Note 1: the abbreviation BTS used throughout this part refers to busbar trunking system. As for Part 1, the term "assembly" is referred to as "BTS" for short.
This part of GB 7251 specifies the definitions, service conditions, structural requirements, technical characteristics and verification requirements of the following low-voltage assembly (see 3.101):
- The assembly with the rated AC voltage not exceeding 1000V and the rated DC voltage not exceeding 1500V;
- Assembly used with power generation, power transmission, power distribution, electric energy conversion and power consumption control equipment;
- Assembly designed for special conditions, such as ships, railway and civil appliance (operated by non-professional personnel) as long as it meets the relevant specific requirements;
Note 2: IEC 60092-302 includes the supplementary requirements of assemblies for ships.
- For assembly designed for electrical equipment of machine, IEC 60204 includes the supplementary requirements of assemblies constituting the constituent part of the machine.
This part is applicable to all assemblies designed, manufactured and inspected at one time or those totally under standardized batch manufacturing.
The original manufacturer may not be responsible for the production and/or assembling (see 3.10.1 and 3.10.2 in Part 1).
This part is not applicable to the separate device and self-contained component meeting their respective product standards, such as motor starter, fuse switch and electronic equipment.
This part is not applicable to specific assemblies in other parts of GB 7251, electrical supply track systems in GB 13961-2008, cable trunking and ducting systems in GB/T 19215 (All Parts) and power track systems in IEC 61534 (All Parts).
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the normative document (including any amendments) applies.
In addition to the following contents, Chapter 2 in GB 7251.1-2013 also applies.
Add:
GB 7251.1-2013 Low-voltage Switchgear and Controlgear Assemblies - Part 1: General Rules (IEC 61439-1:2011, IDT)
GB/T 18380.31-2008 Test on Electric and Optical Fiber Cables under Fire Conditions - Part 31: Test for Vertical Flame Spread of Vertically-mounted Bunched Wires or Cables - Apparatus (IEC 60332-3-10:2000, IDT)
IEC 60439-2:2000 Low-voltage Switchgear and Controlgear Assemblies - Part 2: Particular Requirements for Busbar Trunking Systems (Busways) [Low-voltage Switchgear and Controlgear Assemblies - Part 2: Particular Requirements for Busbar Trunking Systems (Busways)]
IEC 61786:1998 Measurement of Low-frequency Magnetic and Electric Fields with Regard to Exposure of Human Beings - Special Requirements for Instruments and Guidance for Measurements
ISO 834-1:1999 Fire-resistance Tests - Elements of Building Construction - Part 1: General Requirements
3 Terms and Definitions
In addition to the following contents, Chapter 3 in GB 7251.1-2013 also applies.
Add definitions:
3.101
Busbar trunking systems; BTS
Busways
The enclosed assembly composed of conductor system, used for power distribution and electricity control of all loads and applicable to industrial, commercial and similar purposes. This conductor system is composed of busbars separated or supported by the insulating material in pipeline, slot or similar enclosure.
[Source: the revised IEC 60050-441:1984, 441-12-07]
Note 1: see 3.1.1 in GB 7251.1-2013 for the definition of assembly.
Note 2: BTS may be composed of a series of mechanical and electrical elements, e.g.:
- BTU with or without tap-off facility;
- Phase transposition, expansion, flexible, feeder and adapter units;
- Tap-off unit;
- Additional conductors for communication and/or control.
Note 3: for the term "busbar", the geometrical shape, dimension and area of conductor are not preset.
3.102
Busbar trunking unit; BTU
A unit of BTS. This unit is composed of busbar, busbar supporting part and insulating part, enclosure and fixed part and connected part connecting other units. It may or may not be equipped with tap-off facility.
Note: busbar trunking may have different geometrical shapes such as straight, elbow, tee or cross.
3.103
Busbar trunking run; BT run
Multiple BTUs (excluding tap-off unit) connected together to constitute the BTS.
3.104
Busbar trunking unit with tap-off facilities; BTU with tap-off facilities
BTU prefabricated by the original manufacturer designed to enable tap-off units to be installed at one or more points.
3.105
Busbar trunking unit with trolley-type tap-off facilities; BTU with trolley-type tap-off facilities
BTU designed to permit the use of roller- or trolley-type tap-off units.
3.106
Busbar trunking adapter unit; adapter BTU
BTU intended to connect two units of the same system but of different types or different rated currents.
3.107
Busbar trunking thermal expansion unit; thermal expansion BTU
BTU intended to permit a certain movement in the axial direction of the BT run due to thermal expansion of the system.
Note: this term doesn't preset the part allowed to move, e.g. the conductor in enclosure or both the conductor and enclosure.
3.108
Busbar trunking phase transposition unit; phase transposition BTU
BTU intended to change the relative position of the phase conductor in order to balance the inductive reactance or to transpose the phases (such as L1-L2-L3-N to N-L3-L2-L1).
3.109
Flexible busbar trunking unit; flexible BTU
BTU having conductor and enclosure designed to be under assigned direction conversion during installation.
3.110
Busbar trunking feeder unit; feeder BTU
BTU serving as an incoming unit.
Note: see 3.1.9 in GB 7251.1-2013 for the definition of incoming unit.
3.111
Tap-off unit
Outgoing unit, either stationary or movable, which is tapped off from BTU.
Note 1: see 3.1.10, 3.2.1 and 3.2.2 in GB 7251.1-2013 for the definitions of outgoing unit, fixed part and removable part.
Note 2: inserted tap-off unit is a kind of movable tap-off unit which may be manually connected and separated (see 8.5.2).
3.112
Busbar trunking unit for building movements; BTU for building movements
BTU intended to allow for building movements due to thermal expansion, contraction and/or flection.
3.113
Busbar trunking fire barrier unit; fire barrier BTU
BTU or a part of it intended to prevent the flame spread throughout a building structure within specified time under fire conditions.
