MARTINDALE ET4500 - Fault Loop Impedance Measurement Procedure

Martindale ET4000 / ET4500 Measurements
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Fault loop impedance measurement procedure
 Select the Zloop function using the function selector switch.
 Set sub-function to Zloop or Zs rcd 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 5.19 and
Figure 5.26).
 Press the TEST key to perform the measurement.
 Store the result, if required, by pressing the MEM key (ET4500 only).
Figure 5.27: Examples of loop impedance measurement result
Displayed results:
Z .............. fault loop impedance
Isc ........... prospective fault current
Lim .......... upper limit fault loop impedance value
Prospective fault current I
PFC
is calculated from the measured impedance as follows:
factorscalingZ
U
I
PEL
N
PFC
_


where:
Un ........................ Nominal U
L-PE
voltage (see table below),
Scaling factor.......Impedance correction factor (see chapter 4.4.4 Z factor).
U
n
Input voltage range (L-PE)
110 V
(93 V  U
L-PE
 134 V)
230 V
(185 V  U
L-PE
 266 V)
Testing considerations
 Large fluctuations of mains voltage can influence the measurement results (the
noise sign is displayed in the message field). In this case it is recommended
that the measurements are repeated a few times to check if the readings are
stable.

The Zloop measurement will trip-out the RCD in RCD-protected electrical
installations.
 Select the Zs rcd (non-trip) measurement to prevent trip-out of RCD's in RCD
protected installations.
 The measurement of fault loop impedance using the Zs rcd (non-trip) function
does not normally trip an RCD. However, the trip limit may be exceeded if a