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PROTECTIVE EARTH: any terminal which is intended for connection to an external protective conductor for protection against electric shock in case of a fault.


IEC 417 Protective Earth Symbol
 

 

GROUND: terminal which connect to external protective conductor through metal enclosure or through second ground wire from input. (Terminal and/or conductor is not qualify for  protective earth requirement).


IEC 417 Ground Symbol

 

Example of connecting  protective ground to chasis:

Requirement

Protective Earthing Connection

  • Protective earthing terminals: The method use to clamp the conductor should have preventive measure to prevent accidential loosening of the conductor. 
  • The resistance of the connection between the protective earthing terminal or earthing contact and parts required to be earthed shall not exceed 0.1 Ohm. Compliance is check by passing through 12Vdc/ac, 25A current for 1 minutes, the voltage drop between the protective earthing terminal or earthing contact  and the part to be earthed is measured and the resistance is calculated from the  current and this voltage drop. 
  • Protective earthing conductors are permitted to be bare or insulated. If insulated, the insulation shall be green/yellow (conductor size should be 18AWG or better).
  • Terminal:  Pillar/stud type (with locking washer) must have 3 mm  or screw type 3.5mm.  During tightened or loosen it will not work loose, internal wiring is not  subject to stress.


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