Reciprocating internal combustion engine driven alternating current generating sets. Emergency power supply to safety devices|Electric power systems, Electric machines, Prime movers, Electrical safety, Safety devices, Designations, Protected electrical equipment, Electrical equipment, Classification systems, Emergency electrical installations, Electric control equipment, Switchgear, Internal combustion engines, Electrical installations, Electric generators, Alternating current, Alternating-current generators, Design, Reciprocating engines, Performance testing, Electrical testing