2 Functions
204
7SD5 Manual
C53000-G1176-C169-1
tion of this time the fault is considered a permanent failure. This parameter can only
be altered with DIGSI
®
under Additional Settings.
With the release delay Release Delay (address 2108) the release of the zone Z1B
can be delayed. This is only required for the blocking scheme BLOCKING to allow suf-
ficient transmission time for the blocking signal during external faults. This delay only
has an effect on the receive circuit of the teleprotection scheme. Conversely, the per-
missive signal is not delayed by the set time delay T1B of the overreaching zone Z1B.
For Pilot wire comp and Rev. Interlock T1B must be delayed so that there
is enough time between the pickup of the distance protection function and the trip
signal of zone Z1B.
Transient Blocking The parameters TrBlk Wait Time and TrBlk BlockTime serve the transient
blocking with the permissive overreaching schemes POTT and UNBLOCKING. With
permissive underreach transfer trip they are of no consequence.
The time TrBlk Wait Time (address 2109) is a waiting time prior to transient block-
ing. Not before the distance protection recognizes a reverse fault inside this time after
fault detection, will the transient blocking become activated in the permissive over-
reach transfer schemes. 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. This setting is only
possible via DIGSI
®
at Additional Settings.
The transient blocking time TrBlk BlockTime (address 2110) must be definitely
longer than the duration of severe transients resulting from the inception or clearance
of external short circuits. The send signal is delayed by this time with the permissive
overreach schemes POTT and UNBLOCKING if the protection had initially detected a
reverse fault. In the case of the blocking scheme BLOCKING the received (blocking)
signal is prolonged by this time. This setting is only possible via DIGSI
®
at Additional
Settings.
The preset value should be sufficient in most cases.
Echo Function In the case of line ends with weak infeed, the echo function is sensible in conjunction
with permissive overreach transfer schemes POTT and UNBLOCKING with release
signal, so that the feeding line end is also released. The setting lists concerning the
weak infeed are listed in Section 2.10.2.2. The echo function in address 2501 FCT
Weak Infeed can be activated (ECHO only or deactivated (OFF). By means of this
„switch“ the weak infeed tripping function can also be activated (ECHO and TRIP,
refer also to Section 2.10.1).
Please do not fail to observe the notes on the setting of the distance protection stages
at margin heading „Distance Protection Prerequisites“.
The echo delay time Trip/Echo DELAY (address 2502) must be set long enough to
avoid incorrect echo signals resulting from the difference in pickup time of the distance
protection functions at all line ends during external faults (through-fault current).
Typical setting is approx. 40 ms (presetting). This parameter can only be altered with
DIGSI
®
under Additional Settings.
The echo impulse duration Trip EXTENSION (address 2503) may be matched to the
configuration data of the signal transmission equipment. It must be long enough to
ensure that the receive signal is recognized even with different pickup times by the
protection devices at the line ends and different response times of the transmission
equipment. In most cases approx. 50 ms (presetting) is sufficient. This parameter can
only be altered with DIGSI
®
under Additional Settings.
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