Siemens siprotec 7SA6, Manual

Page: 343 / 876

Functions
6-153
7SA6 Manual
C53000-G1176-C156-2
Transient Blocking The setting parameters
TrBlk Wait Time
and
TrBlk BlockTime
are for the tran-
sient blocking with the comparison protection. This setting can only be modified with
DIGSI
®
4 under “Additional Settings”.
The time
TrBlk Wait Time
(address
3209A
) 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.
The transient blocking time
TrBlk BlockTime
(address
3210A
) must definitely be
set longer than the duration of severe transients resulting from the inception or clear-
ance of external faults. The transmit signal is delayed by this time in the case of the
permissive protection schemes
Dir.Comp.Pickup
and
UNBLOCKING
if the protec-
tion had initially detected a reverse fault. In the case of the blocking scheme
BLOCK-
ING
the received (blocking) signal is prolonged by this time.
The preset value should be sufficient in most cases.
Echo Function In the case of line ends with weak infeed, or not sufficient earth fault current, the echo
function is sensible for the permissive scheme so that the infeeding line end can be
released. The echo function may be activated under address
2501 FCT Weak In-
feed
(
ECHO only
) or deactivated (
OFF
). With this “switch” it is also possible to acti-
vate the weak infeed tripping (
ECHO and TRIP
, refer also to Section 6.9).
The comments above regarding the setting of the current stage
3IoMin Teleprot
(address
3105
) must be noted as well as the margin heading “Earth Fault Protection
Prerequisites”.
The echo delay time
Trip/Echo DELAY
(address
2502
) must be set long enough to
ensure that no unwanted echo signals are generated due to differences in the pick-up
times of the earth fault protection fault detection at the two line ends during external
faults (through-fault current). Typical setting is approx. 40 ms (presetting). This setting
can only be modified with DIGSI
®
4 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 set long enough to
ensure that the received signal is reliably detected taking into consideration possible
differences in the operating times of the protection and transmission equipment at the
two line ends. In most cases approx. 50 ms (presetting) is sufficient. This setting can
only be modified with DIGSI
®
4 under “Additional Settings”.
The echo function settings are common to all weak infeed measures and summarized
in tabular form in Section 6.9.
Note:
The “
ECHO SIGNAL
” (FNo
4246
) must be allocated separately to the output relays for
the transmitter actuation, as it is not contained in the transmit signals of the transmis-
sion functions. On the digital protection data interface with permissive overreach
transfer trip mode, the echo is transmitted as a separate signal without taking any spe-
cial measures (Figure 6-55).