Grounding and Bonding is one of the most important in an Electrical System for the protection of property, persons, and equipment. Because when improperly installed, it may result in physical injuries, costly damage to electrical facilities, or even death to an individual. Each utility (power, telephone, cable TV) has its own grounding electrodes. Electrical Grounding and Bonding circuits follow the basic laws of electricity.
Grounded Systems.
- Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.
- Grounding of Electrical Equipment. Non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials.
- Bonding of Electrical Equipment. Non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path.
- Bonding of Electrically Conductive Materials and Other Equipment. Electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path.
- Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a permanent, low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.
Ungrounded Systems.
- Grounding Electrical Equipment. Non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth in a manner that will limit the voltage imposed by lightning or unintentional contact with higher-voltage lines and limit the voltage to ground on these materials.
- Bonding of Electrical Equipment. Non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the supply system grounded equipment in a manner that creates a permanent, low-impedance path for ground-fault current that is capable of carrying the maximum fault current likely to be imposed on it.
- Bonding of Electrically Conductive Materials and Other Equipment. Electrically conductive materials that are likely to become energized shall be connected together and to the supply system grounded equipment in a manner that creates a permanent, low- impedance path for ground-fault current that is capable of carrying the maximum fault current likely to be imposed on it.
- Path for Fault Current. Electrical equipment, wiring, and other electrically conductive material likely to become energized shall be installed in a manner that creates a permanent, low-impedance circuit from any point on the wiring system to the electrical supply source to facilitate the operation of overcurrent devices should a second fault occur on the wiring system. The earth shall not be considered as an effective fault-current path.
FPN No. 1: A second fault that occurs through the equipment enclosures and
bonding is considered a ground fault.
Bonding.
- Is the practice of intentionally electrically connecting metallic items not designed to carry electricity. This brings all the bonded items to the same electrical potential as a protection from electrical shock. The bonded items can then be connected to ground to bring them to earth potential.
Connection of Grounding and Bonding Equipment.
- Grounding conductors and bonding jumpers shall be connected by exothermic welding, listed pressure connectors, listed clamps, or other listed means. Connection devices or fittings that depend solely on solder shall not be used. Sheet metal screws shall not be used to connect grounding conductors or connection devices to enclosures.
What is the difference between grounded conductor and grounding conductor?
- Grounded conductor – a system or circuit conductor that is intentionally grounded.
- Grounding Conductor – a conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode conductor.
Grounded Conductor – a system or circuit conductor that is intentionally grounded.
Grounded Conductor
Grounding Conductor – a conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes.
Service.
- the conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.
- Service Drop – electric utility conductors.
- Service Point – the point of connection between the premises wiring and the utility supply conductors.
- Service Entrance Conductor – premises wiring.
- Service Equipment – The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of the of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply.
Service Equipment-Disconnecting Means – service disconnect must disconnect all service-entrance conductors from the building or structure premises wiring.
The service disconnect must be at a readily accessible location either outside the building or structure or inside nearest the point of entry of the service conductors.
Where the transformer supplying the service is located outside the building, at least one additional grounding connection is required to be made from the grounded service conductor to a grounding electrode, either at the transformer or elsewhere outside the building.
Proper Wiring Installation.
Grounded Improperly.
Earth is Not an Effective Ground-Fault Current Path.
Effective Ground-Fault Current Path.
- An intentionally constructed, permanent, low-impedance electrically conductive path designed and intended to carry current under ground-fault conditions from the point of a ground fault on a wiring system to the electrical supply source, and that facilitates the operation of the overcurrent protective device or ground fault detectors on high-impedance grounded systems.
Ground Fault.
- An unintentional, electrically conducting connection between an ungrounded conductor of an electrical circuit and the normally non–current-carrying conductors, metallic enclosures, metallic raceways, metallic equipment, or earth.
Ground-Fault Current Path.
- An electrically conductive path from the point of a ground fault on a wiring system through normally non–current-carrying conductors, equipment, or the earth to the electrical supply source.
FPN: Examples of ground-fault current paths could consist of any combination of
equipment grounding conductors, metallic raceways, metallic cable sheaths,
electrical equipment, and any other electrically conductive material such as metal
water and gas piping, steel framing members, stucco mesh, metal ducting,
reinforcing steel, shields of communications cables, and the earth itself.
Grounded Properly.
Each Utilities has its Own Grounding Electrode.
Low-Voltage & Intersystem Grounding and Bonding.
Lightning protection systems are designed to mitigate the effects of lightning through connection to extensive grounding systems that provide a large surface area connection to earth. The large area is required to dissipate the high current of a lightning strike without damaging the system conductors by excess heat. Since lightning strikes are pulses of energy with very high frequency components, grounding systems for lightning protection tend to use short straight runs of conductors to reduce the self-inductance and skin effect.
Lightning Protection System. The bonding of a system grounding electrode and a lightning rod grounding electrode.
Electrical Safety.
- It is important to ground metal parts to a suitable grounding electrode, so that in the event of a ground fault, dangerous ground-fault current will be shunted into the earth away from persons, thereby protecting them against electric shock.
- Electrical equipment must be grounded to ensure that dangerous voltage on metal parts resulting from a ground fault can be reduced to a safe value.
- Electrical equipment must be grounded so that sufficient fault current will flow through the circuit protection device to quickly open and clear the ground fault. For example, a 20 A circuit breaker will trip and de-energize a 240 V ground fault to a metal pole that is grounded to a 25 ohm ground rod.
- When electrical current is given multiple conductive paths on which to flow, current will only take the path of least resistance.
Grounding Versus Bonding
Grounding Myths
Sources: Common Mistakes in Electrical Grounding and Bonding by Jaime V. Mendoza, PEE, MTM, en.wikipedia.org, Philippine Electrical Code 2009, MikeholtNEC.
