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Surge Protective Device


to-ya farm Apr 26, 2021 10:18 PM

hi~

I use CR1000X with solar pannel and CR1000X is connected to computer wih RJ45(RS232)

but some sensors use AC 220V (rainfall meter's heater and rain detective).

RJ45 line and AC 220V line in the ground.

so I want to protect against lighting.

do you have good idea?

https://blog.naver.com/jowh4998/222324761121

thx


Nico May 1, 2021 07:39 AM

Your logger seems to be connected to the green Earth wire that comes with the box - I assume you connected the green/yellow wire cable to the outside Earth terminal while the green wire on the inside is what is being connected to the logger in your photo?

What does the green/yellow wire end in outside the box?
Earth Stake in the ground next to your box?

If that's a YES, your logger is safe from surges arriving either via Sensors or the mains powered gear.
The little power brick and whatever is plugged into the right bottom corner will be toast though. You'd need a 230Vac surge arresting between the power cable that comes into your box and that 3 port power board. Problem is, the ones that have sockets/plugs on them do not give you an options to connecct a to a local Earth, while the Din Rail versions will expose the dangerous life wires to you unless you put them into a little Din Rail box.. not to mention that wiring on 230Vac in most countries when done by non-professionals will give you a lot of legal trouble if something happens.

Lightning is another story.. a direct hit into your post or anywhere close will still cause damage/total loss.

The 230Vac line where it comes from will be a risk to that grid too.
You might want to have someone install a Surge Arrester between the cable there and it's socket in the building(?) to protect everything that is on the grid where your power comes from.
Might be enough to use a surge arresting powerboard that you plug your long 230Vac cable into.

Now onto Ethernet.
There are surge arresters with two ports you just plug in.
I successfully used those cheap ones (~10-15 $US) that come in a metal casing and have a RJ45 socket on each end.
Or these (https://www.ui.com/accessories/ethernet-surge-protector/).
You will need TWO (*).
One is for your logger box (connect the green/yellow wire that comes out of the surge arrester to Earth) and plug the grey Ethernet cable in one end and then use a patch cable from the SA to your logger.
Then do the same on the OTHER end of that grey Ethernet cable to protect any gear from where your Ethernet is comming from (* unless they hve surge protection there already?).
And yeah, have fun getting to a proper Earth there ;-)

But again those SAs - Ethernet or 230Vac - you can plug into are only considered fine protection for surges that the long wires you have running between equipment pick up when there is lightning in the vicinity.

Protection against close or direct hits need a bit more than that and probably need an electrician to set up correctly.

Did you connect the logger box metal post to that Earth Stake as well?
You want a beefy wire there to be on the safe side of things.. say 6 mm^2 or more.

But again.. if a direct lightning bolt hits your post there will be damage.
If your post is exposed and lightning is likely seeking help on a forum like this will not be enough.
You then need proper help/advice. There are engineers out there that do nothing else than this.

PS: I deal with this too and got 2 engineering books about it in my mother tongue.. but I would still seek professional help if there is any chance your station is exposed and you have a chance of getting lightning strikes near or into it.
I'm lucky as the area I'm operating in doesn't have that much lightning and I also do keep the gear islanded (solar power, wireless coms) as I had my fair share of bad experiences when there are coms or power connections running to gear over a couple tens of meters and destroying things.

PPS: the idea behind surge protection is that you treat the wires running between two points as antennas that pick up EMI which then appears on either end as high voltages/currents that seeks a way to flow to Earth with your ger providing that path, heh.
SAs are designed so, that under normal conditions they do not conduct, but do when overvoltage occurs.
This is why BOTH ends of long cables need to be connected via SAs, to protect the respective gear that the cable plugs into on EITHER end.
And as you got 230Vac and Ethernet here to worry about you need 2 for each.

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