Direct Underreach Transfer Trip - Siemens siprotec 7SA6 User Manual

Functions
6.4.1.3

Direct Underreach Transfer Trip

Principle
6-80
The permissive transfer trip only functions for faults in the forward direction.
Accordingly, the first zone Z1 and the overreaching zone Z1B of the distance
protection must definitely be set to )RUZDUG: address  2S PRGH = and 
2S PRGH =%, refer also to Sub-section 6.2.4.2 under the margin heading
"Independent Zones Z1 up to Z5" and "Controlled Zone Z1B".
On two terminal lines, the signal transmission may be done phase segregated. On
three terminal lines, the transmit signal is sent to both opposite line ends. The receive
signals are then combined with an OR logic function. By means of the parameter /LQH
&RQILJ (address ) the device is informed whether it has one or two opposite
ends.
During disturbance of the signal transmission path, the overreaching zone Z1B may
be activated by an automatic reclosure via the binary input "!(QDEOH $5]RQHV" and
address  "VW $5 ! =%" set to "Yes" (refer also to Figure 6-38 bottom).
If at one line end there is weak or zero infeed, so that the distance protection does not
pick up, the circuit breaker can still be tripped. This "weak-infeed tripping" is referred
to in Section 6.7.
As is the case with permissive transfer trip via pick-up or zone acceleration, a fault in
the first zone Z1 is transmitted to the opposite line end by means of a transfer trip
signal. The signal received there causes a trip without further queries after a short
(settable under address  7ULS 7LPH '(/$<) (Figure 6-46).
security margin T
v
The transmit signal can be prolonged by T
3URORQJ), to compensate for possible differences in the pick-up time at the two line
ends. The distance protection is set such that the first zone reaches up to
approximately 80 % of the line length. On three terminal lines Z1 is also set to
approximately 80 % of the shorter line section, but at least beyond the tee off point.
The overreaching zone Z1B is not required here. It may however be activated by
internal automatic reclosure or external criteria via the binary input "!(QDEOH
$5]RQHV" (refer also to Figure 6-38 bottom).
The advantage compared to the other permissive underreach transfer trip schemes
lies in the fact that both line ends are tripped without the necessity for any further
measures, even if one line end has no infeed. There is however no further supervision
of the trip signal at the receiving end.
The direct underreach transfer trip application is not provided by its own selectable
teleprotection scheme setting, but implemented by setting the teleprotection
supplement to operate in one of the permissive underreach transfer trip schemes
(address  7HOHSURW 'LVW = 3877 or 3877 ZLWK SLFNXS), and using
the binary inputs for direct external trip at the receiving end. Accordingly, the transmit
circuit in Subsection 6.4.1.1 (Figure 6-43) or 6.4.1.2 (Figure 6-45) applies. For the
receive circuit the logic of the "external trip" as described in Section 6.8 applies.
On two terminal lines, the transmission can be phase segregated. On three terminal
lines the transmit signal is sent to both opposite line ends. The receive signals are then
combined with a logical OR function.
(settable under address  6HQG
S
7SA6 Manual
C53000-G1176-C133-1