Performance designed to prevent dangerous failures of the product itself. GB 4776-1984 Electrical Safety Terminology GB4776-1984 Standard download decompression password: www.bzxz.net

1 Basic concepts 1.1 Safety Fail-safe National Standard of the People's Republic of China Electrical safety terminology Performance designed to prevent dangerous failures of the product itself. 1.2 Normal condition The state in which all facilities used to prevent danger are intact. 1.3 Electrical accident Electric accident UDC 621. $:614.8:001. 4 GB 4776—84 An event that directly or indirectly causes damage to building facilities and electrical equipment, casualties to people and animals, and fires and explosions due to electric current, electromagnetic fields, lightning, static electricity, and certain circuit failures. 1.4 Electric shock Pathological and physiological effects caused by electric current passing through the human or animal body. 1.5 injury due to electromagnetic field injury caused by the absorption of energy by the human body under the action of electromagnetic field. 1.6 disruptive discharge dielectric breakdown the phenomenon of loss of dielectric strength of solid, liquid, gaseous medium and their combination under high voltage. During destructive discharge, the voltage between electrodes drops rapidly to zero or close to zero. short circuit the connection between two points or points in a circuit that are normally at different voltages by accident or intention through relatively small resistance or impedance. 1.8 insulation fault insulation fault abnormal drop in insulation resistance. 1.9 earth fault earth fault the fault caused by the connection of the conductor to the ground or the insulation resistance to the ground becoming less than the specified value. 1.10 Overcurrent
National Bureau of Standards Issued on November 30, 1984
Implementation on 1985-0T-01
overcurrent
Current exceeding the rated current.
Overvoltage
orervoltage
Voltage exceeding the rated voltage.
1.12 Overload
Load exceeding the rated load.
Conductive part
Conductive part
GB 4776—84
Part capable of conducting electricity but not necessarily carrying working current. 1.14 Live part
live part
Conductor or conductive part which is de-energized when in use, it includes the neutral conductor, but by convention does not include the protective neutral conductor (PEN conductor).
Note: This term does not necessarily imply a risk of electric shock. 1.15 Exposed conductive part
exposed condurtive part
Conductive part of electrical equipment that can be touched. It is not live in normal conditions, but may be live in the event of a fault. Note: Conductive parts of electrical equipment that can only be live through exposed conductive parts in the event of a fault are not considered to be external conductive parts. 1.16 External conductive part
external conductive part
conductive part that is not part of the electrical installation and is easily led to a potential (usually the ground potential). Simultaneously accessible parts
simultaneously accessible parts Conductors or conductive parts that can be touched by people at the same time, or conductors or conductive parts that can be touched by animals at the same time in certain places. Note: Simultaneously accessible parts can be:
①Live parts
②Exposed conductive parts
External live parts,
①Protective conductor,
@ground electrode.
1.78 Direct contact
dircct contact
Contact between a person or animal and a live part.
Indirect contact
indirect contact
Contact between a person or animal and an external conductive part that becomes live under fault conditions. 1.20
Touch voltage
touch voltage
The voltage that appears between simultaneously accessible parts when the insulation is damaged. Note: ① By convention, this term is only used in connection with indirect radiation protection. ② In some cases, the value of the touch voltage may be significantly affected by the impedance of the person touching these parts. 1.21 Step voltage
step voltagc
GB 4776—84
The voltage applied between the two feet of a person standing on the ground through which current flows. Safety extra-low voltage (SELV) is a circuit that is isolated from the power supply line by a safety isolation transformer or a converter with independent windings, and the effective value of the AC voltage between the conductors or between any conductor and the ground does not exceed 50 volts. 1.23 Voltage to earth voltage to earth the potential difference between a charged body and the earth (the earth potential is zero). Overvoltage to earth voltage to earth higher than the normal peak voltage to earth (corresponding to the highest system voltage), expressed as a peak voltage. 1.25 Shock current current that passes through the human or animal body and has the characteristics of possibly causing pathological or physiological effects. 1.26 Threshold of perception current the minimum current value that can cause any sensation when the current passes through the human body under given conditions. 1.27
Threshold of let-go current
The maximum current value that a person holding the electrodes can get rid of under given conditions. Threshold of yentricuarfibrillation current
The minimum current value that causes ventricular fibrillation under given conditions. Fault current
Fault current
The current caused by insulation damage or insulation short-circuiting. Overload current (of a circuit)
Overload current (of a circuit) Overcurrent that occurs in a circuit when there is no electrical fault. Short-circuit current
short-circuit current
Overcurrent that occurs when a short circuit is caused by a fault in a circuit. 1.32 Residual current
residual current
The algebraic sum of the instantaneous values ​​of the current flowing through all the live conductors in the circuit at one point of an electrical device. 1.33
total impedance of the human body
the sum of the body impedance and the skin impedance of a human body. 1.a4
safety impedance
safety impedance
the impedance connected between live parts and accessible conductive parts, the value of which can limit the current to a safe value under normal use and possible faults of the equipment and maintain its reliability throughout the life of the equipment. t.35
fault withstandability
GB 4776—84
the ability of an electrical device to withstand the effects of a specified electrical fault current without exceeding the specified degree of damage. 1.36 Unsafe temperature
unsafe temperature
Temperature that may cause combustion and/or may cause the operator to take dangerous actions that are particularly unintentional. 2 Basic elements
2.1.1 Insulation (property)
insulation (property)
All properties obtained after the conductor is insulated. 2.1.2 Insulation (material)
insulation (material)
All materials used to insulate devices.
2.1.3 Insulation structure
insulation system
A combination of one or more insulating materials. According to the characteristics and size requirements of electrical equipment, the conductor parts are designed as a whole to isolate the conductive parts with potential difference. Let: There are several different insulation structures allowed in Taipower's steam equipment. 2.1.4 Basic insulation Basic insulation Insulation that provides basic protection against electric shock on live parts. 2.1.5 Supplementary insulation Supplementary insulation Independent insulation used outside basic insulation to prevent electric shock in the event of damage to basic insulation. 2.1.6 Double insulation Double insulation Insulation that has both basic insulation and supplementary insulation 2.1.7 Reinforced insulation Reinforced insulation A single insulation structure equivalent to the degree of protection of double insulation. 2.1.8 Insulation resistance Insulation resistance between two conductors separated by insulating materials under specified conditions. 2.1.9 Dielectric strength Dielectric strength Dielectric strength
The highest electric field strength that a material can withstand without being damaged. 2.1.10 Dielectric strength test
dielectric test
A short-time test of the rated medium voltage of the circuit insulation specified by the manufacturer by applying a specified voltage to the insulation to check whether it complies with the manufacturer's requirements. 2.1.11 Leakage current
leakage current
GB 4776-84
The current that flows into the earth or the external conductive part of the circuit in the absence of a fault. Non: This current may include the capacitive component caused by the intentional use of capacitors. 2.1.12 Dielectric loss
Dielectric loss
The power absorbed by the dielectric from the time-varying field and dissipated in the form of heat. 2.1.13 Loss angle (under sinusoidal condition) Its tangent is the angle of the ratio of the absolute value of the active power to the reactive power. 2.1.14 Quality factor
Q factor
quality factor
ratio of the absolute value of reactive power to active power. 2.1.15 enclosure
enclosure
parts that protect equipment from certain external influences and direct contact from any direction. 2.1.16 prolective cover
part of an enclosure or baffle provided to prevent accidental contact with potentially hazardous parts. 2.1.17 harrier
parts that protect against direct contact from any direction of frequent approach. 2.1.18 obstacle
parts that prevent unintentional direct contact but do not prevent intentional self-contact. Spacing
2.2.1 clearance
the shortest straight-line distance between two conductive parts. 2.2.2 Prolective gap The gap between live parts and ground to limit the maximum overvoltage that may occur. 2.2.3 Creepage distance The shortest distance along the surface of insulating material between two conductive parts. Formerly known as leakage distance 2.2. 4 Isolation To isolate a device or circuit from another device or circuit. b. To provide a certain degree of protection to any live circuit by separating them. 2.2.5 Safe distance To prevent human body from touching or approaching live parts, and to prevent vehicles or other objects from colliding or approaching live parts, and to maintain a certain distance in the process of switching.
2.2.6 Arm's reach
arm's reach
GB 4776-84
The range measured from any point on the surface on which a person stands or walks to the limit of the hand that can be reached in any direction without the need for assistance.
Current-carrying capacity
(continuous)current-carrying capacity(of a conductor)The maximum current that a conductor can carry continuously under specified conditions without causing its stable temperature to exceed the specified value. 2.4
2.4.1 Safety marking
safety marking
A mark composed of safety colors, geometric figures, graphic symbols and text to express specific safety information. 2.4.2 Supplementary marking
suppiementary marking
A mark that must be used together with a safety sign to provide a textual description of the safety sign. 2.4.3 Safety colour
safety colour
The colour used to express safety information, such as prohibition, warning, instruction, prompt, etc. 8 Basic measuresbZxz.net
Protection system
3.1.1 TN system
TN system
A system in which the power supply system has one point directly grounded, and the exposed conductive parts of the load equipment are connected to this grounding point through a protective conductor. According to the arrangement of the neutral conductor and the protective conductor, there are three types of TN systems: TN-S system: There are separate neutral conductors and protective conductors in the whole system. a.
b.TN-CS system: The functions of some neutral conductors and protective conductors in the system are combined on the root conductor. C. TN-C system: The functions of the neutral conductor and the protective conductor are combined on the root conductor in the whole system. Line: The first letter T indicates that a point in the power system is directly grounded, and the second letter N indicates the exposed conductive part of the equipment; the power system grounding point is directly electrically connected
The letter S indicates that the neutral conductor and the protective conductor are separate. The letter C indicates that the functions of the neutral conductor and the protective conductor are combined in one conductor. Lt
Central source system grounding
Exposed conductive part
Figure IATN-S system
3.1.2TT system
Power system grounding
Power system connected
TT system
GB4776-B4
Exposed conductive part
TN-CS system
External conductive part
Figure ICTNC system
A system in which one point in the power system is directly grounded, and the grounding of the exposed conductive part of the equipment is electrically independent of the grounding of the power system. Note: The first letter T indicates that one point of the power supply system is directly grounded. The second letter T indicates that the grounding of the exposed conductive parts of the equipment is electrically independent of the grounding of the power supply system. Ll
Use the original system to! Multiple ground
External phosphorus surface
Figure 2TT system
a.1.3[T system
IT system
GB 4776-B4
A system in which the live parts of the power supply system are not grounded or are grounded through impedance, and the exposed conductive parts of the electrical equipment are grounded. Note: The first letter I indicates that all live parts of the power supply system are not grounded or are grounded through impedance at one point. The first letter T indicates that the grounding of the exposed conductive parts of the equipment is electrically independent of the grounding of the power supply system. 1.1
Source system grounding
3.1.4 Neutral point effectively grounded system
External net line
Figure 3 IT system
system with effectively earthed neutral A system with neutral point directly grounded or grounded via low impedance. Usually, the ratio of zero-sequence reactance to positive-sequence reactance is less than or equal to 3
3, and the ratio of zero-sequence resistance to stop-sequence reactance is less than or equal to 1. This system can also be called a large grounding current system. 3.1.5 System with non-effectively earthed neutral
System with non-effectively earthed neutral.
A system with a neutral point that is not earthed, or that is grounded by high impedance or harmonic grounding. Usually, the ratio of zero-sequence reactance to positive-sequence reactance in this system is greater than 3,
>3, and the ratio of zero-sequence resistance to positive-sequence reactance is greater than 1. This system can also be called a small grounding current system. 3.2
Safety technical measures
3.2.1 Inspection earthing
Inspection earthing
When inspecting equipment and lines, cut off the power supply and temporarily connect the conductive parts of the equipment and lines to the earth to prevent electric shock accidents.
3.2.2 Working earthing
working carthing
Grounding for circuits or equipment to meet operating requirements, such as grounding of the low-voltage neutral point of a transformer. 3.2.3 Protective earthing Earthing that tightly connects conductive parts that may have dangerous voltage to earth in the event of a fault to the earth. 3.2.4 Iterative earth Earthing that reconnects the protective neutral conductor to the earth at one or more points through a grounding device. 3.2.5 Fault earthing The accidental connection of a conductor to the earth. When the impedance of the connection is small enough to be ignored, this connection is called "complete earthing". 3.2.6 Earthing resistance Resistance of an earthed conductor Carthing resistance The sum of the resistance of the grounding lead between the grounded body and the grounding electrode at the zero potential surface of the ground, the resistance of the grounding electrode, the transition resistance between the grounding electrode soil and the overflow resistance of the soil fill. Earth fault factor
earth fault faclor
Under a certain system structure, when a ground fault occurs (a phase or multiple phases at any point in the system are faulty to ground), the ratio of the highest power frequency voltage to ground of a selected point (generally the equipment installation point) in the three-phase system to the effective value of the power frequency voltage to ground at the selected point when there is no fault.
3.2.8 Earth fault current
Fault current flowing to the earth.
3.2.9 Earth short circuit current
Earth short circuit current
Earth current caused by system grounding causing a short circuit in the system. 3.2.10 Overcurrent protection
Overcurrent protectiar
A protection mode that causes the protection device to operate when the current exceeds the predetermined value. 3.2.11 Overvoltage protection Overvoltage protection A type of protection that disconnects the power supply or reduces the voltage of the controlled equipment when the voltage exceeds a predetermined value. 3.2.12 Open-phase protection A type of protection that disconnects the protected equipment by the disappearance of the current in the phase conductors of a multiphase circuit or prevents the application of power to the protected equipment by the loss of voltage in one or more phases of a multiphase system. 3.2.13 Protection against direct contact, protection against shock in normal service: basic protection Protection against direct contact Protection against shock in normal service: basic protection Protection against dangerous contact between humans or animals and live parts. 3.2.14 Protection against indirect contact Protection against shock in the case of a fault, supplementary protection Protection against dangerous contact between humans or animals and exposed conductive parts, external conductive parts that may become live in the event of a fault. 3.2.15 Equipotential bonding
equipotential bonding
An electrical connection in which the potentials of all exposed conductive parts and external conductive parts are substantially equal. 3.2.16 Dust-protected Prevent dust from entering the enclosure to a level that is harmful to the electrical product. 3.2.17 Splash-proof Protected against splashing GB4776—84 Prevent water splashing from any direction from entering the enclosure to a level that is harmful to the electrical product. 3.2.18 Dropping water Protected against dropping water Prevent vertical dripping water from entering the enclosure to a level that is harmful to the electrical product. 3.2.19 Immersion-proof Protected against the effects of immersian When an electrical product is immersed in water under specified pressure and time, it can prevent water from entering its exterior to a level that is harmful to the product. 3.2.20 Submersible Submersion Protection that does not allow water to enter the interior of an electrical product when it is submerged for a long time according to the conditions specified in the manufacture. Note: For some types of electrical products, "submersion proof" means that water can be allowed to enter the interior, but it should not reach a harmful level. 3.3
Protective equipment and devices
Safety circuits and devices
safety circuits and devices
Circuits and devices designed to prevent endangerment to people, animals and damage to equipment during abnormal and accidental operation, 3.3.20 equipment
class0 equipment
Relies on basic insulation for protection against electric shock, that is, there is no connection between the accessible conductive parts (if any) and the protective conductor in the fixed wiring of the equipment, and in the event of damage to the basic insulation, it relies on the surrounding environment for protection. 3.3.3I equipment
class Iequipment
Not only relies on basic insulation for protection against electric shock, but also includes an additional safety measure, that is, the easily accessible conductive parts are connected to the protective (grounding) conductor in the fixed wiring of the equipment, so that the easily accessible conductive parts will not become live parts when the basic insulation fails.
3.3.4 Class II equipment
class I equipment
Not only relies on basic insulation for protection against electric shock, but also includes additional safety measures (such as double insulation or reinforced insulation), but the protective grounding or dependent equipment conditions are not specified. 3.3.5 Class II equipment
class Ⅲ equipment
rely on safety extra-low voltage power supply for protection against electric shock, and the voltage generated by it will not be higher than the safety extra-low voltage.
3.3.6 Overcurrent protective device
overcurrent protective device A device that disconnects the power supply of the circuit due to overcurrent. Release (of a mechanical switching device) A device that is used to release the holding mechanism to break or close the switch and is mechanically connected to the mechanical switch. 3.3.8 Protective relay A protective relay that can be used alone or in combination with other relays to form a protective device. A protective relay responds to abnormal conditions of the protected object, operates according to predetermined requirements, issues a warning signal, or clears the fault. (Single-phase neutral) earthing reactor GB4776—84 A reactor connected between the neutral point of the transformer and the ground, used to limit the line-to-ground current when a fault occurs in the system. (single-phase neutral) earthing reactor 3.8.10 earthed circuit a combination of conductors permanently earthed at one or more points. 3.3.11 earthing switch a mechanical switch used for the earthing portion of a circuit, which can carry current under abnormal conditions (e.g. short-circuit current) for a certain period of time, but is not required to carry current under normal circuit conditions. Note: An earthing switch may have a short-circuit connection capacity. earthing conductor earthing conductor a protective conductor connecting the main earthing terminal or main earthing bar to the earthing electrode. 5.3.13 main earthing terminal main earthing bar a terminal or earthing bar connecting the protective conductor, including the equipotential bonding conductor and the working earthing conductor (if any), to the earthing device.
3.3.14 Residual current circuit-breaker
A switch that automatically operates when the residual current in the circuit exceeds a predetermined value. 3.3.15 Interlocking device
Interlocking device
A mechanical connection mechanism designed between several switching devices or components to ensure that the switching devices or their components operate in a specified order or to prevent false operation.
3.3.16 Arc-extinguishing device
Arc-control device
A device that surrounds the arc contact of a mechanical switch to limit the arc and help extinguish the arc. Safety isolating transformer
A transformer that electrically separates the input winding from the output winding through insulation at least equivalent to double insulation or strong insulation. This transformer is designed to supply power to distribution circuits, electrical appliances or other equipment at a safety extra-low voltage. 3.3.18
Circuit-breaker
A mechanical switch that can connect, carry and disconnect current under normal circuit conditions, and can also connect, carry and disconnect current for a specified time under specified abnormal circuit conditions (such as short circuit). 3.3.19Fuse
An electrical appliance that disconnects the circuit by melting the fuse with the heat generated by itself when the current exceeds the specified value for a specified time. 3.3.20Surge arrester
Lightning arrester
A device that protects electrical equipment from transient overvoltage and limits the duration and amplitude of the continuous current. Protective capacitor
GB 4776—84
Capacitor for yoltage protection A capacitor connected between the power line and the ground to suppress surge overvoltage. a,3.22 Safety switch
safety
safety switch
device that disconnects the power supply before approaching the live parts. 3.3.23. Protective circuit
protective circuit
part of a special circuit or control circuit for the purpose of protection. 3.3.24 Limited current circuit
limited turrent circuit
circuit in which the current flowing will not cause danger under normal conditions and under certain possible fault conditions. 3.3.25 Protective current [voltage] transformer protective current [voltage] transformer a transformer that transmits information to the protection device and control device in the form of current [voltage]. 3.3.26
insulation monitoring and warning device
insulation monitoring and warning device a device that sends a signal when the insulation resistance drops. 8. 3.27 Protective conductor Protective conductor A conductor required by certain protection measures against electric shock and used to make electrical connections with any of the following parts. a. External conductive part: External conductive part: Main earthing terminal; Grounding electrode: Power supply grounding point or neutral point. Note: Protective conductor is represented by the symbol PE. Neutral conductor Neutral conductor A conductor connected to the neutral point of the system and capable of transmitting electrical energy. Note: Neutral conductor is represented by the symbol N.
Protective neutral conductor
PEN conductor
PEN conductor
An earthing conductor that has both the functions of a neutral conductor and a protective conductor. Note: The abbreviation PEN is a combination of the symbols PE for protective conductor and N for neutral conductor. Equipotential bonding conductor
equipotential bonding conductor A protective conductor used to ensure equipotential bonding.24 limited current circuit limited turrent circuit a circuit in which the current flowing through it will not cause danger under normal conditions and under certain possible fault conditions. 3.3.25 protective current [voltage] transformer a transformer that transmits information to the protection device and control device in the form of current [voltage]. 3.3.26 insulation monitoring and warning device a device that sends a signal when the insulation resistance to the ground drops. 8. 3.27 protective conductor protective conductor a conductor required by certain protection measures against electric shock to make electrical connection with any of the following parts. a. external conductive part: external conductive part: main earth terminal; grounding electrode: power supply grounding point or human neutral point.
Note: The protective conductor is represented by the symbol PE.
Neutral conductor
Neutral conductor
A conductor connected to the neutral point of the system and capable of transmitting electric energy. Note, the neutral conductor is represented by the symbol N.
Protective neutral conductor
PEN conductor
PEN conductor
A grounding conductor that has the dual functions of a neutral conductor and a protective conductor. Note, the abbreviation P EN is a combination of the symbol PE for protective conductor and the symbol N for neutral conductor. Equipotential bonding conductor
equipotential bonding conductorA protective conductor used to ensure equipotential bonding.24 limited current circuit limited turrent circuit a circuit in which the current flowing through it will not cause danger under normal conditions and under certain possible fault conditions. 3.3.25 protective current [voltage] transformer a transformer that transmits information to the protection device and control device in the form of current [voltage]. 3.3.26 insulation monitoring and warning device a device that sends a signal when the insulation resistance to the ground drops. 8. 3.27 protective conductor protective conductor a conductor required by certain protection measures against electric shock to make electrical connection with any of the following parts. a. external conductive part: external conductive part: main earth terminal; grounding electrode: power supply grounding point or human neutral point.
Note: The protective conductor is represented by the symbol PE.
Neutral conductor
Neutral conductor
A conductor connected to the neutral point of the system and capable of transmitting electric energy. Note, the neutral conductor is represented by the symbol N.
Protective neutral conductor
PEN conductor
PEN conductor
A grounding conductor that has the dual functions of a neutral conductor and a protective conductor. Note, the abbreviation P EN is a combination of the symbol PE for protective conductor and the symbol N for neutral conductor. Equipotential bonding conductor
equipotential bonding conductorA protective conductor used to ensure equipotential bonding.
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