Lightning - what can you do?

[rojash]

Over the last few months I've lost a two motherboards, a processor, 3 ADSL filters.

Today, I'm happily working away (with my 3 week old motherboard) when there's a terrific crack and both monitors turn black. The monitors are OK now.

This time, the filter has survived, but my router's blown.

Fortunately I have a spare, but on replacing it I find that the on-board nic of my main machine (the one with the new board) is also blown.

Lightning strikes without warning, so it's not like I can just stop work when it's thundering.

Currently my 'phone line comes into the office, passes through a line protector on one of my UPSs, splits to the router and my ISDN box. The second analog line from the ISDN box then goes via a line protector on one of the other UPSs up to the house.

Keeping in mind that this is Greece and OTE (Greek BT) are not the least interested in my problem, has anyone any suggestions?

[ACtheTROLL]

I lost my reading glasses yesterday ... but you just sound irresponsible - start taking notice of where you are leaving them ;-0

You sound to be having a bit of a rough time ... zeus must be targeting you

I live on a mountain - so we get a bit of weather -
(but not in your league)

Is it emp or direct hits?
I've seen equipment rooms with tinfoil wallpaper for emp.

I have gas discharge tubes on the phoneline - I just knocked on the door of our local telephone exchange and kept talking until the guy gave me a handful (he he)
you must have them over there ... (they are used in all our exchanges to protect the exchange eqipment).
1 leg in, 1 leg out ... and a bonded earth at less than 5 ohms - never had any problems since they were fitted ... but also never taken a direct hit

I have a 10A surge protector in my mains supply
(blagged from an office clearence).
same on all telly kit as well

One of my chums swears by his floating UPS
laptops do seem much more tolerant

don't know how you'd protect the network... I've lost the odd router ... but never a nic
metal trunking?

A baco foil helmet sounds like a good idea also

[weeal]

Haha ^ bad move

I use a surge protector which takes 7 items and it has a 25yr guarantee so if it didnt work Im covered up to a certain value - cant remember how much, but the protector only cost about �15. Well worth it

[tamborine]

get a proper conductor:

http://www.danielbarenboim.com/


If a storm is rolling in from the west I trip the fuse box.

[weeal]

rofl ^^^

[Postdog]

Didn't john travolta sing a song about this......?

[solera]

gOING BACK A FEW YEARS we had similar problems with fire and burglar alarms in the middle east and we had good results with a choke on both sides of the mains input, have a word with a local alarm installer for the chokes and their value, sorry to be a bit vague but I am thinking back about 25 to 30 years.

[Hymie]

I would agree with ACtheTROLL, gas discharge tube (GDT) protection is the way to go.
These devices operate orders of magnitude faster than Metal Oxide Varistors.
Within nano seconds of the voltage exceeding the flash-over voltage, these devices go short circuit, preventing excessive voltages reaching your sensitive electronics.

For the ultimate protection, a GDT should be connected between all phone lines, and all phone lines to a good earth.

Remember that the phone ringing voltage is around 120Vac, any GDT�s proving protection on your telecomms line should have a flash-over voltage of at least 200V to avoid activation under normal operation.

[rojash]

Thanks for the advice guys.

Unfortunately, it turns out that I already have GDT protection - in fact I have combined GDT and Varistor protection. Apparently GDT is good cos it can handle lots of energy, but it's slow. Varistors are good cos they're quick but can't handle so much energy.

I have 3 1.1KVA UPSs from APC, each of which has a Hybrid phone line protector.

I'm fairly certain that the surges are coming from the line, as apart from the one time I actually saw a bolt come through the shutters (when I lost a printer), I've only ever lost anything connected to the phone.

Also the bang and flash always come from the corner of the office where the phone sockets are.

I've just been and bought three replacement hybrid protectors, as apparently it's possible for them to fail after repeated strikes, and there doesn't seem to be a way to check whether they're in working order or not.

I'm also wondering if maybe the Earth in the office is not good enough. The power for my office travels underground from the house to the granny annexe, and then internally from there to the office - I guess it's about 150 Metres.

Anyone know anything about earthing? I'm thinking of having an earthing spike put in just outside the office, but unfortunately the ground is almost solid rock (and rubble from the '53 earthquake). If I did this, I would connect it to the earth in the junction box.

[ACtheTROLL]

your spill earth needs to be less than 5 ohms ... and in rock you aren't going to get that (not without a very weak bladder ... and lots of beer)

you could possibly bond all your earths and run the biggest piece of copper you can afford back to the entry point.

I'm in yorkshire ... and there is just about every combination of good and cr@p earth it's possible to have.
out in the dales I've seen holes blasted and drilled (deep)
not practical (unless there is another earth quake (fingers crossed eh!)

I think your best bet is to bond everything in sight ... and use a link cable that's a serious piece of copper. If you manage to bang in a spike as well it won't hurt (unless you hit your thumb).

[Hymie]

Usually, commercially available telecoms line protection consists of a GDT in series with an MOV. The reason for this arrangement is that once the GDT fires, as long as sufficient current flows, they will remain short circuit. This could have serious consequences in terms of a potential fire, as a result of the current flow. With an MOV in series, once the voltage drops below the MOV conduction voltage, no further current flows (allowing the GDT to switch off).

Although you may not be able to determine the voltage ratings from the marking of the components within your telecoms protection � you can be fairly certain that they will have a very generous margin compared to the normal operating voltages.

I would recommend you add GDTs only, at a flash-over rating not much over 200V. To protect the circuit against excessive current flows, the telecoms lines should be fitted with fuses (1A should be adequate).

I would disagree with your comments relating to the speed of GDTs, they are very fast and preferable to MOVs � but suffer from remaining short circuit (undesirable in certain applications).

[rojash]

Thanks for the further advice guys.

I've got a bloke coming round later today to seriously investigate the earth situation.

Hymie, the reason I prefaced those comments with "apparently" was that (having spent most of the night googling the subject), I'd come across that statement on a couple of sites, but wasn't sure of the veracity.

So are you saying that whatever other measures I take, I can just bung a couple of 1 amp fuses on the incoming line, and that will increase the protection without an deleterious effects on the line?

[ACtheTROLL]

again the bt way is to use quick blow fuses (the ones with the ikkle spring)

in the old days of two copper wires from the pole to pots the line termination went through two ginormous - 2 - 21/2 inch long ceramic shelled fuses I seem to remember they were 2 amp ...
but within reason ... 80000000000000000000 volts will blow pretty much any fuse rating ;-)

the key is fast ... and a big gap to prevent arcing.

thinking about the ground - while you don't have the ability to spill directly to earth ... presumably a ground strike won't get through to you either

in effect you will turn into an enormous capacitor
so seriously ... how about building a Faraday cage out of chicken wire .... line the roof space and earth it as best you can (less embarrassing than wearing a tinfoil hat)

you'll never beat lightening .... but emp can be diverted
https://www.youtube.com/watch?v=bZwlD-Z0zmE

[Hymie]

I believe that fusing the telecoms lines in the USA is a common technique, especially where there are long line runs, subject to lightening strike and/or power line crosses.

Fuses alone may not solve the problem, since the damaging excessive voltage may reach your equipment before the fuses operate. Combined with GDTs, this should give you good protection.

I would also take on board ACtheTROLL�s comments re good earthing � and supply a dedicated (permanent) earth connection to your protection circuitry.

[rojash]

Ok, I'm having a new earth as close as possible to the office, but avoiding the rocks, and connected by an enormous cable, PLUS fuses on the incoming, PLUS GDTs wire direct to the new earth.

Ac, your suggestion re a Faraday cage - apparently at least two of the buildings in this area, a private home and the Lidl supermarket, have exactly that - so if the above don't help, I'll try that.

If I get hit again after all that, I'll post my next question in "Religion & Spirituality"

Thanks to all for the advice.

[Hymie]

A few pointers to assist you in the design of your telecoms protection.

The clamping voltage of your APC telecoms line protection will be of the order of 600V, by fitting GDTs at around 200V, you will have a significant head start on reducing the voltage spikes entering your system (due to lightening strikes).

The fuses are to protect your wiring in the event of a lightening strike (or power line cross), the lower the amp rating the better. However, once your fuse value is significantly less than 0.5A, there will be a small (but significant) resistance added. This may effect your broadband speed � this also holds true for any increased inductance or capacitance. Therefore you should ensure you minimize any additional resistance/capacitance/inductance, as a result of adding the protection circuitry.

You cannot place two 100V GDTs in series to achieve a 200V rating � the nature of the device is that such an arrangement would still flash over at 100V. If it would give you more confidence in your protection, there is nothing wrong with placing MOVs in parallel with the GDTs, but remember whichever has the lower voltage rating, will operate (conduct) first.

[tamborine]

my old un-used tv arial has been left on roof but with copper wire fitted running down house & into earth, to allay strike. This was done to west lightening continually striking property. open plain to the west of property.