Lightning protection for metal roofed residential housing in the UK?

Hello Andrew:

I wish I knew the real answer. I was told this by local solar panel installers.

Maybe it was connected with getting zapped by the developed voltage.

Last night on TV  they had a news item (solar panels mounted on a regular single roof) in which the mounting holes in the roof (that are made for the solar panel mounting legs) had not been sealed correctly. This allowed the roof to leak rain water into the house and do extensive damage.

By the way we can get up to 4-5 inches of rain over a couple of hours.  It is now our rainy season!

Peter Brooks

Palm Bay 

And I thought we had it bad for rain! Manchester’s average hourly rainfall during the rainy season ( If I’ve looked this up correctly) is a mere 0.0037 inches, a modest drizzle. 

Hello Andrew:

The grass loves the rain. It is growing very fast. Also the grass is not the fine stuff you get in the UK - it is very coarse and one needs a high powered self propelled gas mower to cut it.

Recently we have an armadillo digging big holes in the lawn overnight, looking for grubs.

Peter Brooks

Palm Bay 

Peter, Regarding metal roofed residential housing, what are your thoughts on grounding them ? 

Here is Florida many houses are protected from lightening strikes (according to our Power company)  by the shielding from the mounted high voltage power line on our wooden poles through which (via a mounted fused transformer) we received our house AC power.

I presume these are similar to what I saw in the northern US - very tall wooden poles (at least twice as high as we normally have over here) running along the edge of most roads even in built up areas - carrying just about everything - HV (although a bit lower than our usual 11kV or 33kV), transformers, LV distribution (to quite a small area), phone lines, road signs, even traffic lights.

I can see they would provide a kind of LPS mesh for the neighbourhood - although having a fairly decent connection (if reduced by the ratio of the transformer) to your electricity supply leading directly into your buildings, perhaps gives an additional route for damage into the house. Do you have a lot of SPDs?

   - Andy.

Hello Andy:

In my specific area there are two parallel power line on adjacent streets - One the main feeder line on concrete poles and mine (actually on my back lot line) on wooden poles with transformers feeding every 6-8 houses. The HV line is at the top, followed by the three home power lines, then the cable service and finally the phone line. The local woodpeckers like to make holes in the wood poles.

The power transformers last for about 25 years - We have had two go while in this house.

Not too sure about the term SPD but after a each time a  Cat 2 hurricane eye went over house (twice it has happened) a power line snapped and fell live onto our garden.

We had one case where the wire clamp (near the pole) got loose on the neutral line and the voltage doubled and blew the computer and TV - the Power company paid us for the loss.

The other problem we get is other people planting fast growing trees which touch the HV power line when the wind gets up causing arcing and power glitches.   

Peter Brooks

Palm By 

SPD == Surge Protective Device - a non linear resistor that breaks over and passes a large current above some threshold voltage, and clamps short duration spikes that would otherwise be at the kV level, usually based on metal oxide. Common inside electronics for years, and now showing up in a more expensive DIN Rail format inside modern consumer units - the idea being to minimise damage to electronics from switching spikes and voltages induced in overhead lines by thunderstorms some distance away.

Required by recent regs in places with significant electronics to protect (so nowadays most places) 

Very large versions of the same thing are seen outside built into insulator on our overhead lines to protect transformers and so on, again to clip very short duration over-voltages, replacing or augmenting the insulator horns that are there to encourage any flash-over to take place away from damaging the insulators and supports.

Mike.

Hello Mike: The same three or four alpha codes are used over and over again in different fields. At least it wasn't STD.

I currently use them (they plug into our AC wall sockets) for the computer or TV set. Sometimes they are sold in portable power strips.

One of the companies I worked for, purchased RCA which owned a plant making them in Ireland just south of the Northern Ireland border.

The had a production problem with the fluidized bed used in the coating process, and we had to send a chemist over from the US to fix it.

Peter Brooks

Palm Bay 

We had one case where the wire clamp (near the pole) got loose on the neutral line and the voltage doubled and blew the computer and TV - the Power company paid us for the loss.

Similar to our "broken PEN" problems we have here then. Presumably your installation's earthing (grounding) is derived from the supply N, so did you have your grounded metalwork sitting at about 120V?

   - Andy.

Hello Andy: That's a good question I don't know.

The three lines from the power pole go through the edge of the roof down to the meter. From the meter the cabling goes to the main power switch on the outside wall, then inside the concrete wall up to the attic and across to the main fuse panel.

However also coming out of the meter is metal tubing (assume with a cable inside) that goes directly into the ground.

As I am not allowed to get inside the Power company meter I always assumed it was directly connected to the neutral cable.

Peter Brooks 

Palm Bay