1 Scope
This part of GB 7251 lays down the definitions and states of the service conditions, construction requirements, technical characteristics and verification requirements for low voltage switchgear and controlgear assemblies (hereinafter referred to as “ASSEMBLY”) (see 3.1.1).
This standard cannot be used alone to specify an ASSEMBLY or used for a purpose of determining conformity. ASSEMBLIES shall comply with the relevant part of the GB 7251 series; Parts 2 onwards.
This part applies to low-voltage switchgear and controlgear assemblies (ASSEMBLIES) only when required by the relevant ASSEMBLY standard as follows:
- ASSEMBLIES for which the rated voltage does not exceed 1000V in case of a.c. or 1500V in case of d.c.;
- stationary or movable ASSEMBLIES with or without enclosure;
- ASSEMBLIES intended for use in connection with the generation, transmission, distribution and conversion of electric energy, and for the control of electric energy consuming equipment;
- ASSEMBLIES designed for use under special service conditions, for example in ships and in rail vehicles provided that the other relevant specific requirements are complied with;
Note 1: supplementary requirements for ASSEMBLIES in ships are covered by GB/T 7061.
- ASSEMBLIES designed for electrical equipment of machines provided that the other relevant specific requirements are complied with.
Note 2: supplementary requirements for ASSEMBLIES forming part of a machine are covered by the GB 5226 series.
This part applies to all ASSEMBLIES whether they are designed, manufactured and verified on a one-off basis or fully standardized and manufactured in quantity.
The manufacture and/or assembly may be carried out other than by the original manufacturer (see 3.10.1).
This standard does not apply to individual devices and self-contained components, such as motor starters, fuse switches, electronic equipment, etc. which will comply with the relevant product standards.
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 referenced document (including any amendments) applies.
GB/T 2423.17-2008 Environmental Testing for Electric and Electronic Products - Part 2: Test Method - Test Ka: Salt Mist (IEC 60068-2-11:1981, IDT)
GB/T 2423.2-2008 Environmental Testing for Electric and Electronic Products - Part 2: Test Methods - Test B: Dry Heat (IEC 60068-2-2:2007, IDT)
GB/T 2423.4-2008 Environmental Testing for Electric and Electronic Products - Part 2: Test method - Test Db: Damp Heat, Cyclic (12h+12h Cycle) (IEC 60068-2-30:2005, IDT)
GB/T 4025-2010 Basic and Safety Principles for Man-machine Interface (MMI), Marking and Identification - Coding Principles for Indicators and Actuators (IEC 60073:2002, IDT)
GB/T 4205-2010 Basic and Safety Principles for Man-machine Interface (MMI), Marking and Identification - Actuating Principles (IEC 60447:2004, IDT)
GB 4208-2008 Degrees of Protection Provided by Enclosure (IP Code) (IEC 60529:2001, IDT)
GB/T 5013.3-2008 Rubber Insulated Cables of Rated Voltages up to and Including 450/750V - Part 3: Heat Resistant Silicone Insulated Cables (IEC 60245-3:1994, IDT)
GB/T 5169.10-2006 Fire Hazard Testing for Electric and Electronic Products - Part 10: Glow/Hot-wire Based Test Methods - Glow-wire Apparatus and Common Test Procedure (IEC 60695-2-10:2000, IDT)
GB/T 5169.11-2006 Fire Hazard Testing for Electric and Electronic Products - Part 11: Glow/Hot-wire Based Test Methods - Glow-wire Flammability Test Method for End-products (IEC 60695-2-11:2000, IDT)
GB/T 5169.5-2008 Fire Hazard Testing for Electric and Electronic Products - Part 5: Test Flames-Needle Test Method - Apparatus Confirmatory Arrangement and Guidance (IEC 60695-11-5:2004, IDT)
GB/T 9341-2008 Plastics - Determination of Flexural Properties (ISO 178:2001, IDT)
GB/T 16895.10-2010 Low-voltage Electrical Installations - Part 4-44: Protection for Safety - Protection against Voltage Disturbances and Electromagnetic Disturbances (IEC 60364-4-44:2007, IDT)
GB 16895.21-2011 Low-voltage Electrical Installations - Part 4-41: Protection for Safety - Protection Against Electric Shock (IEC 60364-4-41:2005, 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 17626.11-2008 Electromagnetic Compatibility - Testing and Measurement Techniques - Voltage Dips, Short Interruptions and Voltage Variations Immunity Tests (IEC 61000-4-11:2004, IDT)
GB/T 17626.13-2006 Electromagnetic Compatibility - Testing and Measurement Techniques - Harmonics and Interharmonics Including Mains Signaling at A.C. Power Port, Low Frequency Immunity Test (IEC 61000-4-13:2002 ), IDT)
GB/T 17626.4-2008 Electromagnetic Compatibility - Testing and Measurement Techniques - Electrical Fast Transient/Burst Immunity Test (IEC 61000-4-4:2004, IDT)
GB/T 17626.5-2008 Electromagetic Compatibility - Testing and Measurement Techniques - Surge (Impact) Immunity Test (IEC 61000-4-5:2005, IDT)
GB/T 20138-2006 Degrees of Protection Provided by Enclosures for Electrical Equipment Against External Mechanical Impacts (IK Code) (IEC 62262:2002, IDT)
GB/T 24276-2009 A Method of Temperature-rise Assessment by Extrapolation for Partially Type-tested Assemblies (PTTA) of Low-voltage Switchgear and Controlgear (IEC/TR 60890:1987+IEC/TR 60890:1987/Amd 1:1995, IDT)
IEC 60085:2007 Electrical Insulation - Thermal Evaluation and Designation
IEC 60216 (All Parts) Electrical Insulating Materials - Properties of Thermal Endurance (All Parts)
IEC 60227-3:1993 Polyvinyl Chloride Insulated Cables of Rated Voltages up to and Including 450/750 V - Part 3: Non-sheathed Cables for Fixed Wiring
IEC 60245-4:1994 Rubber Insulated Cables - Rated Voltages up to and Including 450/750 V - Part 4: Cords and Flexible Cables
IEC 60364 Low-voltage Electrical Installations (All Parts)
IEC 60364-5-52:2009 Low-voltage Electrical Installations - Part 5-52: Selection and Erection of Electrical Equipment - Wiring Systems
IEC 60364-5-53:2001 Electrical Installations of Buildings - Part 5-53: Selection and Erection of Electrical Equipment – Isolation, Switching and Control
IEC 60364-5-54:2011 Low-voltage Electrical Installations - Part 5-54: Selection and Erection of Electrical Equipment - Earthing Arrangements and Protective Conductors
IEC 60439 (All Parts) Low-voltage Switchgear and Controlgear Assemblies (All Parts)
IEC 60445:2010 Basic and Safety Principles for Man-machine Interface, Marking and Identification - Identification of Equipment Terminals, Conductor Terminations and Conductors
IEC 60865-1:1993 Short-circuit Currents - Calculation of Effects - Part 1: Definitions and Calculation Methods
IEC 60947-1:2007 Low-voltage Switchgear and Controlgear - Part 1: General Rules
IEC 61000-4-2:2008 Electromagnetic Compatibility (EMC) -Part 4-2: Testing and Measurement Techniques - Electrostatic Discharge Immunity Test
IEC 61000-4-3:2006 Electromagnetic Compatibility (EMC) - Part 4-3: Testing and measurement Techniques - Radiated, Radio Frequency, Electromagnetic Field Immunity Test )
IEC 61000-4-6:2008 Electromagnetic Compatibility (EMC) - Part 4-6: Testing and Measurement Techniques - Immunity to Conducted Disturbances, Induced by Radio-Frequency Fields
IEC 61000-4-8:2009 Electromagnetic Compatibility (EMC) - Part 4-8: Testing and Measurement Techniques - Power Frequency Magnetic Field Immunity Test
IEC 61000-6-4:2006 Electromagnetic Compatibility (EMC) - Part 6-4: Generic Standards - Emission Standard for Industrial Environments )
IEC 61082-1 Preparation of Documents Used in Electro-technology - Part 1: Rules
IEC 61180 (All Parts) High-voltage Test Techniques for Low-voltage Equipment (All Parts)
IEC 61201:2007 Extra-low Voltage (ELV) - Limit Values
IEC 61439 (All Parts) Low-voltage Switchgear and Controlgear Assemblies (All Parts)
IEC 62208 Empty Enclosures for Low-voltage Switchgear and Controlgear Assemblies - General Requirements
IEC 81346-1 Industrial Systems, Installations and Equipment and Industrial Products - Structuring Principles and Reference Designations - Part 1: Basic Rules
IEC 81346-2 Industrial Systems, Installations and Equipment and Industrial Products - Structuring Principles and Reference Designations - Part 2: Classification of Objects and Codes for Classes
IEC/CISPR 11:2009 Industrial, Scientific and Medical Equipment - Radio-frequency Disturbance Characteristics - Limits and Methods of Measurement )
IEC/CISPR 22 Information Technology Equipment - Radio Disturbance Characteristics - Limits and Methods of Measurement
ISO 179 (All Parts) Plastics - Determination of Charpy Impact Strength (All Parts)
ISO 2409:2007 Paints and Varnishes - Cross-cut Test
ISO 4628-3:2003 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 4892-2:2006 Plastics - Methods of Exposure to Laboratory Light Sources - Part 2: Xenonarc Lamps
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
3.1.2
ASSEMBLY system
Full range of mechanical and electrical components (enclosures, busbars, functional units, 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 (of an ASSEMBLY)
All the conductive parts of an ASSEMBLY included in a circuit which is intended to transmit electrical energy
[IEC 60050-441:1984, 441-13-02]
3.1.4
Auxiliary circuit (of an ASSEMBLY)
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.
Foreword i
Introduction v
1 Scope
2 Normative References
3 Terms and Definitions
3.1 General Terms
3.2 Constructional Units of ASSEMBLIES
3.3 External Design of ASSEMBLIES
3.4 Structural Parts of ASSEMBLIES
3.5 Conditions of Installation of ASSEMBLIES
3.6 Insulation Characteristics
3.7 Protection against Electric Shock
3.8 Characteristics
3.9 Verification
3.10 Manufacturer/User
4 Symbols and Abbreviations
5 Interface Characteristics
5.1 General
5.2 Voltage Ratings
5.3 Current Ratings
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
6.3 Device and/or Component Identification
7 Service Conditions
7.1 Normal Service Conditions
7.2 Special Service Conditions
7.3 Conditions during Transport, Storage and Installation
8 Constructional Requirements
8.1 Strength of Materials and Parts
8.2 Degree of Protection Provided by an ASSEMBLY Enclosure
8.3 Clearances and Creepage Distances
8.4 Protection against Electric Shock
8.5 Incorporation of Switching Devices and Components
8.6 Internal Electrical Circuits and Connections
8.7 Cooling
8.8 Terminals for External Conductors
9 Performance Requirements
9.1 Dielectric Properties
9.2 Temperature Rise Limits
9.3 Short-circuit Protection and Short-circuit Withstand Strength
9.4 Electromagnetic Compatibility (EMC)
10 Design Verification
10.1 General
10.2 Strength of Materials and Parts
10.3 Degree of Protection of ASSEMBLIES
10.4 Clearances and Creepage Distances
10.5 Protection against Electric Shock and Integrity of Protective Circuits
10.6 Incorporation of Switching Devices and Components
10.7 Internal Electrical Circuits and Connections
10.8 Terminals for External Conductors
10.9 Dielectric Properties
10.10 Verification of Temperature Rise
10.11 Short-circuit Withstand Strength
10.12 Electromagnetic Compatibility (EMC)
10.13 Mechanical Operation
11 Routine Verification
11.1 General
11.2 Degree of Protection 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
Appendix A (Normative) Minimum and Maximum Cross-section of Copper Conductors Suitable for Connection to Terminals for External Conductors (See 8.8)
Appendix B (Normative) Method of Calculating the Cross-sectional Area of Protective Conductors with regard to Thermal Stresses due to Currents of Short Duration
Appendix C (Informative) User Information Template
Appendix D (Informative) Design Verification
Appendix E (Informative) Rated Diversity Factor
E.1 General
E.2 Rated Diversity Factor of An ASSEMBLY
E.3 Rated Diversity Factor of A Group of Outgoing Circuits
E.4 Rated Diversity Factor and Intermittent Duty
Appendix F (Normative) Measurement of Clearances and Creepage Distances
F.1 Basic Principles
F.2 Use of Ribs
Appendix G (Normative) Correlation between the Nominal Voltage of the Supply System and the Rated Impulse Withstand Voltage of the Equipment
Appendix H (Informative) Operating Current and Power Loss of Copper Conductors
Appendix I (Void)
Appendix J (Normative) Electromagnetic Compatibility (EMC)
J.1 General
J.2 Terms and Definitions
Appendix K (Normative) Protection by Electrical Separation
K.1 General
K.2 Electrical Separation
K.3 Class II Equipment or Equivalent Insulation
Appendix L (Informative) Clearances and Creepage Distances for North American Region
Appendix M (Informative) North American Temperature Rise Limits
Appendix N (normative) Operating Current and Power Loss of Bare Copper Bars
Appendix O (Informative) Guidance on Temperature Rise Verification
O.1 General
O.2 Temperature Rise Limits
O.3 Test
O.4 Calculation
O.5 Design Rules
Appendix P (Normative) Verification of the Short-circuit Withstand Strength of Busbar Structures by Comparison with a Tested Reference Design by Calculation
P.1 General
P.2 Terms and Definitions
P.3 Method of Verification
P.4 Conditions for Application
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
Figure E.3 Example 2: Table E.1 – Functional Unit Loading for an ASSEMBLY with a Rated Diversity Factor of
Figure E.4 Example 3: Table E.1 – Functional Unit Loading for an ASSEMBLY with a Rated Diversity Factor of
Figure E.5 Example 4: Table E.1 – Functional Unit Loading for an ASSEMBLY with a Rated Diversity Factor of
Figure E.6 Example of Average Heating Effect Calculation
Figure E.7 Example Graph for the Relation between the Equivalent RDF and the Parameters at Intermittent Duty at t1=0.5 s, I1=7I2 at Different Cycle Times
Figure E.8 Example Graph for the Relation between the Equivalent RDF and the Parameters at Intermittent Duty at I1=I2 (No Starting Overcurrent)
Figure F.1 Measurement of Ribs
Figure J.1 Examples of Ports
Figure O.1 Temperature Rise Verification Methods
Figure P.1 Tested Busbar Structure (TS)
Figure P.2 Non Tested Busbar Structure (NTS)
Figure P.3 Angular Busbar Configuration with Supports at the Corners
Table 1 Minimum Clearances in Air a (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 Cross-sectional Area of Copper Protective Conductors (PE, PEN) (8.8)
Table 6 Temperature-rise Limits (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 and Control 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 4000A (10.10.2.3.2)
Table 13 Short-circuit Verification by Comparison with a Reference Design: Check List (10.5.3.3, 10.11.3 and 10.11.4)
Table 14 Relationship between Prospective Fault Current and Diameter of Copper Wire
Table A.1 Cross-section of Copper Conductors Suitable for Connection to Terminals for External Conductors
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 Template
Table D.1 List of Design Verifications to be Performed
Table E.1 Examples of Loading for an ASSEMBLY with a Rated Diversity Factor of
Table E.2 Example of Loading of a Group of Circuits (Section B – Figure E.1) with a Rated Diversity Factor of
Table E.3 Example of Loading of a Group of Circuits (Sub-distribution Board – Figure E.1) with a Rated Diversity Factor of
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℃
Table H.2 Reduction Factor k1 for Cables with a Permissible Conductor Temperature of 70℃
Table J.1 Tests for EMC Immunity for Environment A
Table J.2 Tests for EMC Immunity for Environment B
Table J.3 Acceptance Criteria when Electromagnetic Disturbances are Present
Table K.1 Maximum Disconnecting Times for TN Systems
Table L.1 Minimum Clearances in Air
Table L.2 Minimum Creepage Distances
Table M.1 North American Temperature Rise Limits
Table N.1 Operating Current and Power Loss of Bare Copper Bars with Rectangular Cross-section, Run Horizontally and Arranged with Their Largest Face Vertical, Frequency 50 Hz~60 Hz
Table N.2 Factor k4 for Different Temperatures of the Air inside the ASSEMBLY and/or for the Conductors
