Mesh Potatoes Lightning Protection

[Carlos Rey-Moreno]

Good afternoon,

We're about to deploy a network fo 8 - 10 nodes in a community without electricity where pieces of metal are scarce bu lightning storms are very common. So, I was wondering whether any of you has any experience with lightnings and Mesh Potatoes or solar installations. That is, if they are enough as for attracting lightnings and protection needs to be provided.

In case they are, I would be very thankful if you could share the approach you've followed for installing the lightning arrestor and grounding wells as for protecting not only the devices but the surrounding households. I am worried that by installing the arrestor we're actually attracting the lightnings and that the induced fields of the impact can damage surrounding properties or individuals.

Thanks you very much in advance.

Carlos

[Elektra]

Hello Carlos -

I am not a proper lightning protection engineer. Rather than writing about a subject that I only have very limited expertise, I'd like to point you to a few online resources:

http://en.wikipedia.org/wiki/Lightning_rod
http://www.lightningsafety.com/nlsi_lhm/lpts.html

Here a quote from the forementioned site:

"The phenomenology of lightning strikes to earth, as presently understood, follows an approximate behavior:

1. The downward Leaders from a thundercloud pulse towards earth seeking out active electrical ground targets.

2. Ground-based objects (fences, trees, blades of grass, corners of buildings, people, lightning rods, etc., etc.) emit varying degrees of electric activity during this event. Upward Streamers are launched from some of these objects. A few tens of meters off the ground, a "collection zone" is established according to the intensified local electrical field.

3. Some Leader(s) likely will connect with some Streamer(s). Then, the "switch" is closed and the current flows. We see lightning."


Any object that you put in a exposed position increases the likelyhood of a lightning strike, even more so if it is conductive and connected to a electric system with long wires leading to or close to the ground.

A Mesh-Potato or Solar system will never survive a direct "hit". In order to protect the installation, the MP or the solar system should not be the highest conducting object in close proximity. If there is a lightning rod, the system should be lower than the lightning rod and not attached to it, of course. A well known safety precaution should always be observed: Don't touch or use any electrical installation during a thunderstorm.

By putting any installation on a roof (TV antenna, wire antenna, pole with WiFi router) you are increasing the risk of originating a Streamer which finds a Leader, according to lightning theory. However I can not quantify how much the risk increases if you put a broomstick with a MP attached to it on the roof of a house. Any object above the ground can originate a Streamer.

With regards to safety any house where people stay during a thunderstorm should have proper lightning protection. But I have seen many houses that don't have lightning arrestors installed and people live with the risk. We have often used existing TV antenna poles to mount MPs, so there is no change in the risk that people were already willing to accept (or simply not considering, for that matter).

My current home is constructed like a Faraday cage, so I feel very safe and comfortable during a thunderstorm ;)

Cheers,
Elektra

[Andrés Leopoldo Pacheco Sanfuentes]

..which begs the question of whether adding chicken wire to the mix of
bricks (adobe, cement, clay..) would make it possible to build houses
as Faraday cages by default...:-) (a little off-topic, but since we're
talking about lightning strikes and people's oblivion to the risks
involved in not being protected, especially in many tropical places,
where lightning is a common occurrence..)

Best Regards | Cordiales Saludos | Grato,

Andrés L. Pacheco Sanfuentes
<al...@acm.org>
+1 (817) 271-9619
SITA - Socio-Técnica, Informática y Telecomunicaciones Aplicadas
una división de Mayarí Services
Keller, TX, USA
Skype: alps-dfwccs
Gtalk & Yahoo Messenger: alps6085

"The internet is less of a technology than it is a philosophy of ‘the
effectiveness of decentralized, bottom-up innovation"
Joi Ito, the director of MIT MediaLab

"Creo en los poderes creadores del pueblo" (same thing)
Aquiles Nazoa, Venezuelan Artist - Writer, Journalist, Poet and Humorist

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[Carlos Rey-Moreno]

Thank you very much for your answer and for the links, Elektra. Thanks
to them and some conversations with some of my former workmates in EHAS
I have a better idea now of what to consider for the lightning
protection system, although I still need to study" a bit more about the
lighning theory and visit the area again to be sure of whether it's need
or not.

Best,

Carlos