Grounding, bonding, shielding, and isolation of electronic signals

All input power systems must be grounded for protection of personnel, property, and to insure the proper performance of the electrical system. Solidly grounding of the in-plant low-voltage systems is accepted and the preferred practice. When the voltage source for instrument and control systems is supplied by a separately derived system (transformer), a break from the plant grounding system is possible and desirable. The plant power grounding system and the separately derived control power grounding system(s) must be effectively bonded together reducing injuries caused when normally nonenergized structures become energized by a fault, static, lightning, or otherwise. This can be accomplished at the grounding electrode source. Two (or more) separate but equal grounding systems can exist if they are bonded together. The instrument and control system wires must be shielded from extraneous currents produced by magnetic fields or other induced voltages such as static and high frequency (arcing) transmissions. These sensitive conductors should not be put in harms way, but isolated and separated to the greatest possible extent