According to IEC 62271-200, three types of accessibility to the enclosure of metal-enclosed switchgear and controlgear at the site of installation are defined:
- Accessibility Type A: restricted to authorized personnel only.
- Accessibility Type B: unrestricted accessibility, including that of the general public.
- Accessibility Type C: restricted by installation out of reach and above a general public area.
For accessibility type A and B the sides of the enclosure which meet the criteria of the internal arc test are designated as
- F for front side
- L for lateral side
- R for rear side
The front side shall be clearly stated by the manufacturer. Classified sides do not apply to switchgear and controlgear of accessibility type C.
As an example, the designation of switchgear internal arc as IAC AFL 20 kA, 0,5 s indicates a switchgear with accessibility type “A” which can be accessed by authorized personnel from both front and lateral sides; the arc fault current is 20 kA and the arc fault duration is 0,5 s.