With proper grounding system,people are protected from electrical shock and also to ensure residual current devices (RCD) or Ground Fault device (GFCI) activate properly.
Intentional grounding is required for the safe operation of electrical systems and equipment. Unintentional or accidental grounding is considered a fault in electrical wiring systems or circuits.
What is a grounding? Basic definition is the intentional connection of a current carrying conductor to the earth. For AC premises wiring systems in buildings and similar structures, this ground connection is made on the line side of the service equipment and the supply source, such as a utility transformer.
Why we must grounding for all electrical installation and equipment? The main reasons for grounding are:
1) To limit the voltage surges caused by lightning, utility system operations, or accidental contact with higher-voltage lines.
2) To provide a ground reference that stabilizes the voltage under normal operating conditions.
3) To facilitate the operation of current leakage or ground fault devices such as circuit breakers, fuses, and relays under ground-fault conditions.
What is a Bonding? For basic understanding,bonding is the permanent joining together of metal parts that aren’t intended to carry current during normal operation, which creates an electrically conductive path that can safely carry current under ground-fault conditions.
Why a bonding is so important for electrical installation and equipment? The main reasons for bonding are:
1) To establish an effective path for fault current that facilitates the operation of current leakage protective devices .
2) To minimize shock hazard to people by providing a low-impedance path to ground. Bonding limits the touch voltage when non-current-carrying metal parts are inadvertently energized by a ground fault.
System of Grounding
A grounding system has two distinct parts: system grounding and equipment grounding. System grounding is the electrical connection of one of the current carrying conductors of the electrical system to the ground.
Equipment grounding is the electrical connection of all the metal parts that do not carry current of all electrical equipment to the ground. Conductors that form parts of the grounding system include the following:
1) Equipment grounding conductor (EGC)
This is an electrical conductor that provides a low-impedance ground path between electrical equipment and enclosures within the distribution system.
2) Grounded conductor
This is a conductor that has been intentionally grounded.
3) Grounding electrode conductor
This is a conductor used to connect the equipment grounding conductor or the grounded conductor (at the service or at the separately derived system) to the grounding electrode(s).
* SOURCE FROM : Electric Motors and Control System by FRANK D. PETTRUZELLA