Functional Earthing vs. Protective Earthing (FE vs PE)

The distinction between functional earthing (FE), which serves solely to ensure the correct operation of equipment — for example as a reference potential for electronic signal processing, EMC filters or surge arresters in telecom and ICT installations — and protective earthing (PE), which is specifically intended to prevent a hazardous touch voltage on conductive parts in the event of an insulation fault, in accordance with IEC 60364-4-41. A functional earth conductor may never be regarded as the sole protective measure against electric shock, even if it is physically connected to the same rail as the PE. If FE and PE are combined into a single conductor, that combined conductor must meet all requirements for a PE conductor (minimum cross-section, uninterrupted continuity, no switch in series) in accordance with IEC 60364-5-54, regardless of whether the functional application would allow less stringent requirements.