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GB 14050-2008: Types and safety technical requirements of system earthing
GB 14050-2008
Types and safety technical requirements of system earthing
ICS 91.140.50
K09
National Standards of People's Republic of China
Replacing GB 14050-1993
The type of system grounding and safety technical requirements
Posted 2008-09-24
2009-08-01 implementation
Administration of Quality Supervision, Inspection and Quarantine of People's Republic of China
Standardization Administration of China released
Table of Contents
Preface Ⅰ
1 Scope 1
2 Normative references 1
3 Terms and definitions
4 system grounding type 2
4.1 TN system 3
4.2 TT system 4
4.3 IT systems 4
5 system grounding safety technical requirements 5
5.1 Basic requirements 5
5.2 TN system 6
5.3 TT system 6
5.4 IT systems 7
Foreword
All the technical contents of this standard is mandatory.
This standard replaces GB 14050-1993.
This standard compared with GB 14050-1993, the main contents of the revised as follows.
--- According to GB/T 1.1 editorial changes, the increase in Chapter 2, normative references.
--- Section 3, modify and add the following terms and definitions.
3.2 exposed conductive parts;
3.3 external conductive parts;
3.4 protective conductor (symbol PE);
3.5 grounding conductor;
3.10 grounding system;
3.11 protective earth;
3.12 Equipotential Bonding;
3.13 supplementary equipotential bonding.
--- 5.1.2 and 5.1.3 added at the end a "general equipotential bonding conductor must conform respectively in 544.1 GB 16895.3-2004
Provisions. "And" supplementary equipotential bonding conductor must conform to the provisions of 544.2 in GB 16895.3-2004. "
--- 5.1.4 increase "if necessary, install the residual current protection device classification and fire monitoring systems, and in accordance with the provisions of GB 13955."
--- 5.1.8 is amended as. "the protective conductor cross-section, by reference to the provisions of GB 16895.3-2004."
--- 5.2.3 the first paragraph is amended as.
"TN system mainly to provide protection against electric shock by the overcurrent protective devices. If you use the overcurrent protective devices can not meet 5.2.2
When the request should be used or the total equipotential local equipotential measures may also be an additional residual current protection device,
Or a combination of the use of protective measures and other indirect contact potential connection measures and additional residual current operated protective devices to meet the requirements. "
--- Delete the original Appendix A.
--- Other editorial changes.
The electrical safety standards by the National Standardization Technical Committee (SAC/TC25) proposed.
This standard by the National Standardization Technical Committee of Electrical Safety and focal point responsible for the interpretation.
This standard is drafted by. Shanghai Electric Tool Research Institute, Beijing Electrical Machinery Industry Technical and Economic Research Institute, Guangdong Entry-Exit Inspection
Quarantine Bureau Technology Center, Schneider Electric (China) Investment Co., Ltd. Shanghai Branch, Siemens (China) Co., Ltd.
The main drafters of this standard. Liu Jiang, Zeng Yan Hong, Pei Xiaobo, Zhang Ping, Fan Yibing.
This standard replaces the standards previously issued as follows.
--- GB 14050-1993.
The type of system grounding and safety technical requirements
1 Scope
This standard specifies the type of system grounding and safety technical requirements, which aims to protect the safety of people and equipment.
This standard applies to nominal system voltage of AC 220/380V grid.
2 Normative references
The following documents contain provisions which, through reference in this standard and become the standard terms. For dated references, subsequent
Amendments (not including errata content) or revisions do not apply to this standard, however, encourage the parties to the agreement are based on research
Whether the latest versions of these documents. For undated reference documents, the latest versions apply to this standard.
GB/T 4776-2008 term electrical safety
GB 13955 residual current operated protective devices to install and run
Select GB 16895.3-2004 Electrical installations of buildings - Part 5-54 electrical equipment installation and configuration of the ground, to protect guide
Body protection and bonding conductor (IEC 60364-5-54.2002, IDT)
3 Terms and Definitions
The following terms and definitions apply to this standard.
3.1
In order to achieve a combination of electrical equipment associated with one or several specific purposes.
3.2
Easily accessible conductive parts and live parts, while not yet in case of failure can become partially charged.
[GB/T 4776-2008, the definition 3.1.10]
3.3
Not part of the electrical device, and easy introduction potential (usually ground potential) of the conductive portion.
[GB/T 4776-2008, the definition 3.1.11]
3.4
Connected to the system neutral and can provide transmission of electrical energy conductors.
[GB/T 4776-2008, defined 3.3.3.11]
3.5
Electric shock protection measures for preventing the use of conductors in case of failure.
[GB/T 4776-2008, defined 3.3.3.10]
The standard refers to any of the following portion electrically connected to the conductor.
--- Exposed conductive parts;
--- External conductive parts;
--- Total ground terminal or the main ground conductor;
---Grounding;
--- Power or artificial neutral ground.
3.6
PEN conductor
Both protective earth and neutral conductors function conductor.
[GB/T 4776-2008, defined 3.3.3.13]
Note. The acronym PEN is a combination of the symbol PE protective conductor and the neutral conductor N symbol made.
3.7
For equipment, devices or systems to the point of electrical connection between the electrode and the ground, and has a low impedance conductor.
[GB/T 4776-2008, the definition 3.3.3.9]
3.8
Unexpected voltage between two points of the body at the same time to reach.
[GB/T 4776-2008, the definition 3.2.4]
Note 1. As usual, this term only in the aspects related to the protection and indirect contact.
Note 2. In some cases, the contact voltage value significantly affect the reach of these sections may be people impedance.
3.9
Impedance negligible electrical device failure may occur highest touch voltage.
3.10
A certain point (usually neutral) earthing system power side.
3.11
For security purposes set on the apparatus, device or system grounding point or points.
[GB/T 4776-2008, the definition 3.3.2.3]
3.12
MEB
So that all the exposed outer conductor may be conductive and electrically conductive parts of the device may be substantially equal to the potential of the electrical connection.
3.13
SEB
Conductor conductive portion communicates directly between two objects, so that the potential substantially equal.
4 types of system grounding
Systems Grounding the Latin alphabet for the code, its meaning is.
The first letter indicates the relationship between the power supply terminal and ground
T --- a little supply terminal directly to ground;
I --- all live parts supply terminal ungrounded or impedance grounded by a little.
The second letter indicates the relationship between electrical installations exposed conductive parts and ground.
T --- electrical installations exposed conductive parts directly grounded, the ground is electrically independent of the supply side of the ground;
N --- electrical installations exposed conductive parts of the electrical termination locations have a direct electrical connection.
A dash (-) after the letters used to represent a combination of the neutral conductor and the protective conductor.
S --- neutral conductor and protective conductor are separate;
C --- neutral conductor and protective conductor are one.
Grounding system has the following several types.
4.1 TN system
Supply side a little exposed conductive parts directly grounded, electrical installations protected by a neutral conductor or connect to the protective conductor connection
location.
According to the neutral conductor and protective conductor combinations of type TN system has the following three ways.
a) TN-S system. neutral conductor and protective conductor are separated throughout the system (see Figure 1).
1 TN-S system of FIG.
b) TN-C system. neutral conductor and protective conductor of the whole system is unity (see Figure 2).
Figure 2 TN-C system
c) TN-C-S system. The system part of the line neutral conductor and protective conductor are one (see Figure 3).
Figure 3 TN-CS system
4.2 TT system
Supply terminal directly to ground a little, exposed conductive parts directly grounded electrical installations, this ground electrically independent of the power supply terminal
A ground (see Fig. 4).
Figure 4 TT system
4.3 IT systems
Live parts supply terminal through a little ungrounded or exposed conductive parts directly grounded impedance grounding, electrical installations (see Figure 5).
Figure 5 IT systems
5 pairs of safety grounding system technical requirements
5.1 Basic requirements
5.1.1 System automatically cut off the power supply ground for the introduction of the indirect contact protection measures to provide the necessary conditions. To ensure the supply automatically cut off
Reliable and efficient electricity measures, required.
a) When the electrical device fault (or protective conductor) between the part and the exposed conductive parts occurs when charged, the configured protection
Appliances should be able to automatically cut off the power supply failure portion, and to ensure that does not happen. a more than AC 50V (effective
Value) is expected to persist in contact voltage enough to produce dangerous to human physiological effects (in the human body when it comes to it).
In some cases the type associated with the system ground [as in 5.2.2 b)], regardless of the size of contact voltage, cutting the time allowed
Raised to no more than 5s.
NOTE. For IT systems, in the event of the first fault, it is usually not required to automatically cut off the power supply, but must give a warning signal generated by the insulation monitoring device.
b) electrical installations exposed conductive parts, should be connected by a protective conductor pole or neutral conductor and grounding protection, to ensure
The formation of the fault loop.
Where exposed conductive parts can be touched at the same time the human body, it should be connected to the same ground system.
5.1.2 The system should try to implement the total equipotential bonding.
The building of general equipotential bonding conductor should be connected to these conductive parts to each other.
a) Total protective conductor (protection line trunk);
b) The grounding conductor (ground wire trunk) or the total ground terminal;
Public metal pipes and similar metal components c) within the building (such as water pipes, gas pipes, etc.);
d) structural metal parts, central heating and air conditioning systems.
Conductive body from the outside of the building should be as close as possible in the building at the entrance of the equipotential bonding conductor connection.
Equipotential bonding conductor must conform to the provisions of 544.1 in GB 16895.3-2004.
5.1.3 In the following cases should consider implementing supplementary equipotential bonding.
--- In the local area, automatically cut off the power when the time does not meet the requirements of protection against electric shock;
--- In certain places, the need for a lower contact voltage required measures against electric shock;
--- Having a lightning immunity requirements and information systems.
Supplementary equipotential bonding conductors should be interconnected with the following conductive parts of the region.
All exposed conductive parts simultaneously reach a) fixed equipment;
b) protective conductor (included within the device and socket);
c) electrical installations outside the conductive parts (if applicable, should also include the main reinforced concrete structures).
Supplementary equipotential bonding conductor must conform to the provisions of 544.2 in GB 16895.3-2004.
5.1.4 if necessary, install the residual current protection device classification and fire monitoring systems, and in accordance with the provisions of GB 13955.
5.1.5 protective devices shall be installed in the protective conductor and switch circuit, but only allowed to set up a connection point with the tools to open.
5.1.6 prohibited to gas pipes, metal components (such as a metal water pipe) used as protective conductors.
5.1.7 exposed conductive part of the electrical installations shall not be used to protect transition junction tandem conductor.
5.1.8 protective conductor must have a sufficient cross-section, the minimum cross section shall comply with the provisions of 543.1 in GB 16895.3-2004.
5.1.9 connection to the protective conductor (or PEN conductor), must ensure good electrical continuity. In case of copper conductor and aluminum conductor is connected and
Aluminum conductors and aluminum conductors are connected, more effective measures should be taken (such as using special connectors) prevent poor contact failure.
5.2 TN system
TN system addition to meeting the requirements of 5.1, it must also meet the requirements of each of the following.
5.2.1 grounding system shall comply with the provisions of 4.1.
5.2.2 Impedance protection system installed in the electrical characteristics and circuits should satisfy equation (1) the conditions expressed, to ensure that electrical devices
Set anywhere within the phase conductor and the protective impedance conductor (or exposed conductive parts) can be negligible failure to protect
Electrical power supply which can be cut within a specified period of time.
ZS · Ia≤U0 (1)
Where.
Fault loop impedance ZS --- ohms (Ω);
Ia --- guaranteed protection of electrical operation at a specified time automatically cut off the power supply current in amperes (A);
U0 --- ground nominal voltage in volts (V).
Cut off the power supply time formula (1) with Ia related means.
a) With the power supply socket outlet without end loop or directly (or runni...