User Manual

28 GMC-I Messtechnik GmbH
Settings for Calculating Short-Circuit Current – Parameter I
K
Short-circuit current I
K
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
K
must be
greater than tripping current Ia (see table 6 in section 19.1). The
variants which can be selected with the “Limits” key have the fol-
lowing meanings:
I
K
: Ia The measured value displayed for I
K
is used without
any correction to calculate Z
L-PE
.
I
K
: Ia+∆% The measured value displayed for Z
L-PE
is corrected
by an amount equal to the test instrument’s measuring
uncertainty in order to calculate I
K
.
I
K
: 2/3 Z In order to calculate I
K
, the measured value displayed
for Z
L-PE
is corrected by an amount corresponding to
all possible deviations (these are defined in detail by
VDE 0100-60 as Z
s(m)
≤ 2/3 x U
0
/Ia).
I
K
: 3/4 Z Z
s(m)
≤ 3/4 x U
0
/Ia
I
K
Short-circuit current calculated by the instrument (at nominal voltage)
Z Fault loop impedance
Ia Tripping current (see data sheet for circuit breakers / fuses)
∆ % Test instrument inherent error
Special case I
k
> I
kmax
If the short-circuit cur-
rent value does not lie
within the measured val-
ues defined in the
PROFITEST INTRO, this is
indicated by displaying
“>IK-max”.
In this case, manual
evaluation of the mea-
surement results is
required.
Measurement Cable Compensation
The resistance of the respectively connected measurement cable or the
country-specific measuring adapter must be compensated for each line
impedance measurement, i.e. it must be subtracted from the measure-
ment results as an offset. Proceed as described in section 4.5 under
„OFFSET RL-PE / RN-PE / RL-N“ on page 12 to this end in order to
ascertain offset values
RLPE-OFFSET and RNPE-OFFSET
Start Measurement
Display of U
L-N
(U
N
/ f
N
)
If the measured voltage value lies within a range of ±10% of the
respective nominal line voltage of 120 V, 230 V or 400 V, the
respectively corresponding nominal line voltage is displayed. In
the case of measured values outside of the ±10% tolerance, the
actual measured value is displayed.
Displaying the Fuse Table
After measurement has been performed, allowable fuse types can
be displayed by pressing the HELP key.
The table shows maximum allowable nominal current dependent
upon fuse type and breaking requirements.
Key: Ia = breaking current, I
K
= short-circuit current,
I
N
= nominal current, tA = tripping time
Semiautomatic measurement
See also section 5.8 regarding the AUTO
parameter. L-PE relationships are not
possible here. The neutral L-N relationship
is not offered during automatic sequenc-
ing to the right of the auto entry!
Polarity selection
Limit Value:
I
K
< limit value
LIMIT
I
K