Caution – HT instruments SPEED418 User Manual

Page 36

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400

Series

EN - 35

6.5. LOOP:

MEASUREMENT OF LINE/LOOP IMPEDANCE

This function is performed according to standard IEC/EN61557-3 and allows measuring
the line impedance, the earth fault loop impedance and the prospective short circuit
current. The following operating modes are available:

P-N the instrument measures impedance between the phase conductor and the

neutral conductor and calculates the prospective phase-to-neutral short circuit
current

P-P the instrument measures impedance between two phase conductors and

calculates the prospective phase-to-phase short circuit current

P-PE the instrument measures the fault loop impedance and calculates the

prospective fault current


CAUTION

The measurement of line impedance or fault loop impedance involves the
circulation of a maximum current according to the technical specifications of
the instrument (§ 12.1). This could cause the tripping of possible
magnetothermal or differential protections at lower tripping currents.

Fig. 15: Instrument connection for 230V single-phase or double-phase P-N line impedance

and P-PE fault loop impedance measurement through shuko cable

Fig. 16: Instrument connection for 230V single-phase or double-phase P-N line impedance

and P-PE fault loop impedance measurement through single cables and remote probe

Fig. 17: Instrument connection for 400V + N + PE three-phase P-N line impedance and

P-PE fault loop impedance measurement through single cables and remote probe

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