Manual

Gossen Metrawatt GmbH 57
14 Measuring Supply Impedance (Z
L-N
Function)
Measuring Method (internal line resistance measurement)
Supply impedance Z
L-N
is measured by means of the same
method used for loop impedance Z
L-PE
(see section 13 on page
54). However, the current loop is completed via neutral conductor
N rather than protective conductor PE as is the case with loop
impedance measurement.
Select Measuring Function
Connection
Schuko
Connection
2-Pole Adapter
Set Parameters
Press the softkey shown at the left in order to switch
back and forth between the country-specific plug
insert, e.g. SCHUKO, and the 2-pole adapter. The
selected connection type is displayed inversely
(white on black).
Settings for Calculating Short-Circuit Current – Parameter I
SC
Short-circuit current I
SC
is used to test shutdown by means of an
overcurrent protective device. In order for an overcurrent protec-
tive device to be tripped on time, short-circuit current I
SC
must be
greater than tripping current I
a
(see table 6 in section 25.1). The
variants which can be selected with the “Limits” key have the fol-
lowing meanings:
I
SC
:I
a
The measured value displayed for I
SC
is used
without any correction to calculate Z
L-N
.
I
SC
:I
a
+% The measured value displayed for Z
L-N
is cor-
rected by an amount equal to the test instrument’s
measuring and intrinsic uncertainties in order to
calculate I
SC
.
I
SC
: 2/3 Z In order to calculate I
SC
, the measured value dis-
played for Z
L-N
is corrected by an amount corre-
sponding to all possible deviations (these are
defined in detail by IEC 60364-6 as
Z
s(m)
 2/3 × U
0
/I
a
).
I
SC
:3/4 ZZ
s(m)
 3/4 × U
0
/I
a
Z Loop impedance
I
SC
Short-circuit current
U Momentary voltage at the test probes, “U
N
” is displayed if
U
max.
deviates from nominal voltage by 10%
f Frequency of the applied voltage,
“fN” is displayed if frequency f
max.
deviates from nominal
frequency by 1%
I
a
Tripping current
(see data sheet for circuit breakers / fuses)
% Test instrument intrinsic error
Z
L-N
Nom. current: 2 … 160 A, 9999 A
Diameters: 1.5 … 70 mm
Cable type: NY…, H07…
Number of wires: 2 … 10-wire
Tripping characteristics:
A, B/L, C/G, D, E, H, K, GL/GG & factor
Semiautomatic Measurement
See also section 10.9 regard-
ing the AUTO parameter.
L-PE relationships are not
possible here.
Polarity Selection
Limit Value:
I
SC
< Limit Value
U
L
 R
L
I
SC