Functions
2.7 Teleprotection for Distance Protection (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
189
2.7.3
PUTT (Pickup)
The following scheme is suited for conventional transmission media.
Principle
The PUTT function scheme is shown in Figure 2-83. In the case of a fault inside zone Z1, the transfer trip signal
is sent to the opposite line end. The signal received there initiates the trip, provided that the protection function
has picked up. The transmit signal can be prolonged by T
S
(settable in address
2103
Send Prolong.
), to
compensate for possible differences in the pickup time at the two line ends. The distance protection is set such
that the first zone reaches up to approximately 85% of the line length. On three terminal lines Z1 is also set to
approximately 85 % of the shorter line section, but at least beyond the tee-off point.
The overreach zone Z1B is without consequence for the teleprotection scheme in this operating mode. It may,
however, be controlled by the automatic reclosing function (see also section 2.17).
Figure 2-83
Operation scheme of the permissive underreach transfer trip (PUTT) method
Sequence
The permissive transfer trip signal is only sent for faults in forward direction. Accordingly, the first zone Z1 of
the distance protection must definitely be set to
Forward
in address
1601
Op. mode Z1
, refer also to Section
2.5.1 under the margin heading „Independent Zones Z1 up to Z6“.
On two terminal lines, the signal transmission may be phase segregated. In this case, send and receive circuits
operate separately for each phase. On three terminal lines, the signals are sent to both opposite line ends. The
received signals are then combined with an OR logic function. With the parameter
Type of Line
(address
2102
) the device is informed as to whether it has one or two opposite line ends.
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 described in Section 2.11.2.