Re: Sistema de prevenção contra raios.
Citação:
Postado originalmente por
rubem
Sem ligação com o solo o risco é justamente a torre ficar com a polarização que o vento trouxer, diferente da do solo, aí o centelhamento vai ocorrer na fonte chaveada mais próxima, entre o negativo da saída DC (Ligado até o negativo da antena, as vezes preso no metal da torre) e o neutro ou alguma fase da tomada, porque o neutro é aterrado em algum ponto e a fase apesar de não ser aterrada é ligada ao solo pelo enrolamento grosso de um transformador, o caminho da descarga acaba sendo circular pelo meio de algum CI da fonte (Na construção interna tem trilhas a 0,2mm uma da outra quando muito).
Rubem, eu te admiro como uma das pessoas que mais tem conhecimento aqui no forum, uma pessoa que tem um conhecimento técnico profundo em diferentes áreas, mas o pessoal da MTO da Turquia está dizendo que não há necessidade disso que as cargas que se acumulam na torrem se acumulam e se dissipam pelos dissipadores independente da torre ser pintada ou não, ainda cita o exemplo de um clientes deles na Africa, o qual as torres são todas pintadas e nos ultimos 10 anos nenhuma torre foi mais atingida e nenhuma precisou de um condutor adicional. Eles inclusive aconselham a retirar esse condutor. Não sei se você lê em inglês, caso queira traduzo a mensagem deles a qual comentarei abaixo em inglês.
Citação:
Postado originalmente por
ErdemOzkan
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Dear Rau,
Thank you for your feedback. Regarding the pricing issue, I have nothing to say, you should discuss it with Silvia who is responsible for marketing and pricing details. Once again, if you can get in touch with her, I believe that she may find a middle way.
Regarding the grounding and conductor issue. I understand the concern. 5 ohm or less is a regulation for the site itself, not for EvoDis System. It is a regulation for all telecom sites to have a proper grounding system which is in a equapotential position, which means all groundings (system, tower, etc) should be bonded to eachother. This is not for EvoDis System, but to avoid any surges from the main power.
EvoDis System does not require a conductor cable even if the tower is painted or not. EvoDis Units dissipate whatever ground charge reaches to them and there is no need for a "more conductive path" to achieve this. Conductor cable is for lightning arrester devices because when the current is caught, it should be sent to ground through a conductive path which is the conductor cable. However, once again, it doesn't work for metal towers because even if the tower is painted or not, even if the cable is isolated or not, lightning current prefers larger surfaces to flow, not a tiny cable. Even if it start to run through the cable for a few meters on the top, it jumps on the tower leg because it is a faster and easier path for the current to flow.
I don't know why other "dissipater" products require a conductor cable, please ask to their manufacturers for a logical answer. And this is why I keep saying that this is not a solution to be gambling on, it should be taken serious and should be applied by professionals. I have seen the links above for "self-made" dissipaters. If anyone wants to take a chance, be my guest. But when the tower gets struck again, do not say that "dissipaters don't work" because it is not the dissipater, it is the non-calculated amateur application to blame.
We have installed EvoDis Units on hundreds of painted towers in Africa where lightning is nothing like anywhere else all around the world, and no more lightning strikes on the towers seen for the past 10+ years. Paint on the tower is not a fact to avoid the charges to climb up on the tower and reach to EvoDis Units. This is why, we never apply and additional conductor and the existing conductor is not necessary anymore. But the lightning rod must be taken down because it creates a strike point and affects the performance of EvoDis System.
Regards,
Erdem
Right, I got it!
There is two dissipation system manufacturers that claims that the dissipators need to be grounded. I'm gonna ask them why.
Rubem is our forum coleague and has a high knowledge in many subjects and helps people a lot here. He stated that if you don't directly ground the dissipator, there is a risk for it to get to the same polarity the wind brings around the tower, which is different from the polarity of the soil, the earth as he said above in one of his messages. Is it true?
About the grounding system of one of our towers, yes we have a grounding system for the electronics and the house itself and it is equipotencial with the power company neutral ground, but it is not equipotencial with the lightning rod/arrester ground, they are separated grounds due tue difficulties we had to run a copper cable to where the power company ground rods are located at. In order to do that, whe would have to brake many things, to dig a 30 meters long ditch in the terrain where there is a house by the side, brake all the floor and there is tiles in part of the path and the cable would have be as long as 30 meters until it arrives our main ground rods, where the power meter is located, so... We have Surge Protectors installed in all signal and electrical cables...
If we decide to buy your product we will follow your instructions. I just wanna understand what other people are talking about, right?
Thanks!
Re: Sistema de prevenção contra raios.
Rubem, eu sinceramente não sei o que é mais prudente fazer, o pessoal da MTO diz pra não aterrar o dissipador deles, já você e outras dizem pra aterrar. Essa empresa no Brasil, parece trabalhar com esse tipo de dissipadores, e tb fala pra aterrar:
https://www.idealengenharia.com.br/s...o-de-raios_p_7