17/03/2022
Signal earthing provides return paths for signals usually at low voltages. It is also used as reference potential for radio frequency signals and ideally it should be kept at zero reference voltage regardless of the amount of current flowing into or out of the earth. Signal earthing creates a potential reference for different parts in
the signal system. Signal earthing if properly designed reduces electric, magnetic, electromagnetic and conductive noise coupling
Similar to the facts discussed related to earthing for power system; earthing system designed for lightning protection is able to function as signal earthing system as well since earthing for lightning protection is done with the aim of equipotentializing the ground surface as well as to neutralize immense amount of charges which gave rise to high potential rises compared to the low potentials
that signal earthing intended to handle.
Another major purpose of earthing is to address issues regarding
Electrostatic Discharge (ESD). Earthing serves as a medium for neutralization of static charges which if not properly attend,
may accumulate up to a limit which may cause ignition of objects and sparking. The amount of charge carried by lightning strikes far out number the amount of static charge generated within any building especially those with conveying belts, gas or steam tanks and other objects which may give rise to static electricity.
Therefore, earthing system good enough for lightning protection is again good enough for ESD protection. Based on the above discussions, a conclusion can be drawn in that an earthing system fit for lightning protection is also fit for power system earthing, signal earthing as well as ESD earthing.
Scientists and professionals for the past century or so has since upon realizing the hazards of lightning strike and hence the dire need of a good earthing system, devoted concentrated attention on matters
pertaining earthing for lightning protection purpose thus giving rise to a few standards with the more notable ones include IEEE
Green Book (IEEE Std 142: Grounding of Industrial and Commercial
Power Systems), IEC 62305 (Protection against lightning – Part 3:
Physical damage to structures and life hazard), BS7430 (Code of
Practice for Earthing), and NFPA 70. Due to the complexity of the
nature of lightning and hence the hazards that associated with it,
these standards are still constantly being improved.