Re: Types of Earthing (as per IEC Standards)

Home Electrical Engineering Forum General Discussion Types of Earthing (as per IEC Standards) Re: Types of Earthing (as per IEC Standards)

Spir Georges GHALI

Dear ;

Refer to this Topic, I would mention to the following points :


– About “ TN-C ” :

The following remark should be also mentioned :

– If the supply of a load is “ 3Ph + N ” and we will use only “ 1 cable of PEN ” between the network and that load, the connection of PEN should be done as follow “ the PEN cable should be firstly connected to the earth point at Load, then to the neutral point ”.


– About “ TN-C-S ” :

It’s mentioned that “ Usually, the combined PEN conductor is used near the source of the system ”, but it’s better to say :

1- For the big networks where the installed power is big or too big, we use TN-C at the 1st and maybe also at the 2nd levels of the network, then we use TN-S.

2- By this way we can decrease the installation’s costs for these 2 levels.

3- We can’t never ever use firstly “ TN-S ” then “ TN-C ”.


– About “ TT ” :

Also, it’s better to add :

– As we can use many independent Earthing points at consumers side only, this system is approximately used all around the world in LV Distribution Networks to supply Housings and buildings.


– About “ IT ” :

We should also mention to the following :

1- If the connection of the transformer is “ ∆ ” ( no neutral point ) we can connect one phase to earth via high impedance.

2- Two main types of “ IT ” that are :

     – IT with distributed Neutral

     – IT without distributed Neutral.

3- With this Earthing system, It’s absolutely necessary to use special devices called “ Insulation Monitoring Devices ” to detect and indicate any insulation fault .