? ? ? Well you certainly all know my preoccupations regarding Health & Safety - This time I tip my cap to all of you. We certainly need guidance on all aspects of earth safety. Well done to Ian for making us aware of the subject & thanks to Trevor & Geoff for making sure that this gets the priority it deserves as a talk / lecture.
? ?
? ? Ian G4UAQ.
? ( P.S. - I hope you find this colour easier on the eye Geoff ? ).
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On Wed, Aug 1, 2012 at 8:23 AM, Trevor Collins
<trev@...> wrote:
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Hi All,
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This is a very important and very misunderstood subject which needs to be given very good coverage in great detail.
Unfortunately it is also a subject that is hard for the un initiated to get to grips with.? It has become clear to me over the past years that as the editions of the regulations roll by and each one has a different story to tell, it becomes harder and harder to find anyone who really understands this subject. For Bruce:? I have somewhere a copy of CON SP1 which is the Basis of all of this work. I feel that we need to formulate a presentation that can be used as a basis for a Rad Comm Article and can be included in the RAE Syllabus as an essential part of the training.
Trevor
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----- Original Message -----
From: ian hope
Sent: 07/31/12 07:38 PM
To: g3trf@...
Subject: RE: [g3trf] rf earthing and pme supplies
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hi dave, you've hit the nail on head
it is about correctly sized cables etc and your right the ultimate would be a TT supply to your shack
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----- Original Message -----
From: Dave Bruce
Sent: 07/31/12 07:30 PM
To: g3trf@...
Subject: RE: [g3trf] rf earthing and pme supplies
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Ian,
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I will unlikely be able to make your talk
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But here¡¯s my take on the subject
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The hazard ?is not related to the RF earth but to exposed metal systems such as masts and towers that are connected to the mains earthing system via the screens of the coax cables.
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If the bonding is incorrect or inadequately sized and a supply network neutral fault occurs? the screens can end up carrying the neutral current of a number of network customers.
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The other issue is related to touch voltages that can exist external to the equipotential zone under fault conditions.
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An RCD offers no protection in the above scenarios¡.the answer is to ensure that bonding is correct and adequately sized.
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Or better still for ultimate safety don¡¯t use the PME earth terminal and make your system in to a TT system with? a 30mA RCD with measures to reduce touch potentials outside to less than 25V.
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73 Dave
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From: g3trf@... [mailto:g3trf@...] On Behalf Of ian hope
Sent: 31 July 2012 18:39
To: g3trf@...
Subject: [g3trf] rf earthing and pme supplies
?
?
Hi all
RF earthing with a pme supply.
This has come up as a topic several times at the club, mainly due to it's inclusion in the exam syalbus.
I have Today after speaking to the IET who write the 17th Edition wiring regulations got a definative answer to how a rf earth system should be installed if you have a pme supply to your house.
With Trevors help I now propose one evening to do a short talk on this.
Anyone suggest a evening?
Ian
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