1. The need for protection

1.1 Role and composition of installations

Thanks to its ease of use, regulation and automation, electrical energy has become indispensable to everyday life.

• In domestic installations, offices and small commercial premises (e.g. shops), it mainly powers lighting, small motors, electronic and IT equipment, air conditioning (heating, refrigeration), elevators, etc. Total power requirements range from a few kilowatts in the domestic sector to several hundred kilowatts in the small commercial sector.

  Distribution is carried out via tree-like networks of cables, almost exclusively at low voltage (LV: 230/400 V), single-phase or three-phase depending on the nature and power of the applications connected, and exceptionally...