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GB/T 16895.21-2020: Low-voltage electrical installations - Part 4-41: Protection for safety. Protection against electric shock
Status: Valid GB/T 16895.21: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivered in | Standard Title (Description) | Status | PDF |
| GB/T 16895.21-2020 | English | 474 |
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Low-voltage electrical installations - Part 4-41: Protection for safety. Protection against electric shock
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GB/T 16895.21-2020
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| GB 16895.21-2011 | English | 959 |
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[GB/T 16895.21-2011] Low-voltage electrical installations -- Part 4-41: Protection for safety -- Protection against electric shock
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GB 16895.21-2011
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| GB 16895.21-2004 | English | 879 |
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Electrical installations of buildings -- Part 4-41: Protection for safety -- Protection against electric shock
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GB 16895.21-2004
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PDF similar to GB/T 16895.21-2020
Basic data | Standard ID | GB/T 16895.21-2020 (GB/T16895.21-2020) | | Description (Translated English) | Low-voltage electrical installations - Part 4-41: Protection for safety. Protection against electric shock | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | K09;Q77 | | Classification of International Standard | 13.260; 91.140.50 | | Word Count Estimation | 25,253 | | Date of Issue | 2020-12-14 | | Date of Implementation | 2021-07-01 | | Older Standard (superseded by this standard) | GB/T 16895.21-2011 | | Quoted Standard | IEC 60364-5-52; IEC 60364-5-54; IEC 60364-6; IEC 61084-1; IEC 61084-2; IEC 61140; IEC 61386-1; IEC 61386-21; IEC 61386-22; IEC 61386-23; IEC 61386-24; IEC 61386-25; IEC 61439-1; IEC 61439-2; IEC 61439-3; IEC 61439-4; IEC 61439-5; IEC 61439-6; IEC 61439-7 | | Adopted Standard | IEC 60364-4-41-2017, IDT | | Regulation (derived from) | National Standard Announcement No. 28 of 2020 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | | Summary | This standard specifies the basic requirements for protection against electric shock, including basic protection (direct contact protection) and failure protection (indirect contact protection) for humans and livestock. In addition, the application and combination of the above requirements are also specified according to external influence conditions. This standard also specifies the requirements for additional protection in specific situations. | GB/T 16895.21-2020: Low-voltage electrical installations - Part 4-41: Protection for safety. Protection against electric shock
---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
ICS 13.260;91.140.50
K09;Q77
National Standards of People's Republic of China
Replace GB/T 16895.21-2011
Released on 12-14-2020
2021-07-01 implementation
State Administration for Market Regulation
Released by the National Standardization Management Committee
1 Scope
This part of GB/T 16895 specifies the basic requirements for protection against electric shock, including the basic protection for humans and livestock (direct contact protection)
protection) and fault protection (protection against indirect contact). In addition, the application and combination of the above requirements are specified according to the external influence conditions.
This section also specifies the requirements for additional protection in specific cases.
410.2 Normative references
The following documents are indispensable for the application of this document. For dated references, only the dated version applies to this document
pieces. For undated references, the latest version (including all amendments) applies to this document.
IEC 60364-5-52 Low-voltage electrical installations Part 5-52.Selection and installation of electrical equipment Wiring system (Low-voltage
IEC 60364-5-54 Low-voltage electrical installations Part 5-54.Selection and installation of electrical equipment Earthing arrangements and protective conductors
IEC 61558-2-6 Safety of power transformers, power supply units and similar products Part 2-6.General purpose safety isolating transformers
IEC Guide104 Guidelines for the preparation of safety publications and the application of basic safety publications and multi-specialty shared safety publications (The
3 General requirements
3.1 Unless otherwise specified, the voltages in this section refer to the following voltages.
--- AC voltage root mean square value (rms);
--- Ripple-free DC voltage.
According to the customary definition, no ripple means that the root mean square value of the fingerprint wave voltage does not exceed 10% of the DC component.
3.2 Protective measures should include.
--- An appropriate combination of basic protection provisions and independent fault protection provisions; or
--- Reinforced protection regulations that combine basic protection and fault protection.
Additional protection means that under certain external influence conditions and in a certain special place (see the corresponding protection in the IEC 60364 series of standards
Part 7) is an integral part of the internal protective measures.
Note 1.For special-purpose protective measures, the concept expressed in this article may not be followed (see 410.3.5 and 410.3.6).
Note 2.Reinforced insulation is an example of enhanced protective measures.
3.3 Each part of the electrical installation should adopt one or more protective measures according to the external influence conditions.
The following protective measures are usually available.
--- Automatically cut off the power supply (see Chapter 411);
--- Double or reinforced insulation (see Chapter 412);
--- Electrical separation for supplying power to a single consumer (see Chapter 413);
--- Extra low voltage [safety extra low voltage (SELV) and protective extra low voltage (PELV)] (see Chapter 414).
During the selection and installation of the equipment, consideration should be given to the application of the above protective measures in the installation.
See 410.3.4~410.3.9 for special devices.
Note. The most commonly used protective measure in electrical installations is to automatically cut off the power supply.
3.4 For special devices or places, special protective measures specified in Part 7 of IEC 60364 should be adopted.
3.5 The protective measures specified in Appendix B, that is, the use of barriers and protective measures placed out of arm's reach, should only be used for the following persons
Devices accessible only to personnel.
--- Skilled technicians or trained personnel; or
--- Personnel under the supervision of skilled technicians or trained personnel.
3.6 The protective measures specified in Appendix C are.
--- Non-conductive places;
--- Ungrounded local equipotential bonding;
--- Electrical separation for supplying power to multiple electrical equipment.
The above protective measures can only be used on electrical devices under the operation or management of skilled technicians or trained personnel to prevent
3.7 When certain requirements for protective measures cannot be met, additional protective regulations should be adopted to obtain the same degree of safety effect as required.
Note. See 411.7 for an example of the application of this provision.
3.8 Different protective measures applied to the same device, part of a device or inside the equipment shall not affect each other so that a protective measure
failure to jeopardize another protective measure.
3.9 The following parts may not adopt the fail-safe provisions.
--- Metal brackets for overhead line insulators attached to buildings and located outside the reach of the arm;
---The unreachable steel bars in reinforced concrete poles of overhead lines;
---Small size (approximately less than 50mm×50mm), or because of its parts, it is impossible to be caught by people or it will not have a large area with human body parts
exposed conductive parts that are difficult or unreliable to connect with the protective conductor;
Note. The above examples are bolts, rivets, nameplates and cable clamps.
--- Metal pipes for laying wiring or metal enclosures for protecting equipment that meet the requirements of Chapter 412.
4 Protection measures. automatically cut off the power
4.1 General
When using automatic power cut off as a protection measure, it is required that.
--- The live part adopts the basic insulation, fence or external protection that meets the requirements of Appendix A as the basic protection; and
---Adopt the protection equipotential bonding that meets the requirements of 411.3~411.6 and automatically cut off the power supply under fault conditions as fault protection.
Note 1.When using this protective measure, Class Ⅱ equipment can also be used.
When there are specific regulations, a residual current protector with a rated residual operating current not exceeding 30mA that meets the requirements of 415.1 can be used
(RCD) as an additional protective measure.
Note 2.The residual current monitor (RCM) is not a protective device, but can be used to monitor the residual current of electrical installations. When the residual current exceeds a predetermined value,
The RCM sends out an audible signal or an audible signal and a visual signal.
4.2 Requirements for basic protection
All electrical equipment shall adopt one of the basic protection regulations described in Appendix A (and Appendix B where appropriate).
4.3 Requirements for fault protection
4.3.1 Protective earthing and protective equipotential bonding
4.3.1.1 Protective earthing
According to the specific conditions of the various system grounding types described in 411.4~411.6, the exposed conductive part should be connected to the protective conductor.
The exposed conductive parts that can be touched at the same time should be connected to the same earthing system individually, in groups or collectively.
The protective earthing conductor shall meet the requirements of IEC 60364-5-54.
Each circuit shall have a protective conductor connected to the associated earthing terminal.
4.3.1.2 Protective equipotential bonding
Protective equipotential bonding conductors shall be used for metal parts of non-electrical installations that enter each building and are likely to introduce dangerous potential differences.
Connect to the main ground terminal. These incoming metal parts may include.
---Pipes that provide services to buildings, such as gas, water, district heating systems, etc.;
---External conductive structural parts;
--- Accessible reinforcement on reinforced concrete structures.
The above-mentioned conductive parts introduced from outside the building shall be close enough to the home for equipotential bonding.
Metal pipes with insulating sections at the entrance to the building do not require protective equipotential bonding.
Note. For other connections to the main grounding terminal, see 542.4.1 of IEC 60364-5-54.2011 for details.
4.3.2 Automatic power cut-off in case of fault
4.3.2.1 When a fault with negligible impedance occurs between the line conductor of the circuit or equipment and the exposed conductive part or protective conductor,
The protective device shall automatically cut off the line conductor of the circuit or equipment within the cut-off time required by 411.3.2.2, 411.3.2.3 or 411.3.2.4.
The appliance shall be suitable for at least isolated line conductors.
Note. For the IT system in the first failure (see 411.6.1), it is not necessary to automatically cut off the power supply. For a second fault on a different live conductor
For the requirements of automatic power cut off, please refer to the regulations in 411.6.3.2 for details.
4.3.2.2 For the terminal circuit whose rated current does not exceed the following, the longest power-off time shall comply with the provisions in Table 41.1.
--- 63A for circuits with one or more sockets; and
--- The circuit that only supplies power to fixedly connected electrical equipment is 32A.
4.3.2.3 For the power distribution circuit in the TN system and the circuit other than those specified in 411.3.2.2, the time for cutting off the power supply shall not exceed 5s.
4.3.2.4 For the power distribution circuit in the TT system and the circuit other than those specified in 411.3.2.2, the time for cutting off the power supply shall not exceed 1s.
4.3.2.5 When it is not feasible to use an overcurrent protector to cut off the power supply in accordance with the provisions of 411.3.2 or it is not feasible to use a residual current protector (RCD)
When appropriate, see the protective regulations in Appendix D for details.
However, disconnecting the power supply may be for reasons other than protection against electric shock.
4.3.2.6 If the time to automatically cut off the power supply cannot meet the requirements of 411.3.2.2, 411.3.2.3 or 411.3.2.4 specified in 411.3.2.1
Requirements, shall adopt auxiliary protective equipotential bonding measures in accordance with the provisions of 415.2.
4.3.3 Power supply requirements for socket outlets and outdoor portable equipment
Residual current protective devices (RCD) with a rated residual operating current not exceeding 30mA are used as additional protection for.
---AC socket-outlets with a rated current not exceeding 32 A for general personnel and for general purposes, and;
---Outdoor AC mobile equipment with a rated current not exceeding 32A.
This article does not apply to IT systems whose fault current does not exceed 15mA when the first fault occurs.
Note. Additional protection for DC systems is under consideration.
4.3.4 Additional requirements for luminaire circuits in TN and TT systems
For the AC terminal circuit that supplies power to lamps and lanterns in houses of single households, a residual current with a rated residual operating current of no more than 30mA shall be provided.
current protector.
4.4 TN system
4.4.1 In the TN system, the integrity of the grounding of the electrical device depends on the reliable and effective connection of the PEN or PE conductor to the ground. like
If the grounding of the electrical installation is set in the public power supply system or other power supply systems, the staff of the power supply system shall be responsible for the electrical installation.
Electrical liability related to external conditions.
4.4.2 The neutral point or intermediate point of the power supply system should be grounded. If the system has no neutral or intermediate point or its neutral or intermediate point
If contact is not possible, one line conductor shall be grounded.
The exposed conductive parts of the electrical installation shall be connected to the main earthing terminal of the electrical installation through the protective conductor, and the main earthing terminal shall be connected to
Earthing point of the power supply system.
If there are other effective earth connection points, it is advisable to connect the protective conductor to those earth points as far as possible. additional grounding point
It should be evenly distributed, which can make the potential of the protective conductor as close as possible to the ground potential when a ground fault occurs.
Considering the shunting of the neutral conductor current caused by multi-point grounding of the PEN conductor, the protective conductor (PE and PEN) should be grounded at the point where it enters any building.
4.4.3 If the requirements of 543.4 in IEC 60364-5-54 can be met, a conductor can also be used as a protective conductor for fixedly installed electrical installations.
body and neutral conductors (i.e. PEN conductors). No switching or isolating devices shall be inserted in the PEN conductors.
4.4.4 The characteristics of the protective device (see 411.4.5) and the impedance of the circuit should satisfy the formula (1).
4.4.5 The following protective devices can be used as fault protection (indirect contact protection) for TN systems.
---overcurrent protector;
--- Residual current protector (RCD).
Note 1.When using RCD as fault protection, it is also advisable to use an overcurrent protective device that meets the requirements of IEC 60364-4-43 to protect the circuit.
Residual current protectors should not be used in TN-C systems.
Note 2.If protection selectivity is required between RCDs, see 535.3 of IEC 60364-5-53.2001.
4.5 TT system
4.5.1 All exposed conductive parts protected by the same protective device shall be connected to the common ground of these conductive parts through protective conductors.
on the poles. When multiple protective devices are used in series, all exposed conductive parts protected by each protective device must meet this requirement respectively.
The neutral point or intermediate point of the power supply system should be grounded. If neither a neutral nor an intermediate point exists or is inaccessible, one of the line conductors should be grounded.
4.5.2 In TT system, RCD should usually be used for fault protection. When the impedance ZS value of the fault circuit is sufficiently small (see 411.5.4), and
Ensure that its value is reliable and stable, and an overcurrent protection device can also be selected for fault protection.
Note 1.When using RCD as fault protection, it is also advisable to use an overcurrent protective device that meets the requirements of IEC 60364-4-43 to protect the circuit.
Note 2.This section does not involve the application of fault voltage operated protectors.
4.5.3 When the residual current protector is used as fault protection, the following conditions shall be met.
4.5.4 When over-current protective devices are used, formula (2) shall be satisfied.
4.6 IT system
4.6.1 In the IT system, the live parts should be insulated from the ground or grounded through a sufficiently large impedance. The grounding point can be at the neutral point of the system
Or an intermediate point, or an artificial neutral point. The latter can be grounded directly if the impedance of the artificial neutral is sufficiently high at the system frequency. if not
There is a neutral point or an intermediate point, which can ground the first-line conductor through a large impedance.
When a single fault occurs from a live conductor to the exposed conductive part or to the ground, since the fault current is small, if it can meet the requirements of 411.6.2
conditions, it is not necessary to automatically cut off the power supply according to the requirements of 411.3.2.However, protective provisions should be taken to avoid two faults occurring at the same time, so as to
To avoid the risk of harmful pathophysiological effects caused by simultaneous exposure of the human body to exposed conductive parts of different potentials.
Note. In order to reduce overvoltage or attenuate voltage oscillation, it may be necessary to ground through impedance or artificial neutral point. The characteristics of this grounding should be consistent with the installation
Adapt to the specific requirements of the location.
4.6.2 The exposed conductive parts should be grounded individually, in groups or collectively.
Formula (3) should be satisfied.
4.6.3 The IT system can use the following monitors and protective devices.
--- Insulation Monitor (IMD);
--- Residual current monitor (RCM);
--- Insulation fault location system (IFLS);
---overcurrent protector;
--- Residual current protector (RCD).
Note 1.If RCD is used as protection, when the first fault occurs, the malfunction of RCD cannot be ruled out due to capacitive leakage current.
Note 2.In the case of failure of two different Class I electrical equipment powered by different line conductors, only when each electrical equipment is protected by a separate RCD,
Two fault loops are possible to protect the action. It is also suitable to use an overcurrent protector.
4.6.3.1 When the IT system is designed not to cut off the power supply when the first failure occurs, one of the following monitoring measures shall be taken when the first failure occurs.
--- Insulation Monitor (IMD) may cooperate with Insulation Fault Location System (IFLS), or;
--- Residual current monitor (RCM), as long as the residual current is large enough to be detected.
4.6.4 When a second fault occurs on a different live conductor after the first fault occurs, the conditions for automatically cutting off the power supply shall meet the following requirements.
a) When all exposed conductive parts are connected to the same grounding system through the protective conductor, its automatic power cut-off condition is the same as that of the TN system
The situation of the system is similar, that is, formula (4) and formula (5) should be satisfied.
4.7 Functional Extra Low Voltage (FELV)
4.7.1 General
For functional reasons using a nominal voltage not exceeding 50 V a.c. or 120 V d.c., but failing to meet the
All requirements of SELV or PELV, and when SELV or PELV is not required, the requirements described in 411.7.2 and 411.7.3 shall apply
Additional measures to ensure basic protection and fault protection. This combined protection regulation is known as FELV.
Note. For example, when the circuit contains equipment (such as transformers, relays, remote switches, contactors) that do not have sufficient insulation for higher voltage circuits,
This situation is possible.
4.7.2 Requirements for basic protection
Basic protection should be achieved by one of the following measures.
--- Adopt the basic insulation that complies with the nominal voltage of the primary circuit of the power supply in A.1 of Appendix A;
---Installation of barriers or external protections in accordance with A.2 of Appendix A.
4.7.3 Requirements for failsafe
When the primary circuit adopts the protective measures for automatically cutting off the power supply specified in 411.3~411.6, the equipment in the FELV circuit should be exposed
The conductive part is connected to the protective conductor of the primary circuit of the power supply.
4.7.4 Power supply
The power supply of the FELV system shall be a transformer with at least a simple separation between the windings, or a power supply complying with the requirements of 414.3.
Note. If the FELV system is powered by a higher voltage system via a device, but the device does not have a connection between the higher voltage and the FELV system, it is at least simple
Separate conditions (such as autotransformers, potentiometers, semiconductor devices, etc.), the output circuit can only be regarded as an extension of the input circuit, and
The FELV circuit should be protected by protective measures installed on the input circuit.
4.7.5 Plugs and sockets
Plugs and sockets for FELV systems shall meet the following requirements.
---The plug should not be inserted into the socket of other voltage systems;
---The socket should not be inserted by plugs of other voltage systems;
--- The socket should have a protective conductor contact.
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