Earthing and the radio Amateur
Just received the latest Radcom and I read that there is a lot of discussion regarding earthing and what you have to look out regarding the electricity supply to your home.
There is a lot of confusion as the do`s and the don'ts with different type of supply that you may have.
Now all homes, here in the UK in any case can have a different supply set up and here I will try to summarise.
There are generally three distinct supply types normal to the UK.
1 A conventional supply with separate Live Neutral and Earth , the supply type known is TNS and this is what would have been supplied to a lot of houses pre 1970`s
2 A PME supply , where we have a Live and also a neutral /earth combined. The distinction here is the neutral and earth are combined in the incoming supply cable, this then splits just as it connects to your consumers unit. The PME abbreviation means "protective multiple earthing" It is also known in the industry as TNC-S and would have been supplied to most houses from 1970`s onward.
3 A Supply known in the industry as TT, here there is no earth supplied by the electricity network provider, the household has its own independant earth, this type of supply has been and still is provided but normally the supply for this type is from an overhead network.
All supply types are fine and you would never know which type you have until..Something Goes Wrong !
If you have a type 1 supply above you will have the least problems with network issues and household faults.
If you have a type 2 supply above you can have some real problems if there is a network fault affecting in particular the network neutral/earth conductor. In this type of fault any grounded type of aerial will become your and possibly your neighbours neutral return and cause all sorts of problems !.
If you have a type 3 supply above you too can have all sorts of issues if you have a grounded type of aerial, again if you lose your neutral , or have a live to earth fault and a poor earth then everything thats plugged in can have its exposed metalwork go to phase potential.
So what can you do to help yourself ?
First find out what type of supply you have and if you are at risk.(faults are rare , but do happen)
Ungrounded aerials like dipoles help a lot as there is no path to earth.(beware of your mast..it may be grounded)
If you have ground radials either elevate them off the ground or use counterpoises of the ground. You could always completely insulate them(stops corrosion anyway).
Some supply types like the TT (type 3 above)system can be improved if you make sure you have a decent earth with low values under 1 ohm.
The RSGB has a new leaflet on PME that you can download which I have read and can confirm is good advice.
As always get professional advice or if you don't know what you're doing then ask someone who really does know what they are talking about . Dont listen to the self made do gooders , they will not be paying for any issues !
And yes I do work in the Electricity Industry with practical experience :)
There is a lot of confusion as the do`s and the don'ts with different type of supply that you may have.
Now all homes, here in the UK in any case can have a different supply set up and here I will try to summarise.
There are generally three distinct supply types normal to the UK.
1 A conventional supply with separate Live Neutral and Earth , the supply type known is TNS and this is what would have been supplied to a lot of houses pre 1970`s
2 A PME supply , where we have a Live and also a neutral /earth combined. The distinction here is the neutral and earth are combined in the incoming supply cable, this then splits just as it connects to your consumers unit. The PME abbreviation means "protective multiple earthing" It is also known in the industry as TNC-S and would have been supplied to most houses from 1970`s onward.
3 A Supply known in the industry as TT, here there is no earth supplied by the electricity network provider, the household has its own independant earth, this type of supply has been and still is provided but normally the supply for this type is from an overhead network.
All supply types are fine and you would never know which type you have until..Something Goes Wrong !
If you have a type 1 supply above you will have the least problems with network issues and household faults.
If you have a type 2 supply above you can have some real problems if there is a network fault affecting in particular the network neutral/earth conductor. In this type of fault any grounded type of aerial will become your and possibly your neighbours neutral return and cause all sorts of problems !.
If you have a type 3 supply above you too can have all sorts of issues if you have a grounded type of aerial, again if you lose your neutral , or have a live to earth fault and a poor earth then everything thats plugged in can have its exposed metalwork go to phase potential.
So what can you do to help yourself ?
First find out what type of supply you have and if you are at risk.(faults are rare , but do happen)
Ungrounded aerials like dipoles help a lot as there is no path to earth.(beware of your mast..it may be grounded)
If you have ground radials either elevate them off the ground or use counterpoises of the ground. You could always completely insulate them(stops corrosion anyway).
Some supply types like the TT (type 3 above)system can be improved if you make sure you have a decent earth with low values under 1 ohm.
The RSGB has a new leaflet on PME that you can download which I have read and can confirm is good advice.
As always get professional advice or if you don't know what you're doing then ask someone who really does know what they are talking about . Dont listen to the self made do gooders , they will not be paying for any issues !
And yes I do work in the Electricity Industry with practical experience :)
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