MI 3125 EurotestCOMBO
Fault loop impedance
39
5.6 Fault loop impedance and prospective fault current
Fault loop is a loop comprised by mains source, line wiring and PE return path to the
mains source. The instrument measures the impedance of the loop and calculates the
short circuit current. The measurement is covered by requirements of the EN 61557-3
standard.
See chapter
4.1 Function selection
for
instructions on key functionality.
Figure 5.24: Fault loop impedance
Test parameters for fault loop impedance measurement
Test
Selection of fault loop impedance
sub-function
[Zloop, Zs
rcd
]
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
Lim
Minimum short circuit
current
for selected fuse.
See Appendix A for reference fuse data.
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 5.25: Connection of plug cable and universal test cable
