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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 connection 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 displacement voltage emerged
may be too small. This can be checked via operational measured values.
Important! If parameters were changed for this test, they must be returned to their original state after comple-
tion of the test !
Figure 3-29
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
Polarity testing for I
, example with current transformers configured in a Holmgreen-connection
N
(VTs with broken delta connection -- e-n winding)
Mounting and Commissioning
3.3 Commissioning
343
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