GB 5959.1-1986 Safety of electric heating equipment Part 1 General requirements
Some standard content:
1 Introduction
National Standard of the People's Republic of China
Safety of electric heating equipment
Part 1, General requirements
Safety in electroheat installationsPart 1, General requirementsUDC621.365-75||tt ||GB5959.1-86
1.1
This standard applies to all types of industrial electric heating equipment, such as direct electric arc furnaces, submerged arc furnaces, other arc heating equipment, electroslag remelting furnaces, and plasma heating Equipment, induction melting furnace, induction heating equipment, resistance furnace, infrared radiation heating equipment, high frequency dielectric heating equipment, electric heating equipment with electron gun, microwave heating equipment and laser heating equipment. This standard does not apply to household electrical appliances for cooking and heating, welding equipment and heating systems. 1.2: Safety requirements for electric heating equipment, including "General Requirements" applicable to all electric heating equipment and "Special Requirements" applicable to various types of electric heating equipment. This standard is only the "General Requirements" applicable to all electric heating equipment. All types of electric heating equipment should meet the provisions of this standard and the "Special Requirements". In the case of "Special Requirements", the "Special Requirements" should complete, modify or replace the "General Requirements". Electric heating equipment that has not yet formulated "Special Requirements" should meet the provisions of this standard. In addition, electric heating equipment should also comply with relevant national standards. Note: In this standard, "General Requirements" and "Special Requirements" refer respectively to the "General Requirements" part and the "Special Requirements" parts in the "Safety of Electric Heating Equipment" standard.
1.3 The above safety standards focus particularly on protecting persons from hazards caused by electricity, but also address hazards caused by non-electrical factors.
These standards not only apply to the normal operating status of electric heating equipment, but also take into account the ability to ensure personal safety in the event of misoperation and equipment failure.
1.4 The electric heating equipment to which this standard applies should be operated and maintained by skilled or trained personnel who meet the requirements of Sections 2.2.22 and 2.2.23.
1.5 This standard refers to the second edition of the international standard IEC519-1 (1984) "Safety of Electric Heating Equipment Part 1 General Requirements" (referred to as IEC519-1 in this standard). 2 Terminology
2.1 In this standard and in each "Special Requirements", unless otherwise stated, in the case of AC, "voltage" and "current" refer to the effective value. The electrical quantity terms preceded by the word "rated", unless otherwise stated, generally refer to the electric heating device itself. The terms "rated voltage", "rated current" or "rated power" refer to the voltage (in a three-phase system, line voltage), current or power value specified by the manufacturer and marked on the electric heating device. 2.2 Except for the following nouns and terms In addition, the definitions of other electrical and electric heating terms used in this standard can be found in the various chapters of GB2900 "Electrical Terminology", especially GB2900.23-83 "Electrical Terminology, Industrial Electric Heating Equipment" 2.2.1. Electrical device
Any device used to generate, transform, transmit, distribute or use electrical energy, such as rotating electrical machines, transformers, switching devices, capacitors, measuring instruments, protective devices, wiring materials and devices 2.2.2 Rated. Voltage range
National Bureau of Standards i986-04-02 releasebZxz.net
1987-04-01 implementation
GB5959.1—86
is specified by the manufacturer and marked on the electric heating The voltage range between the lowest voltage and the highest voltage on the device. 2.2.3 The power grid
is not a separate power transmission and distribution system for electric heating equipment. 2.2.4TN type power grid
The TN type power grid is a bit direct. Grounding, the exposed conductive part of the load equipment is connected to this point through the protective wire. According to the combination of the neutral wire and the protective wire, there are three types of TN power grid: a. TNS type: neutral wire in the entire power grid. It is separated from the protection line, b. TN-C-S type: In a certain part of the power grid, the neutral line and the protection line use the same wire, TN-C type: In the entire power grid, the neutral line and the protection line The wires use the same wire. c
L,o
L, o
Lso
PE
Grid grounding
Lt
L
L.
PEN
Power grid grounding
Externally required conductive part
Figure 1TN-S type grid
PE
outer conductive part
Figure 2TN-CS type grid
2.2.5TT type grid
L,||tt| |L.
L,
PEN
Power grid grounding
GB 5959.1-86
Externally required conductive part
Figure 3TN-C Type grid
TT type grid has one point directly grounded, and the exposed conductive part of the load equipment is also grounded, but the ground electrode of the latter is on the electrical appliance and there is no wire connection with the ground electrode of the grid L||tt. ||0
L,
N
Grid grounding
2.2.6 Live parts
Exposed conductive parts
Figure 4 TT type Grid
Conductors or conductive parts that are live during normal use, including neutral wires, but usually excluding PEN wires. 2.2.7 Electrical connection
Allows or ensures the flow of current between two conductive parts. means or actual state. 2.2.8 Equipotential bonding
The electrical connection that puts the exposed conductive parts and additional conductive parts in an equipotential state. 2.2.9 Exposed conductive part
An easily accessible conductive part of an electrical installation that is not live under normal conditions but may become live under fault conditions. Note: Conductive parts of an electrical installation that become live through exposed conductive parts in the event of a fault are not considered exposed conductive parts. 2.2.10 Protective wire (symbol PE)
A wire required for electric shock protection measures and used for electrical connection with any of the following parts: a. Exposed conductive parts;
b. Conductive parts outside the device:
Main ground terminal:
c.
d． Ground pole:
e. Power supply ground point or artificial neutral point. 2.2.11 Neutral wire (symbol N)
GB 5959.1-86
A wire in the power grid that is connected to the neutral point and can transmit electrical energy. 2.2.12 PEN wire
is a grounding conductor that functions as both a protective wire and a neutral wire. 2.2.13 Ground wire
The protective wire connected to the main ground terminal or ground busbar and the ground electrode. 2.2.14 Leakage current in equipment
Under normal circumstances, the current flowing to the earth or to external conductive parts. Note: ① This current may contain capacitive components caused by the use of capacitors. ②Leakage current values ??may be different in hot and cold states. 2.2.15 Isolation
Disconnect all or an independent part of the electric heating equipment from any power source. The purpose is to ensure the safety of personnel working on or near live parts that are in danger of direct contact. 2.2.16 Disconnect for mechanical maintenance
Disconnect one or several parts of the electric heating equipment from the power supply. The purpose is to avoid accidents when mechanical maintenance (non-electrical maintenance) is performed on these parts.
2.2.17 Emergency cut-off
In order to avoid accidents, quickly cut off the power supply in emergency situations. An emergency cut-off to prevent dangerous movement is called an emergency stop.
2.2.18 Function switching (or control)
"Turn on" or "off" the power supply, or convert the power supply to a certain part of the equipment or electrical device in order to realize the control of the equipment or Control of normal operation of electrical installations.
2.2.19 Fixed connection
When the connection between the electric heating device and the fixed power supply circuit requires the use of tools to assemble and disassemble, this connection is called a fixed connection. Connections other than this are called non-fixed connections.
2.2.20 Fixed flexible wire
A flexible wire connected to an electric heating device that can only be removed using a tool. 2.2.21 Arm reach range
The range reached by extending bare hands in any direction from any point on the surface where a person often stands or walks. 2.2.22 Skilled Personnel
Personnel who have received professional education, have professional knowledge and experience, and are able to identify possible hazards in the equipment they operate and use. 2.2.23 Trained personnel
Workers and maintenance personnel who can prevent possible dangers of electric heating equipment under the strict guidance and supervision of skilled personnel. 3Classification of electric heating devices according to voltage and frequency
3.1 Classification by voltage
Electric heating devices are classified as follows according to their power supply voltage under normal operating conditions. 3.1.1 Devices in the first voltage section
Devices whose rated voltage does not exceed AC 50V or smooth DC 120V. 3.1.2 Devices in the second voltage section
Devices with a rated voltage higher than AC 50V, but not exceeding 1000V, or higher than smooth DC 120V, but not exceeding 1500V. 3.1.3 Devices in the third voltage section
GB5959.1-86
Devices with a rated voltage higher than AC 1000V or smooth DC 1500V. 3.2 Classification by frequency
3.2.1 Low-frequency devices
Devices whose operating frequency is lower than or equal to the power frequency. 3.2.2 Power frequency device
A low-frequency device whose working frequency is equal to the power frequency. 3.2.3 Intermediate frequency device
A device whose operating frequency is higher than the power frequency, but lower than or equal to 10kHz. 3.2.4 High-frequency devices
devices with operating frequencies higher than 10kHz but lower than or equal to 300MHz. 3.2.5 Microwave devices
Devices whose operating frequency is higher than 300MHz but lower than or equal to 300GHz. 4 General requirements
4.1 Electric heating device
4.1.1 Each part of the electric heating device shall be designed and manufactured according to its operating voltage and operating frequency and taking into account the operating mode of the device and current national and professional standards. Note on installation: For example, for a device whose rated frequency is given but the frequency can vary within a certain range, the frequency that is most detrimental to safety should be considered. 4.1.2 The design and manufacture of electric heating devices should be such that when installed and used according to the manufacturer's instructions, they will not cause danger to workers and the surrounding environment. In special cases and when necessary, according to the agreement between the manufacturer and the user, preventive measures should be taken against certain situations that are expected to cause danger, such as mechanical shock, vibration, overheating, moisture, pressure and chemical effects 4.1.3 The electric heating device shall be manufactured and installed so that it is sufficiently strong and stable under various normal conditions of use. The handles, operating levers and similar parts of the device should be securely fixed. The operating direction of operating levers and controllers should be as consistent as possible with the direction of motion of the machinery they control. 4.1.4 Measures should be taken, such as installing safety valves or temperature limiters, to avoid excessive pressure. 4.1.5 The design of electric heating devices that can tilt, rotate or move should take into account that no matter whether the electric heating device is in the end position or in the process of movement, its electrical devices and related accessories will not be subject to excessive mechanical stress. stress. 4.2 Electrical devices of electric heating equipment
4.2.1 The design and manufacture of electrical devices should ensure the safety of workers and prevent the risk of fire and explosion under normal operating conditions.
The device should also have sufficient mechanical strength to prevent possible damage. In addition, the structural design of the electrical installation should ensure that the current flowing through it under normal operating conditions does not cause excessive temperatures in the conductors, insulating materials and adjacent parts of the electric heating equipment. Electrical devices should comply with the current relevant national standards and professional standards, and should also comply with the complete set of requirements for electric heating equipment. 4.2.2 Electric shock protection measures should be taken (see Chapter 10). 4.2.3 The circuit composed of transformers, inductors and capacitors should be designed to avoid continuous overvoltage or overcurrent that may cause accidents to the above electrical appliances and people.
4.2.4 Discharge of capacitors
4.2.4.1 Each capacitor device should have a directly connected discharge device, but when it is connected to other electrical devices that can provide a discharge path, such as inductors and transformers Except for direct connection without isolating switch, fuse or series capacitor inserted in the middle. 4.2.4.2 The discharge device directly connected to the capacitor should be able to reduce the residual voltage of the capacitor from /2U (rated voltage) to no more than 50V within the specified time after the power supply is disconnected. For capacitors with a rated voltage not higher than 660V, this time is 1 minute, and for capacitors with a rated voltage higher than 660V, it is 5 minutes.
Note: When there are capacitors connected in series in the capacitor bank, due to the cumulative effect of the residual voltage, the discharge device installed on each capacitor may not meet the requirements of this section GB5959.1-86
. If this situation occurs due to high supply voltage, an additional external discharge device is required and should be connected directly across the capacitor bank. 4.2.4.3 When the capacitor may be switched within a short time interval, the capacitor bank shall be designed so that the switching time interval and the discharge efficiency of the discharge device are properly matched, so that when the capacitor is connected to voltage again, the voltage on its terminals Not more than 10% of the rated voltage. 4.2.4.4 Although there is a discharge device, the terminals or busbars of each capacitor should still be short-circuited and grounded before people come into contact with the live parts of the capacitor bank.
Note: Due to the nonlinear characteristics of the medium caused by the blown fuse, disconnection of internal connections or overvoltage, residual charges often appear at the interconnections of series capacitors. Therefore, these interconnections should be shorted to ground before human contact. 4.2.5 When capacitors are installed in groups, they must be in accordance with the manufacturer's instructions. 4.2.6 The layout of electrical devices should be such that they will not be affected by physical and chemical effects (such as heat from the surrounding environment, sputtering of molten materials and salts, moisture, oil, impact or friction, etc.) during normal operation. and suffered damage. If necessary, appropriate measures should be taken on the structure, such as setting up protective trenches, etc. 4.2.7 In order to facilitate maintenance, all parts of the electrical device, especially the vulnerable parts, should be as accessible as possible. 4.2.8 When forced cooling is used, measures should be taken to monitor its cooling effect. If cooling is insufficient, an alarm signal should be issued. If necessary, the power supply to the electric heating device should be cut off or other methods should be used to ensure safety. 4.2.9 The sensors of the temperature controller, temperature limiter and temperature protection device should be placed appropriately so that they can correctly reflect the measured temperature without being affected by ambient temperature, mechanical effects and electromagnetic induction. 4.3 Interlock protection and alarm
Each relevant part of the electric heating equipment should have necessary interlock protection devices and/or alarm devices to ensure the safe operation of the equipment. 4.4 Electrostatic charges and stray fields
4.4.1 Electrostatic charges that may endanger the normal operation of electric heating devices or the safety of workers should be suppressed or made harmless, such as taking measures such as grounding, shielding or providing sufficient distance. 4.4.2 Preventive measures similar to the above should also be taken for the effects caused by electromagnetic leakage (stray fields), such as eddy currents, induced voltages, etc.
4.5 Electromagnetic fields and ionizing radiation
4.5.1 For electric heating devices that radiate electromagnetic fields to the outside, if the radiation intensity is high enough to be harmful to the human body, the protection of the operator should be taken into consideration when designing the device Protected from electromagnetic fields. 4.5.2 Electric heating devices emitting ionizing radiation should comply with regulations established for protection against ionizing radiation. 4.6 Liquid cooling
4.6.1 For live parts that are cooled by liquid, such as inductors, transformers, capacitors, busbars, cables or mechanical components, etc., the quality of the coolant, the length of the hose, and the The materials used in the pipe should be able to limit the leakage current to a non-hazardous level. 4.6.2 The formation of air bubbles in the cooling system should be avoided as much as possible. Note: Pay special attention to the pipe fittings used. 4.6.3 In order to reduce the pollution and loss of coolant, closed circuit cooling should be given priority. 4.6. Each part of the 4-way coolant should be designed to withstand 1.5 times the rated working pressure. 4.6.5 Measures should be taken to limit the effects of corrosion and the formation of deposits and gases. Condensation should be avoided as much as possible. 4.6.6 The equipment manufacturer should provide the following cooling data:. Type and properties of coolant (physical, chemical and electrical properties): b. Required flow rate;
c. Minimum and maximum inlet temperature and maximum outlet temperature; d. The minimum required pressure difference between the inlet and outlet. 5. It is prohibited to use the earth as part of the effective circuit. 5.1. Unless otherwise specified in the "Special Requirements", it is prohibited to use the earth, protective wires, shells and structural parts as part of the effective circuit. GB5959.1-86
. However, this provision does not apply to situations where the neutral point can be grounded or a safety facility using the earth as a return circuit is used. 5.2 Guide rails may be used as return circuits, provided that in the event of an accident, the impedance of the circuit concerned is low enough to limit the step voltage and the contact voltage between the guide rail and adjacent ground is not greater than 25V. 6 Nameplate contents, markings and circuit diagrams
Unless otherwise specified in the "Special Requirements", the nameplate shall include the following data related to the electric heating device: 6.1
a. Name of the manufacturer or Mark,
Model or product code,
b.
Manufacturing date or date code:
c.
d.
Out Broadcast number:
e.Rated voltage or rated voltage range (V or kV), Note; when the device can be powered by several different rated voltages, each voltage value and its corresponding connection method should be clearly marked on the nameplate. f. Rated current (A or kA)
g. Rated power (kW or MW)
Note: For electric heating devices with several voltage ranges, the maximum input power value of each voltage range should be indicated. . h, connected load (kVA or MVA):
Note: For electric heating devices with auxiliary devices, the installation load (kVA) of the auxiliary device should be marked. The type of current, frequency or frequency range should be marked, and standard graphic symbols should be used; J. Used to represent the characteristics of electric heating devices, including other important parameters or text including non-electrical characteristics. 6.2 The contents specified in Article 6.1 should be marked on the name tag, and the writing should be clear and durable. The nameplate should be installed on the main part of the electric heating equipment or electric heating device so that the operator can clearly see it when starting the equipment. Unless otherwise agreed, the nameplate shall be in the language of the user's country.
6.3 All working positions of operating and control components should be clearly marked with letters, words, numbers or symbols. 6.4 Product instructions including circuit diagrams and equipment lists should be provided in a timely manner. Note: Other data necessary for transportation, installation and handling, such as weight and dimensions, should be indicated on the box and instruction card. 6.5 Electrical components and their relationship with the circuit diagram should be marked with durable markings, which should be consistent with those on the circuit diagram. 6.6 Control components and signal components should be marked with letters, words and/or symbols. 6.7 Where there is a circuit label on the circuit diagram, the circuit label should be marked on the end of the connecting wire. The markings should be clear and durable, and comply with the provisions of GB4026-83 "General Rules for the Identification of Electrical Terminals and the Marking of Terminals with Alphanumeric Symbols". 7 Overcurrent protection
Overcurrent protection measures should be provided for electric heating equipment in accordance with relevant standards. 8 Isolation and opening and closing
Electric heating equipment should be equipped with switch or button circuits for isolation, disconnection for mechanical maintenance, emergency cut-off, function opening and closing (or control), etc., and should comply with the provisions of relevant standards. 8.1 Depending on the usage, some circuits do not need to be disconnected, such as a. Used to connect lighting and socket circuits of maintenance tools, such as lamps, electric drills, etc. (regardless of their voltage levels); b. Under-voltage automatic trippers that work under the grid voltage, but are not used for control and circuit breaker closing The power supply circuit of the device and release; the auxiliary circuit whose voltage does not exceed the first voltage section; c.
d Other important devices that are not allowed to be powered off during the power grid interruption period, such as: various pumps and fans and other auxiliary power supply circuits. When the voltage exceeds the first voltage section, the power cord of the above circuit should use cables or insulated wires, and should not be led out from the outgoing side of the power isolating switch, but should be led out through specially designed sealed terminals on the incoming side of the power isolating switch. And equipped with separate isolation switch. In the case described in item b. of Article 8.1, this switch can be omitted. GB5959.1-86
Circuits that are not disconnected through the power isolation switch should be written on the instructions. 8.2 The high-voltage circuit breaker can also be used for closing, disconnecting and isolating the power supply if it meets the following conditions: there is an obvious isolation distance (such as using a knife type or handcart type circuit breaker), a.
Facilities equipped with a locking mechanism at the location and with the lead cable reliably grounded: b.
c.
This high-voltage circuit breaker is dedicated to the power supply of electric heating equipment. 8.3 Control circuit
The rated voltage of the control circuit power supply should not exceed 250V. 8.3.1
8.3.2 The control circuit can be directly powered by TN or TT power grid. 8.3.3 The short-circuit protection mechanism should be fully calibrated so that it can function as a switching element in the control circuit. 8.3.4 If the control circuit is powered by a transformer with one end of the secondary winding grounded, the short-circuit protection component should be connected to the non-grounded conductor of the secondary winding. If the short-circuit protection component on the primary side can ensure the same safety, there is no need to connect a short-circuit protection component on the secondary side. .8.3.5 If the control circuit is powered by a transformer with the center tap of the secondary winding grounded, both ends of the secondary side of the control circuit should be connected to short-circuit protection components.
8.4 Grounding of control circuits
8.4.1 Any ground fault in the control circuit shall neither cause the load to be switched on incorrectly nor prevent the load from being disconnected. In order to meet this requirement, it is recommended that one side of the control transformer be grounded and the coils and contacts should be connected appropriately (see paragraph 8.4.3). Non-grounded control circuits powered by transformers should be equipped with insulation monitoring devices to indicate ground faults or to automatically cut off the circuit after a ground fault occurs. The DC internal resistance of the insulation monitoring device should be at least 15k. The required DC internal resistance value for some electronic devices may be much higher than 15k. A differential relay should be used when the control transformer has a grounded center tap. Note: The operation of the insulation monitoring device may be affected by DC points. 8.4.2 In control circuits that require one end to be grounded due to operational reasons, such as in internally grounded electromagnetic clutches or in control circuits with electronic components, the manufacturer should consider grounding issues. In this case, separate control transformers should be used or a control transformer with several mutually isolated secondary windings should be used. 8.4.3 Connection of coils and contacts
In the case where one end of the control circuit is connected (or will be connected in the future) to the protection circuit (such as a ground circuit), each electromagnetic operating device (or other electrical appliance) One end of the working coil (preferably with the same mark) should be directly connected to the end where the control circuit and the protection circuit are connected, and all contacts of the control device that makes the coil (or appliance) function should be connected in series to the coil ( or electrical appliance) and the end of the control circuit that is not connected to the protection circuit. For the above provisions, the following exceptions are allowed: a. If the connecting conductors between the contacts of a protective relay (such as an overload relay) and the coil of the control device it controls are in the same control cabinet, these contacts can be connected in the control cabinet. Between the end of the circuit connected to the protection circuit and the coil of the control device. b. Different arrangements of contacts simplify the external electrical connection of external controls, such as those for vehicles and hoisting machines, as well as multi-way plugs, etc. In this case, the requirements of the first paragraph of Clause 8.4.1 still need to be met. Note: For the situation of item b., care should be taken when designing to avoid danger in the event of failure. . Connection to the power grid and internal connections
9.1 General requirements
9.1.1 The connection between the electric heating equipment and the power grid depends on the type of the power grid, and the markings of various conductors should be in accordance with the relevant standards. The color of the wires should comply with the regulations of GB2681-81 "Colors of Wires in Complete Electrical Equipment". 9.1.2 Measures should be taken to ensure that the connecting wires are not subject to various abnormal mechanical stresses, such as tension, bending force, torsion, friction and vibration, or the effects of heat, moisture and steam during normal operation. And damaged. 9.1.3 The protective cover of the conductor should ensure that it can protect the insulation layer of the conductor from wear and scratches, and protect the conductor from tension and torsion.
9.2 Fixed connection
GB 5958.1--86
9.2.1 The device used to avoid tensile stress in the conductor shall not be live, and shall not be used in accordance with 9.1.2 The wire is damaged by abnormal pulling force.
9.2.2 At the entrance of the fixed connecting wire, the bending radius of the wire should be large enough to prevent the wire from being damaged. When the wire is introduced, the wire and its insulation layer should not be damaged.
9.3 Non-fixed connections and flexible conductors
9.3.1 Electric heating devices that are not permanently connected to the power grid should be equipped with flexible cables that can only be removed with the help of tools. 9.3.2 All flexible conductors shall be covered with protective sheaths in accordance with the requirements of Section 9.1.3, and shall not be subject to tension or torsion. The measures taken for this purpose should be easily identifiable. No temporary fixing measures are allowed. 9.3.3 At the connection point of the electric heating device, excessive bending of the flexible wire should be avoided, and the protective device should be firmly fixed and of sufficient length. 9.3.4 Consideration should be given to the introduction of flexible conductors so that the insulation layer of the flexible conductors will not be damaged when they are introduced. Insulating sleeves, etc. can be used to meet this requirement.
9.3.5 A certain space should be left for the power leads inside the electric heating or electrical device so that the wires can be easily introduced and connected. If a cover or cover is fitted, it shall be able to be easily fixed in place without damaging the conductors. 9.3.6 When sliding contact connections are used, protective measures should be taken to make the live parts inaccessible (according to GB4208-84 "Shell Protection", whether they are assembled or separated but still live). Classification of Grades" Provisions on finger testing). 9.3.7 Where plugs and sockets are used for connection, live parts should be made inaccessible when plugged in and disconnected. 9.3.8.Connecting conductors used for movable installations shall include all power supply conductors and protective conductors necessary for their operation and safety. All these wires with different electrical functions should be laid together. 9.3.9 Using multiple plugs in a set of equipment may cause confusion, thus affecting the normal operation and safety of the equipment. Therefore, the type of each plug used (e.g. shape, size, special markings) should be taken into account to eliminate such risks. The same applies to plugs and socket-outlets connected with flexible conductors.
10 Protection against electric shock
10.1 Measures to protect against electric shock should be taken for electric heating equipment. The design of electric heating equipment should meet the requirements of Section 4.9.1 of GB4064-83 "Guidelines for Safety Design of Electrical Equipment".
For equipment with operating frequency higher than low frequency, separate detailed provisions must be made in the "Special Requirements". 10.2 If required due to the type or operating conditions of the electric heating equipment, the following conditions are allowed as a supplementary condition to the direct contact protection provisions of GB4064 item 4.9.1.2.3. This condition is: the rated voltage of the electric heating equipment does not exceed the second voltage range; and other effective protective measures have been taken, such as setting up an insulating platform and using insulated or grounded tools, etc., to prevent operators from contacting live equipment during normal operation. parts in contact. 10.3 If required due to the type or operating conditions of the electric heating equipment, the following conditions are allowed as a supplementary condition to the indirect contact protection provisions of GB4064 item 4.9.1.3. This condition is: the rated voltage of the electric heating equipment does not exceed the second voltage section, and other protective measures have been taken, such as wearing insulating clothing, insulating gloves, insulating shoes, protective caps and goggles and other personal protective equipment, and setting up insulating platforms and Use common measures such as insulated or grounded tools to protect operators from the risk of electric shock in the event of an accident. 10.4 Grounding protection
Grounding protection should comply with the relevant provisions in GBJ65-83 "Code for Grounding Design of Industrial and Civilian Electric Power Installations". 10.4.1 Certain accessible metal parts of electric heating devices may become charged accidentally when the insulation is damaged. There should be safe and reliable electrical connections between these metal parts and between them and the ground terminal or the ground contact of the connecting plug, and the connecting wire should be as short as possible. If this is not possible at high frequencies due to the characteristics of the device itself, the provisions of the Special Requirements should be followed. The above requirements do not apply to small isolated metal parts such as screws and rivets. 10.4.2. Electric heating equipment fixedly connected to the power grid or electric heating equipment with fixed flexible conductors should be equipped with a grounding terminal. 10.4.3 Under normal working conditions, the metal of the ground terminal should not corrode when in contact with the metal of the ground wire. When the ground terminal comes into contact with aluminum alloy parts, appropriate protective measures should be taken to prevent corrosion caused by contact between different metals.
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