IEC product standards classify electrical equipment products into four categories: 0, I, II and III according to the different requirements of preventing indirect contact electric shock.
Class I equipment refers to equipment that not only relies on basic insulation for electric shock protection, but also includes an additional safety measure, that is, in the fixed wiring of equipment, the accessible conductive part is connected to the protective (grounding) conductor, so that the accessible conductive part will not become a live part when the basic insulation fails.
Extended data:
Insulation requirements for Class I equipment:
This kind of equipment only has basic insulation, but it is attached with measures to facilitate the connection between its bare conductor and protective wire, that is, protective terminals. The safety of this kind of equipment depends on the protective measures set in the place of use, that is, the measures that users should take in the design and construction of power engineering.
Class I equipment without power cord should have clearly marked protective terminals (commonly known as grounding bolts). For Class I equipment with power cord, there should be a special protective cord in the power cord, and if there is a power plug, there should be a protective cord pin in the plug.
Class I equipment can ensure that the accessible conductive part is not electrified after the basic insulation fails, because the accessible conductive part is included in the automatic cut-off protection system through the protective conductor.
References:
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