2 Functions
148
7SA522 Manual
C53000-G1176-C155-3
With the release delay 5HOHDVH'HOD\ (address ) the release of the zone Z1B
can be delayed. This is only required for the blocking scheme %/2&.,1* 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; conversely the permissive
signal is not
delayed by the set time delay T1B of the overreaching zone Z1B.
Transient Blocking The parameters 7U%ON:DLW7LPH and 7U%ON%ORFN7LPH serve the transient
blocking with the permissive overreaching schemes POTT and UNBLOCKING. With
permissive underreach transfer trip they are of no consequence.
The time 7U%ON:DLW7LPH (address ) 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 7U%ON%ORFN7LPH (address ) 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 3277 and 81%/2&.,1* if the protection had initially detected a
reverse fault. In the case of the blocking scheme %/2&.,1* 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 Subsection 2.9.2.2. The echo function at address )&7
:HDN,QIHHG can be activated ((&+2RQO\ or deactivated (2))). By means of this
“switch” the weak infeed tripping function can also be activated ((&+2DQG75,3,
refer also to Section 2.9.1).
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 7ULS(FKR'(/$< (address ) must be set long enough to
avoid incorrect echo signals resulting from the difference in fault detection pick-up time
of the distance protection functions at all line ends during external faults (through-fault
current). Typical setting is approx. 40 ms (presetting). This setting is only possible via
DIGSI
®
at Additional Settings.
The echo impulse duration 7ULS(;7(16,21 (address ) 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 pick-up 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 setting is only
possible via DIGSI
®
at Additional Settings.
An endless echo signal between the line ends can be avoided (e.g. interference cou-
pling in the signal path) by blocking a new echo for a certain time (FKR%/2&.7LPH
(address ) after each output of an echo signal. The typical setting is approx. 50
ms. After the distance protection signal was sent, the echo is equally blocked for the
time (FKR%/2&.7LPH. This setting is only possible via DIGSI
®
at Additional Set-
tings.
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