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Functions
2.8 Earth Fault Protection in Earthed Systems (optional)
Blocking
The earth fault protection can be blocked by the differential protection to give preference to the selective fault
clearance by the differential protection over tripping by the earth fault protection. Triggering the differential pro-
tection only causes a blocking of the trigger logic for the earth fault protection. Already started delay times are
reset. The trigger messages of the earth fault protection continue to be output, while the interaction with the
signal transmission method / Echo is performed. Blocking of the earth fault protection by means of differential
trips is maintained 40 scan cycles (length of the earth fault protection filter) after blocking is OFF. This prevents
a false pickup of the earth fault protection for extremely fast reset of the blocking.
The earth fault protection can be blocked by the distance protection. If in this case a fault is detected by the
distance protection, the earth fault protection will not trip. This gives the selective fault clearance by the distance
protection preference over tripping by the earth fault protection. The blocking can be restricted by configuration
to single-phase or multi-phase faults and to faults in distance zone Z1 or Z1/Z1B. The blocking only affects the
time sequence and tripping by the earth fault protection function and after the cause of the blocking has been
cleared, it is maintained for approximately 40ms to prevent signal race conditions. It is issued as fault indication
„EF TRIP BLOCK" (No. 1335).
The earth fault protection can also be blocked during the single-pole dead time of an automatic reclose cycle.
This prevents an incorrect measurement resulting from the zero-sequence current and voltage signals arising
in this state. The blocking affects optionally the entire protection function or the individual stages and is main-
tained for approximately 40ms after reclosure to prevent signal race conditions. If the complete function is
blocked, the indication „E/F BLOCK" (No. 1332) is output. The blocking of individual stages is signaled by the
indications 14080 to 14083.
232
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
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