IEC 60439-2:2005 pdf download.Low-voltage switchgear and controlgear assemblies
1.1 Scope and object
Add the following paragraphs:IEC 60439-2 applies to busbar trunking systems (BTS) and their accessories for feeding and distributing electrical power in residential, retail, public， agricultural and industrial premises. It also applies to busbar trunking systems which are designed to incorporate communication and/or control systems or intended to supply luminaires through tap-off units but does not apply to supply track systems in accordance with IEC 60570.
The busbar trunking systems considered in this standard are type-tested ASSEMBLIES (TTA) when tested in accordance with clause 8 of this standard; variations in length and angles of bends are considered to be covered.
2.3.5 busbar trunking unit
unit of a busbar trunking system complete with busbars, their supports and insulation,external enclosure and any fixing and connecting means to other units， with or without tap-off facilities
NOTE Trunking units may have different geometrical shapes such as straight length, elbow, tee or cross.
2.12.3.6 busbar trunking unit with tap-off facilities
busbar trunking unit designed to enable tap-off units to be installed at one or more points as predetermined by the manufacturer
The connection of tap-off units to the busbar trunking unit may or may not require the busbar system to be disconnected from the supply
2.3.7 busbar trunking unit with trolley-type tap-off facilities
busbar trunking unit designed to permit the use of roller- or brush-type tap-off units
2.3.8 busbar trunking adapter unit
busbar trunking unit intended to connect two units of the same system but of different type or of different rated current
2.3.9 busbar trunking thermal expansion unit
busbar trunking unit intended to permit a certain movement in the axial direction of the busbar trunking due to thermal expansion of the system
NOTE The expansion element may apply to the conductor within the enclosure or both enclosure and conductors according to the design.
2.3.13 tap-off unit
outgoing unit for tapping-off power from the busbar trunking unit with tap-off facilities (see 2.3.6), such as rollers, brushes or plug-in devices A tap-off unit may also be permanently connected and can be intended for one or any combinations of power, communication or control circuits.
A tap-off unit may contain accessories, such as protective devices (for example fuse, fuse-switch, switch-fuse, circuit- breaker, residual current circuit- breaker), electronic apparatus for communication or remote control, contactors, socket-outlets, connecting facilities such as prewired, screw-type or screw-less type terminals, etc.
2.3.15 busbar trunking fire barrier unit
busbar trunking unit or a part of a busbar trunking unit, with or without additional parts,intended to prevent the propagation of fire for a specified time under fire conditions
2.3.16 busbar trunking fire resistant unit
busbar trunking unit, with or without additional parts, intended to maintain electrical circuit integrity for a specified time under fire conditions.IEC 60439-2 pdf download.