KYORITSU 4116A - Measurement of Line Impedance and Prospective Short Circuit Current

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6.3 MeasurementofLineImpedanceandProspectiveShortCircuitCurrent
LineImpedanceonsingle-phasesystemistheimpedancemeasured
betweenphaseandneutralterminals.
Measurementprincipleusedinsidetheinstrumentisexactlythesameasat
Fault Loop Impedance measurement, but the measurement is carried out
betweenLandNterminals.
Breakingcurrentcapacityofinstalledover-currentprotectiondevicesshould
behigherthanProspectiveShort-Circuitcurrent,otherwiseitisnecessaryto
changetheratedcurrentofinvolvedover-currentprotectiondevice.
Practicalexampleoflineimpedancetestandprospectiveshort-circuit
currenttest(onlyformodels4120Aand4118A):
ThefigurebelowshowsinmarkedlinetheLineimpedancephasetoneutral
forTNsystem.
Fig.11
WARNING
(OLD-TTsystemonly)
●
DO NOT PRESS
the"Testbutton"ifthedisplayreadsavalueof
220V!
TheRCDcouldtripduringthetestsalsowithmodel4120A.
CAUTION
● TheD-LOK circuit of4120A can notworks with 127Vbetween
phasetoearth.
L1
L2
L3
N
PE
R
O
RCD
L
PE
N