System earthings in LV

This "Cahier Technique" proposes a survey of potential hazards that insulation faults may create for safety of persons and property. It emphasises the influence of system earthings on the availability of electrical power. It presents the three most common system earthings defined in standard IEC 60364 and used to varying degrees in all countries. Each system earthing is analysed in terms of dependability (safety, maintainability and availability). All system earthings are equivalent as far as safety of persons is concerned, but each system earthing has its own advantages and disadvantages regarding the operation of electrical installation. The user must therefore be guided according to his needs, with the exception, however, of prescription or of standard or legislative bans. Readers interested in the practices of various countries and in evolution of system earthings should read "Cahier Technique" no. 173: System earthings worldwide and evolutions.