , after so much time loss finally we have detected problem is at electrical trench ,we have separated both the lines till then no such problems. any how application and accuracy of the process and your equipment senciblily influence this subject.

K.Srinivas.

Sr.Vice President (Manufacturing)

Withhold some payment and tell him you're going to back charge him when it doesn't work and you have another vendor come in and do it right.

Electromagnetic Shield wrapped around control cables-if lead sheath is not enough- should keep every one happy.

It depends on the signal in the control cable and the structure of the cable. 4-20mA analog signals in shielded cable as either singles or multipairs are largely immune. If the cable is unshielded and carrying some elegant data signal then it's certainly not good practice. Most codes go for a separation distance and require crossings to be made at right angles.

Where is the cable supposed to run, and was the contractor instructed to do that instead of how it turned out? If so, then the contractor re-runs it in the previously-instructed manner at his expense before the final invoice is paid. If not, then the contractor is entitled to an 'extra' for re-running the cable in the manner that he wasn't told about prior to installing it.

The best way to solve this would be to calculate the coupling impedance between the two cable systems.

Than you will calculate the induced voltage. If the calculated voltage exceeds the maximum cable strenght to 60 Hz aplied voltage, then you cannot allow him to install the cables this way.

In some cases, a possibility is to install barriers between the two systems.

But certainly the best way would be to install the two cable systems in different trays.

Regards

I would have to say NO!!

If you run the control cables with the power cables you will get reference noise in the lines. Especially if your running VFD's off the controls. It causes a lot of difficulty when the are run in close proximity of one another and the signals will most definately get confused mainly from the EMF caused by high voltage.

thanks all for the suggestions, now we requested our contractor to ensure good shield cable for data link, and we are checking the Chinese electric code.

another question: we asked the contractor to use twisted screen cable for data link, however, the contractor comes out with shield non-twisted cable, they say the shield cable (cables wrapped with a thin layer of copper) is better than the screen cable because there is "no leaking" comparing to the screen cable??? it such comment true? any advice?

I always understood that twisted pair was intended as a less expensive alternative to shielded cable, meaning that if they prefer to use shielded cable for no additional cost that would be better. (maybe the shielded cable was left over from some other job so they don't need or want to buy twisted pair)

As for the 2 cables in the same trench, don't let them bury it until it has been proven to work to specs. If it doesn't work as specifieded it is easy to pull the control cable out of the trench creating the separation you have recommended and see if that makes it work.

My suggestion would be.

1) don't bury the lines until it is tested so that cables are taken out.

2) Shieldedcable sfor control cables should be ok.

3) Try to separate them with barricade wherever possible with physical distance.

4) TRY TO AVID IF AT ALL POSSIBLE AND CHECK THE CHINES E CODES.