In a panel with IAC classification, the accessibility type says who can be nearby: authorized personnel (A), anyone including the public (B) or no one, because it is out of reach above a public area (C). The letters F, L and R indicate the sides that passed the internal arc test.
Short answer
The IAC classification of a switchgear panel does not only say how much arc current it withstood. It also says who can be nearby and on which sides. IEC 62271-200, 2011 edition, expresses this with two letters of the designation: the accessibility type (A, B or C, clause 4.101.2) and the classified sides (F, L and R, clause 4.101.3). If either of these data is missing, the classification is not complete.
The three accessibility types
Clause 4.101.2 defines three forms of access to the enclosure at the installation site:
| Type | What it means |
|---|---|
| A | Access restricted to authorized personnel |
| B | Unrestricted access, including the general public |
| C | Access restricted by installation out of reach and above a public area |
Type C is intended for pole-mounted switchgear. For it, the manufacturer declares a minimum approach distance, and the minimum installation height is that distance plus 2 m.
A panel tested for type B protects anyone near it. One tested for type A protects the authorized personnel who operate next to it.
The classified sides
For types A and B, the sides of the enclosure that meet the criteria of the internal arc test are designated with a letter:
- F: front side.
- L: lateral side.
- R: rear side.
The manufacturer must clearly declare which side is the front. Classified sides do not apply to type C.
A side that does not appear in the designation is not classified. The standard warns that allowing personnel into an area not designated as accessible can cause injuries.
How to read the designation
The designation includes classification, accessibility type, sides, and the arc current and duration. It goes on the rating plate. The examples in clause 8.104.6 show how to read it:
| Designation | What it says |
|---|---|
| IAC BFLR 12.5 kA, 0.5 s | Public access at front, sides and rear; 12.5 kA for 0.5 s |
| IAC BF-AR 16 kA, 1 s | Front with public access; rear restricted to operators; sides not accessible; 16 kA for 1 s |
If the manufacturer also assigns a single-phase-to-earth current, it is added in parentheses, as in the designation IAC AFLR 20 kA, 0.5 s (IAe: 2 kA, 1 s) of example 3 of the standard.
- Who can be near the switchgear in service?
- Only authorized personnel: Type A, with sides F, L or R where personnel stand
- Anyone, including the public: Type B, with the sides accessible to the public
- No one, pole-mounted equipment out of reach above a public area: Type C, with the declared minimum distance
How each type is tested
Annex AA of the standard describes the indicators, which are pieces of black cotton cloth of 150 mm by 150 mm placed on each classified side on a frame. Their distance and fabric depend on the type:
| Type | Fabric | Distance to the panel | Placement |
|---|---|---|---|
| A | Black cotton of about 150 g/m² | 300 mm | Vertical, up to 2,000 mm height, and horizontal at 2,000 mm above the floor if there is no ceiling at that height |
| B | Black cotton fabric of about 40 g/m² | 100 mm | Vertical, up to 2,000 mm, and horizontal above the panel if it is less than 1,900 mm tall |
| C | Black cotton fabric of about 40 g/m² | The declared minimum approach distance, below the sample | Horizontal, covering a 3 m by 3 m square centered on the pole |
The indicators are distributed in a checkerboard pattern, covering 40 % to 50 % of the area. The standard notes that 150 g/m² cotton represents work clothing and 40 g/m² cotton represents the public’s light summer clothing. That is why type B is more demanding: the fabric is thinner and closer.
If normal operation requires people to stand or walk on the equipment, the horizontal indicators are placed over the accessible upper surface, regardless of the height of the panel.
How to choose according to risk
Clause 8.104.4 guides the selection:
- Not every panel is IAC, nor is every one withdrawable or fitted with a door that can be closed in the defined positions.
- If the risk is considered negligible, a panel with IAC classification is not needed.
- If the risk is relevant, only IAC switchgear should be used.
- In that case, the selection must compare the maximum foreseeable fault current and duration with the rated values of the tested equipment, and follow the manufacturer’s installation instructions.
- The location of personnel during an internal arc is important. The manufacturer must indicate which sides are classified as accessible and the user must follow those instructions.
The protection of people also depends on the installation conditions, not only on the design and the classification.
The IAC classification that accessibility belongs to is covered in internal arc classification (IAC). The energy a person receives in front of the panel is calculated in the arc flash study, and the protective clothing is chosen with the arc flash PPE categories.
What not to do
- Do not specify type A for a panel in a corridor with public traffic: type B is the one that applies.
- Do not allow anyone to stand on the side of a panel that is not listed in the designation.
- Do not assume IAC protects during maintenance: the classification covers normal operation with the panel closed.
- Do not compare panels by arc current without comparing the accessibility type and the sides.
When to call us
At Tiza Group we define with you the accessibility type, the sides and the arc values worth requiring of your medium-voltage switchgear. Learn about our primary engineering design service. Write to us and we will quote it. The design is adapted to the local code and the requirements of the utility.
Related guides
- Internal arc classification IAC of a switchgear panel
- Arc flash study: IEEE 1584 and NFPA 70E
- Medium-voltage compact substation: parts, IAC and tests
- Arc flash PPE categories: how they are defined
- Medium-voltage switchgear: parts, functions and tests
References
- IEC 62271-200, High-voltage switchgear and controlgear - Part 200: AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV, 2011 edition, clauses 4.101.2, 4.101.3, 5.101, 8.104.4, 8.104.6 and Annex AA (AA.2.1 and AA.2.2).
Frequently asked questions
What does IAC BFLR 12.5 kA, 0.5 s mean on a switchgear rating plate?
That the panel is classified against internal arc (IAC), for a public access location (B) on the front (F), lateral (L) and rear (R) sides, and was tested at 12.5 kA for 0.5 s. It is example 1 of clause 8.104.6 of IEC 62271-200.
What is the test difference between type A and type B?
The distance and the fabric of the indicators. In type A they are placed at 300 mm, with cotton of about 150 g/m². In type B they are placed at 100 mm, with a fabric of about 40 g/m². The standard considers that they represent work clothing and light clothing of the public.
Do sides F, L and R apply to type C?
No. Classified sides do not apply to type C equipment. The standard associates it with pole-mounted equipment, installed out of reach and above a public area, and the manufacturer declares the minimum approach distance.