Definition and Purpose of Grounding
– Ground in electrical engineering serves as a reference point for voltage measurements.
– It provides a common return path for electric current.
– Grounding protects users from electrical shock by connecting exposed conductive parts of equipment to ground.
– It allows circuit breakers to interrupt power supply in case of faults.
– Grounding limits the build-up of static electricity and reduces the risk of electric shock.
Historical Background
– The use of ground as a return path in telegraph systems was discovered in the 19th century.
– German scientist Carl August von Steinheil made the principle known to telegraph engineers.
– Problems with this system arose due to high resistance during dry weather.
– The two-wire or metallic circuit system was reintroduced when telephony replaced telegraphy.
– Interference caused by induced currents led to the reintroduction of the two-wire system.
Grounding in Building Wiring Installations
– Grounding limits the voltage that can appear on distribution circuits.
– It dissipates potentials and prevents a rise in voltage of the grounded system.
– Equipment bonding conductors provide a low impedance path for fault currents.
– Equipment ground conductors protect against shocks by connecting non-current carrying metallic parts.
– Grounding electrode conductors connect the system grounded conductor or equipment to a grounding electrode.
Grounding in Permanently Installed and Portable Electrical Equipment
– Permanently installed electrical equipment has permanently connected grounding conductors.
– Portable electrical devices with metal cases may be connected to earth ground through attachment plugs.
– The size of power grounding conductors is regulated by wiring regulations.
– Grounding is required to limit voltage imposed by lightning events and contact with higher voltage lines.
– Grounding is also important for radio antennas and lightning protection systems.
Earthing Systems
– Earthing system defines the electrical potential of conductors relative to Earth’s conductive surface.
– Choice of earthing system affects safety and electromagnetic compatibility of power supply.
– Regulations for earthing systems vary between countries.
– Functional earth connection carries current during normal operation of devices like surge suppression and measurement instruments.
– Protective earth system is also used as a functional earth, but requires caution. Source: https://en.wikipedia.org/wiki/Electrical_ground
In electrical engineering, ground or earth may be a reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth.
Electrical circuits may be connected to ground for several reasons. Exposed conductive parts of electrical equipment are connected to ground, to protect users from electrical shock hazard. If internal insulation fails, dangerous voltages may appear on the exposed conductive parts. Connecting exposed parts to ground will allow circuit breakers (or RCDs) to interrupt power supply in the event of a fault. In electric power distribution systems, a protective earth (PE) conductor is an essential part of the safety provided by the earthing system.
Connection to ground also limits the build-up of static electricity when handling flammable products or electrostatic-sensitive devices. In some telegraph and power transmission circuits, the ground itself can be used as one conductor of the circuit, saving the cost of installing a separate return conductor (see single-wire earth return and earth-return telegraph).
For measurement purposes, the Earth serves as a (reasonably) constant potential reference against which other potentials can be measured. An electrical ground system should have an appropriate current-carrying capability to serve as an adequate zero-voltage reference level. In electronic circuit theory, a "ground" is usually idealized as an infinite source or sink for charge, which can absorb an unlimited amount of current without changing its potential. Where a real ground connection has a significant resistance, the approximation of zero potential is no longer valid. Stray voltages or earth potential rise effects will occur, which may create noise in signals or produce an electric shock hazard if large enough.
The use of the term ground (or earth) is so common in electrical and electronics applications that circuits in portable electronic devices, such as cell phones and media players, as well as circuits in vehicles, may be spoken of as having a "ground" or chassis ground connection without any actual connection to the Earth, despite "common" being a more appropriate term for such a connection. That is usually a large conductor attached to one side of the power supply (such as the "ground plane" on a printed circuit board), which serves as the common return path for current from many different components in the circuit.
