how do i go about calculating the induced voltage and understand if the thermalcouple is okie for temperature sensing for the job?

Power cable= 132kv.
Full load current=565Amps

will provide other details if u need more.

kevin

 

Kevin I have a particular application where a T/C cable must be routed near a 2000 ampere current flow. The TC is subjected to pressures in excess of 65 kilobars so no other sensor will survive, but we do manage to pull it off. Occasionally a maintenance tech will not route the TC wires through the prescribed path but will take a shortcut, and then we have problems with the reading. The voltage in the cable is not your primary concern, but rather the current flowing in it. The current is what will induce voltage on the TC line. The farther away you can route the two cables from each other the better. It will help if you can shield the TC cable and even better if you can get it in a conduit by itself. There are some insulation rating issues here as well but you weren't specific enough to address them.

 

Basically if it is possible, get a transmitting head for the thermocouple, then you can run single pair shielded cable (4-10ma)

 

Most on the list would ask "Why do it"? That said, then, lacking detail regarding length, spacing, orientation, parameters, construction, etc, all that anyone can provide at this point are Rules-Of-Thumb.

The one precaution that is most often overlooked is the inductive effect of fault-current flow in the power cable, especially, if a ground (earth) fault. Although you state that full-load current is 565 A, fault-current could be substantially higher. Furthermore, any ground-fault current will try to flow in close-proximity to that of the
power cable.

If you have no other option in mind and the arrangement mentioned is... in the words of Yogi Berra... already fait accompli, then, I suggest the use of an optical link.

Regards,
Phil Corso, PE
(Boca Raton, FL)

 

Further to my earlier response to Kevin Leow:

If, on the other hand, you want to do the calculation, because, like the mountain climber, it is there (or because you are a typical engineer in search of truth), I suggest you contact a Siemens rep.

Some years ago, Siemens' produced a book covering cable. It was titled "Power Cables and their Applications." One section covered interference
of power cables upon control and communication cables. Detailed investigative procedures, reduction methods, and applicable formulas
cover a number of situations... yours included. BTW, in general, the inductive-coupling effect of balanced 3-phase currents is virtually nil if the power cable is properly sheathed or shielded, as I'm sure the 132 kV line is. However, interference, could result if there is an
unbalanced condition such as a ground (earth) fault.

If you are unable to locate the book, contact me.

An aside. Investigated a ground-fault condition that persisted for several hours in a 100-mile OVH power line. The power source was the
Guri Dam in Venezuela. The interference in nearby communication circuits, wire-fences, pipelines and the like caused quite a bit of property damage, some cows, but no loss of human life.

The system's protective devices failed to detect the fault. Of course, phone and walkie-talkie communications were rendered inoperable as well.
Contact with the power station operator was finally established, no, not by over-land pony-express, but by jeep.

Regards,
Phil Corso, PE
TAL-2(at)webtv.net
(Boca Raton, FL)