Sonel MPI-520 - Prospective Short-Circuit Current

MPI-520 OPERATING MANUAL version 3.4
19
- Remaining issues connected with the measurements as well as the messages displayed are the
same as those described for measurements L-PE circuit.
- The function works for residual current devices of nominal current ≥ 30 mA.
3.4.4 Prospective short-circuit current
The meter always measures impedance. The short-circuit current is calculated according to the
following formula:
S
n
k
Z
U
I 
where: U
n
– nominal voltage of the network being tested selected in MENU, Z
S
– impedance meas-
ured.
On the basis of U
n
nominal voltage selected (point 2.1.1), the meter automatically recognizes
the measurement at phase voltage or phase-to-phase voltage and takes it into account in the calcula-
tions.
If the voltage of the network being tested is outside the tolerance range, the meter will not be
able to determine a proper nominal voltage for the short-circuit current calculation. In such a case,
horizontal dashes will be displayed instead a short-circuit current value. The following diagram shows
voltage ranges for which short-circuit current value is calculated.
230
400
440
U [V]
207
253
360
115
127
180
200
220
220
380
418
198
242
342
373
415
440
216
240
264
103
440
U [V]
440
U [V]
U [V]
U =115V
n
U =220V
n
U =230V
n
U =240V
n
110
121
171
190
209
99
440
U [V]
U =110V
n
127
140
198
220
242
114
440
U [V]
U =127V
n
99
99
99
99
99
Voltage range for which impedance
measurement is made
U voltage ranges for which short-
circuit current value is calculated
U
L-L
voltage ranges for which short-
circuit current value is calculated