Routing I/O on power poles? Good Practice?

Hello,

I have a site with a rather unusual design. We have several locations where I/O is present. It's the usual DI/DO/AI stuff. Problem is, at least for analog, the obvious ways to remote this I/O are:

Fiber
Straight runs (they are less than 1,000')
Copper Network (Devicenet, Profibus, Modbus)
Wireless

Now, the trick. There are power poles carrying 480v 3phase which we must run our network on. Also, I'd like to eliminate the added expense of remote I/O drops, but this might be necessary, and is for my Fiber proposal.

I proposed fiber. The utility contractor can bundle this along with the HV and terminate into remote I/O cabinets I assume? Then all I need is a remote I/O (literally 10 I/O mixed each cabinet, so expensive per I/O...)

There is also one trenched HV line as well that we must run signals into.

I just felt that copper network or straight I/O would not be good judgment...

Any thoughts guys and gals? I appreciate any head-check here!

The actual physical layout is not clear at all from your description.
What is the total distance ?
What is the distance between nodes ?
Do the cables have to run outdoors between buildings ?
Update speed of the i/o ?
Is this a critical application ("nice to have" category, or "someone will get fired if it does not run" category) ?

If very long runs, then you will run into problems with high potential voltage differences.
If outdoors, then you will have to think about protection against ligthning strike.

It gets convoluted if you try to adapt a copper based network to these conditions.

Thanks Jesper for the response, the distances from MCS to remote are not very long (assuming 4-20ma):

MCS to Location 1 2,000' - outdoor, pole
MCS to Location 2 1,500' - outdoor, pole and trench combination
MCS to Location 3 400' - Buried (trench)
MCS to Location 4 500' - outdoor, pole
MCS to Location 5 300' - outdoor, pole

If I run a network or fiber, I need remote I/O drops.

Speed is not critical, but availability is, of course. Most of these are simple analog transmitters and only about 10 I/O per drop.

Hope this clears things up.

Tim

Also, if I am NOT running analog, but only looking at switches... can I get away with using a multi-conductor cable bundled with the high voltage?

If so, is 2000' too far to use 24VDC, or do you folks recommend 120VAC for switch contacts at this distance, assuming 14 AWG wire, I calculated about a 2.5 voltage drop per run, which is within the PLC's tolerance of 20-30VDC on the input...

Thanks!

I will suggest DUPLINE (aka "barbed wire bus").
It is designed for exactly your situation.

This seems like a great application for wireless. Check these out:
http://www.phoenixcontact.com/signal-level-matching/31240_15483.htm