Protection classes in electrical engineering
Protection class
In electrical engineering, protection classes serve to categorize and label electrical devices to indicate the safety measures in place to protect against electric shocks. For electrical devices, the protection classes indicate the hazard level involved if a person touches the device.
All devices that are labelled with protection class III, that are not provided with a protective conductor terminal or not provided with a protective insulation mark must be connected to a safe low voltage source. For inductive proximity sensors, this may be SELV or PELV. What must be borne in mind? Never dismantle devices with protective insulation; the protective effect may not be maintained when it is reassembled. Devices with damaged housings are no longer protectively insulated.
Protective insulation
This is insulation in addition to the operational insulation; they are independent of each other. The protective insulation could consist in that all parts that could become live if the operational insulation were to fail are permanently and securely covered with insulating material. Devices with protective insulation are marked with the standard symbol that can be found on the rating plate.
SELV Safety Extra Low Voltage
Specification as a SELV system involves a protective measure against direct and indirect contact with hazardous voltages in the form of 'secure separation' within the device.
PELV Protective Extra Low Voltage
Low voltage with secure separation (this is an earthed variant of SELV). Specification as a PELV System according to IEC364-4-41 involves two protective measures (double insulation) against direct and indirect contact with hazardous voltages in the form of 'secure separation' of the primary and secondary circuits within the device.
„For electrical devices, the protection classes indicate the hazard level involved if a person touches the device.“
Patrick Targonski
Product Manager at autosen
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