Fault Loop Impedance And Prospective Fault Current - METREL MI 3122 Instruction Manual

MI 3122 Smartec Z Line-Loop / RCD

5.2 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 and contact voltage. The measurement is covered by requirements of
the EN 61557-3 standard.
See chapter 4.1 Function selection for instructions
on key functionality.
Test parameters for fault loop impedance measurement
Test Selection of fault loop impedance sub-function [Zloop, Zs
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
Ro R
E
Figure 5.9: Connection of plug cable and universal test cable
Figure 5.8: Fault loop impedance
30
Fault loop impedance
]
rcd
L1
L2
L3
N
PE
N PE L