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Old 15-03-2019, 03:59 AM
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Earthing/Grounding remote setup

A recent reply from Alex to a DIY Wind Power thread raised an important point about grounding remote installations as an anti-lightning measure.

Whether it is, like mine, an isolated wind turbine/solar power setup with all the usual electrics and wires/cables, or a remote observatory, it is an important consideration in the design and construction.

Obviously, grounding is a good and necessary safety issue to be sure you don't accidentally cook yourself, but how much use is it against a lightning strike? Anyone got any ideas on this?

As an example - my solar/wind install sits on a hilltop about 1 km away from my house. It provides power to a small lookout and BBQ area I built in a small orchard so we can use it to entertain and just chill out and watch the sunset. The setup consists of a tower with wind turbine and a few solar panels that are cabled underground to a little tin garden shed 20 yards away which houses a battery bank, charge controllers and inverters and a pump to push water around the orchard. Power for the lookout/BBQ lights comes out of there also.

The tower has 5 ground rods - one on each set of guy wires and one on the pole. The shed has only one and it is connected to the negative pole on the battery bank since everything else in there - one way or another - links back to it. I'm not sure if this is exactly kosher though.

I'll throw this one open to others with more knowledge of electrics.

Peter
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Old 15-03-2019, 08:22 AM
Wavytone (Nick)
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The problem for you to consider right now is that by putting a tower on a hilltop that’s the most likely target which lightning will strike, but the impulse will travel along all the stuff you have connected via cabling. High chance of the electrics/electronics being damaged in various ways if it is hit - this is still problem with electronics in remote areas where an impulse would travel kilometres down a power line. Often the gear sort of works afterwards but is dodgy in some way.

While I doubt you’ll be at an outside BBQ or tin shed in a thunderstorm, the problem is the house and the electricals inside, if the hilltop is hit these will receive the impulse too.

Anyone in close proximity - or touching it - is at risk of a serious shock, possibly fatal - this is why you really shouldn’t use a wired telephone in a thunderstorm. A wireless phone is fine (though the base station may be fried).

In this respect I would suggest the hilltop setup is best left in glorious isolation not connected to anything at a distance.

The alternative is to install lightning protection - it does work BTW and is effective. Your problem will be finding someone to do it.
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Old 15-03-2019, 10:20 AM
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Thanks Nick.

You made the point:

" In this respect I would suggest the hilltop setup is best left in glorious isolation not connected to anything at a distance."

I agree but point out that I did say that this installation is isolated and 1 km away from my house. It is self-contained - stand-alone. It is on a hill because it is a wind turbine and height is king with those. So the issue for me and the one I thought I raised is the usefulness of multiple ground rods as a lightning defence.

Peter;
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Old 15-03-2019, 11:59 AM
Wavytone (Nick)
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Peter,

There's also a significant earthing issue - the ground at the top of the hill almost certainly isn't at the same potential as the ground in the electrical wiring in your house. It has two consequences.

Firstly there is a risk of a touch potential between the stuff earthed at the hill, if you are at the remote end (ie in the house); at 1km this could easily give you a shock.

The second is more invisible and a long-term issue. Connecting the two without an isolating transformer creates an earth loop and the result is electrolytic corrosion of whatever metal bits are stuck in the earth - starting with the earth connections and very often your plumbing. It may also corrode steel reinforcing in concrete (if you have a slab).

1 current of 1A per year equates to 1kg of metal dissolved so consider what that could do to weaken things or make pinholes in pipework.

One solution is to have all the components at the house which are connected to the hill double-insulated, and in such a way people in the house cannot come into contact with anything metallic wired to the hill. That's not so easy.

The proper solution is to use alternating current in that cable and isolate the hill from the house with an isolating transformer, so that the earth of the hill is separated from the earth at the house, and the secondary side of the transformer (active and neutral) supplying the house are also electrically isolated from the hill.

PS if you don't have an isolating transformer what you have currently is already hazardous and possibly in breach of the wiring rules.
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Old 15-03-2019, 01:49 PM
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Hi again Nick.

I have to thank you for the thought and effort you've put into these responses. And I have to apologise as well because I obviously did not make it clear that when I spoke about the hilltop installation being isolated and remote, I meant to say - and obviously should have said - there is no connection between the house and the hill. None, zip, nada. So we have at least eliminated that source of trouble/risk.

What are your thoughts about the efficacy of the half-dozen earthing poles I have on the turbine pole and the shed - the shed contains the battery bank and the inverter plus the charge controllers etc.

The earthing is via a bus-bar to which the inverter and battery bank negative poles are connected to the ground pole beside the shed.

The solar panels are also earthed and have their own ground pole. I forgot to mention that one - so that makes it 7 all up.

The turbine pole has 5 ground poles - one on the pole itself and one each on the 4 sets of guy wires. I had originally thought I might connect them all up into a sort of Faraday cage but by the time I got to that stage I was pretty sick of digging trenches.

Peter
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Old 16-03-2019, 02:04 PM
Wavytone (Nick)
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Thanks Peter - I'm familiar with LV installations in the railway where things are often hundreds of metres from the nearest distribution board.

Lightning rods work on the basis that the highest one provides a protection zone under it rather like a large umbrella. Lower ones close by are a bit pointless.
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Old 16-03-2019, 03:27 PM
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Quote:
Originally Posted by Wavytone View Post
Thanks Peter - I'm familiar with LV installations in the railway where things are often hundreds of metres from the nearest distribution board.

Lightning rods work on the basis that the highest one provides a protection zone under it rather like a large umbrella. Lower ones close by are a bit pointless.
So all those ground rods are next to useless as lightning protection but, I suppose alright for general electrical earthing. I remember reading some of Ben Franklin's thoughts on lightning and the high multi-pronged arrays he proposed.
I imagine I could construct a suitable bracket to support such a device above the height of the turbine
That might help.
Peter
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Old 16-03-2019, 04:54 PM
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Fascinating discussion. I had no idea grounding and distance could be such an issue, never even thought about electrolytic corrosion in those conditions. You learn something new everyday. One would think things scale up pretty easily, they obviously don't.
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Old 16-03-2019, 08:40 PM
Wavytone (Nick)
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Ha, well I look at as things scaling but perhaps in a different way.

The earth your house sits on is not a perfect conductor - when measuring an earth stake at the base of a power pole for example, if its in dry sandstone country the resistance may be as high as 50 ohms.

In an electrical fault where one phase shorts to the earth, the current can be high - just like a lightning bolt. the current flowing in the ground raises the local voltage - and because the current can fan out in all directions, the result is a radial voltage gradient. The voltage gradient can reach hundreds or thousands of volts per metre - enough that if you take a step, you will be electrocuted between your feet.

The same happens in a lightning strike too, the voltage gradient in the ground is huge. This is why people can be seriously injured if they were near a strike but not directly hit.

Last edited by Wavytone; 17-03-2019 at 12:56 PM.
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Old 17-03-2019, 08:24 AM
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I was on the phone and lightning hit the roof or somewhere close at the old place..I heard a very loud bang is all .I woke up on the floor with three dogs licking my face. We all went and sat on the bed terrified until the storm passed. As Nick said things dont work quiet right afterwards.
I was by myself for another ten days and had an unsatisfiable obsession to write..I dont know what I wrote but I did not seem to stop..I drained every pen and used every piece of paper and in the end was getting charcoal out of the fire to write on the floor.

But I am fine these days as anyone can see☺.

What should I do here?
The wind generator tower is maybe 50 meters from the house and is connected somehow to the house according to the electrical board. The lead from the tower goes to the back of a 240 vlt power point in the shed near the tower so I expect it comes to the house that way but how it charges I just dont know.

My thoughts are to strap some cable to the tower and drive a pipe into the ground as from memory there is nothing like that on it..
Also we dont use the land line...maybe dig up the line and get that away from the house.
If you saw my post in general chat re lightning damage you can see what happened to the pit.

Having had the experience with the phone I am fearful of lightning...when I sailed a mates boat down from Brisbane we could not make it into Balina before nightfall with the bar unpassable and had to stay at sea all night...well all around on the horizon was lightening and it was all I could do to keep it together...mast and lightning worried me sick ... I went 27 hours at the helm and put the experience as one of the most difficult times to stay calm...my mate had lost it hours earlier when the gale was blowing us to the rocks at Byron ..he had never sailed before (yet bought a sail boat) and it was all a bit too much for him.

I have been worrying about this wind tower all night.
Alex

Last edited by xelasnave; 17-03-2019 at 08:36 AM.
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Old 17-03-2019, 08:25 AM
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Quote:
Originally Posted by Wavytone View Post
this is still problem with electronics in remote areas where an impulse would travel kilometres down a power line. Often the gear sort of works afterwards but is dodgy in some way.
Does this mean houses in higher density residential areas are more protected? Safety in numbers / spreading the load? What kind of protection can be done against those impulses?
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Old 17-03-2019, 09:14 AM
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I looked and there is a small earth wire going to a half inch rod and that wire goes to the genny.
Alex
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Old 17-03-2019, 09:48 AM
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Quote:
Originally Posted by xelasnave View Post
I looked and there is a small earth wire going to a half inch rod and that wire goes to the genny.
Alex
Well, generators should be grounded as a general rule although it's one that most people overlook if the genny is being used occasionally and away from the house - i.e. camping and the like.

If yours is one of those generators that automatically switch on if there is a power failure, it most certainly should be grounded. And if it is just used for running the odd light or fridge in the house during a blackout, it should be grounded also. One way or the other, it sounds like yours is.

From what Nick has said here, merely putting in an earthing bar/rod does not do much against lightning though. IThose play more of a role in protection against electrocution. Have a quick Google around the subject of lightning protection and Benjamin Franklin and you'll get the drift.

There are lightning arrestors and suppressors that can be wired into your fusebox, I believe. I don't really know the difference between them though.

Peter
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Old 17-03-2019, 10:26 AM
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Sorry Peter I was talking about the wind genny. All the petrol gennys are grounded.
Alex
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Old 18-03-2019, 09:42 PM
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Anywhere there are aerial telephone wires there is risk from a lightning strike hitting the poles and wires.

I am told that in the country we should unplug modems etc in a lightning storm. Particularly in flat open country.

Surprisingly there are still many overhead telephone wires in Sydney and the Illawarra suburbs so no safety in numbers there.
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Old 19-03-2019, 12:44 AM
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I'm finding this thread is really focusing my attention on the issue of what devices I/we should be using to safely ground our remote installations - particularly those that have battery banks and inverters to power equipment.

There are fuses, relays, arrestors, supressors, and a whole parade of bits and Bob's that get mentioned. But which to use and what size/capacity etc is best for which part of the installation.

Getting in a sparkle to a remote site is expensive if not impossible. A degree of self help is inevitable. But apart from youTube where can you go for some guidance?
Peter
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Old 19-03-2019, 10:16 AM
Sunfish (Ray)
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Well apart from using the lightning tracker on BOM , and disconnecting the tower and all your modems etc when lightning is about, can some type of specialised fuse be added into the system?

I should ask my solar installer as I suppose this is a similar problem with a Solar panel where the frame is required to be fully isolated from the structure.

What stops the inverter electronics getting fried?

http://media.bom.gov.au/releases/371...ureau-website/
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Old 19-03-2019, 01:50 PM
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Hi Peter,

You might like to look at a standard such as IEC 61024-1-2, "Protection of structures against lightning".

http://www.zinoglobal.com/wp-content...1024-1-2-1.pdf

This is a vast topic but suffice to say unless a structure was designed
from the get-go to have best practice protection, any associated electrical
systems will always be vulnerable.

Broadly, there are what are termed "air termination networks" which are
connected to what are termed "down conductors". There are usually
multiple down conductors placed uniformly around the periphery of
a building.

Air termination networks are typically designed using either vertical or
horizontal conductors. It use to be thought that vertical pointed rods
were the best design for air termination conductors but in more
recent years studies have shown they are not as effective as they were
thought to be and so most modern air termination systems on larger buildings
use a horizontal mesh. For example a mesh size with 5m square
segments.

Owing to the very fast di/dt's, lightning doesn't always do what one
intuitively thinks electricity should do. For example, at such fast rise times
it will take the path of least impedance which often means the path of
least inductance rather than what you might measure with your
multimeter at DC as the path of least resistance.

For example, say one has diverted it through an air termination network
and the current path is starting to flow down one of the down conductors
toward the earth. If there is a nearby grounded structure, such as a pipe
or metal surface of a building, it will happily side flash across through air
via a path of lesser impedance. Side flashes such as these have been
known to start fires.
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Old 20-03-2019, 08:37 AM
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Hi Gary.

I'm a bit overawed by it all, to be honest. I understand (in a fashion) what you say about protecting structures with air-mesh and down-conducters. And this, of course, relates to substantial buildings and the like. Well enough. But there doesn't seem much I can sensibly hope to do to protect one 6 meter 50mm gal pipe sticking out of the ground with a little cheap chinese turbine on top. In my world, that is the issue I have to confront. It seems to me that the law of diminishing returns has well and truly kicked in.

Beyond what I have already done (and described several times in this and other threads), it becomes more a case of "fingers crossed and hope for the best" it seems to me.

Peter
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