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

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.....

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.....