Siemens siprotec 7SA6 User Manual page 281

Transient Blocking
Echo Function
7SA6 Manual
C53000-G1176-C133-1
With the release delay 5HOHDVH 'HOD\ (address ) the release of the zone Z1B
can be delayed. This is only necessary for the blocking scheme %ORFNLQJ, 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 the
permissive signal is not delayed by the set time delay T1B of the overreaching zone
Z1B. For SLORW ZLUH FRPSDULVRQ and UHYHUVH LQWHUORFNLQJ 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.
The parameters 7U%ON :DLW 7LPH and 7U%ON %ORFN7LPH serve the transient
blocking with the permissive overreaching schemes PUTT and UNBLOCKING. With
permissive underreach transfer trip they are of no consequence. This setting can only
be changed with DIGSI
The time 7U%ON :DLW 7LPH (address  ) is a waiting time before transient
blocking. Only once the distance protection recognizes a reverse fault inside this time
after fault detection, will the transient blocking become activated in the permissive
overreach transfer schemes. With the blocking scheme this waiting time prevents a
transient blocking if the blocking signal from the opposite line end is received very
rapidly. There is no transient blocking with the setting ∞.
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 faults. The send signal is delayed by this time with the permissive
overreach schemes 3277 and 8QEORFNLQJ if the protection had initially detected a
reverse fault. With the blocking scheme %ORFNLQJ the (blocking) receive signal is
prolonged by this time.
The preset value is generally sufficient.
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 echo function can be enabled
under address  )&7 :HDN ,QIHHG ((&+2 RQO\) or disabled (2))). With this
"switch" the weak infeed tripping function can also be activated ((&+2 DQG 75,3,
refer also to Section 6.7).
The notes regarding the setting of the distance stages above, and the margin
headings "Distance Protection Prerequisites" must in any event be noted.
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 the two line ends during external faults (through-
fault current). A typical setting is approximately 40 ms (presetting). This setting can
only be changed with DIGSI
The echo impulse duration 7ULS (;7(16,21 (address ) can be set to adapt to
the circumstances 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. Generally a setting of approximately 50 ms (presetting) is sufficient. This
setting can only be changed with DIGSI
The setting for the echo function is the same for all measures taken against weak
infeed and summarised in tabular form in Section 6.7.
®
4 under "Additional Settings".
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4 under "Additional Settings".
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4 under "Additional Settings".
Functions
6-99