Earthing can classified in two ways:
- System earthing;
- Equipment earthing.
System earthing is essential to the proper operation of the system, whereas equipment earthing concerns the safety of personnel and plant.
A key function of equipment earthing is to provide a controlled method to prevent the build up of static electricity, thus reducing the risk of electrical discharge in potentially hazardous environments.
Generally, a resistance to earth of less than 106 Ω.m will ensure safe dissipation of static electricity in all situations.