Weird Ethernet Issues

We have one customer with a weird situation going on . Ethernet ports on four plant wide switches keep blowing and or hanging. When I mean blowing, I mean the ports literally become fried and unusuable. We suspect major electrical interference from 'somewhere' as there is one main ethernet run from the plant to the office that the customer strung themselves taking the shortest path from the plant to the office where the main SCADA PC resides.

We have our electrical crew going in the plant this Sunday to ensure all ethernet runs are isolated and do not run parallel with any motor leads that have VFDs.

After that, were are replacing all ethernet switches with the N-Tron type that has a high ESD rating, but are very expensive and we are afraid we may blow those as well if the original problem is not solved. A few months ago, one of our techies actually received a shock from one of the Cat5 cables while troubleshooting.

We have been looking at those high end Fluke line monitoring instruments, but at $9K it is quite an investment.

We inherited this plant and its ethernet issues which have dramatically become worse since 4 VFDs were installed in the plant within the last 9 months.

curlyandshemp said:

We have one customer with a weird situation going on . Ethernet ports on four plant wide switches keep blowing and or hanging. When I mean blowing, I mean the ports literally become fried and unusuable. We suspect major electrical interference from 'somewhere' as there is one main ethernet run from the plant to the office that the customer strung themselves taking the shortest path from the plant to the office where the main SCADA PC resides.

We have our electrical crew going in the plant this Sunday to ensure all ethernet runs are isolated and do not run parallel with any motor leads that have VFDs.

After that, were are replacing all ethernet switches with the N-Tron type that has a high ESD rating, but are very expensive and we are afraid we may blow those as well if the original problem is not solved. A few months ago, one of our techies actually received a shock from one of the Cat5 cables while troubleshooting.

We have been looking at those high end Fluke line monitoring instruments, but at $9K it is quite an investment.

We inherited this plant and its ethernet issues which have dramatically become worse since 4 VFDs were installed in the plant within the last 9 months.

Click to expand...

I'd start with the 4 newer VFDs, may lead you to the problem and get them running without having to shut down production due to ports blowing up.
Then tackle the actual pre-4VFD existing Ethernet issues on your own pace.
Running the "main" Ethernet run in a conduit may cure some of the issues right away.
The above can be done while the entire system is up and running and switch over during down time.

curlyandshemp said:

We have one customer with a weird situation going on . Ethernet ports on four plant wide switches keep blowing and or hanging. When I mean blowing, I mean the ports literally become fried and unusuable. We suspect major electrical interference from 'somewhere' as there is one main ethernet run from the plant to the office that the customer strung themselves taking the shortest path from the plant to the office where the main SCADA PC resides.

We have our electrical crew going in the plant this Sunday to ensure all ethernet runs are isolated and do not run parallel with any motor leads that have VFDs.

After that, were are replacing all ethernet switches with the N-Tron type that has a high ESD rating, but are very expensive and we are afraid we may blow those as well if the original problem is not solved. A few months ago, one of our techies actually received a shock from one of the Cat5 cables while troubleshooting.

We have been looking at those high end Fluke line monitoring instruments, but at $9K it is quite an investment.

We inherited this plant and its ethernet issues which have dramatically become worse since 4 VFDs were installed in the plant within the last 9 months.

Click to expand...

If your tech received a shock from a CAT5 cable, I bet that the plant has issues with their Power Distribution Grids (Grounding, Substations, etc)

Use fiber instead of Cat5. Problem solved.

Most likely is a grounding issue oe maybe induced voltage

Wow, bizarre !

Are these shielded cables ? Any chance there's a PoE injector somewhere in the mix ?

Looking at an RJ45 connector, I think it would be difficult to get a fingertip into contact with any of the pins, which is why I ask about maybe the presence of a metal collar and shield wire.

Definitely don't plug a FlukeView in until you've figured out where the voltage is coming from !

plc noob said:

Use fiber instead of Cat5. Problem solved.

Most likely is a grounding issue oe maybe induced voltage

Click to expand...

With all due respect, if it is a grounding problem then replacing Cat-5 with fiber doesn't solve the real problem and is a rather expensive solution. Sure, fiber would give other advantages too but I believe the actual problem should be fixed.

dogleg43 said:

With all due respect, if it is a grounding problem then replacing Cat-5 with fiber doesn't solve the real problem and is a rather expensive solution. Sure, fiber would give other advantages too but I believe the actual problem should be fixed.

Click to expand...

Also look at where the switch is getting its AC power from. The N-tron I use are all DC so you won't have a problem with losing a neutral reference to ground like you could with an AC switch. Make sure the neutral and ground on the 120 feeding the switch is bonded somewhere (back at the power feed). I have seen several installations where the neutral and ground had hundreds of volts between them.

If not that, then the next likely cause would be induced voltages. This is where fiber would solve the problem.

With all due respect, if it is a grounding problem then replacing Cat-5 with fiber doesn't solve the real problem and is a rather expensive solution. Sure, fiber would give other advantages too but I believe the actual problem should be fixed.


You are correct. It should be solved.

Fiber is expensive. It was just a quick post and a broad solution.

Broad because we have little info on the route and conditions of the cat5 cable.

I have with my own eyes seen cat5 ran along a conduit for a 4,160 medium voltage motor load at a distance of 270 feet. It was wire tied to the conduit and the customer had this exact same problem of blowing ports on the switch.

No one was ever shocked or injured on this installation to the best of my knowledge.

But this was the best way to run the media because of the plant layout and machine access,etc.

In the end it was replaced with fiber and the problem of blowing up switches lost and corrupted data packets,etc was solved.

Just giving him something to think about.

Is it one specific cable that keeps blowing out different ports, or a specific group of cables? Hopefully someone has been writing down what cable was in the port when things went south. If you can isolate the problem to one (or a couple) cables, then you should be able to track down the problem much better.

Check the blue and brown pairs of the Ethernet cables to see if you have voltage on them (normally they aren't used unless you are providing POE - power over Ethernet). If I remember correctly fast ethernet signalling is in the 2-3 volt range. If you can figure out how to monitor the connection with a scope meter, you could see if you've got voltage outside this range on any of your pairs.

http://pinouts.ru/Net/Ethernet10BaseT_pinout.shtml

If POE is being used, then you may have up to 48Vdc on one of the pairs. It might explain the IT tech getting shocked. I've never messed with it though, so I don't know too much. This link looks like a pretty decent overview:

http://www.altair.org/labnotes_POE.html

Here's a transient surge suppressor for Ethernet that I stumbled across. I don't think it will help with induced voltage or grounding issues, but if it's big spikes that are blowing out the ports on the switch it may help.

http://www.semtech.com/products/circuit_protection/low-capacitance/tclamp2502n/

Finally, is there a field bus in use that might use RJ-45 connectors as well that could have been accidentaly confused and plugged into the ethernet switch? I have a memory of horror stories of guys trying to plug their laptops into the RS-485 port of an AB Powerflex drive and frying the Ethernet card. Maybe a tech or operator with too much time on their hands trying to see if they can get online with the RS-485 device?

I highly recommend using shielded ethernet cable (S/STP). You should ground all cables at one point to a common ground, make sure, the grounding wire runs along the ethernet cables and earth the grounding cable at a single earthing rod, the same the earthes the building. Don't create earthing loops, which happens, if you earth at more than one location.

curlyandshemp
It's been a couple of weeks since you described the problem. Did you find anything???

I echo BruceChase, "any update?"