3 Mounting and Commissioning
504
7SD5 Manual
C53000-G1176-C169-1
DANGER!
Energized equipment of the power system! Capacitive coupled voltages at discon-
nected equipment of the power system !
Non-observance of the following measure will result in death, severe personal injury
or substantial property damage.
Primary measurements must only be carried out on disconnected and earthed equip-
ment of the power system!
The configuration shown in Figure 3-32 corresponds to an earth current flowing
through the line, in other words an earth fault in the forward direction.
At least one stage of the earth fault protection must be set to be directional (address
31xx of the earth fault protection). The pickup threshold of this stage must be below
the load current flowing on the line; if necessary the pickup threshold must be reduced.
The parameters that have been changed, must be noted.
Figure 3-32 Polarity check of I
4
, example with earth current from a power transformer star point
After switching the test source on and off again, the direction indication must be
checked: in the fault log the messages „EF Pickup“ and „EF forward“ must at
least be present. If the directional pickup alarm is missing, a connection error of the
earth current connection I
4
is present. If the wrong direction is indicated, the earth
current connection I
4
has a swapped polarity. In the previous case the connection
must be rectified after the test source has been switched off. The measurements must
then be repeated.
If the pickup alarm is missing altogether, this may be due to the fact that the test
current is too small.
Note
If parameters were changed for this test, they must be returned to their original state
after completion of the test !
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