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Proven Energy tower local earth
by Alexei Vodopianov at 2009-06-25 15:28:37 (Ask an Expert)
I would like to install the Proven 6 at home in Cyprus.If some one knows
how to earth the tower.I ve heard the Proven towers have a earth point.I also know lot of towers connected to the earth rod with 16 sq.mm cable.Is ity thesame with 15 m Proven tower?Any ideas will be much appriciated.
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AVV

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AVV

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Proven Energy tower local earth Alexei Vodopianov - 2009-06-25 15:28:37
Re: Proven Energy tower local earth BigSkeff - 2009-06-26 03:32:20
Hi Alexei,

There are a set of photos on the bigskeff.com website that show us preparing our foundations and THIS PHOTO shows the 2.4M earth rod that was driven into the ground beside the pipe where the cable emerges. It has a bit of green tape on its top. It is inside the tower when erected and so can't be seen.

The earth rod came in 2 parts and screws together, it was about 12mm diameter with a clamp on top to fix the earth wire to.

There is also a set of photos showing the installation. I hope they might make the whole process a bit easier to understand.

Give me a shout if you need further info.
Good luck with your project.

James
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Planet 'B' presumed nonexistent.

Re: Proven Energy tower local earth Alexei Vodopianov - 2009-06-26 15:56:52
Dear James
Thank you very much for allowing me to look at your photos.The whole process has become more and less clear for me.
Also thanks for giving me a chance to ask you more questions in case I will be stuck on something.
Take care
Regards
Alexei

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AVV
Re: Proven Energy tower local earth Bryan Rendall - 2009-07-09 18:50:02
Unfortunately, there is no one size fits all for earthing. The 2 main factors to consider are;

1. The regulations (or codes) in your locality or country

2. The soil resistivity at the turbine location.

In the UK, the main reference standard is BSEN 62305 (formerly BS6651) - "Protection Against Lightning" and requires that the local earth is 10 ohms or less. The resistance may be different in other countries.

The soil resistivity varies widely depending on moisture content and soil composition. There are 2 main ways to ensure you end up with an earth electrode of the target resistance or less - Firstly, you can measure the soil resistivity at the target depth, and calculate the amount of copper you need to achieve that final resistance, or, you can put some copper in the ground, measure the resistance of the copper to earth, and if too high, keep adding more copper till the total resistance comes down to target.

If you have too high a resistance, caused either my insufficient conductor in the ground, or too high soil resistivity, then if your turbine gets hit by lightning, the lightning may well travel down the cable to your house rather than dissipate safely into the ground.
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Bryan Rendall

Re: Proven Energy tower local earth Alexei Vodopianov - 2009-07-12 21:39:16
Thank you very much Bryan for your advice.
I actually have used a method of puting some copper in the ground and measuring the resistance of the copper to earth.I am thinking to use 12 mm diameter earth rod.
Not sure but some people adviced to use also lightening arrestors.
I thought the rod together with right soil resistivity will do the job.
What you think?
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AVV
Re: Proven Energy tower local earth Bryan Rendall - 2009-07-13 18:29:12
Alexei,

No problem to have both earth and arrestors - Compared to an inverter, arrestors are cheap. Most good inverters have some form of arrestors on the input, but if these get taken out, the inverter will probably shutdown till you get the MOV's replaced. However, lightning is odd stuff and can sometimes defeat the internal protection offered by an MOV by jumping elsewhere.

Here in Orkney, Scotland, installations in schools require additional arrestors to be fitted where the turbine cable enters the school, so we fit them there.

Bear in mind that the arrestor also needs a good earth - It cannot sink a lightning impulse into fresh air! So it needs to have a good, low resistance connection to earth, otherwise it will be worthless.

12mm rod is fairly typical (5/8" is common in UK) so you cannot predict the final resistance from earth rod diameter alone. The soil resistivity on its own has a much greater effect! I remember about 10 years ago, trying to get a good earth for a 1.3 MW turbine up here in Orkney on the infamous Burgar Hill. We drove down 5/8" rods coupled together to a depth of 9 or 10 feet below the bottom of the foundation using a power driver (the rock was too hard for hand driving!), which, by the time the foundation was backfilled, would have put the bottom of the rods about 17 feet down. We managed to get 3 sets of rods down between cracks in the rock, hoping that they would find something moist down there. When we coupled the 3 sets together and tested the resulting resiatance we had over 150 ohms! Hopeless, when our target was under 10 ohms!

So we abandoned those and installed what are now more conventional horizontal electrodes, and I don't think we have driven an earth rod since! Everything we do now, whether individual small 6 kW turbines, or windfarms, uses horizontal electrodes. Takes a lot more copper, but gives more predictable results.

Good luck with the "drive and test" method! If you have access to an earth tester, and it is capable of testing soil resistivity (4 terminal), you may want to try that first to see if 1 are 2 rods are going to give anything like the target you are looking for. If not, then bashing copper into the ground is a bit of a waste of time (and copper!)
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Bryan Rendall

Re: Proven Energy tower local earth Alexei Vodopianov - 2009-07-15 14:37:36
Thanks Bryan.Your advice is a very important.We have a lot of lightening in winter time.I thought I can get away with not meassuring the soil resistance.After your advice and experience I rather meassure the resistance.
Hope it won t be very expencive to find some one who does that.
Thanks again
Regards
Alexei

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AVV

Re: Proven Energy tower local earth Alexei Vodopianov - 2009-07-15 14:39:40
Sorry I ment the soil resistivity
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AVV
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