MI 3101 EurotestAT: Measurements
Fault loop impedance
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5.4 Fault loop impedance and prospective fault current
Fault loop is a loop comprising mains source, line wiring and PE return path to the mains
source. The instrument has ability to measure impedance of mentioned loop and calculate
short circuit current and contact voltage regarding the selected circuit breaker type. The
measurement is covered by requirements of the EN 61557-3 standard.
See
4.2 Single test
for active keys.
Figure 5.18: Fault loop
impedance
Test parameters for fault loop impedance measurement
Protection
Selection of main
protection device
in fault loop [RCD, FUSE]*
Fuse type
Selection of
fuse
type
[---, NV, gG, B, C, K, D] **
Fuse I
Rated current
of selected fuse
Fuse T.
Maximum
breaking time
of selected fuse
Isc_lim
Minimum short circuit
current
for selected fuse combination.
See Appendix A for reference fuse data.
* Select RCD to prevent trip-out of RCD in RCD protected installation.
** --- Means no fuse selected.
Circuits for measurement of fault loop impedance
L1
L2
L3
N
PE
R
E
Ro
L
PE
N
L/L
1
N/L2
PE/L3
Figure 5.19: Connection of plug cable and universal test cable
