Ethernet Protection for equipment on separate circuits

[Anonymous user]

I've got Ethernet-related equipment connected to three different branch circuits through APC UPS and APC TVSS products. The "gateway" device is a cable modem, whose coax input is protected by a ProtectNet device grounded to the TVSS screw on a SUA1500. The modem itself and other network equipment (e.g. router, central server, switches) are all connected via short Cat-5e cable runs for data, and via power cords connected to that same SUA1500.

I've got my main workstation setup connected to a SMT1500 on another branch circuit. The network cable run from the switch to the workstation is 25ft and is not yet protected by a Protectnet device.

A secondary workstation setup is connected to a P11VNT3 on a third branch circuit. The network cable run from the switch to the workstation is much longer, and since the TVSS supports it anyway I'm relaying the Ethernet cable through it.

My understanding about the use of data line transient protection is that surges can come from three sources.

1) The transient can enter through the service line to the outside world (telephone/cable/satellite/etc.)
2) Lightning and other disturbances can induce a voltage differential in a cable
3) A power line transient shunted to ground can create a ground loop, and the resulting voltage differential between network devices can cause damage

My current setup as described above seems to protect network equipment from (1), but I'm not so sure about (2) and (3). Is it really necessary to place a Protectnet or similar device in every data cable? How likely are the events that such protections would defend against?

Does it matter whether the network equipment is powered off the same branch circuit and UPS/TVSS? For example, most of the networking gear is connected to the SUA unit, so hopefully a ground loop would not be an issue and ProtectNet devices are not necessary to protect against (3) above. However, what about the main workstation on the SMT unit connected to a different branch circuit? Is that a more appropriate place to put a Protectnet or is it still overkill?

Thanks!

[Anonymous user]

I've got Ethernet-related equipment connected to three different branch circuits through APC UPS and APC TVSS products. The "gateway" device is a cable modem, whose coax input is protected by a ProtectNet device grounded to the TVSS screw on a SUA1500. The modem itself and other network equipment (e.g. router, central server, switches) are all connected via short Cat-5e cable runs for data, and via power cords connected to that same SUA1500.

I've got my main workstation setup connected to a SMT1500 on another branch circuit. The network cable run from the switch to the workstation is 25ft and is not yet protected by a Protectnet device.

A secondary workstation setup is connected to a P11VNT3 on a third branch circuit. The network cable run from the switch to the workstation is much longer, and since the TVSS supports it anyway I'm relaying the Ethernet cable through it.

My understanding about the use of data line transient protection is that surges can come from three sources.

1) The transient can enter through the service line to the outside world (telephone/cable/satellite/etc.)
2) Lightning and other disturbances can induce a voltage differential in a cable
3) A power line transient shunted to ground can create a ground loop, and the resulting voltage differential between network devices can cause damage

My current setup as described above seems to protect network equipment from (1), but I'm not so sure about (2) and (3). Is it really necessary to place a Protectnet or similar device in every data cable? How likely are the events that such protections would defend against?

Does it matter whether the network equipment is powered off the same branch circuit and UPS/TVSS? For example, most of the networking gear is connected to the SUA unit, so hopefully a ground loop would not be an issue and ProtectNet devices are not necessary to protect against (3) above. However, what about the main workstation on the SMT unit connected to a different branch circuit? Is that a more appropriate place to put a Protectnet or is it still overkill?

Thanks!

[Erasmus_apc]

By "APC TVSS products" are you just referring to the surge protectors like the P11VNT3 you mentioned or do you also use our panelmount surge devices (meant for protecting an entire house/building at the service entrance level) such as the PMP/PMF units, etc.?

If there is a data line input somewhere off this branch circuit/room environment in question that is not surge protected, you are leaving yourself open to a possible data line surge issue. It's even better to put the ProtectNets before the primary switch/network devices, if feasible, and not just on a single workstation. This will protect the entire system that is "past" the root dataline input. So no, not every data cable needs a ProtectNet, just the root inputs that supply multiple secondary and tertiary devices, or at least on your most critical equipment.

[Anonymous user]

Thanks for your reply, I think you answered at least one of my questions. Let's simplify the site to the following:

AC Circuit A --> UPS A -->
Cable Modem (Coax in from wall)
Router/Firewall (Cat-5 in from Modem)
Network Switch (Cat-5 in from Router)

AC Circuit B --> UPS B -->
Computer (Cat-5 in from Switch)

I've got a coax ProtectNet just before the cable modem and grounded to UPS A. I believe that this should protect the cat-5 ethernet network behind the cable modem, as this represents the root dataline input that you mentioned. In a single-circuit installation, it makes sense that this should be sufficient.

My other question is whether network devices powered by other circuits require dataline protection as well. The reason for this is that a lot of TVSS products shunt surges to the ground line, and this can create a relative ground difference between network devices on the different circuits. In other words, the diverted surge could raise the ground level of devices in other circuits, and this could also lead to a ground difference in the network as well.

Does that make sense? Does such a risk actually exist? Any other thoughts? Thanks!

[Erasmus_apc]

In regards to your UPS A setup and your statement about the protect net protecting the "root" of the data line entry and what is "past it" in that setup, yes that is correct, everything has been covered at that root failure point and should be perfectly safe. I say "should" because transients and surges can also be caused by equipment or other wiring issues within a circuit/configuration and so unfortunately the "safety" of equipment in this regard can to some degree can only be assessed by the end user. See this white paper devoted to data line protection for more info on data line surges, protection, and electrical details.

As for your second question, yes this concept does make sense although this should not happen in a properly set up and, for lack of better words, circuit/panel configuration that is in "good status". The reasoning for this is that the ground connection should be the "easiest" path, i.e. the path with the lowest resistance for surges returning from the source circuit to the panel and then out to ground. If for some reason a different circuit had much less resistance than the path to ground, it's plausible that the surge would partially or completely pass through to that other circuit. Also, if there is ground bond corrosion or any miswires, I suppose this could also contribute to a surge not going completely to ground and in so doing affect another circuit. So in terms of data lines, the network devices having a voltage difference "change" or being affected by an off-circuit surge should not be a factor.

Protecting the data line "sources" themselves and identifying any equipment with potential for feeding back onto the circuit would be the best approach. Also, if you are concerned about multiple circuits being affected by surges, you could use our panel mount surge protection units to cover ALL circuits on that panel from surges across power lines/wiring, whether they come from utility power or from a protected circuit.

[Anonymous user]

Thanks again for your help. Do you know of any plans to replace or resume production of model number "PV"? It's an APC ProtectNet device for Coax data lines. I can't seem to find it anywhere, either through retailers, distributors, or from APC itself. There's a rackmountable coax protectnet unit but it doesn't seem to be rated for providing the same level of protections as the standalone unit. Thanks!

[Erasmus_apc]

As of now I am not aware of any plans for replacing the PV product in the near future, or at all. I'm surprised that no resellers or distributors have any for sale or a reference to someone who has stock. The rackmount coax protectnet should be sufficient for most IT equipment, however we also have A/V units and Back-UPS units that come with coaxial protection as well. We just don't have the standalone unit any longer.

[Anonymous user · Accepted solution]

Littelfuse just published a paper on ESD protection of ethernet data lines. It covers ethernet products susceptibility to ESD events when the cable is disconnected from the Ethernet port and how the ESD pulse can be introduced directly into the open port, or into the disconnected end of the cable. Thought this might be of interest.