Electrical and electronic equipment protection against electric shock classification
The standard reference to the classification of the international standard IEC 536 (1976) "electrical and electronic equipment protection against electric shock."
1 Subject and Scope
This standard specifies the low-voltage electrical and electronic equipment connected to the external power supply basic insulation failure classification and definition of done the way of protection against electric shock.
This standard applies to the rated voltage does not exceed the rms AC 660V electrical and electronic equipment. When necessary, the relevant professional standards can be used for higher voltage equipment, or for other purposes.
This standard applies to homes, offices, factories, schools, farms and similar use, as well as medical electrical electronic equipment.
This standard does not apply to open-type equipment, does not apply to touch the live parts of equipment does not have to prevent.
2 reference standards
GB 2900.1 electrical terminology terminology
GB of 3805 safe voltage
GB of 4208 shell protection grade classification
GB 4708 electrical safety terminology
3 Terms
3.1 Basic Insulation Basic insulation
Insulation of live parts of electric shock from the protective effect.
3.2 Additional insulation supplementary insulation
Independent insulation in addition to basic insulation in order to prevent electric shock, in the case of basic insulation damage.
3.3 double insulation of a double insulation
With basic insulation and supplementary insulation insulation.
3.4 reinforced insulation reinforced insulation
Degree of protection equivalent to double insulation separate insulated structure.
Note: The insulation structure "The term does not mean that the insulation must be similar. It can not by a few like basic insulation or additional insulation as a separate test of the insulation layers.
3.5 Safety impedance safety impedance.
Connected to the impedance between live parts and conductive easy part, its value in the case of the normal use of equipment and possible failure current limit within a safe value, and to maintain its reliability during the entire life of the equipment.
3.6 Safety extra low voltage, the safety extra-low voltage (SELV)
The safety isolating transformer or converter and power supply with separate windings dry group to isolate the circuit between the conductor or any valid value between a conductor and ground does not exceed 50V AC voltage.
Note: (1) different industries on safety extra low voltage limit regulations by the relevant industry standards.
② allow the limits of direct contact with live parts see GB 3805.
③ regardless of full load or no load should not exceed the voltage limits. This definition assumes that any transformer or converter are rated supply voltage.
4 Equipment Classification
The breakdown indicates that the device only to protection against electric shock does not reflect the level of security of the equipment.
According to this classification, protection against electric shock provided by the surrounding environment, the device itself or the power supply system. See Table A1 of Appendix A (reference case).
Equipment, non-electric shock protection by provisions in other national standards such as the level of protection provided by enclosures, see GB 4208.
4.1 0-class equipment
Alone basic insulation as a protection against electric shock devices, when the conductive part of equipment that could be reached that part of facilities in the fixed wiring protection (ground) line is connected, once the basic insulation failure, the security depends entirely on the The use of the environment.
4.2 I devices
Electric shock protection devices not only by basic insulation, and also includes an additional safety measures will soon be able to touch the conductive part of the facilities for fixed wiring protection (ground) wire is connected.
Note: (1) equipment for the use of flexible cords or flexible cables, flexible cords or flexible cables should have a protection
(Ground) wire.
② by the standards allow any part of at least basic insulation and equipped with a ground terminal, but the power
Cord without a grounding wire, grounding prong plug can not be inserted into the ground jack power outlet
Equipment, as long as the line of protection and the protection of the (ground) line in the fixed wiring connections, to see
For Class 0 devices, but in all other respects, the grounding of the equipment should fully comply with the requirements of Class Ⅰ equipment.
4.3 Class II equipment
Equipment protection against electric shock, not only by basic insulation also have additional security like double insulation or reinforced insulation
Measures. This device does not use measures to protect ground, does not depend on the installation conditions.
II devices can help maintain the protection of ground loop continuity device, but must be within the device, and
The requirements of the class II and to touch a conductive surface insulation.
Class II equipment where metal can be taken when necessary, equipotential cable connection with the shell.
II devices may work (conservation purposes) the reasons to take a means of connection with the earth, but must
Technically not detract from the level of safety.
In exceptional circumstances such as the signal terminals of certain class II electronic devices, in charge of departments that need security
The total impedance, and technically not detract from the level of safety class II devices can use the security impedance.
② some cases, All insulation shell "and" metal shell "class II device need to be distinguished.
4.4 III devices
Equipment protection against electric shock relies on the Safety Extra Low Voltage (SELV) power supply, voltage equipment may not be higher than the safety extra low voltage.
Class Ⅲ equipment shall have protective grounding means. Necessary, due to work (conservation purposes) reasons, to take the means of connection with the earth, but to be technically non-destructive to complete the level.
The metal casing of class III devices when necessary, to take the means of equipotential bonding line and shell connections.
Appendix A
The main features of the equipment and safety measures table
(Reference case)
A1 Table A1 lists the equipment, pointing out that the protection against electric shock classification of the main features of the basic insulation failure safety measures.
Table A1
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│ Category
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Project │ 0 │ Class Ⅰ │ │ Class Ⅱ III class
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Device main │ no insurance │ protective grounding │ additional insulation │ designed by security
Characteristics of the ground │ │ │ care need to be protected ground │ ultra-low voltage power supply
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Security measures │ │ environment │ grounding line and the fixed wiring, double insulation │
Shi │ │ ground insulation protection (ground) cable │ or reinforced insulation │ safety extra-low voltage power supply
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