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Posted By Topic: Data Cable in Switchboard

Oct 13 2018 17:24

I\'ve had some jobs where we have been required to install current transformers on mains in switchboards for monitoring.

The general practice of the people I work with is to just run in a cat5/6 cable and hook it up but I don\'t believe this is compliant due to rules around segregation? (I can\'t find the specific rules so if someone could help me there that\'d be awesome)

Basically I wanted to ask how other people do it and there methods? I was told by some people that if the cat5/6 is brought up to an acceptable low voltage rating for the cable then it\'s fine? But where does it say that this is ok and how do you go about achieving it?

Sleeving the cat5/6? Is there cat5/6 that comes pre rated for these values?


Oct 13 2018 17:52

There are two issues

Induction between the power cables and the dats cables and the only method is by magnetic screening and having a large distance between the cables to prevent problems in the data cabling.

Insulation is covered by segregation (AS/NZS 3000 clause 3.9.8) between the cables by insulating for the highest voltage.

Look at each cable and see what it is rated for, standard 2/2.5 mm2+ E TPS is 450/600 V and some data cables (for exanple cat 5) are often marked at 600 V and this would be OK for a 230 V supply.


Oct 20 2018 19:46

what about the aerials they use on some smart meters, don\'t recall seeing any ratings on these?

Oct 21 2018 08:36

rarrar Oct 20 2018 19:46
your comment

what about the aerials they use on some smart meters, don\'t recall seeing any ratings on these?

My comment
The Smart (really thay are dumb) meter in my electrical installation the aerial coax cable has a 600 V rating marking on it, if it didn\'t, if would NOT have been installed (as I was around when it was fitted); or, the metering contractor would be back to make it comply!


Oct 21 2018 11:19

The smart meters around these parts don\'t have external antennas; the radio module and its antenna is inside the meter assembly, its on the back of the terminals cover. So the meter is a standard meter, with different terminal covers for the different radio standards they use, either cellular or mesh.

The cable to the radio looks like standard telecoms flat cable that goes to a RJ connector.

In the wider context, acceptable Cat5 cable to use inside switchboards adjacent to mains is available, perhaps the best example being the pink Clipsal Cat5 used for CBus.

Most of the time when Cat5 is used, the signal being carried is on a balanced twisted pair (eg Ethernet, RS485), and you can run that literally adjacent to mains wiring for miles and miles and there will be no interference to the data; the balanced data receivers reject the common mode interference from the mains.

Oct 21 2018 22:33

I have never experienced Cat-VI cables (high impedance) that are laid close to reasonably high current (low impedance) supply cables being interfered with. One is analogue and one is digital. I reckon this is an irrelevant risk apart from the required 50mm separation which relates to the safety issue and not the interference issue.