The principal reason for separating an assembly is to facilitate access to a part of the assembly while other parts may remain energised and in service.

Separation provides:
  • Protection against contact with live parts belonging to the adjacent functional units
  • Protection against the passage of solid foreign bodies from one unit of an assembly to an adjacent unit
  • Limit the probability of initiating an arc fault

Forms of segregation reference

Form 1 No internal separation of the busbars, functional units and terminals from each other.
Form 2a Separation of the busbars from the functional units. Terminals are not separated from the busbars.
Form 2b As for 2a, but with the terminals are not separated from the functional units.
Form 3a Separation of busbars from functional units and functional units each other. Terminals of functional units are not separated from each other.
Form 3b As per 3a, but with the terminals separated from the busbar (and functional units).
Form 4a Separation of busbars from functional units and functional unit each other. Separation of terminals for a functional unit from the busbars and those of any other unit.
Form 4b As per 4a, but with the terminals for each functional unit enclosed in their own space.

IP Rating Examples

Protected against a solid object greater than 1.0mm, such as a wire. Protected against vertically falling drops of water w/ enclosure tilted 15° from vertical. Limited ingress permitted.
Dust Protected. Limited ingress of dust permitted. Protected against water splashed from all directions. Limited ingress permitted.

IP Rating Reference Chart

IP Example Solid Protection IP Example Liquid Protection
Protected against a solid object greater than 50mm, such as a hand. Protected against vertically falling drops of water. Limited ingress permitted.
Protected against a solid object greater than 12.5mm, such as a finger. Protected against vertically falling drops of water w/ enclosure tilted 15° from vertical. Limited ingress permitted.
Protected against a solid object greater than 2.5mm, such as a screwdriver. Protected against sprays to 60° from vertical. Limited ingress permitted.
Protected against a solid object greater than 1.0mm, such as a wire. Protected against water splashed from all directions. Limited ingress permitted.
Dust Protected. Limited ingress of dust permitted. Protected against jets of water. Limited ingress permitted.
Dust Tight. Zero ingress of dust permitted. Protected against strong jets of water. Limited ingress permitted.
Protected against the effects of immersion between 15cm and 1 metre.
Protected against long periods of immersion under pressure.