Standard No.:	GB/T 7251.1-2013
English Name:	Low-voltage switchgear and controlgear assemblies―Part 1:General rules
Chinese Name:	低压成套开关设备和控制设备 第1部分:总则
Chinese Classification:	K31    Low-voltage distribution electrical equipment
Professional Classification:	GB    National Standard
Issued by:	AQSIQ, SAC
Issued on:	2013-12-31
Implemented on:	2015-1-13
Status:	superseded
Superseded by:	GB/T 7251.1-2023 Low-voltage switchgear and controlgear assemblies—Part 1: General rules
Superseded on:	2024-3-1
Abolished on:	2024-03-01
Superseding:	GB 7251.1-2005 低压成套开关设备和控制设备 第1部分：型式试验和部分型式试验 成套设备
Language:	English
File Format:	PDF
Word Count:	50500 words
Price(USD):	140.0
Delivery:	via email in 1 business day

Low-voltage Switchgear and Controlgear Assemblies – Part 1: General Rules 低压成套开关设备和控制设备 第1部分:总则 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/Amd1:1995, 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. Note: The auxiliary circuits of an ASSEMBLY include the control and the auxiliary circuits of the switching devices. [IEC 60050-441:1984, 441-13-03, modified] 3.1.5 Busbar Low-impedance conductor to which several electric circuits can be separately connected. Note: the term "busbar" does not presuppose the geometrical shape, size or dimensions of the conductor. 3.1.6 Main busbar Busbar to which one or several distribution busbars and/or incoming and outgoing units can be connected 3.1.7 Distribution busbar Busbar within one section which is connected to a main busbar and from which outgoing units are supplied. Note: Conductors that are connected between a functional unit and a busbar are not considered as a part of the distribution busbars. 3.1.8 Functional unit Part of an ASSEMBLY comprising all the electrical and mechanical elements including switching devices that contribute to the fulfillment of the same function. Note: Conductors which are connected to a functional unit but which are external to its compartment or enclosed protected space (e.g. auxiliary cables connected to a common compartment) are not considered to form part of the functional unit. 3.1.9 Incoming unit Functional unit through which electrical energy is normally fed into the ASSEMBLY. 3.1.10 Outgoing unit Functional unit through which electrical energy is normally supplied to one or more external circuits. 3.1.11 Short-circuit protective device; SCPD Device intended to protect a circuit or parts of a circuit against short-circuit currents by interrupting them. [2.2.21 of IEC 60947-1:2007] 3.2 Constructional Units of ASSEMBLIES 3.2.1 Fixed part Part consisting of components assembled and wired on a common support and which is designed for fixed installation. 3.2.2 Removable part Part consisting of components assembled and wired on a common support which is intended to be removed entirely from the ASSEMBLY and replaced whilst the circuit to which it is connected may be live. 3.2.3 Connected position Position of a removable part when it is fully connected for its intended function 3.2.4 Removed position Position of a removable part when it is outside the ASSEMBLY, and mechanically and electrically separated from it. 3.2.5 Insertion interlock Device preventing the introduction of a removable part into a location not intended for that removable part. 3.2.6 Fixed connection Connection which is connected or disconnected by means of a tool. 3.2.7 Section Constructional unit of an ASSEMBLY between two successive vertical delineations. 3.2.8 Sub-section Constructional unit of an ASSEMBLY between two successive horizontal or vertical delineations within a section. 3.2.9 Compartment Section or sub-section enclosed except for openings necessary for interconnection, control or ventilation. 3.2.10 Transport unit Part of an ASSEMBLY or a complete ASSEMBLY suitable for transportation without being dismantled. 3.2.11 Shutter Part which can be moved between: ——a position in which it permits engagement of the contacts of a removable part with fixed contacts, and ——a position in which it becomes a part of a cover or a partition shielding the fixed contacts. [IEC 60050-441:1984, 441-13-07, modified] 3.3 External Design of ASSEMBLIES 3.3.1 Open-type ASSEMBLY ASSEMBLY consisting of a structure which supports the electrical equipment, the live parts of the electrical equipment being accessible. 3.3.2 Dead-front ASSEMBLY Open-type ASSEMBLY with a front cover; live parts may be accessible from directions other than the front. 3.3.3 Enclosed ASSEMBLY ASSEMBLY which is enclosed on all sides with the possible exception of its mounting surface in such a manner as to provide a defined degree of protection. 3.3.4 Cubicle-type ASSEMBLY Enclosed ASSEMBLY of the floor-standing type which may comprise several sections, sub-sections or compartments. 3.3.5 Multi-cubicle-type ASSEMBLY Combination of a number of mechanically joined cubicle-type ASSEMBLIES. 3.3.6 Desk-type ASSEMBLY Enclosed ASSEMBLY with a horizontal or inclined control panel or a combination of both, which incorporates control, measuring, signalling apparatus, etc. 3.3.7 Box-type ASSEMBLY Enclosed ASSEMBLY, intended to be mounted on a vertical plane 3.3.8 Multi-box-type ASSEMBLY Combination of box-type ASSEMBLIES mechanically joined together, with or without a common supporting frame, the electrical connections passing between two adjacent boxes through openings in the adjoining faces. 3.3.9 Wall-mounted surface type ASSEMBLY ASSEMBLY for installation on the surface of a wall. 3.3.10 Wall-mounted recessed type ASSEMBLY ASSEMBLY for installation into a wall recess, where the enclosure does not support the portion of wall above. 3.4 Structural Parts of ASSEMBLIES 3.4.1 Supporting structure Structure forming part of an ASSEMBLY designed to support various components of the ASSEMBLY and any enclosure. 3.4.2 Mounting structure Structure not forming part of an ASSEMBLY designed to support an ASSEMBLY. 3.4.3 Mounting plate Plate designed to support various components and suitable for installation in an ASSEMBLY. 3.4.4 Mounting frame Framework designed to support various components and suitable for installation in an ASSEMBLY. 3.4.5 Enclosure Housing affording the type and degree of protection suitable for the intended application. [GB/T 2900.73-2008, 195-02-35]. 3.4.6 Cover External part of the enclosure of an ASSEMBLY. 3.4.7 Door Hinged or sliding cover. 3.4.8 Removable cover Cover which is designed for closing an opening in the external enclosure and which can be removed for carrying out certain operations and maintenance work. 3.4.9 Cover plate Part of an ASSEMBLY which is used for closing an opening in the external enclosure and designed to be held in place by screws or similar means. Note 1: It is not normally removed after the equipment is put into service. Note 2: The cover plate can be provided with cable entries. 3.4.10 Partition Part of the enclosure of a compartment separating it from other compartments. 3.4.11 Barrier Part providing protection against direct contact from any direction of access. [GB/T 2900.73-2008, 195-06-15, modified] 3.4.12 Obstacle Part preventing unintentional direct contact, but not preventing direct contact by deliberate action. [GB/T 2900.73-2008, 195-06-16, modified] Note: obstacles are intended to prevent unintentional contact with live parts but not intentional contact by deliberate circumvention of the obstacle. They are intended to protect skilled or instructed persons but are not intended to protect ordinary persons. 3.4.13 Terminal shield Part enclosing terminals and providing a defined degree of protection against access to live parts by persons or objects. 3.4.14 Cable entry Part with openings which permit the passage of cables into the ASSEMBLY. 3.4.15 Enclosed protected space Part of an ASSEMBLY intended to enclose electrical components and which provides defined protection against external influences and contact with live parts. 3.5 Conditions of Installation of ASSEMBLIES 3.5.1 ASSEMBLY for indoor installation ASSEMBLY which is designed for use in locations where the normal service conditions for indoor use as specified in 7.1 are fulfilled. 3.5.2 ASSEMBLY for outdoor installation ASSEMBLY which is designed for use in locations where the normal service conditions for outdoor use as specified in 7.1 are fulfilled. 3.5.3 Stationary ASSEMBLY ASSEMBLY which is designed to be fixed at its place of installation, for instance to the floor or to a wall, and to be used at this place. 3.5.4 Movable ASSEMBLY ASSEMBLY which is designed so that it can readily be moved from one place of use to another. 3.6 Insulation Characteristics 3.6.1 Clearance The distance between two conductive parts along a string stretched the shortest way between these conductive parts. [IEC 60050-441:1984, 441-17-31] 3.6.2 Creepage distance The shortest distance along the surface of a solid insulating material between two conductive parts. [GB/T 2900.83-2008, 151-15-50] Note: A joint between two pieces of insulating material is considered part of the surface. 3.6.3 Overvoltage Any voltage having a peak value exceeding the corresponding peak value of the maximum steady-state voltage at normal operating conditions. [Definition 3.7 of GB/T 16935.1-2008] 3.6.4 Temporary overvoltage Overvoltage at power frequency of relatively long duration (several seconds). [Definition 3.7.1 of GB/T 16935.1-2008, modified] 3.6.5 Transient overvoltage Short duration overvoltage of a few milliseconds or less, oscillatory or non-oscillatory, usually highly damped. [GB/T 2900.57-2008, 604-03-13] 3.6.6 Power-frequency withstand voltage r.m.s. value of a power-frequency sinusoidal voltage which does not cause breakdown under specified conditions of test. [Definition 2.5.56 of IEC 60947-1:2007] Note: the power-frequency withstand voltage is equivalent to the short-term temporary overvoltage in GB/T 16935.1. 3.6.7 Impulse withstand voltage Highest peak value of impulse voltage of prescribed form and polarity which does not cause breakdown of insulation under specified conditions. [Definition 3.8.1 of GB/T 16935.1-2008] 3.6.8 Pollution Any addition of solid, liquid or gaseous foreign matter that can result in a reduction of the dielectric strength or surface resistivity of insulation. [Definition 3.11 of GB/T 16935.1-2008, modified] 3.6.9 Pollution degree (of environmental conditions) Conventional number based on the amount of conductive or hygroscopic dust, ionized gas or salt, and on the relative humidity and its frequency of occurrence resulting in hygroscopic absorption or condensation of moisture leading to reduction in dielectric strength and/or surface resistivity. Note 1: the pollution degree to which the insulating materials of devices and components are exposed may be different from that of the macro-environment where the devices or components are located because of protection offered by means such as an enclosure or internal heating to prevent absorption or condensation of moisture. Note 2: for the purpose of this standard, the pollution degree is of the micro-environment. [Definition 2.5.58 of IEC 60947-1:2007] 3.6.10 Micro-environment (of a clearance or creepage distance) Immediate environment of the insulation which particularly influences the dimensioning of the creepage distances. Note: The micro-environment of the creepage distance or clearance and not the environment of the ASSEMBLY or components determines the effect on the insulation. The micro-environment may be better or worse than the environment of the ASSEMBLY or components. [Definition 3.12.2 of GB/T 16935.1-2008] 3.6.11 Overvoltage category (of a circuit or within an electrical system) Conventional number based on limiting (or controlling) the values of prospective transient overvoltages occurring in a circuit (or within an electrical system having different nominal voltages) and depending upon the means employed to influence the overvoltages. Note: In an electrical system, the transition from one overvoltage category to another of lower category is obtained through appropriate means complying with interface requirements, such as an overvoltage protective device or a series-shunt impedance arrangement capable of dissipating, absorbing, or diverting the energy in the associated surge current, to lower the transient overvoltage value to that of the desired lower overvoltage category. [Definition 2.5.60 of IEC 60947-1:2007] 3.6.12 Surge arrester Surge protective device; SPD Device designed to protect the electrical apparatus from high transient overvoltages and to limit the duration and frequently the amplitude of the follow-on current. [Definition 2.2.22 of IEC 60947-1:2007] 3.6.13 Insulation co-ordination Correlation of insulating characteristics of electrical equipment with the expected overvoltages and the characteristics of overvoltage protective devices on the one hand, and with the expected micro-environment and the pollution protective means on the other hand. [Definition 2.5.61 of IEC 60947-1:2007] 3.6.14 Inhomogeneous (non-uniform) field Electric field which has not an essentially constant voltage gradient between electrodes. [Definition 2.5.63 of IEC 60947-1:2007] 3.6.15 Tracking Progressive formation of conducting paths which are produced on the surface of a solid insulating material, due to the combined effects of electric stress and electrolytic contamination on this surface. [Definition 2.5.64 of IEC 60947-1:2007] 3.6.16 Comparative tracking index CTI Numerical value of the maximum voltage in volts at which a material withstands 50 drops of a defined test liquid without tracking. Note: the value of each test voltage and the CTI should be divisible by 25. [Definition 2.5.65 of IEC 60947-1:2007, modified] 3.6.17 Disruptive discharge Phenomena associated with the failure of insulation under electrical stress, in which the discharge completely bridges the insulation under test, reducing the voltage between the electrodes to zero or nearly zero. Note 1: a disruptive discharge in a solid dielectric produces permanent loss of dielectric strength; in a liquid or gaseous dielectric, the loss may be only temporary. Note 2: the term "sparkover" is used when a disruptive discharge occurs in a gaseous or liquid dielectric. Note 3: the term "flashover" is used when a disruptive discharge occurs over the surface of a dielectric in a gaseous or liquid medium. Note 4: the term "puncture" is used when a disruptive discharge occurs through a solid dielectric. 3.7 Protection against Electric Shock 3.7.1 Live part Conductor or conductive part intended to be energized in normal operation, including a neutral conductor, but by convention not a PEN conductor. Note: This term does not necessarily imply a risk of electric shock. [GB/T 2900.73-2008, 195-02-19, modified] 3.7.2 Hazardous live part Live part which, under certain conditions, can give a harmful electric shock. [GB/T 2900.73-2008, 195-06-05] 3.7.3 Exposed conductive part Conductive part of the ASSEMBLY, which can be touched and which is not normally live, but which may become a hazardous live part under fault conditions. [GB/T 2900.71-2008, 826-12-10, modified] 3.7.4 Protective conductor (Identification: PE) Conductor provided for purposes of safety, for example protection against electric shock [GB/T 2900.71-2008, 826-13-22] Note: as an example the protective conductor can electrically connect the following parts: ——exposed conductive parts; ——extraneous conductive parts; ——main earthing terminal; ——earth electrode; ——earthed point of the source or artificial neutral. 3.7.5 Neutral conductor N Conductor electrically connected to the neutral point and capable of contributing to the distribution of electric energy. [GB/T 2900.73-2008, 195-02-06, modified] 3.7.6 PEN conductor Conductor combining the functions of both a protective earthing conductor and a neutral conductor. [GB/T 2900.73-2008, 195-02-12] 3.7.7 Fault current Current resulting from an insulation failure, the bridging of insulation or incorrect connection in an electrical circuit. 3.7.8 Basic protection Protection against electric shock under fault-free conditions. [GB/T 2900.73-2008, 195-06-01] Note: Basic protection is intended to prevent contact with live parts and generally corresponds to protection against direct contact. 3.7.9 Basic insulation Insulation of hazardous live parts, which provide basic protection. [GB/T 2900.73-2008, 195-06-06] Note: this concept does not apply to insulation used exclusively for functional purposes. 3.7.10 Fault protection Protection against electric shock under single-fault conditions (e.g. failure of basic insulation). [GB/T 2900.73-2008, 195-06-02, modified] Note: fault protection generally corresponds to protection against indirect contact, mainly with regard to failure of basic insulation. 3.7.11 Extra-low voltage; ELV Any voltage not exceeding the relevant voltage limit specified in IEC 61201. 3.7.12 Skilled person Person with relevant education and experience to enable him or her to perceive risks and to avoid hazards which electricity can create. [GB/T 2900.71-2008, 826-18-01] 3.7.13 Instructed person Person adequately advised or supervised by skilled persons to enable him or her to perceive risks and to avoid hazards electricity can create. [GB/T 2900.71-2008, 826-18-02] 3.7.14 Ordinary person Person who is neither a skilled person nor an instructed person. [GB/T 2900.71-2008, 826-18-03] 3.7.15 Authorized person Skilled or instructed person, who is empowered to execute defined work. 3.8 Characteristics 3.8.1 Nominal value Value of a quantity used to designate and identify a component, device, equipment or system. [GB/T 2900.83-2008, 151-16-09] Note: the nominal value is generally a rounded value. 3.8.2 Limiting value In a specification of a component, device, equipment or system, the greatest or smallest admissible value of a quantity. [GB/T 2900.83-2008, 151-16-10] 3.8.3 Rated value Value of a quantity used for specification purposes, established for a specified set of operating conditions of a component, device, equipment, or system. [GB/T 2900.83-2008, 151-16-08] 3.8.4 Rating Set of rated values and operating conditions. [GB/T 2900.83-2008, 151-16-11] 3.8.5 Nominal voltage (of an electrical system) Approximate value of voltage used to designate or identify an electrical system [GB/T 2900.50-2008, 601-01-21 modified] 3.8.6 Short-circuit current Ic Over-current resulting from a short circuit due to a fault or an incorrect connection in an electric circuit. [IEC 60050-441:1984, 441-11-07] 3.8.7 Prospective short-circuit current Icp r.m.s. value of the current which would flow if the supply conductors to the circuit are short circuited by a conductor of negligible impedance located as near as practicable to the supply terminals of the ASSEMBLY (see 10.11.5.4). 3.8.8 Cut-off current Let-through current Maximum instantaneous value of current attained during the breaking operation of a switching device or a fuse. Note: this concept is of particular importance when the switching device or the fuse operates in such a manner that the prospective peak current of the circuit is not reached. [IEC 60050-441:1984, 441-17-12]. 3.8.9 Voltage ratings 3.8.9.1 Rated voltage Un Highest nominal voltage of the electrical system, a.c. (r.m.s.) or d.c., declared by the ASSEMBLY manufacturer, to which the main circuit(s) of the ASSEMBLY is (are) designed to be connected. Note 1: in polyphase circuits, it is the voltage between phases. Note 2: transients are disregarded. Note 3: the value of the supply voltage may exceed the rated voltage due to permissible system tolerances. 3.8.9.2 Rated operational voltage (of a circuit of an ASSEMBLY) Ue Value of voltage, declared by the ASSEMBLY manufacturer, which combined with the rated current determines its application. Note: in polyphase circuits, it is the voltage between phases. 3.8.9.3 Rated insulation voltage Ui r.m.s withstand voltage value, assigned by the ASSEMBLY manufacturer to the equipment or to a part of it, characterizing the specified (long-term) withstand capability of the insulation. [Definition 3.9.1 of GB/T 16935.1-2008, modified] Note 1: in polyphase circuits, it is the voltage between phases. Note 2: the rated insulation voltage is not necessarily equal to the rated operational voltage of equipment, which is primarily related to functional performance. 3.8.9.4 Rated impulse withstand voltage Uimp Impulse withstand voltage value, declared by the ASSEMBLY manufacturer, characterizing the specified withstand capability of the insulation against transient overvoltages. [Definition 3.9.2 of GB/T 16935.1-2008, modified] 3.8.10 Current ratings 3.8.10.1 Rated current In Value of current, declared by the ASSEMBLY manufacturer which can be carried without the temperature-rise of various parts of the ASSEMBLY exceeding specified limits under specified conditions. Note: for rated current of the ASSEMBLY (InA) see 5.3.1, and for rated current of a circuit (Inc) see 5.3.2. 3.8.10.2 Rated peak withstand current Ipk Value of peak short-circuit current, declared by the ASSEMBLY manufacturer, that can be withstood under specified conditions. 3.8.10.3 Rated short-time withstand current Icw r.m.s value of short-time current, declared by the ASSEMBLY manufacturer, that can be withstood under specified conditions, defined in terms of a current and time. 3.8.10.4 Rated conditional short-circuit current Icc Value of prospective short-circuit current, declared by the ASSEMBLY manufacturer, that can be withstood for the total operating time (clearing time) of the short-circuit protective device (SCPD) under specified conditions. Note: the short-circuit protective device may form an integral part of the ASSEMBLY or may be a separate unit. 3.8.11 Rated diversity factor; RDF Per unit value of the rated current, assigned by the ASSEMBLY manufacturer, to which outgoing circuits of an ASSEMBLY can be continuously and simultaneously loaded taking into account the mutual thermal influences. 3.8.12 Rated frequency fn Value of frequency, declared by the ASSEMBLY manufacturer, for which a circuit is designed and to which the operating conditions refer. Note: A circuit may be assigned a number or a range of rated frequencies or be rated for both a.c. and d.c. 3.8.13 Electromagnetic compatibility; EMC Note: for EMC related terms and definitions, see J.3.8.13.1 to J.3.8.13.5 of Appendix J. 3.9 Verification 3.9.1 Design verification Verification made on a sample of an ASSEMBLY or on parts of ASSEMBLIES to show that the design meets the requirements of the relevant ASSEMBLY standard. Note: design verification may comprise one or more equivalent methods, see 3.9.1.1, 3.9.1.2 and 3.9.1.3. 3.9.1.1 Verification test Test made on a sample of an ASSEMBLY or on parts of ASSEMBLIES to verify that the design meets the requirements of the relevant ASSEMBLY standard. Note: verification tests are equivalent to type tests. 3.9.1.2 Verification comparison Structured comparison of a proposed design for an ASSEMBLY, or parts of an ASSEMBLY, with a reference design verified by test. 3.9.1.3 Verification assessment Design verification of strict design rules or calculations applied to a sample of an ASSEMBLY or to parts of ASSEMBLIES to show that the design meets the requirements of the relevant ASSEMBLY standard. 3.9.2 Routine verification Verification of each ASSEMBLY performed during and/or after manufacture to confirm whether it complies with the requirements of the relevant ASSEMBLY standard. 3.10 Manufacturer/User 3.10.1 Original manufacturer Organization that has carried out the original design and the associated verification of an ASSEMBLY in accordance with the relevant ASSEMBLY standard. 3.10.2 ASSEMBLY manufacturer Organization taking the responsibility for the completed ASSEMBLY Note: the ASSEMBLY manufacturer may be a different organization to the original manufacturer. 3.10.3 User Party who will specify, purchase, use and/or operate the ASSEMBLY, or someone acting on their behalf 4 Symbols and Abbreviations Alphabetical list of terms with symbols and abbreviations together with the clause where they are first used: Symbol/Abbreviation Term Clause CTI comparative tracking index 3.6.16 ELV extra-low voltage 3.7.11 EMC electromagnetic compatibility 3.8.13 fn rated frequency 3.8.12 Ic short-circuit current 3.8.6 Icc rated conditional short-circuit current 3.8.10.4 Icp prospective short-circuit current 3.8.7 Icw rated short-time withstand current 3.8.10.3 InA rated current of the ASSEMBLY 5.3.1 Inc rated current of a circuit 5.3.2 Ipk rated peak withstand current 3.8.10.2 N neutral conductor 3.7.5 PE protective conductor 3.7.4 PEN PEN conductor 3.7.6 RDF rated diversity factor 3.8.11 SCPD short-circuit protective device 3.1.11 SPD surge protective device 3.6.12 Ue rated operational voltage 3.8.9.2 Ui rated insulation voltage 3.8.9.3 Uimp rated impulse withstand voltage 3.8.9.4 Un rated voltage 3.8.9.1 5 Interface Characteristics 5.1 General The characteristics of the ASSEMBLY shall ensure compatibility with the ratings of the circuits to which it is connected and the installation conditions and shall be declared by the ASSEMBLY manufacturer using the criteria identified in 5.2 to 5.6. 5.2 Voltage Ratings 5.2.1 Rated voltage (Un) (of the ASSEMBLY) The rated voltage shall be at least equal to the nominal voltage of the electrical system. 5.2.2 Rated operational voltage (Ue) (of a circuit of an ASSEMBLY) The rated operational voltage of any circuit shall not be less than the nominal voltage of the electrical system to which it is to be connected. If different from the rated voltage of the ASSEMBLY, the appropriate rated operational voltage of the circuit shall be stated. 5.2.3 Rated insulation voltage (Ui) (of a circuit of an ASSEMBLY) The rated insulation voltage of a circuit of an ASSEMBLY is the voltage value to which dielectric test voltages and creepage distances are referred. The rated insulation voltage of a circuit shall be equal or higher than the values stated for Un and for Ue for the same circuit. Note: for single-phase circuits derived from IT systems (see IEC 60364-5-52), the rated insulation voltage should be at least equal to the voltage between phases of the supply. 5.2.4 Rated impulse withstand voltage (Uimp) (of the ASSEMBLY) The rated impulse withstand voltage shall be equal to or higher than the values stated for the transient overvoltages occurring in the electrical system(s) to which the circuit is designed to be connected. Note: the preferred values of rated impulse withstand voltage are those given in Table G.1 of Appendix G.

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 70ºC Table H.2 Reduction Factor k1 for Cables with a Permissible Conductor Temperature of 70ºC 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