METREL MI 3122 Instruction Manual page 31

MI 3122 Smartec Z Line-Loop / RCD
Fault loop impedance measurement procedure
Select the
Z-LOOP

Select test parameters (optional).

Connect test cable to the top of the Smartec Z Line-Loop / RCD.

Connect test leads to the item to be tested (see figure 5.9 ).

Press the TEST key to perform the measurement.

Store the result by pressing the MEM key (optional).

Figure 5.10: Examples of loop impedance measurement result
Displayed results:
Z .............. Fault loop impedance,
I ............ Prospective fault current,
SC
Lim .......... Low limit prospective short-circuit current value or high limit fault loop
impedance value for the UK version.
Prospective fault current I
where:
Un ........ Nominal U
L-PE
ksc ....... Correction factor for Isc (see chapter 4.2.6 ).
Notes:
High fluctuations of mains voltage can influence the measurement results (the noise

sign is displayed in the message field). In this case it is recommended to repeat
few measurements to check if the readings are stable.
This measurement will trip-out the RCD in RCD-protected electrical installation if

test Zloop is selected.
Select Zs
rcd

function using the function selector switch.
is calculated from measured impedance as follows:
SC
I
SC
voltage (see table below),
U Input voltage range (L-PE)
n
110 V (93 V  U
230 V (185 V  U
to prevent trip-out of RCD in RCD protected installation.

Un k

SC
Z
 134 V)
L-PE
 266 V)
L-PE
31
Fault loop impedance
UK version