MARTINDALE ET4500 - 5.6.1 Line impedance and prospective short circuit current; Line Impedance Measurement Procedure

Martindale ET4000 / ET4500 Measurements
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5.6.1 Line impedance and prospective short circuit current
Circuits for measurement of line impedance
Figure 5.30: Phase-neutral or phase-phase line impedance measurement
Line impedance measurement procedure
 Select the Z LINE function using the function selector switch.
 Set sub-function to Zline using UP / DOWN keys.
 Select test parameters (optional).
 Connect the test leads to the instrument.
 Connect the test leads to the installation wiring to be tested (see Figure 5.30).
 Press the TEST key to perform the measurement.
 Store the result, if required, by pressing the MEM key (ET4500 only).
Figure 5.31: Examples of line impedance measurement result
Displayed results:
Z .............. line impedance
Isc ........... prospective short-circuit current
Lim .......... upper limit line impedance value
Prospective fault current I
PFC
is calculated from the measured impedance as follows:
factorscalingZ
U
I
LNL
N
PFC
_
)(



where:
Un ........................ Nominal U
L-N
or U
L1-L2
voltage (see table below),
Scaling factor ....... Impedance correction factor (see chapter 4.4.4 Z factor).