Earthing Systems

Here is some information related to earthing systems.

Before reading on, go on the link below and see if you can identify all 10 items that make up a circuit. Pause before 10 seconds

Circuit Arrangement

There are 3 main types of earthing system based in the UK. They are:

• TT System
• TNS System
• TNCS

TT Systems

Generally found in rural areas of the UK. This system is likely to be used where the electricity company installation is fed from overhead cables, where no earth terminal is supplied. With this type of system the earth electrode on the consumer side is used to connecting the CPC's to earth. With this type of system it is difficult to obtain an effective earth, therefore an RCD should be installed 

It has a high earth loop impedance due to the fact that that any fault currents in the installation are returned back through the ground. Below is a video of how this is done.

TN-S Systems

This type of system is used where the electricity company's installation is fed from underground cables. In this type of system the earth terminal is connected by the supply authority by their protective conductor through the metal sheath/armour of the underground cable network, which provides a continuous path back to the start point of the supply transformer, which is connected to earth