According to IEC 439-1, Clause 7.7 Forms of Assemblies can be obtained by means of partitions or barriers (metallic or non-metallic) into separate compartments or barriered sub-section.
Why is Forms of Assemblies is very important?
1. to enable a functional unit to remains in service - to reduce the risk of making accidential contact with the live part or adjacent units of busbars
2. to reduce the risk of loose part, tools, or even debris falling into or otherwise passing into an adjacent compartment
3. to limit the probability that ionised gas created by the operation of a short-circuit protective device, could cause flash over accross adjacent equipments or busbars
4. protection against contact with live parts belonging to the adjacent functional units
Note :
The above are a summarisation of Form Code IEC 439-Part 1, Clause 7.7 - FORUM
