Lightning conductor for ametuer radio antenna mast - electrician says regular PVC sheated yellow green wire is ok from mast to earth rod

mapj1:

well, there are 2 questiions here -

1)is taking the PME earth outside on the coax an issue - probably not to the radio user, there are PME earthed lamp posts and bus shelter lights up and down the land, and each and every morning we are not sweeping up a huge pile of dead bodies because of it.

There is a research paper that looks at the risk of pme earth for car charging which may give some  ideas I will try and link to in a minute.

try this link


If you are in control of who is in the garden, then the risk of a shock between bare feet on the grass an a  hand on the mast may be further reduced . Or paint it.



2) lightning - from where you are in the country, we can look at the lightning map, an see the chance of a strike per square km in any one  year, (see map on page 5 of this article (based on NI but the map is whole of UK )) and then work out the odds of your mast being struck by converting the vertical height to a capture area.

Thanks for the article, I did go through a similar discussion about Open PEN and PME earth risks for EV charging as I have the charger for my Tesla outdoors. We went for an Open PEN detection device in addition to a Schnider Type B EV RCBO with an isolator to provide the multiple points of safety before using PME Earth on that. I believe we used this device from a quick google search - https://library.e.abb.com/public/08cefc79cc241acec125713f0033df9f/1SDC210015D0201.pdf?x-sign=ZFxYXI8m02t6tkgZa8IUsSY5LN3RqThEat97kcLHH61nrn71lr676pH9hdRxN08Q


The antenna is mounted just below the first floor roof so there is zero touch risk, only the coax comes down from it.


Very concerned about safety considering I have 0 DIY skills....

John Peckham:

Earthing of a 33kV primary sub is outside my skill set. Is this an overhead or underground 33kV supply?


In any case driving in an earth electrode near the 33kV transformer earth is likely to be dangerous as your earth electrode will be  connected to the HV earth via the soil.  In the event of a fault to earth on the HV a high voltage will appear on your earthing system, the voltage will depend if this is a hot or cold site. 


You do not need the earth for propagation as you aerial is a near balanced impedance on the end of the co-ax.  Lightning protection, if required is a different matter. The usual method is to have a spark gap or surge protection outside near the ground connected to an earth electrode which is back to the question of the earth electrode. 


I did a CPD on line course this week and on one of the slides shown was LPS protection for a roof mounted satellite disk. That was a a rod set off parallel to the disk terminating higher than the disk, the off set support was 2, about 2m long, GRP rods. 

 

Hi John,


Everything is underground (I believe it is 33kv because on the map it says HV and the last time the DNO was doing some work I looked at what they were digging up and there were almost 15 cables coming out and atleast 1 or 2 of them was as wide as my wrist.


I have another metal fence (metal unknown) running at the rear of my property that is almost 1.5 times the height of my antenna and several trees that are twice the height of the property - does that further reduce my risk of attracting lightning?


Given the comments considering the HV earth mat right next to my house I might just skip the idea of a TT island or grounding the antenna mast altogether.....

For some reason the Earth Mat is under my property ! I have no idea how they managed to do that or if it is even accurate.

I believe it is 33kv because on the map it says HV

FaeLLe:

. . . Everything is underground (I believe it is 33kv because on the map it says HV and the last time the DNO was doing some work I looked at what they were digging up and there were almost 15 cables coming out and atleast 1 or 2 of them was as wide as my wrist. . . 

The size of the cable indicates it’s current carrying ability, not its voltage. The voltage should be written on the substation door / gate along with its name. I very much doubt it 33kV. It is likely to be 11kV, but depending on where you live could be 22kV. 


Regards,


Alan. 

AJJewsbury:

For some reason the Earth Mat is under my property ! I have no idea how they managed to do that or if it is even accurate.

If it is on your land, you might be due some payments from the DNO. My Dad used to have a couple of HV poles and a transformer in his garden and got a few quid a year on account that it served next door as well as him. He missed out on the payments for several years when he first moved in as apparently they payments don't transfer automatically when the land changes hands, so each new owner has to make a specific claim. I'm sure the money wouldn't be significant to you, but the process of making a claim might be an easy way of getting the DNO to establish exactly what's on your land and what isn't. I know from experience that such services maps are not always accurate - I know of a house whose sale was delayed because the water authorities map showed a main sewer crossing the front garden - in reality their database was missing one inspection chamber on the bend of the road outside and the computer had just joined the dots and so shown the sewer as a straight line between two distant man holes, cutting the corner of the road.

 

   - Andy.

 

But then they will want to add leeway rights on the title deed and any further development on that plot of land will need their approval.

If I left it in-situ in the future if I wanted to rebuild over it I could just serve them notice and proceed to dig out whatever is there (will allow a 60 day time or whatever for rectification).


Apparently the DNO offered the land to the previous owners for sale but they did not take it up, would love to buy it off them just do not know whom to contact :)