Whole house surge protectors not available in UK?

[bernardgreen]

Surges and spikes in the USA mains supply are far more common and often have far more disruptive energy than here in the UK. The reason is the short cable distance between supply transformer (11Kv to 110 + 110) in the USA and the subsequent lack of significant stray cable capacitance and reactance between transformer and domestic socket. This capacitance and reactance is much greater in the UK and provides a filter for spikes generated at the transformer when the loading changes.

In the USA there are many places a few houses share one "tin can" transformer on a pole in the street. If one of those houses reduces its load on the transformer by turning off an appliance then the transformer reacts by creating a single cycle transient over voltage spike which easily reaches the other houses.

A 2Kw reduction of the total load of three houses has a far greater affect on a small transformer than the same reduction of the load of 30 houses on a larger transformer.

Hence the need to protect against surges and spikes is far higher in the USA where "tin can" transformers are very very common

 

[electronicsuk]

IMO, if you are concerned, you would be better off using surge supressors local to the equipment such as those 4 gang extensions you can get, or fit a few MK filtered sockets.

They are selling for a tenner each at B&Q. They are normally about £40 trade, so they are a real bargain.

Clicky

Wise advice. As has already been mentioned, there's not a lot you can do to protect against a direct lightning strike. However, it makes more sense to protect against spikes/surges locally each piece of equipment as RF suggests above.

Bearing in mind that electrical disturbances may enter the wiring at somewhere other than via the consumer unit, you are providing a greater degree of protection by having multiple TVSSs around the house plugged into the items you want to protect.

For example, local lightning strike causes surge to enter property via telecoms wiring. If you only have protection at the consumer unit then spike is free to make its way into the mains electrical wiring via bridging your cordless phone (assuming the voltage is high enough) and then into the rest of your precious electronics. The only thing the surge protector at the consumer unit will do then is prevent the spike escaping your property. A number of separate surge strips will localise the damage to the cordless phone and possibly any other devices sharing the same surge protected extension strip.

 

[bernardgreen]

There is also ( I am told but have not investigated ) some concern that the coil in the MCB can create an transient over voltage when the load on that MCB is reduced. Another reason for suppression at the equipment to a direct to ground earth and not relying on the safety earth in the domestic wiring which due to bends and turns will be high impedence to fast rising voltage spikes.

 

[jabuzzard]

For example, local lightning strike causes surge to enter property via telecoms wiring. If you only have protection at the consumer unit then spike is free to make its way into the mains electrical wiring via bridging your cordless phone (assuming the voltage is high enough) and then into the rest of your precious electronics. The only thing the surge protector at the consumer unit will do then is prevent the spike escaping your property. A number of separate surge strips will localise the damage to the cordless phone and possibly any other devices sharing the same surge protected extension strip.

Remember the lightning strike is trying to find the lowest impedance path to earth. Therefore a a whole property surge protection at the consumer unit will in the event described above provide the lowest impedance path to earth, which the lightning will then take. Coupled with plug in surge protection at a device, and they may survive. Plug in protection in this scenario is useless.

However your consumer unit, and most of your mains wiring will be shot to pieces. Plaster blown off the wall, scorched wall paper and melted insulation after a lightning strike is a common occurrence Your mains wiring is not designed to dissipate the energy in a lightning strike..

You also get lots of wacky stuff due to temporarily raised earth potentials. So the lightning strikes the lamp post on the street outside. Because the soil is not a terribly good conductor, for a short while it's potential is much higher than say the earth at the other end of the telephone wire down at the exchange. As a result it can decide to take that path coming out the local earth and making it's way to the exchange, destroying stuff on it's way.

 

[datadiffusion]

Surges and spikes in the USA mains supply are far more common and often have far more disruptive energy than here in the UK. The reason is the short cable distance between supply transformer (11Kv to 110 + 110) in the USA and the subsequent lack of significant stray cable capacitance and reactance between transformer and domestic socket. This capacitance and reactance is much greater in the UK and provides a filter for spikes generated at the transformer when the loading changes.

In the USA there are many places a few houses share one "tin can" transformer on a pole in the street. If one of those houses reduces its load on the transformer by turning off an appliance then the transformer reacts by creating a single cycle transient over voltage spike which easily reaches the other houses.

A 2Kw reduction of the total load of three houses has a far greater affect on a small transformer than the same reduction of the load of 30 houses on a larger transformer.

Hence the need to protect against surges and spikes is far higher in the USA where "tin can" transformers are very very common

Sorry to bump an old topic, but this is very interesting. Just come back from a remoteish campsite where every single MOV has been blown sky high, and every HAGER RCBO is now U/S thanks to what must have been a surge. There were actually no campers there at the time, so virtually no load other than the owners house. Damage has been estimated at £1500 so far, and there was no known lightening in the area. The feed? Split phase from a 'tin can' type transformer on a pole at the end of the field... Plus (the only) neighbour also has a feed from this and has similar broken devices (PC and boiler controls) in the house. DNO are of course denying everything All we can do is write them a letter with pictures of the broken devices, and a fresh EIC showing all circuits are clear... Does anyone trade or otherwise have any experience of claims?

 

[SimonH2]

I'm no expert, but I do have a certain amount of first hand experience

While it's an old thread that's just bumped up, it's worth pointing out that ALL circuits into an item of equipment must go through the same protection for that protection to help. If that isn't the case then it's possible for the protection to make things worse !

So say (for example) you plug the mains of your computer into a "protected" extension lead. You get a common mode surge in the mains which may well be within what the PSU can deal with (the PSU is after all designed to handle mains voltages). Instead of going through into the PSU as a common mode surge where it will only stress the input filter and isolation components (normally rated to minimum 1kV ?) - it gets diverted to the earth wire in the extension lead. Given the length and impedance (note, impedance, not resistance) of this wire, there is now a surge transferred to the earth (chassis) of the computer.

But, your computer is connected to a modem which is in turn connected to the phone line - yeah, a bit of an old fashioned example but they do still exist. You have now created a surge between the modem electronics and phone line - and the modem "stops working". Stuff doesn't work once you let the smoke out.

Now, if you'd routed the phone line as well through the same protection point then it would all have been OK - apart from shunting part of the surge down the phone line.

Similarly, just protecting the computer will not prevent the surge coming in via the phone line and destroying the computer.


This same issue is why you can get a serious surge that destroys the laptop, printer, etc - but leaves the (ordinary) phone and table lamp intact. The difference is that the phone and table lamp don't have any other connection (particularly to earth, directly or indirectly) and so you can't force current through them with a common mode surge. That's a real example BTW, and was a spectacularly well destroyed laptop and printer I got brought in by a customer back from Madagascar (they get a lot of lightning there) some years ago. In that case I could see where the energy from the phone line lightning strike had partially melted the modem socket, blown the top off the chip in the modem, leapt across the small gap to the main logic board, and then exited via the printer who's inline PSU had it's case peeled open like a banana

So if going "whole house" protection, you must route everything (that includes phone lines, TV aerials, satellite dish feeds, etc) via one point and protect them with one set of protection. Running a cable more than a few inches won't work - at the sort of rise times you get with lightning discharges, a piece of earth cable has a very high impedance and won't help too much. There must also NOT be earths which don't go via the same point.

On the later point, I've had dozens of serial devices taken out in the office & factory by earth differentials caused by a nearby ground strike - earth in one part of the electrical system is different to earth in another part where it's been bonded to a different set of structural steelwork. RS232 will only take so much voltage before the interface chips (if you are lucky) act as fuses and protect the rest of the device.

 

[jabuzzard]

So if going "whole house" protection, you must route everything (that includes phone lines, TV aerials, satellite dish feeds, etc) via one point and protect them with one set of protection. Running a cable more than a few inches won't work - at the sort of rise times you get with lightning discharges, a piece of earth cable has a very high impedance and won't help too much. There must also NOT be earths which don't go via the same point.

I would point put that as it reads what you suggest is impossible. Basically you cannot protect the incoming mains, the incoming telephone and any aerial lead with the same device. You will need a separate device with different characteristics for each.

However they must all share the same earth and the connections between them protection devices and the protective earh need to be short; I believe the recommendation is less than 3m and with very thick copper cable; 10mm or better. Also a single earth rod is not usually considered adequate, you will have four or nine arranged in a grid about 1m apart and all linked with heavy duty copper strips/wire.

Generally speaking the primary protection is called insurance because even with whole house protection a direct strike to the house will cause more damage than a few bust electrical devices.

 

[AssociatedAlarms]

I have seen one very large property take a severe "strike" which took out several cameras a few alarm panels and VHS recorders (Few years back). Also the Red care units (6 were on site then), and the "new fangled" DVR`s they had for the entertainment systems. 5 cars on trickle charge also went "bang" and their electronics needed to be replaced.
We replaced everything that day or the next ( Our Arab friends have no concept of waiting). Also anti surge was fitted by us where ever possible and the site electricians were also going insane trying to get other protective devices fitted at all intakes. The strike came down the phone lines, Ariel`s and the overhead power lines in the area owned by the Sultan.

 

[SimonH2]

I would point put that as it reads what you suggest is impossible. Basically you cannot protect the incoming mains, the incoming telephone and any aerial lead with the same device. You will need a separate device with different characteristics for each.

I said same set of protection, not same device. You are correct, they need to be all together at one point, but will be different devices for the different services.

However they must all share the same earth and the connections between them protection devices and the protective earh need to be short; I believe the recommendation is less than 3m and with very thick copper cable; 10mm or better.

From what I've been told, 3m of 10mm cable (between separate devices) would not be that effective ! The inductance of the cable would be very significant for the rapid rise times involved in a lightning induced surge - but I guess that does depend where the surge is entering and how far it's already come (if it's already travelled a distance through cables then it will have lost some of it's "oomph"). I've seen a demonstration of how to make a filter (for that demo, it was a power supply filter for a DC motor) ineffective (noise was still conducted up the supply cables) by earthing it to the aluminium plate of the demo rig with about a foot of braided earth strap. Pushing it down on it's shock mounts (it was in a military contractor environment) till the bolts met suddenly made it work. The rise times involved with lightning mean you have to think more in terms of high frequency (radio) than DC or 50Hz AC.

Generally speaking the primary protection is called insurance because even with whole house protection a direct strike to the house will cause more damage than a few bust electrical devices.

Yup. In the case of the blown serial ports I mentioned, we reckon it was a ground strike perhaps a 1/4 to 1/2 mile away and that was bad enough just through earth potential differences across the building. I've read about and seen pictures of what can happen to buildings (and the things in them) with a direct strike - I think all bets are off for that.

But, depending on your circumstances, house building protection may well be better than individual device protection which can shift the problem elsewhere within the building.

 

[bernardgreen]

There is another problem that no surge suppression can deal with. This is the electromagnetic pulse that is created by the current in the lightning strike. This magnetic pulse will create potentials in all metal items and wires and it is often these induced voltages and currents that damage / destroy electrical equipment in the vicinity of a lightning strike.

 

[janner10]

You are either a bit thick or paranoid to buy one of these.

Either way the advertisers dream.

 

[ban-all-sheds]

There is another problem that no surge suppression can deal with. This is the electromagnetic pulse that is created by the current in the lightning strike.

http://teslamania.delete.org/photos/Lightning/Lightling_Kane_Quinnell.JPG

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[ban-all-sheds]

I have seen one very large property take a severe "strike" which took out several cameras a few alarm panels and VHS recorders (Few years back).

In Windmill Lane, Ealing, just North of Osterley Park?

 

[davelx]

I have seen one very large property take a severe "strike" which took out several cameras a few alarm panels and VHS recorders (Few years back).

In Windmill Lane, Ealing, just North of Osterley Park?

Very nice - note how Google StreetView stops either side of it!

 

[ban-all-sheds]

You can't see much from the road except high walls anyway.