What is the difference between independent grounding and shared grounding?
Independent grounding is conductive soil, possessing equipotential, and the potential at any point can be considered zero potential; a conductive body, such as soil or the hull of a steel ship, serves as a return path for the circuit or as a zero-potential reference point; a location or part of a circuit with zero potential relative to the ground.
A grounding conductor or long conductor electrically connects a non-energized metal or part of electrical equipment to a grounding electrode.
A grounding electrode is a conductor or group of conductors in close contact with a patch of soil (earth) to provide an electrical connection to the ground.
A grounding wire is a conductor that forms the ground, connecting equipment, installations, wiring systems, or neutral lines to a grounding electrode.
A grounding grid is a group of interconnected bare conductors buried underground, used to provide a common ground for electrical and electronic equipment and metal structures.
A grounding device is used to form a connection to the ground. It consists of a grounding wire, a grounding electrode, and the earth (soil) surrounding the grounding electrode.
Protective grounding (PE) is a method of connecting to ground required to protect people or electrical and electronic equipment. It is used to electrically connect exposed conductive parts, external conductive parts, main grounding terminals, grounding electrodes, power supply grounding points, or artificial neutral points. It conducts current when a ground fault or human-induced accident occurs in the power circuit, and receives current from surge protectors when lightning overvoltage and overcurrent occur.
A grounding system is a system composed of multiple interconnected grounding devices within a specified area.
Grounding resistance is the ohmic resistance between a grounding electrode and a distant grounding electrode with zero resistance.
Independent grounding refers to each system requiring grounding establishing its own independent grounding network.
Shared grounding, also called unified grounding, refers to connecting all systems requiring grounding to a single grounding network, or connecting the original grounding networks of each system underground or above ground with metal connections, making them electrically connected as a unified grounding network.
Single-point grounding connects the grounding wires of each system to the same point on the grounding busbar or the same metal plane; this connection method is called "single-point grounding."
A ring-type grounding grid is formed by enclosing grounding electrodes in a closed loop around a building.
1. What are the problems with independent grounding grids?
2. Why have they been replaced by shared grounding grids?
Grounding is the most crucial aspect of lightning protection technology. Whether it's a direct lightning strike, induced lightning, or other forms of lightning, the final result is always to send the lightning current to the earth. Therefore, reliable lightning protection is impossible without a proper and effective grounding system.
Modern buildings often contain many different types of electrical equipment, requiring multiple grounding systems; such as lightning protection grounding, electrical safety grounding, AC power supply working grounding, and communication and computer system grounding (also called DC grounding, or logic grounding in digital logic systems).
The grounding of each communication system and AC power supply system is to achieve a zero-potential point. If each system is grounded separately, the potential at the grounding points of each system may differ significantly when lightning strikes. Furthermore, it is very difficult to construct several independent grounding grids within a single building, especially in modern large cities. Because requiring a minimum distance of several meters or even 20 meters between grounding grids, while also maintaining sufficient distance from various underground metal pipes, cable shielding layers, and major metal components, is difficult to achieve. Even if this is achieved during the initial construction of a new grounding system, subsequent maintenance work, where the new operator is unfamiliar with the requirements, can easily compromise these standards. For these two reasons, independent grounding systems are no longer suitable for the rapidly developing landscape of modern communication technology.
If a shared grounding system is used, the high voltage generated by the lightning current I on the impulse grounding resistance will simultaneously exist on the grounding wires of each system. There will be no high potential difference between the grounding wires of different systems mentioned above, nor will there be any breakdown issues between the grounding systems of the same equipment.