Sizing of protective earthing conductor

Below is based on IEC 60364-5-54. This table provides two methods of determining the appropriate c.s.a. for both PE or PEN conductors.

 

 

	c.s.a. of phase conductors Sph (mm2)	Minimum c.s.a. of PE conductor (mm2)	Minimum c.s.a. of PEN conductor (mm2)
			Cu                       AI
Simplified method (1)	Sph≤ 16	Sph(2)	Sph(3)	Sph(3)
	16 < Sph ≤ 25	16	16
	25 < Sph ≤ 35			25
	35 < Sph ≤ 50	Sph/2	Sph/2
	Sph > 50			Sph/2
Adiabatic method	Any size	(3)  (4)

(1) Data valid if the prospective conductor is of the same material as the line conductor. Otherwise, a correction factor must be applied.
(2) When the PE conductor is separated from the circuit phase conductors, the following minimum values must be respected:

§  2.5 mm² if the PE is mechanically protected

§  4 mm² if the PE is not mechanically protected

(3) For mechanical reasons, a PEN conductor, shall have a cross-sectional area not less than 10 mm² in copper or 16 mm² in aluminium.
(4) Refer to table G53 for the application of this formula.

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