Earthing Systems

[Baker1988]

There seems to be a bit of confusion about earthing systems so thought i would post this for any one who wants to know.

The earthing system are classified by the letters that they use.

first letter (relationship between supply and earth)
T ) the supply is connected directly to earth at one or more points (usually at the generator or transformer)
I ) the supply is isolated from earth or 1 point is connected to earth through a high impedance

Second letter (relationship between earth and the exposed conductive parts of the installation)
N ) direct electrical connection of the exposed conductive parts to the earthed point of the supply(earth point in ac is usually the neutral point)
T ) direct electrical connection of the exposed conductive parts to earth independent of the earthing of any part of the supply

any other letters(the arrangement of neutral and the protective conductors)
C ) the neutral and protective functions are combined in a single conductor (the PEN conductor)
S ) the protective function provided by a conductor separate from the neutral conductor or from the earthed phase conductor(usually separate in the installation not the supply)

There is 3 main earthing systems used in the uk there is TN-C-S TN-S and TT

TN-C-S supply uses a common conductor for both the neutral and earth known as protective earthed neutral (PEN) or combined neutral and earth (CNE) conductor, PEN is earthed at many points on the supply side known as protective multiple earth (PEN), basically the supply system is TN-C and the consumer installation is TN-S so this makes a TN-C-S

these are TN-C-S

TN-S this is probily the most commonly used earthing system in the uk (but TN-C-S is slowly working its way up the board) the earth connection is usually through the sheath or armorings of the main incoming swa cable and then by a separate conductor through out the installation impedance is

these are TN-S systems

TT system this system is when the installation has not been provided with a earth terminal by the supply company so you have to put a earth spike into the soil and make your own earth path this is most commonly used in rural areas but i have seen this system in a few of the houses that i have been in

TT system

 

[Paul.M]

Ok so what is earth system then?



Just thought I'd throw a curve ball at you mate.

Ps good thread.

 

[Baker1988]

Ok so what is earth system then?

View attachment 17395

Just thought I'd throw a curve ball at you mate.

Ps good thread.

not 100 percent sure to be honest i would say its a TN-S but cant really see the pic properly haha

 

[Paul.M]

not 100 percent sure to be honest i would say its a TN-S but cant really see the pic properly haha

Load up the picture and look at it full screen and then tell me what you think???

You may come across this once in a blue moon but it is worth knowing and the reason why it is like this.

 

[Baker1988]

Load up the picture and look at it full screen and then tell me what you think???

You may come across this once in a blue moon but it is worth knowing and the reason why it is like this.

the pixel is only low so it just distorts when i look at it full or try and zoom in but to be honest it looks like it is a tn-s and a tn-c-s it looks like the main incomer has a bonding conductor attached like a tn-s then from the isolator to the meter it looks like tn-cs

 

[Paul.M]

the pixel is only low so it just distorts when i look at it full or try and zoom in but to be honest it looks like it is a tn-s and a tn-c-s it looks like the main incomer has a bonding conductor attached like a tn-s then from the isolator to the meter it looks like tn-cs

Yes you are correct, its both. Reason being is that the DNO were changing all the houses on the street to PME and did the connections in the homes first (of course) then the sub station so in the mean time each house had both. That was fun testing it lol. I had to put down a Ze1 and a Ze2 for the first ever time.