MPI-525
– USER MANUAL
19
3.3.4 Prospective short-circuit current
The meter always measures impedance Z
S
. The short-circuit current is calculated according to the
following formula:
S
k
Z
U
I
where: Z
S
- measured impedance, U - voltage that depends on settings of
I
k
button, according to the
following Table:
The selection in
MENU
I
k
(U
n
)
U = U
n
I
k
(U
0
)
U = U
0
for U
0
< U
n
U = U
n
for U
0
≥ U
n
where: U
n
- nominal voltage of the network, U
0
- the voltage during the measurement.
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 calculations.
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-cir-
cuit current value is calculated
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