GB/T 7251.1-2023 Low-voltage switchgear and controlgear assemblies - Part 1: General rules
1 Scope
This document lays down the general definitions and service conditions, construction requirements, technical characteristics and verification requirements for low-voltage switchgear and controlgear assemblies.
Note: Throughout this document, the term assembly (see 3.1.1) is used for a low-voltage switchgear and controlgear assembly.
For the purpose of determining assembly conformity, the requirements of the relevant part of the IEC 61439-2 onwards, apply together with the cited requirements of this document. For assemblies not covered by IEC 61439-3 onward, IEC 61439-2 applies.
This document applies to assemblies only when required by the relevant assembly standard as follows:
——assemblies for which the rated voltage does not exceed 1, 000V AC or 1, 500V DC;
——assemblies designed for a nominal frequency of the incoming supply or supplies not exceeding 1,000Hz;
——assemblies intended for indoor and outdoor applications;
——stationary or movable assemblies with or without an enclosure;
——assemblies intended for use in connection with the generation, transmission, distribution and conversion of electric energy, and for the control of electrical energy consuming equipment.
This document does not apply to individual devices and self-contained components such as motor starters, fuse switches, power electronic converter systems and equipment (PECS), switch mode power supplies (SMPS), uninterruptable power supplies (UPS), basic drive modules (BDM), complete drive modules (CDM), adjustable speed power drives systems (PDS), and other electronic equipment which comply with their relevant product standards. This document describes the integration of devices and self-contained components into an assembly or into an empty enclosure forming an assembly.
For some applications involving, for example, explosive atmospheres, functional safety, there can be a need to comply with the requirements of other standards or legislation in addition to those specified in the IEC 61439 (all parts).
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 2423.2-2008 Environmental testing for electric and electronic products - Part 2: Test methods - Tests B: Dry heat (IEC 60068-2-2: 2007, IDT)
GB/T 2423.4-2008 Environmental testing for electric and electronic products - Part 2: Test methods - Test Db: Damp heat, cyclic (12h+12h cycle) (IEC 60068-2-30: 2005, IDT)
GB/T 2423.17-2008 Environmental testing for electric and electronic products - Part 2: Test methods - Test Ka: Salt mist(IEC 60068-2-11: 1981, IDT)
GB/T 4025-2010 Basic and safety principles for man-machine interface, marking and identification - Coding principles for indicators and actuators (IEC 60073: 2002, IDT)
GB/T 4026-2019 Basic and safety principles for man-machine interface, marking and identification - Identification of equipment terminals, conductor terminations and conductors (IEC 60445: 2017, IDT)
GB/T 4205-2010 Basic and safety principles for man-machine interface (MMI), marking and identification - Actuating principles (IEC 60447: 2004, IDT)
GB/T 5094.1-2018 Industrial systems, installations and equipment and industrial products - Structuring principles and reference designations - Part 1: Basic rules (IEC 81346-1: 2009, IDT)
GB/T 5169.10-2017 Fire hazard testing for electric and electronic products - Part 10: Glowing/hot-wire based test methods - Glow-wire apparatus and common test procedure (IEC 60695-2-10: 2013, IDT)
GB/T 5169.11-2017 Fire hazard testing for electric and electronic products - Part 11:Glowing/hot-wire based test methods - Glow-wire flammability test method for end-products (GWEPT) (IEC 60695-2-11: 2014, IDT)
GB/T 11021-2014 Electrical insulation - Thermal evaluation and designation (IEC 60085: 2007, IDT)
GB/T 16895.6-2014 Low-voltage electrical installations - Part 5-52: Selection and erection of electrical equipment - Wiring systems (IEC 60364-5-52: 2009, IDT)
GB/T 16895.18-2010 Electrical installations of buildings - Part 5-51: Selection and erection of electrical equipment - Common rules (IEC 60364-5-51: 2005, IDT)
GB/T 16935.1-2008 Insulation coordination for equipment within low-voltage systems - Part 1: Principles, requirements and tests (IEC 60664-1: 2007, IDT)
GB/T 17626.4-2018 Electromagnetic compatibility - Testing and measurement techniques - Electrical fast transient/burst immunity test (IEC 61000-4-4: 2012, IDT)
GB/T 17626.6-2017 Electromagnetic compatibility - Testing and measurement techniques - Immunity to conducted disturbances, induced by radio-frequency fields (IEC 61000-4-6: 2013, IDT)
GB/T 17627-2019 High-voltage test techniques for low-voltage equipment - Definitions, test and procedure requirements, test equipment (IEC 61180: 2016, IDT)
GB 17799.3-2012 Electromagnetic compatibility(EMC) - Generic standards - Emission standard for industrial environments (IEC 61000-6-3: 2011, IDT)
Note: There is no technical difference between the referenced content from GB 17799.3-2012 and that from IEC 61000-6-3: 2006/AMD1: 2010.
GB/T 20641-2014 Empty enclosures for low-voltage switchgear and controlgear assemblies - General requirements (IEC 62208: 2011, IDT)
GB/T 24276-2017 A method of temperature-rise verification of low-voltage switchgear and controlgear assemblies by calculation (IEC TR 60890: 2014, IDT)
GB/T 35698.1-2017 Calculation of effects of short-circuit currents - Part 1: Definitions and calculation methods (IEC 60865-1: 2011, IDT)
ISO 178: 2019 Plastics - Determination of flexural properties
Note: GB/T 9341-2008 Plastic - Determination of flexural properties (ISO 178: 2001, IDT)
ISO 179-1: 2010 Plastics - Determination of Charpy impact properties - Part 1: Noninstrumented impact test
Note: GB/T 1043.1-2008 Plastics - Determination of Charpy impact properties - Part 1: Non-instrumented impact test (ISO 179-1: 2000, IDT)
ISO 179-2: 2020 Plastics - Determination of Charpy impact properties - Part 2: Instrumented impact test
Note: GB/T 1043.2-2018 Plastics - Determination of Charpy impact properties - Part 2: Instrumented impact test (ISO 179-2: 1997, IDT)
ISO 2409 Paints and varnishes - Cross-cut test
Note: GB/T 9286-2021 Paints and varnishes - Cross-cut test (ISO 2409: 2020, IDT)
ISO 4628-3: 2016 Paints and varnishes - Evaluation of degradation of coatings - Designation of quantity and size of defects, and of intensity of uniform changes in appearance - Part 3: Assessment of degree of rusting
Note: GB/T 30789.3-2014 Paints and varnishes - Evaluation of degradation of coatings - Designation of quantity and size of defects, and of intensity of uniform changes in appearance - Part 3: Assessment of degree of rusting (ISO 4628-3: 2003, IDT)
ISO 4892-2: 2013 Plastics - Methods of exposure to laboratory light sources - Part 2：Xenonarc lamps
Note: GB/T 16422.2-2014 Plastics - Methods of exposure to laboratory light sources - Part 2: Xenon-arc sources (ISO 4892-2: 2006, IDT)
ISO 7010 Graphical symbols - Safety colours and safety signs - Registered safety signs
Note: GB/T 31523.1-2015 Safety information identification systems - Part 1: Signs (ISO 7010: 2011, MOD)
IEC 60364 (all parts) Low-voltage electrical installations
Note: GB/T 16895 (all parts) Low-voltage electrical installations [IEC 60364 (all parts)]
IEC 60364-1 Low-voltage electrical installations - Part 1: Fundamental principles, assessment of general characteristics, definitions
Note: GB/T 16895.1-2008 Low-voltage electrical installations - Part 1: Fundamental principles, assessment of general characteristics, definitions (IEC 60364-1: 2005, IDT)
IEC 60364-4-41: 2005 Low-voltage electrical installations - Part 4-41: Protection for safety - Protection against electric shock
IEC 60364-4-41: 2005/ AMD1: 2017 Low-voltage electrical installations - Part 4-41: Protection for safety - Protection against electric shock - Amendment 1
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 General terms
3.1.1
low-voltage switchgear and controlgear assembly
assembly
combination of one or more low-voltage switching devices together with associated control, measuring, signaling, protective, regulating equipment, with all the internal electrical and mechanical interconnections and structural parts, as defined by the original manufacturer, which can be assembled in accordance with the original manufacturer’s instructions
Note 1: Throughout this document, the term assembly is used for a low-voltage switchgear and controlgear assembly.
Note 2: The term “switching device” includes mechanical switching devices and semiconductor switching devices, e.g. soft starters, semiconductor relays, frequency converters. The auxiliary circuits may also include electro-mechanical devices, e.g. control relays, terminal blocks, and electronic devices, e.g. electronic motor control devices, electronic measurement and protection devices, bus communication, programmable logic controller systems.
3.1.2
assembly system
full range of mechanical and electrical components (enclosures, busbars, functional units, auxiliary circuits and associated controls, etc.), as defined by the original manufacturer, which can be assembled in accordance with the original manufacturer’s instructions in order to produce various assemblies
3.1.3
main circuit
all the conductive parts of an assembly included in a circuit which is intended to transmit electrical energy
[Source: IEC 60050-441: 1984, 441-13-02]
3.1.4
auxiliary circuit
all the conductive parts of an assembly included in a circuit (other than the main circuit) intended to control, measure, signal, regulate and process data, etc.
Note: The auxiliary circuits of an assembly include the control and the auxiliary circuits of the switching devices.
[Source: IEC 60050-441: 1984, 441-13-03, modified]
3.1.5
busbar
low-impedance conductor to which several electric circuits can be connected at separate points
Note: The term "busbar" is generic and does not presuppose the material, the geometrical shape, dimensions or area of the conductor(s).
[Source: GB/T 2900.83-2008, 151-12-30, modified]
3.1.6
main busbar
busbar to which one or several distribution busbars and/or incoming and outgoing units are connected
Foreword i
Introduction iii
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviations
5 Interface characteristics
5.1 General
5.2 Voltage ratings
5.2.1 Rated voltage (Un) (of the assembly)
5.2.2 Rated operational voltage (Ue) (of a circuit of an assembly)
5.2.3 Rated insulation voltage (Ui) (of a circuit of an assembly)
5.2.4 Rated impulse withstand voltage (Uimp) (of the assembly)
5.3 Current ratings
5.3.1 Rated current of an assembly (InA)
5.3.2 Rated current of a main outgoing circuit (Inc)
5.3.3 Group rated current of a main circuit (Ing)
5.3.4 Rated peak withstand current (Ipk)
5.3.5 Rated short-time withstand current (Icw) (of a main circuit of an assembly)
5.3.6 Rated conditional short-circuit current (Icc) (of an assembly or a circuit of an assembly)
5.4 Rated diversity factor (RDF)
5.5 Rated frequency (fn)
5.6 Other characteristics
6 Information
6.1 Assembly designation marking
6.2 Documentation
6.2.1 Information relating to the assembly
6.2.2 Instructions for handling, installation, operation and maintenance
6.3 Device and/or component identification
7 Service conditions
7.1 Normal service conditions
7.1.1 Climatic conditions
7.1.2 Pollution degree
7.2 Special service conditions
7.3 Conditions during transport, storage and installation
8 Constructional requirements
8.1 Strength of materials and parts
8.1.1 General
8.1.2 Protection against corrosion
8.1.3 Properties of insulating materials
8.1.4 Resistance to ultra-violet (UV) radiation
8.1.5 Mechanical strength
8.1.6 Lifting provision
8.2 Degree of protection provided by an assembly enclosure
8.2.1 Protection against mechanical impact (IK code)
8.2.2 Protection against contact with live parts, ingress of solid foreign bodies and water (IP code)
8.2.3 Assembly with removable parts
8.3 Clearances and creepage distances
8.3.1 General
8.3.2 Clearances
8.3.3 Creepage distances
8.4 Protection against electric shock
8.4.1 General
8.4.2 Basic protection
8.4.3 Fault protection
8.4.4 Additional requirements for class II assemblies
8.4.5 Limitation of steady-state touch currents and charge
8.4.6 Operating and servicing conditions
8.5 Incorporation of switching devices and components
8.5.1 Fixed parts
8.5.2 Removable parts
8.5.3 Selection of switching devices and components
8.5.4 Installation of switching devices and components
8.5.5 Accessibility
8.5.6 Barriers
8.5.7 Direction of operation and indication of switching positions
8.5.8 Indicator lights and push-buttons
8.5.9 Power factor correction banks
8.6 Internal electrical circuits and connections
8.6.1 Main circuits
8.6.2 Auxiliary circuits
8.6.3 Bare and insulated conductors
8.6.4 Selection and installation of non-protected live conductors to reduce the possibility of short-circuits
8.6.5 Identification of the conductors of main and auxiliary circuits
8.6.6 Identification of the protective conductor (PE, PEL, PEM, PEN) and of the neutral conductor (N) and the mid-point conductor (M) of the main circuits
8.6.7 Conductors in AC circuits passing through ferromagnetic enclosures or plates
8.7 Cooling
8.8 Terminals for external cables
9 Performance requirements
9.1 Dielectric properties
9.1.1 General
9.1.2 Power-frequency withstand voltage
9.1.3 Impulse withstand voltage
9.1.4 Protection of surge protective devices
9.2 Temperature-rise limits
9.2.1 General
9.2.2 Adjustment of rated currents for alternative ambient air temperatures
9.3 Short-circuit protection and short-circuit withstand strength
9.3.1 General
9.3.2 Information concerning short-circuit withstand strength
9.3.3 Relationship between peak current and short-time current
9.3.4 Coordination of protective devices
9.4 Electromagnetic compatibility (EMC)
10 Design verification
10.1 General
10.2 Strength of materials and parts
10.2.1 General
10.2.2 Resistance to corrosion
10.2.3 Properties of insulating materials
10.2.4 Resistance to ultraviolet (UV) radiation
10.2.5 Lifting
10.2.6 Verification of protection against mechanical impact (IK code)
10.2.7 Marking
10.2.8 Mechanical operation
10.3 Degree of protection of assemblies (IP Code)
10.4 Clearances and creepage distances
10.5 Protection against electric shock and integrity of protective circuits
10.5.1 General
10.5.2 Effective earth continuity between the exposed-conductive-parts of the class I assembly and the protective circuit
10.5.3 Short-circuit withstand strength of the protective circuit
10.6 Incorporation of switching devices and components
10.6.1 General
10.6.2 Electromagnetic compatibility
10.7 Internal electrical circuits and connections
10.8 Terminals for external conductors
10.9 Dielectric properties
10.9.1 General
10.9.2 Power-frequency withstand voltage
10.9.3 Impulse withstand voltage
10.9.4 Test of enclosures made of insulating material
10.9.5 External door or cover mounted operating handles of insulating material
10.9.6 Test of conductors and hazardous live parts covered by insulating material to provide protection against electric shock
10.10 Temperature-rise
10.10.1 General
10.10.2 Verification by test
10.10.3 Verification comparison
10.10.4 Verification assessment
10.11 Short-circuit withstand strength
10.11.1 General
10.11.2 Circuits of assemblies which are exempted from the verification of the short-circuit withstand strength
10.11.3 Verification by comparison with a reference design - Using a checklist
10.11.4 Verification by comparison with a reference design(s) - Using calculation
10.11.5 Verification by test
10.12 Electromagnetic compatibility (EMC)
11 Routine verification
11.1 General
11.2 Degree of protection against contact with hazardous live parts, ingress of solid foreign bodies and water of enclosures
11.3 Clearances and creepage distances
11.4 Protection against electric shock and integrity of protective circuits
11.5 Incorporation of built-in components
11.6 Internal electrical circuits and connections
11.7 Terminals for external conductors
11.8 Mechanical operation
11.9 Dielectric properties
11.10 Wiring, operational performance and function
Annex A (Normative) Minimum and maximum cross-sectional area of copper cables suitable for connection to terminals for external cables (see 8.8)
Annex B (Normative) Method of calculating the cross-sectional area of protective conductors with regard to thermal stresses due to currents of short duration
Annex C (Informative) User information template
Annex D (Informative) Design verification
Annex E (Informative) Rated diversity factor
E.1 General
E.2 Rated diversity factor for outgoing circuits within an assembly
Annex F (Normative) Measurement of clearances and creepage distances5)
F.1 Basic principles
F.2 Use of ribs
Annex G (Normative) Correlation between the nominal voltage of the supply system and the rated impulse withstand voltage of the equipment 6)
Annex H (Informative) Operating current and power loss of copper cables
Annex I (Informative) Thermal equivalent of an intermittent current
Annex J (Normative) Electromagnetic compatibility (EMC)
J.1 General
J.3 Terms and definitions
Annex K (Normative) Operating current and power loss of bare copper bars
Annex L (Informative) Guidance on verification of temperature-rise
L.1 General
L.2 Temperature-rise limits
L.3 Test
L.4 Verification assessment
L.5 Verification by comparison with a reference design
Annex M (Normative) Verification of the short-circuit withstand strength of busbar structures by comparison with a reference design by calculation
M.1 General
M.2 Terms and definitions
M.3 Verification method
M.4 Conditions for application
Annex N (Informative) List of notes concerning certain countries
Bibliography
Figure E.1 Typical assembly
Figure E.2 Example 1: Table E.1 – Functional unit loading for an assembly with a rated diversity factor of 0.68
Figure E.3 Example 2: Table E.1 – Functional unit loading for an assembly with a rated diversity factor of 0.6 in Section B and 0.68 in Section C
Figure F.1 Measurement of clearance and creepage distances
Figure I.1 Example of average heating effect calculation
Figure J.1 Examples of ports
Figure L.1 Verification of temperature-rise
Figure M.1 Tested busbar structure (TS)
Figure M.2 Nontested busbar structure (NTS)
Figure M.3 Angular busbar configuration with supports at the corners
Table 1 Minimum clearances in air (8.3.2)
Table 2 Minimum creepage distances (8.3.3)
Table 3 Cross-sectional area of a copper protective conductor (8.4.3.2.2)
Table 4 Conductor selection and installation requirements (8.6.4)
Table 5 Minimum terminal capacity for copper protective conductors (PE) (8.8)
Table 6 Temperature-rise limiting values (9.2)
Table 7 Values for the factor na (9.3.3)
Table 8 Power-frequency withstand voltage for main circuits (10.9.2)
Table 9 Power-frequency withstand voltage for auxiliary circuits (10.9.2)
Table 10 Impulse withstand test voltages (10.9.3)
Table 11 Copper test conductors for rated currents up to 400A inclusive (10.10.2.3.2)
Table 12 Copper test conductors for rated currents from 400A to 7, 000A (10.10.2.3.2)
Table 13 Short-circuit verification by comparison with reference designs: checklist (10.5.3.3, 10.11.3 and 10.11.4)
Table 14 Relationship between prospective fault current and diameter of copper wire
Table 15 Climatic conditions
Table A.1 Cross-section of copper cables suitable for connection to terminals for external cables
Table B.1 Values of k for insulated protective conductors not incorporated in cables or bare protective conductors in contact with cable covering
Table C.1 User information template
Table D.1 List of design verifications to be performed
Table E.1 Examples of loading for an assembly
Table F.1 Minimum width of grooves
Table G.1 Correspondence between the nominal voltage of the supply system and the equipment rated impulse withstand voltage
Table H.1 Operating current and power loss of single-core copper cables with a permissible conductor temperature of 70℃(ambient temperature inside the assembly: 55℃)
Table H.2 Reduction factor k1 for cables with a permissible conductor temperature of 70℃ (extract from GB/T 16895.6-2014, Table B.52.14)
Table J.1 Tests for EMC immunity for environment A (see J.10.12.2)
Table J.2 Tests for EMC immunity for environment B (see J.10.12.2)
Table J.3 Acceptance criteria when electromagnetic disturbances are present
Table K.1 Operating current and power loss of bare copper bars with rectangular cross-section, run horizontally and arranged with their largest face vertical, frequency 50Hz to 60Hz (ambient air temperature inside the assembly: 55℃, temperature of the conductor 70℃)
Table K.2 Factor k4 for different temperatures of the air inside the assembly and/or for the conductors
GB/T 7251.1-2023 Low-voltage switchgear and controlgear assemblies - Part 1: General rules
1 Scope
This document lays down the general definitions and service conditions, construction requirements, technical characteristics and verification requirements for low-voltage switchgear and controlgear assemblies.
Note: Throughout this document, the term assembly (see 3.1.1) is used for a low-voltage switchgear and controlgear assembly.
For the purpose of determining assembly conformity, the requirements of the relevant part of the IEC 61439-2 onwards, apply together with the cited requirements of this document. For assemblies not covered by IEC 61439-3 onward, IEC 61439-2 applies.
This document applies to assemblies only when required by the relevant assembly standard as follows:
——assemblies for which the rated voltage does not exceed 1, 000V AC or 1, 500V DC;
——assemblies designed for a nominal frequency of the incoming supply or supplies not exceeding 1,000Hz;
——assemblies intended for indoor and outdoor applications;
——stationary or movable assemblies with or without an enclosure;
——assemblies intended for use in connection with the generation, transmission, distribution and conversion of electric energy, and for the control of electrical energy consuming equipment.
This document does not apply to individual devices and self-contained components such as motor starters, fuse switches, power electronic converter systems and equipment (PECS), switch mode power supplies (SMPS), uninterruptable power supplies (UPS), basic drive modules (BDM), complete drive modules (CDM), adjustable speed power drives systems (PDS), and other electronic equipment which comply with their relevant product standards. This document describes the integration of devices and self-contained components into an assembly or into an empty enclosure forming an assembly.
For some applications involving, for example, explosive atmospheres, functional safety, there can be a need to comply with the requirements of other standards or legislation in addition to those specified in the IEC 61439 (all parts).
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 2423.2-2008 Environmental testing for electric and electronic products - Part 2: Test methods - Tests B: Dry heat (IEC 60068-2-2: 2007, IDT)
GB/T 2423.4-2008 Environmental testing for electric and electronic products - Part 2: Test methods - Test Db: Damp heat, cyclic (12h+12h cycle) (IEC 60068-2-30: 2005, IDT)
GB/T 2423.17-2008 Environmental testing for electric and electronic products - Part 2: Test methods - Test Ka: Salt mist(IEC 60068-2-11: 1981, IDT)
GB/T 4025-2010 Basic and safety principles for man-machine interface, marking and identification - Coding principles for indicators and actuators (IEC 60073: 2002, IDT)
GB/T 4026-2019 Basic and safety principles for man-machine interface, marking and identification - Identification of equipment terminals, conductor terminations and conductors (IEC 60445: 2017, IDT)
GB/T 4205-2010 Basic and safety principles for man-machine interface (MMI), marking and identification - Actuating principles (IEC 60447: 2004, IDT)
GB/T 5094.1-2018 Industrial systems, installations and equipment and industrial products - Structuring principles and reference designations - Part 1: Basic rules (IEC 81346-1: 2009, IDT)
GB/T 5169.10-2017 Fire hazard testing for electric and electronic products - Part 10: Glowing/hot-wire based test methods - Glow-wire apparatus and common test procedure (IEC 60695-2-10: 2013, IDT)
GB/T 5169.11-2017 Fire hazard testing for electric and electronic products - Part 11:Glowing/hot-wire based test methods - Glow-wire flammability test method for end-products (GWEPT) (IEC 60695-2-11: 2014, IDT)
GB/T 11021-2014 Electrical insulation - Thermal evaluation and designation (IEC 60085: 2007, IDT)
GB/T 16895.6-2014 Low-voltage electrical installations - Part 5-52: Selection and erection of electrical equipment - Wiring systems (IEC 60364-5-52: 2009, IDT)
GB/T 16895.18-2010 Electrical installations of buildings - Part 5-51: Selection and erection of electrical equipment - Common rules (IEC 60364-5-51: 2005, IDT)
GB/T 16935.1-2008 Insulation coordination for equipment within low-voltage systems - Part 1: Principles, requirements and tests (IEC 60664-1: 2007, IDT)
GB/T 17626.4-2018 Electromagnetic compatibility - Testing and measurement techniques - Electrical fast transient/burst immunity test (IEC 61000-4-4: 2012, IDT)
GB/T 17626.6-2017 Electromagnetic compatibility - Testing and measurement techniques - Immunity to conducted disturbances, induced by radio-frequency fields (IEC 61000-4-6: 2013, IDT)
GB/T 17627-2019 High-voltage test techniques for low-voltage equipment - Definitions, test and procedure requirements, test equipment (IEC 61180: 2016, IDT)
GB 17799.3-2012 Electromagnetic compatibility(EMC) - Generic standards - Emission standard for industrial environments (IEC 61000-6-3: 2011, IDT)
Note: There is no technical difference between the referenced content from GB 17799.3-2012 and that from IEC 61000-6-3: 2006/AMD1: 2010.
GB/T 20641-2014 Empty enclosures for low-voltage switchgear and controlgear assemblies - General requirements (IEC 62208: 2011, IDT)
GB/T 24276-2017 A method of temperature-rise verification of low-voltage switchgear and controlgear assemblies by calculation (IEC TR 60890: 2014, IDT)
GB/T 35698.1-2017 Calculation of effects of short-circuit currents - Part 1: Definitions and calculation methods (IEC 60865-1: 2011, IDT)
ISO 178: 2019 Plastics - Determination of flexural properties
Note: GB/T 9341-2008 Plastic - Determination of flexural properties (ISO 178: 2001, IDT)
ISO 179-1: 2010 Plastics - Determination of Charpy impact properties - Part 1: Noninstrumented impact test
Note: GB/T 1043.1-2008 Plastics - Determination of Charpy impact properties - Part 1: Non-instrumented impact test (ISO 179-1: 2000, IDT)
ISO 179-2: 2020 Plastics - Determination of Charpy impact properties - Part 2: Instrumented impact test
Note: GB/T 1043.2-2018 Plastics - Determination of Charpy impact properties - Part 2: Instrumented impact test (ISO 179-2: 1997, IDT)
ISO 2409 Paints and varnishes - Cross-cut test
Note: GB/T 9286-2021 Paints and varnishes - Cross-cut test (ISO 2409: 2020, IDT)
ISO 4628-3: 2016 Paints and varnishes - Evaluation of degradation of coatings - Designation of quantity and size of defects, and of intensity of uniform changes in appearance - Part 3: Assessment of degree of rusting
Note: GB/T 30789.3-2014 Paints and varnishes - Evaluation of degradation of coatings - Designation of quantity and size of defects, and of intensity of uniform changes in appearance - Part 3: Assessment of degree of rusting (ISO 4628-3: 2003, IDT)
ISO 4892-2: 2013 Plastics - Methods of exposure to laboratory light sources - Part 2：Xenonarc lamps
Note: GB/T 16422.2-2014 Plastics - Methods of exposure to laboratory light sources - Part 2: Xenon-arc sources (ISO 4892-2: 2006, IDT)
ISO 7010 Graphical symbols - Safety colours and safety signs - Registered safety signs
Note: GB/T 31523.1-2015 Safety information identification systems - Part 1: Signs (ISO 7010: 2011, MOD)
IEC 60364 (all parts) Low-voltage electrical installations
Note: GB/T 16895 (all parts) Low-voltage electrical installations [IEC 60364 (all parts)]
IEC 60364-1 Low-voltage electrical installations - Part 1: Fundamental principles, assessment of general characteristics, definitions
Note: GB/T 16895.1-2008 Low-voltage electrical installations - Part 1: Fundamental principles, assessment of general characteristics, definitions (IEC 60364-1: 2005, IDT)
IEC 60364-4-41: 2005 Low-voltage electrical installations - Part 4-41: Protection for safety - Protection against electric shock
IEC 60364-4-41: 2005/ AMD1: 2017 Low-voltage electrical installations - Part 4-41: Protection for safety - Protection against electric shock - Amendment 1
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 General terms
3.1.1
low-voltage switchgear and controlgear assembly
assembly
combination of one or more low-voltage switching devices together with associated control, measuring, signaling, protective, regulating equipment, with all the internal electrical and mechanical interconnections and structural parts, as defined by the original manufacturer, which can be assembled in accordance with the original manufacturer’s instructions
Note 1: Throughout this document, the term assembly is used for a low-voltage switchgear and controlgear assembly.
Note 2: The term “switching device” includes mechanical switching devices and semiconductor switching devices, e.g. soft starters, semiconductor relays, frequency converters. The auxiliary circuits may also include electro-mechanical devices, e.g. control relays, terminal blocks, and electronic devices, e.g. electronic motor control devices, electronic measurement and protection devices, bus communication, programmable logic controller systems.
3.1.2
assembly system
full range of mechanical and electrical components (enclosures, busbars, functional units, auxiliary circuits and associated controls, etc.), as defined by the original manufacturer, which can be assembled in accordance with the original manufacturer’s instructions in order to produce various assemblies
3.1.3
main circuit
all the conductive parts of an assembly included in a circuit which is intended to transmit electrical energy
[Source: IEC 60050-441: 1984, 441-13-02]
3.1.4
auxiliary circuit
all the conductive parts of an assembly included in a circuit (other than the main circuit) intended to control, measure, signal, regulate and process data, etc.
Note: The auxiliary circuits of an assembly include the control and the auxiliary circuits of the switching devices.
[Source: IEC 60050-441: 1984, 441-13-03, modified]
3.1.5
busbar
low-impedance conductor to which several electric circuits can be connected at separate points
Note: The term "busbar" is generic and does not presuppose the material, the geometrical shape, dimensions or area of the conductor(s).
[Source: GB/T 2900.83-2008, 151-12-30, modified]
3.1.6
main busbar
busbar to which one or several distribution busbars and/or incoming and outgoing units are connected
Contents of GB/T 7251.1-2023
Foreword i
Introduction iii
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviations
5 Interface characteristics
5.1 General
5.2 Voltage ratings
5.2.1 Rated voltage (Un) (of the assembly)
5.2.2 Rated operational voltage (Ue) (of a circuit of an assembly)
5.2.3 Rated insulation voltage (Ui) (of a circuit of an assembly)
5.2.4 Rated impulse withstand voltage (Uimp) (of the assembly)
5.3 Current ratings
5.3.1 Rated current of an assembly (InA)
5.3.2 Rated current of a main outgoing circuit (Inc)
5.3.3 Group rated current of a main circuit (Ing)
5.3.4 Rated peak withstand current (Ipk)
5.3.5 Rated short-time withstand current (Icw) (of a main circuit of an assembly)
5.3.6 Rated conditional short-circuit current (Icc) (of an assembly or a circuit of an assembly)
5.4 Rated diversity factor (RDF)
5.5 Rated frequency (fn)
5.6 Other characteristics
6 Information
6.1 Assembly designation marking
6.2 Documentation
6.2.1 Information relating to the assembly
6.2.2 Instructions for handling, installation, operation and maintenance
6.3 Device and/or component identification
7 Service conditions
7.1 Normal service conditions
7.1.1 Climatic conditions
7.1.2 Pollution degree
7.2 Special service conditions
7.3 Conditions during transport, storage and installation
8 Constructional requirements
8.1 Strength of materials and parts
8.1.1 General
8.1.2 Protection against corrosion
8.1.3 Properties of insulating materials
8.1.4 Resistance to ultra-violet (UV) radiation
8.1.5 Mechanical strength
8.1.6 Lifting provision
8.2 Degree of protection provided by an assembly enclosure
8.2.1 Protection against mechanical impact (IK code)
8.2.2 Protection against contact with live parts, ingress of solid foreign bodies and water (IP code)
8.2.3 Assembly with removable parts
8.3 Clearances and creepage distances
8.3.1 General
8.3.2 Clearances
8.3.3 Creepage distances
8.4 Protection against electric shock
8.4.1 General
8.4.2 Basic protection
8.4.3 Fault protection
8.4.4 Additional requirements for class II assemblies
8.4.5 Limitation of steady-state touch currents and charge
8.4.6 Operating and servicing conditions
8.5 Incorporation of switching devices and components
8.5.1 Fixed parts
8.5.2 Removable parts
8.5.3 Selection of switching devices and components
8.5.4 Installation of switching devices and components
8.5.5 Accessibility
8.5.6 Barriers
8.5.7 Direction of operation and indication of switching positions
8.5.8 Indicator lights and push-buttons
8.5.9 Power factor correction banks
8.6 Internal electrical circuits and connections
8.6.1 Main circuits
8.6.2 Auxiliary circuits
8.6.3 Bare and insulated conductors
8.6.4 Selection and installation of non-protected live conductors to reduce the possibility of short-circuits
8.6.5 Identification of the conductors of main and auxiliary circuits
8.6.6 Identification of the protective conductor (PE, PEL, PEM, PEN) and of the neutral conductor (N) and the mid-point conductor (M) of the main circuits
8.6.7 Conductors in AC circuits passing through ferromagnetic enclosures or plates
8.7 Cooling
8.8 Terminals for external cables
9 Performance requirements
9.1 Dielectric properties
9.1.1 General
9.1.2 Power-frequency withstand voltage
9.1.3 Impulse withstand voltage
9.1.4 Protection of surge protective devices
9.2 Temperature-rise limits
9.2.1 General
9.2.2 Adjustment of rated currents for alternative ambient air temperatures
9.3 Short-circuit protection and short-circuit withstand strength
9.3.1 General
9.3.2 Information concerning short-circuit withstand strength
9.3.3 Relationship between peak current and short-time current
9.3.4 Coordination of protective devices
9.4 Electromagnetic compatibility (EMC)
10 Design verification
10.1 General
10.2 Strength of materials and parts
10.2.1 General
10.2.2 Resistance to corrosion
10.2.3 Properties of insulating materials
10.2.4 Resistance to ultraviolet (UV) radiation
10.2.5 Lifting
10.2.6 Verification of protection against mechanical impact (IK code)
10.2.7 Marking
10.2.8 Mechanical operation
10.3 Degree of protection of assemblies (IP Code)
10.4 Clearances and creepage distances
10.5 Protection against electric shock and integrity of protective circuits
10.5.1 General
10.5.2 Effective earth continuity between the exposed-conductive-parts of the class I assembly and the protective circuit
10.5.3 Short-circuit withstand strength of the protective circuit
10.6 Incorporation of switching devices and components
10.6.1 General
10.6.2 Electromagnetic compatibility
10.7 Internal electrical circuits and connections
10.8 Terminals for external conductors
10.9 Dielectric properties
10.9.1 General
10.9.2 Power-frequency withstand voltage
10.9.3 Impulse withstand voltage
10.9.4 Test of enclosures made of insulating material
10.9.5 External door or cover mounted operating handles of insulating material
10.9.6 Test of conductors and hazardous live parts covered by insulating material to provide protection against electric shock
10.10 Temperature-rise
10.10.1 General
10.10.2 Verification by test
10.10.3 Verification comparison
10.10.4 Verification assessment
10.11 Short-circuit withstand strength
10.11.1 General
10.11.2 Circuits of assemblies which are exempted from the verification of the short-circuit withstand strength
10.11.3 Verification by comparison with a reference design - Using a checklist
10.11.4 Verification by comparison with a reference design(s) - Using calculation
10.11.5 Verification by test
10.12 Electromagnetic compatibility (EMC)
11 Routine verification
11.1 General
11.2 Degree of protection against contact with hazardous live parts, ingress of solid foreign bodies and water of enclosures
11.3 Clearances and creepage distances
11.4 Protection against electric shock and integrity of protective circuits
11.5 Incorporation of built-in components
11.6 Internal electrical circuits and connections
11.7 Terminals for external conductors
11.8 Mechanical operation
11.9 Dielectric properties
11.10 Wiring, operational performance and function
Annex A (Normative) Minimum and maximum cross-sectional area of copper cables suitable for connection to terminals for external cables (see 8.8)
Annex B (Normative) Method of calculating the cross-sectional area of protective conductors with regard to thermal stresses due to currents of short duration
Annex C (Informative) User information template
Annex D (Informative) Design verification
Annex E (Informative) Rated diversity factor
E.1 General
E.2 Rated diversity factor for outgoing circuits within an assembly
Annex F (Normative) Measurement of clearances and creepage distances5)
F.1 Basic principles
F.2 Use of ribs
Annex G (Normative) Correlation between the nominal voltage of the supply system and the rated impulse withstand voltage of the equipment 6)
Annex H (Informative) Operating current and power loss of copper cables
Annex I (Informative) Thermal equivalent of an intermittent current
Annex J (Normative) Electromagnetic compatibility (EMC)
J.1 General
J.3 Terms and definitions
Annex K (Normative) Operating current and power loss of bare copper bars
Annex L (Informative) Guidance on verification of temperature-rise
L.1 General
L.2 Temperature-rise limits
L.3 Test
L.4 Verification assessment
L.5 Verification by comparison with a reference design
Annex M (Normative) Verification of the short-circuit withstand strength of busbar structures by comparison with a reference design by calculation
M.1 General
M.2 Terms and definitions
M.3 Verification method
M.4 Conditions for application
Annex N (Informative) List of notes concerning certain countries
Bibliography
Figure E.1 Typical assembly
Figure E.2 Example 1: Table E.1 – Functional unit loading for an assembly with a rated diversity factor of 0.68
Figure E.3 Example 2: Table E.1 – Functional unit loading for an assembly with a rated diversity factor of 0.6 in Section B and 0.68 in Section C
Figure F.1 Measurement of clearance and creepage distances
Figure I.1 Example of average heating effect calculation
Figure J.1 Examples of ports
Figure L.1 Verification of temperature-rise
Figure M.1 Tested busbar structure (TS)
Figure M.2 Nontested busbar structure (NTS)
Figure M.3 Angular busbar configuration with supports at the corners
Table 1 Minimum clearances in air (8.3.2)
Table 2 Minimum creepage distances (8.3.3)
Table 3 Cross-sectional area of a copper protective conductor (8.4.3.2.2)
Table 4 Conductor selection and installation requirements (8.6.4)
Table 5 Minimum terminal capacity for copper protective conductors (PE) (8.8)
Table 6 Temperature-rise limiting values (9.2)
Table 7 Values for the factor na (9.3.3)
Table 8 Power-frequency withstand voltage for main circuits (10.9.2)
Table 9 Power-frequency withstand voltage for auxiliary circuits (10.9.2)
Table 10 Impulse withstand test voltages (10.9.3)
Table 11 Copper test conductors for rated currents up to 400A inclusive (10.10.2.3.2)
Table 12 Copper test conductors for rated currents from 400A to 7, 000A (10.10.2.3.2)
Table 13 Short-circuit verification by comparison with reference designs: checklist (10.5.3.3, 10.11.3 and 10.11.4)
Table 14 Relationship between prospective fault current and diameter of copper wire
Table 15 Climatic conditions
Table A.1 Cross-section of copper cables suitable for connection to terminals for external cables
Table B.1 Values of k for insulated protective conductors not incorporated in cables or bare protective conductors in contact with cable covering
Table C.1 User information template
Table D.1 List of design verifications to be performed
Table E.1 Examples of loading for an assembly
Table F.1 Minimum width of grooves
Table G.1 Correspondence between the nominal voltage of the supply system and the equipment rated impulse withstand voltage
Table H.1 Operating current and power loss of single-core copper cables with a permissible conductor temperature of 70℃(ambient temperature inside the assembly: 55℃)
Table H.2 Reduction factor k1 for cables with a permissible conductor temperature of 70℃ (extract from GB/T 16895.6-2014, Table B.52.14)
Table J.1 Tests for EMC immunity for environment A (see J.10.12.2)
Table J.2 Tests for EMC immunity for environment B (see J.10.12.2)
Table J.3 Acceptance criteria when electromagnetic disturbances are present
Table K.1 Operating current and power loss of bare copper bars with rectangular cross-section, run horizontally and arranged with their largest face vertical, frequency 50Hz to 60Hz (ambient air temperature inside the assembly: 55℃, temperature of the conductor 70℃)
Table K.2 Factor k4 for different temperatures of the air inside the assembly and/or for the conductors
