The following parts of GB/T 7251 Low-voltage Switchgear and Controlgear Assemblies are planned to be issued:
——Part 0: Guidance to Specifying Assemblies
——Part 1: General Rules
——Part 2: Power Switchgear and Controlgear Assemblies
——Part 3: Distribution Boards Intended to be Operated by Ordinary Persons (DBO);
——Part 4: Particular Requirements for Assemblies for Construction sites (ACS);
——Part 5: Assemblies for Power Distribution in public Networks;
——Part 6: Busbar Trunking Systems (Busways);
——Part 7: Assemblies for Specific Applications such as Marinas, Camping Sites, Market Squares, Electric Vehicles Charging Stations.
This part is Part 5 of GB/T 7251 and shall be jointly used with GB/T 7251.1-2013, and its provisions supplement, modify or replace the corresponding ones in GB/T 7251.1-2013; the clauses in GB/T 7251.1-2013 not being cited in this part are applicable to this part.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This part replaces GB/T 7251.5-2008 Low-voltage Switchgear and Controlgear Assemblies - Part 5: Particular Requirements for Assemblies for Power Distribution in Public Networks. The following technical changes have been made with respect to GB/T 7251.5-2008 (the previous edition):
——The reconstructed standard GB/T 7251 Low-voltage Switchgear and Controlgear Assemblies is made reference to, and the corresponding contents are kept consistent with the relevant applicable structure and technical contents in GB/T 7251.1-2013;
——New verifications are correspondingly introduced;
——The requirements of Substation cable distribution board and cable distribution cabinet are coordinated, and thereby the identification and definition of the two types of assemblies are unnecessary;
——The quantity of types of defined assemblies is reduced, and only the initial is taken for identifying different assemblies, thereby the standard is simplified;
——That the test carried out on the most complicated PENDA may be used to verify assemblies with the same general structure and rating data which are as complicated as or less complicated than the tested PENDA is determined;
——The time/requirements for verifying the impact force withstand of PENDA (public electricity network distribution assembly) in arctic climate are defined;
——The direction for applying force in static load test is corrected.
This part is, by means of translation, identical to IEC 61439-5: 2014 Low-voltage Switchgear and Controlgear Assemblies - Part 5: Assemblies for Power Distribution in Public Networks.
The Chinese counterparts of the international documents given as normative references in this part are:
——GB/T 5169.16-2008 Fire Hazard Testing for Electric and Electronic Products - Part 16: Test Flames - 50W Horizontal and Vertical Flame Test Methods (IEC 60695-11-10: 2003, IDT)
The following editorial changes are made in this part:
——"this standard" is changed into "this part";
——The symbol "," is changed to the decimal point ".";
——Tables and figures newly-added in this part are numbered from 101;
——Foreword in the international standard is deleted.
This part was proposed by China Electrical Equipment Industry Association.
This part is under the jurisdiction of SAC/TC 266 National Technical Committee on Low-voltage Switchgear and Controlgear Assemblies of Standardization Administration of China.
The previous edition replaced by this Part are:
——GB 7251.5-1998 and GB/T 7251.5-2008.
Low-voltage Switchgear and Controlgear Assemblies - Part 5: Assemblies for Power Distribution in Public Networks
低压成套开关设备和控制设备
第5部分：公用电网电力配电成套设备
1 Scope
This part of GB/T 7251 defines the specific requirements for public electricity network distribution assemblies (PENDAs).
PENDAs have the following criteria:
——used for the distribution of electrical energy in three phase systems for which the rated voltage does not exceed 1,000 V a.c. (see Figure 101 for a typical distribution network);
——stationary;
——open ASSEMBLIES are not covered by this part;
——suitable for installation in places where only skilled persons have access for their use however outdoor types may be installed in situations that are accessible to ordinary persons;
——for indoor or outdoor use.
The object of this part is to state the definitions and to specify the service conditions, construction requirements, technical characteristics and tests for PENDAs. Network parameters may require tests at higher performance levels.
PENDAs may also include control and/or signalling devices associated with the distribution of electrical energy.
This part applies to all PENDAs whether they are designed, manufactured 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 of GB/T 7251.1-2013).
This part does not apply to individual devices and self-contained components such as motor starters, fuse switches, electronic equipment, etc. which comply with the relevant product standards.
This part does not apply to specific types of ASSEMBLIES covered by other parts of GB/T 7251 series.
Figure 101 Typical Distribution Network
Notes:
1 If a PENDA is equipped with additional equipment (for example meters), in such a way that the main function is changed considerably, then other standards can also apply as agreed between user and manufacturer (see 8.5 of GB/T 7251.1-2013).
2 Where local regulations and practices permit, a PENDA according to this standard can be used in other than public networks.
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.
Chapter 2 of GB/T 7251.1-2013 applies except as follows.
Addition:
GB/T 7251.1-2013 Low-voltage Switchgear and Controlgear Assemblies - Part 1: General Rules (IEC 61439-1: 2011, IDT)
IEC 60695-11-10: 2013 Fire Hazard Testing - Part 11-10: Test flames - 50 W Horizontal and Vertical Flame Test Methods
ISO 6506-1 Metallic Materials - Brinell Hardness Test - Part 1: Test Method
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 7251.1-2013 and the following apply.
3.1 General terms
Additional terms:
3.1.101 public electricity network distribution ASSEMBLY; PENDA
ASSEMBLY generally for installation in a public electricity network which in use, receives electrical energy from one or more supplies and distributes that energy through one or more cables to other equipment.
Notes:
1 A PENDA is installed operated and maintained solely by skilled persons.
2 Some types of a PENDA were previously known as a cable distribution cabinet (CDC).
3.1.101.1 outdoor public electricity network distribution ASSEMBLY; PENDA-O
Cubicle type public electricity network distribution ASSEMBLY that is suitable for outdoor installation in places that may, or may not, be accessible to the public.
3.1.101.2 indoor public electricity network distribution ASSEMBLY; PENDA-I
Public electricity network distribution ASSEMBLY suitable for installation indoors generally without an enclosure, but including all structural parts necessary to support busbars, functional units and other ancillary devices, necessary to complete the ASSEMBLY.
3.3 External design of ASSEMBLIES
3.3.1 open-type ASSEMBLY
This term of GB/T 7251.1-2013 does not apply.
3.9 Verification
Modifications:
3.9.1 design verification
Delete the note.
3.9.1.2 verification comparison
This term of GB/T 7251.1-2013 does not apply.
3.9.1.3 verification assessment
This term of GB/T 7251.1-2013 does not apply.
4 Symbols and Abbreviations
Chapter 4 of GB/T 7251.1-2013 applies.
5 Interface Characteristics
Chapter 5 of GB/T 7251.1-2013 applies except as follows.
5.4 Rated diversity factor (RDF)
Addition:
In the absence of an agreement between the ASSEMBLY manufacturer and user concerning the actual load currents, the assumed loading of the outgoing circuits of the ASSEMBLY or group of outgoing circuits may be based on the values given in Table 101.
Table 101 Values of Assumed Loading
Number of main circuits Assumed loading factor
2 and 3 0.9
4 and 5 0.8
6 to 9 inclusive 0.7
10 (and above) 0.6
6 Information
Chapter 6 of GB/T 7251.1-2013 applies except as follows.
6.1 Assembly designation marking
Addition to first paragraph:
Designation plates may be placed inside an enclosure of an ASSEMBLY provided their intended place ensures good legibility and visibility when the door(s) is open or the cover is removed.
Replacement of item d):
d) GB/T 7251.5-2013.
6.3 Device and/or component identification
Additional paragraph:
In the case of removable fuse-carriers which are specific to a fuseway, a label shall be placed on the fuse carrier as well as on the fuse base, to avoid incorrect interchangeability of the fuse-carrier.
Additional clause:
6.101 Circuit identification
It shall be possible to identify each functional unit in a clearly visible manner.
7 Service Conditions
Chapter 7 of GB/T 7251.1-2013 applies except as follows.
7.1.1.2 Ambient air temperature for outdoor installations
Replacement of last paragraph with:
Unless the user specifies a PENDA shall be suitable for use in an arctic climate, the lower limit of ambient air temperature is -25℃. For an arctic climate the lower limit of ambient temperature is -50℃.
7.2 Special service conditions
Addition of the following note to item h):
Note: Exposure to vibration arising from traffic and/or occasional ground excavation is a normal service condition for PENDAs.
Additional paragraph:
Additional requirements for a PENDA-O, to be installed where heavy snowfalls occur and where they are adjacent to areas where there is snow clearance by ploughing, are subject to agreement (see Appendix BB) between manufacturer and user.
8 Constructional Requirements
Chapter 8 of GB/T 7251.1-2013 applies except as follows.
8.1 Strength of materials and parts
8.1.1 General
Addition:
A PENDA-O shall be arranged for ground mounting, transformer mounting, pole mounting, surface wall mounting or mounting within a recess within a wall, as agreed between user and manufacturer.
A PENDA may be direct coupled to a transformer by means of a flange coupling or it may connect to its supply by means of cable or via busbars as agreed between user and manufacturer. Outgoing circuits shall be suitable for connection by means of cables.
A reliable locking device shall be provided on outdoor enclosures which prevents access by unauthorized persons. Doors lids and covers shall be so designed that, after they are locked, they do not open due to subsequent moderate ground settlement, nor due to exposure to vibration arising from traffic and/or ground excavation and reinstatement works.
8.1.3.2 Resistance of insulating materials to heat and fire
Additional clause:
8.1.3.2.101 Verification of category of flammability
The insulating materials used for enclosures, barriers and other insulating parts shall have flame retardant properties in accordance with 10.2.3.102 of this part.
8.1.5 Mechanical strength
Additional clause:
8.1.5.101 Verification of mechanical strength
The mechanical properties of a PENDA-O shall comply with 10.2.101 of this part.
Parts of the PENDA-O intended to be embedded in the ground shall withstand the stresses imposed on them during installation and normal service and comply with 10.2.101.9.
Additional clause:
8.1.101 Thermal stability
The thermal stability of a PENDA shall be verified according to 10.2.3.101.
8.2 Degree of protection provided by an ASSEMBLY enclosure
8.2.1 Protection against mechanical impact
8.2.1 of GB/T 7251.1-2013 does not apply.
8.2.2 Protection against contact with live parts ingress of solid foreign bodies and water
Addition:
Open type ASSEMBLIES (IP00) are not covered by this part.
When a PENDA-O is intended to be installed in places accessible to the public, its enclosure shall, when fully-installed in accordance with the manufacturer's instructions, provide a degree of protection of at least IP34D according to IEC 60529. In other locations, the minimum level of protection shall be at least IP33.
PENDA-O's that are intended to be installed in places accessible to the public shall, unless otherwise stated by the user, be designed such that when any temporary cables are connected, the enclosure shall provide a degree of protection of at least IP23C according to IEC 60529. See 8.8 of this part.
Foreword i
1 Scope
2 Normative References
3 Terms and Definitions
4 Symbols and Abbreviations
5 Interface Characteristics
6 Information
7 Service Conditions
8 Constructional Requirements
9 Performance Requirements
10 Design Verification
11 Routine Verification
Annexes
Bibliography
