METREL MI 3125 User Manual

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
LPEN
L
/
L
1
N
/
L
2
P
E
/
L
3
Figure 5.25: Connection of plug cable and universal test cable

METREL MI 3125 Specifications

General

Type	Multifunction Installation Tester
Insulation Resistance	Yes
Continuity Test	Yes
Loop Impedance	Yes
RCD Testing	Yes
Voltage Measurement	Yes
Frequency Measurement	Yes
Display	LCD
Power Supply	6 x 1.5 V AA batteries
Loop Resistance Resolution	0.01 Ω
Frequency	45 - 65 Hz
Line Voltage Resolution	1 V
Insulation Resistance Test Voltage	50 V, 100 V, 250 V, 500 V, 1000 V
Insulation Resistance Resolution	0.01 MΩ
Continuity Resistance Resolution	0.01 Ω
Test Current	200 mA
DC Voltage	Up to 600 V
Loop Resistance	0.0 Ω - 1999 Ω
Line Voltage	Up to 550 V
Line Voltage Accuracy	±2% ±2 digits
Rated Residual Current	10 mA, 30 mA, 100 mA, 300 mA, 500 mA
Insulation Resistance Range	0.01 MΩ to 1 TΩ
Continuity Resistance	0.0 Ω - 1999 Ω
Dimensions	220 x 103 x 55 mm
Operating Temperature	-10°C to 50°C
Storage Temperature	-20°C to +60°C
Safety Standards	EN 61557
Loop Resistance Accuracy	±(5% + 3 digits)