Earthing Systems
In electricity terms, earthing is connecting a conductive element to the ground via a conductive path.

Protective Earthing
Protective earhing (RA) is earthing of metal parts -that do not carry voltage under normal operation but may carry voltage due to a fault- in order to protect people or other living things against hazardous touch or step voltage.
In a low resistance protective earthing, a fault voltage is fed through the faulty circuit during the fault, therefore enabling the breakers to
instantly break the circuit and therefore cut the energy on the faulty circuit.

Operational and Functional Earthing
Operational Earthing (RB) is the earthing of the voltage of active parts of operational devices of an electrical facility that are under voltage
against earth in attempt to keep at a specific value (e.g. star point earthing)
Functional Earthing (RF) is earthing of a communication facility or an operational device in order to resume the desired function.