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3 Mounting and Commissioning
circuit current transformers and set current and voltage transformer connections right
and repeat the check.
Note
If parameters were changed for this test, they must be returned to their original state
after completion of the test!
Measuring the dif-
The test for two ends is terminated with the reading of the differential, restraint and
ferential and re-
load currents. It is simultaneously checked that the current transformer connections
have been correctly restored after the I
straint currents
• Read out the differential, restraint and load currents. They are available for every
With
I
I
I
I
In the „WEB-Monitor" the differential and restraint currents are graphically displayed
in a characteristics diagram. An example is shown in Figure 3-28.
314
phase on the device display or in DIGSI in the measured values.
– The differential currents must be low, at least one scale less than the currents
flowing through. If high charging currents are to be expected in long overhead
lines or cables, these are additionally included in the differential currents.
– The maximum values of the read measured values for the charging current (3
values) are converted to Ampere and entered in I-DIFF>. The recommended
setting for the pickup threshold is 1 · I
– The restraint currents result from the pickup value I-DIFF> (address 1210, see
Section 2.3.2) plus the sum of the fault currents to be tolerated: Such as the
locally permissible current transformer errors according to address 253 E%
ALF/ALF_N (see Section 2.1.2), the permissible current transformer errors at the
other ends according to the respective setting, as well as the internal estimation
of the system errors (frequency, synchronisation and delay time difference er-
rors). With the default values for I-DIFF> (0.3 I
0.05) the following ensues:
the actually flowing current,
the rated operational current (as parameterised),
NB
the primary nominal current of the local current transformers,
N1
the primary nominal current of the current transformers of the remote end.
N2
test (if performed).
4
.
cN
) and E% ALF/ALF_N (5.0 % =
N
7SD610 Manual
C53000-G1176-C145-4
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