Brian Posted January 15, 2012 Share Posted January 15, 2012 An Ethernet cable runs between two buildings via an overhead route. The building each have their own electricity supply which is TT in both cases. From what I remember Ethernet includes, as standard, electrical isolation using transformers on each data pair. There is no POE involved. Should I... a) look at incorporating some sort of proper protection in case of lighting?b) stick in some cheap sacrificial ethernet hubs at each end 'just in case'?c) not worry? Link to comment Share on other sites More sharing options...
timd Posted January 15, 2012 Share Posted January 15, 2012 I'd much rather see that in fibre! The real question is how good are the lightning rods on both buildings, and how much lower is this ethernet run? In the absence of a decent lightning rod, I wouldn't connect anything I hold dear to the mains in either building. The transformers in ethernet kit are there to protect against ground loop damage from two buildings being at different ground potentials, not >100KV spikes! Link to comment Share on other sites More sharing options...
bruce Posted January 15, 2012 Share Posted January 15, 2012 If I was doing it from scratch, I'd be using fibre. I know this doesn't answer your question :) Link to comment Share on other sites More sharing options...
Simon Lewis Posted January 15, 2012 Share Posted January 15, 2012 Given that telephone lines incorporate lightning arrestors, I can see a good argument for doing the same for an externally run and supported CAT5e cable. I know that the frequency of lightning strikes is typically such that extra protection is not always needed in the UK, however for the cost of some simple protection you could have the extra peace of mind. Would this be of use? Link to comment Share on other sites More sharing options...
david.elsbury Posted January 15, 2012 Share Posted January 15, 2012 If using arrestors such as what Simon linked to, is it necessary to place one at each end of the run, or is a single unit sufficient? David Link to comment Share on other sites More sharing options...
Dmills Posted January 15, 2012 Share Posted January 15, 2012 Firstly, almost nothing saves you from a direct hit! The far bigger issue is what happens in the event of a near miss, when you are dealing with what is in effect a large loop aerial, combined with (in the even of one of the buildings lightning protection systems being hit) a momentary difference in ground voltages of many hundreds of volts to a few KV. Personally, I would fit that protection, but note that for it to be effective, it needs a very low impedance connection to earth, and even then the effectiveness tends to be marginal, it goes at both ends. Disposable switches at both ends are a reasonable idea, but you will want to make sure that they are solidly grounded as well, or the pulse will just go straight through and slag whatever is next on the network. Furse of all people seem to be the go to people for this sort of kit these days (Hopefully if is more effective then the lanterns they used to make!). Regards, Dan. Link to comment Share on other sites More sharing options...
Sully Posted January 16, 2012 Share Posted January 16, 2012 If I was doing it from scratch, I'd be using fibre. I know this doesn't answer your question :) If not for the main run you could still use some copper to fibre media converters to isolate that run from the rest of the network. We've actually had internal cabling that was affected by lightning strike some years ago that toasted 8 ports of a 24 port switch (the other ports still actually did work fine). If we acquired such cabling at work we'd replace with fibre (and have done in the past at one site), it's not necessarily that expensive and could just be something as simple as a long fibre patch lead or pre-terminated fibre connecting in to a media converters attached to the re-terminated ends of the original cat5 cable. David. Link to comment Share on other sites More sharing options...
Don Allen Posted January 16, 2012 Share Posted January 16, 2012 Could not really make out any gas arrestors in that picture. You need good quality gas arrestors to ground on each leg and the gas arrestor ground needs to be a very low impedance to ground to divert the surge away from the equipment input. Fibre or wireless would be more resiliant. There is no guarrantee that a lightning strike will not take out your fibre interface. Link to comment Share on other sites More sharing options...
sound-geek Posted January 18, 2012 Share Posted January 18, 2012 I would suggest you run your connection in Fibre or CAT6, You will get a much faster and more reliable connection. It would also need to be CAT6 if your cable run was over 100m. Thanks, Link to comment Share on other sites More sharing options...
bruce Posted January 18, 2012 Share Posted January 18, 2012 I would suggest you run your connection in Fibre or CAT6, You will get a much faster and more reliable connection.It would also need to be CAT6 if your cable run was over 100m. Sorry, but that post is wrong in so many ways.... ! CAT6 max length is still 100m CAT6 and CAT5 will be equally susceptible to lightning problems (which is what the original post is about) and as for "fibre being faster than CAT5" - well 1Gb/s is 1Gb/s, no matter what the media ;) There are areas where CAT6 is desireable - I've just specified the installation of several thousand of them - but I don't think this is one of them. Link to comment Share on other sites More sharing options...
sound-geek Posted January 18, 2012 Share Posted January 18, 2012 Correction ... Cat 5e (1 Gigabitps) is 75m actually. Cat 5/6 is 100m Link to comment Share on other sites More sharing options...
david.elsbury Posted January 18, 2012 Share Posted January 18, 2012 WTF?? No one in this topic so far, except for you has mentioned "Gigabitps" [sic]. No one even mentioned length. Edit: The discussion relates to an ethernet run between 2 buildings and how to protect it from lightening strikes. Are you just trying to get your post count up? If so, how about making some posts that actually contribute to the discussion we are having? David Link to comment Share on other sites More sharing options...
sound-geek Posted January 18, 2012 Share Posted January 18, 2012 I was simply putting it out there that this would need to be considered. Then correcting my previous statement which mention length. Very sorry David and I hope I have not upset you. But I am unsure as to how/ why I would be trying too boost my post count, I only post when I feel I have anything too add. Link to comment Share on other sites More sharing options...
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