Need Help: Earthing System in explosive areas

Thread Starter


Joined Jul 10, 2009
Hello, pardon my sudden appearance; I am new to this forum.

I would just like to know the best explanation on what and why only a certain earthing system is used in petrol kiosks.

My current understanding is as follows:
TN-C combines earth and neutral wires into one in a closed building
TN-S has no combined earth-neutral wires at any point, each earth and neutral wire exists and serves their respective purpose. They are, however, earthed together at the generator.
TN-C-S also has seperate wires, but the neutral and earth wire is connected with each other somewhere outside of the closed building. They are also earthed at many points.
TT system on the other hand, has no earth point given. Earthing is done locally around the closed building; independant of any connection to the generator.
I have also got to know that the use of TN-C-S is inadvisable in situations such as petrol stations, where there is a combination of lots of buried metalwork and explosive gases.
But from here my question is, is it then TN-S system the best to be used? If it is, what extra measures are taken to earth unwanted currents if in case that the earth wire is faulty? (Please help explain for the TN-C system as well)
Also, what are the risks involved if we have cables earthed nearby a petrol station? Won't the buried metalwork itself act as the earth conductor?

I am also very new to earthing, I hope I can get this cleared and I would like to thank anyone who wouldn't mind giving me an aid.

Thread Starter


Joined Jul 10, 2009
Hey guys, I know that i shudnt b doing this, but can anyone help me?


Joined Nov 9, 2007
It's a question of Risk Assesment.

In normal situations the biggest risk is the possibility of a metal part becoming live and directly killing or injuring someone.

Earthing introduces a short term (large) current to provide disconnection and thus help prevent this.

In a flammable gasses situation the biggest risk is the risk of an explosion caused by an(even a small) electrical discharge or fault current killing or injuring many people.