Functions
2.8 Earth Fault Protection in Earthed Systems (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
233
Figure 2-114 Logic diagram of single-pole tripping with phase selector
If the device is combined with an external automatic reclose device or if single-pole tripping can result from a
separate (parallel tripping) protection device, the earth fault protection must be blocked via binary input during
the single-pole open condition.
Switching onto an earth fault
The line energisation detection can be used to achieve fast tripping when energising the circuit breaker in case
of an earth fault. The earth fault protection can then trip three-pole without delay. Parameters can be set to de-
termine to which stage(s) the non-delayed tripping following energisation applies (see also logic diagrams from
Figure 2-104 to Figure 2-108).
The non-delayed tripping in case of line energization detection is blocked as long as the inrush-stabilization
recognizes a rush current. This prevents instantaneous tripping by a stage which, under normal conditions, is
sufficiently delayed during energization of a transformer.
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