IEC 61010 Category I corresponds to which description?

• A. Receptacle outlet circuit; plug-in loads
• B. Distribution wiring including mains
• C. Protected Electronic circuits
• D. Origin of installation at the Utility level

Answer: (C)

Category I covers circuits that are not connected to the standard mains distribution and have energy-limited fault conditions. It applies to protected electronic circuits and other equipment that operates from isolated or low-energy sources, such as battery-powered gear or circuitry within equipment that is isolated from the mains by a protective barrier. The important idea is that the energy available during faults is limited and there’s no direct connection to the building's distribution system. Receptacle outlet circuits and plug-in loads are connected to mains, which fits Category II. Distribution wiring including mains is Category III because it involves wiring inside a building’s distribution network beyond the service equipment. The origin of installation at the Utility level is Category IV, covering service entrance equipment exposed to the highest energy and surges.