The earth is made up of materials that are electrically conductive. A fault current will flow to 'earth' through the live conductor, provided it is earthed. This is to prevent a potentially live conductor from rising above the safe level. All exposed metal parts of an electrical installation or electrical appliance must be earthed.
What are the Objectives of Earthing?
Provide an alternative path for the fault current to flow so that it will not endanger the user
Ensure that all exposed conductive parts do not reach a dangerous potential and maintain the voltage at any part of an electrical system at a known value so as to prevent over current or excessive voltage on the appliances or equipment.
What are the qualities of good Earthing System?
Must be of low electrical resistance
Must be of good corrosion resistance
Must be able to dissipate high fault current repeatedly
What are the uses of the earth?
The earth is to provide an alternative path for the fault current to follow. This is to protect consumers from danger.
What type of tools should I use when I do not know if the load is live or neutral?
Use a test-pen, it is able to detect whether the load has any current
What are the causes of over current?
Short Circuit -Two or more live conductors touching each other
Overload -Adding loads greater than that of the rated value
Earth fault -A phase conductor touching productive conductor either directly or in-directly