Siemens SIPROTEC 7SA522 Manual page 229

Mixed Lines Over-
head Line/Cable
Initiation
7SA522 Manual
C53000-G1176-C155-3
Figure 2-99 Reach control before first reclosure, using distance protection
If the distance protection is operated with one of the signal transmission methods de-
scribed in Section 2.6 the signal transmission logic controls the overreaching zone, i.e.
it determines whether an undelayed trip (or delayed with T1B) is permitted in the event
of faults in the overreaching zone (i.e. up to the reach limit of zone Z1B) at both line
ends simultaneously. Whether the automatic reclosure device is ready for reclosure or
not is irrelevant, because the teleprotection function ensures the selectivity over 100%
of the line length and fast, simultaneous tripping. The same applies for the earth fault-
direction comparison protection (Section 2.8).
If, however, the signal transmission is switched off or the transmission path is dis-
turbed, the internal automatic reclosure circuit can determine whether the overreach-
ing zone (Z1B in the distance protection) is released for fast tripping. If no reclosure is
expected (e.g. circuit-breaker not ready) the normal grading of the distance protection
(i.e. fast tripping only for faults in zone Z1) must apply to retain selectivity.
Fast tripping before reclosure is also possible with multiple reclosures. Appropriate
links between the output signals (e.g. 2nd reclosure ready: ´$5 &\F=RQH5HOµ)
and the inputs for enabling/releasing undelayed tripping of the protection functions can
be established via the binary inputs and outputs or the integrated user-definable logic
functions (CFC).
On mixed lines with cables and overhead lines, it is possible to use the distance zone
signals to distinguish between cable and overhead line faults to a certain extent. The
automatic reclosure circuit can then be blocked by appropriate signals generated by
means of the user-programmable logic functions (CFC) if there is a fault in the cable
section.
Starting the automatic reclosure function means storing the first trip signal during a
network fault that was generated by a protection function which operates with the au-
tomatic reclose function. In the case of multiple reclosure, starting therefore only takes
place once with the first trip command. The detection of the actual circuit breaker po-
sition is necessary for the correct functionality of the auto reclose function.
Starting is important when the first trip command has not appeared before expiry of an
action time (see below under "Action times").
Automatic reclosure is not started if the circuit breaker has not been ready for at least
one TRIP–CLOSE–TRIP–cycle at the instant of the first trip command. This can be
achieved by setting parameters. For further information, please refer to "Interrogation
of Circuit Breaker Ready State".
2.13 Automatic reclosure function (optional)
229