Forms of Separation (2) – Fundamentals

Separation of an assembly elements

In accordance with the Standard, separation of the various elements of an Assembly: busbars, functional units, terminals, can be claimed providing one or more of the following criteria are met:

1. “Protection against contact with live parts belonging to adjacent functional units. The degree of protection shall be at least IP2X or IPXXB”

As a minimum, finger contact with live parts in adjacent functional units is prevented. With Assemblies supplied by EIEMA Member Companies this is extended to include protection against finger contact between: functional units, adjacent busbars and busbar connections, and terminals as required for the particular form of separation being considered.

The requirement is proven with the standard test finger.

Note: A second amendment to IEC 439-1 is presently being considered. This effectively removes this requirement from the Standard, since no common repeatable method of testing could be arrived at internationally.

EIEMA Members meet this non specific and probabilistic requirement by; good design practices and ensuring, usually by type test, the operation of switching and short circuit protective devices does not adversely affect adjacent functional units or busbars.

The minimum requirement is proven by the standard test finger not being able to touch live parts in adjacent units and a 12mm ball not being able to pass between units. In practice a higher degree of protection may be required for horizontal partitions to prevent small objects from falling between compartments and should be identified in the contract specification.

These three fundamental criteria are interrelated. EIEMA Member Companies will therefore ensure all three are fully met in respect of the particular form of separation offered.

Achieving Separation

The fundamental requirements in the Standard are performance criteria and not constructional details on how separation should be achieved. There is a requirement that Assemblies are divided by means of partitions or barriers (metallic or non-metallic) into separate compartments or barriered sub-sections, but not for example:

• each functional unit to be in its own compartment;
• partitions and barriers to be manufactured from earthed metal, etc.