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Functions
2.9 Teleprotection for Earth Fault Protection (optional)
Figure 2-129
Time Settings
The send signal prolongation Send Prolong.(address 3203) must ensure that the send signal reliably
reaches the opposite line end, even if there is very fast tripping at the sending line end and/or the signal trans-
mission time is relatively long. In the case of the permissive schemes Dir.Comp.Pickup and UNBLOCKING,
this signal prolongation time is only effective if the device has already issued a trip command. This ensures the
release of the other line end even if the short-circuit is cleared very rapidly by a different protection function or
other stage. In the case of the blocking scheme BLOCKING, the transmit signal is always prolonged by this time.
In this case, it corresponds to a transient blocking following a reverse fault. This parameter can only be altered
in DIGSI at Display Additional Settings.
In order to detect steady-state line faults such as open circuits, a monitoring time Delay for alarm is started
when a fault is detected (address 3207). Upon expiration of this time the fault is considered a permanent fail-
ure. This parameter can only be altered in DIGSI at Display Additional Settings.
The release of the directional tripping can be delayed by means of the permissive signal delay Release
Delay (address 3208). In general, this is only required for the blocking scheme BLOCKING to allow sufficient
transmission time for the blocking signal during external faults. This delay only has an effect on the receive
circuit of the teleprotection. Conversely, tripping by the comparison protection is not delayed by the set time
delay of the directional stage.
Transient Blocking
The setting parameters TrBlk Wait Time and TrBlk BlockTime are for the transient blocking with the
comparison schemes. This parameter can only be changed in DIGSI at Display Additional Settings.
The time TrBlk Wait Time (address 3209) is a waiting time prior to transient blocking. In the case of the
permissive schemes, only once the directional stage of the earth fault protection has recognized a fault in the
reverse direction, within this period of time after fault detection, will the transient blocking be activated. In the
case of the blocking scheme, the waiting time prevents transient blocking in the event that the blocking signal
reception from the opposite line end is very fast. With the setting ∞ there is no transient blocking.
Note
The TrBlk Wait Time must not be set to zero to prevent unwanted activation of the transient blocking TrBlk
BlockTime when the direction measurement is not as fast as the pick-up (signal transients). A setting of 10
ms to 40 ms is generally applicable depending on the operating (tripping) time of the relevant circuit breaker
on the parallel line.
262
Possible unfavourable current distribution on a three terminal line during an external earth fault
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
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