IEC 60439-2:2005 pdf free download – Low-voltage switchgear andcontrolgear assemblies
2.3.11 flexible busbar trunking unit
busbar trunking unit having conductors and enclosures designed to be bent during installation
2.3.12 busbar trunking feeder unit
busbar trunking unit serving as any incoming unit.The connection of the feeder unit to thesupply may or may not require the supply to be disconnected
2.3.13 tap-off unit
outgoing unit for tapping-off power from the busbar trunking unit with tap-off facilities (see2.3.6), such as rollers, brushes or plug-in devices
A tap-off unit may also be permanently connected and can be intended for one or anycombinations 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 forcommunication or remote control,contactors，socket-outlets，connecting facilities such asprewired,screw-type or screw-less type terminals, etc.
Tap-off units may be partially type-tested assemblies (PTTA).
2.3.14 busbar trunking unit for building movements
busbar trunking unit intended to allow for building movements due to thermal expansion andcontraction of the building
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 circuitintegrity for a specified time under fire conditions
5.1 Nameplate
After the first paragraph add the following paragraph:
One nameplate shall be located near one end of each busbar trunking unit and one on eachtap-off unit. lf the busbar trunking enclosure is used as a PE conductor and if a terminal isprovided for external connection to the enclosure， this terminal should be marked accordingto 7.6.5.2.
Add the following items u) and v):
u) resistance,reactance and impedance values of the system (see 4.9.1);
v)resistance, reactance and impedance values of the system under fault conditions (see 4.9.2).
7.1.1.6Busbar trunking fire barrier unit
A busbar trunking fire barrier unit shall be designed to prevent the propagation of fire, for aspecified time,under fire conditions，when the busbar trunking system passes throughhorizontal or vertical building divisions (for example,wall or floor).
Compliance is checked by the fire-resistance test according to 8.2.15.7.1.1.7Maintenance of circuit integrity under fire conditions
A fire-resistant busbar trunking unit may be designed to maintain the integrity of electricaldistribution circuits, for a specified time, under fire conditions.
A test for circuit integrity under fire conditions is under consideration (see annex L).7.1.2.3.4Clearances
After the first paragraph，add the following paragraph:
Clearances shall be dimensioned, when the busbar trunking system is correctly assembled inaccordance with the manufacturer’s instructions and mounted as in service, to withstand therequired impulse voltage stated by the manufacturer，considering the overvoltage categoryand the maximum of the rated operational voltage to earth， as specified in IEC 60439-1,table G.1.
Unless otherwise stated by the manufacturer,the dimensioning of the clearances of thesystem shall be based on:
overvoltage category: IV(origin of installation) or lll (distribution circuit level);- pollution degree: 3.
NOTE Clearances values for basic and functional insulation are dimensioned as specified in IEC 60439-1,table 14,case A. Clearance values of supplementary insulation are not less than those specified for basicinsulation. Clearance values for reinforced insulation are dimensioned to the rated impulse voltage one step higherthan those specified for basic insulation.
Parts of the system provided with double insulation where basic insulation and supplementary insulation cannot betested separately are considered as reinforced insulation.