The use and abuse of insulated/isolated grounding

Various issues concerning insulated/isolated grounding (IG) are addressed. It is unclear whether the IG form of grounding is effective in reducing the effects of common-mode noise on AC supply circuits. Its effects also may be undesirable under some conditions of installation where the observed noise may actually be seen to increase. Solid grounding (SG) can be expected to behave in a manner similar to that of the IG form. The length of the IG circuit or SG circuit can have a considerable effect on the amount of common-mode noise being conducted on the circuit. Large open-loop areas in affected wiring circuits are prone to common-mode noise currents being induced into them from radiated fields. Such loop areas generally must be reduced in order to improve matters. IG and SG forms of grounding may not be helpful in resolving these kinds of problems, while HF forms of grounding, bonding, and shielding are. Zero signal reference grids and planes are recommended as the primary mechanism for common-mode noise current control when they can be installed in a practical manner. It is also noted that the use of flexible metal conduit or liquid-tight flexible metal conduit on IG circuits creates special conditions where an additional ESGC must be installed for the proper safety grounding and bonding of the conduit itself