Siemens siprotec SJ62 User Manual page 437

3 Mounting and Commissioning
435
n windings of the voltage transformer is foreseen, the corresponding phase is discon-
nected on the secondary side (see Figure 3-39). Only the current of the transformer
which is not provided with voltage in its voltage path is fed into the current path. If the
line carries resistive-inductive load, the protection is in principle subjected to the same
conditions that exist during a ground fault in line direction.
The directional ground fault protection must be configured to enabled and activated
(address 116 or 131). Its pickup threshold must be below the load current of the line;
if necessary the pickup threshold must be reduced. The parameters that have been
changed, must be noted.
After switching the line on and off again, the direction indication must be checked: In
the fault log the messages „67N picked up" and „Ground forward" must at
least be present. If the directional pickup is not present, either the ground current con-
nection or the displacement voltage connection is incorrect. If the wrong direction is
indicated, either the direction of load flow is from the line toward the busbar or the
ground current path has a swapped polarity. In the latter case, the connection must be
rectified after the line has been isolated and the current transformers short-circuited.
If the pickup message is missing, the measured ground (residual) current or the dis-
placement voltage emerged may be too small. This can checked via operational mea-
sured values.
Important! If parameters were changed for this test, they must be returned to their
original state after completion of the test !
Figure 3-38 Polarity testing for I
Holmgreen-connection (VTs with broken delta connection -- e-n winding)
, example with current transformers configured in a
N
C53000-G1140-C147-A, Edition 07.2015
SIPROTEC 4, 7SJ62/63/64 Handbuch