Siemens siprotec 7SA6 User Manual page 367

7SA6 Manual
C53000-G1176-C133-1
A few seconds are generally sufficient. In regions with frequent storms and
thunderstorms a shorter reclaim time is advisable to reduce the risk of a final trip due
to repeated lightning strikes or cable flashovers.
A long reclaim time must be selected in conjunction with multiple reclosure (see
above) if the circuit-breaker can not be monitored (e.g. due to missing auxiliary
contacts and CB–ready–information). Then the reclaim time must be longer than the
recovery time of the circuit-breaker.
The blocking duration following Manual–Close–detection 7%/2&. 0& (address
) must guarantee safe switching on and off of the circuit-breaker (0.5 s to 1 s). If
a fault is detected by a protection function within this time after detected closing of the
circuit-breaker, no reclosure takes place and a final three-pole trip is issued. If this is
not desired, address  is set to .
The options for the treatment of evolving faults are described in Section 6.12.1 under
the Sub-section "Handling of Sequential Faults" (page 6-174). The treatment of
evolving faults is not necessary on line ends where the adaptive dead time is applied
(address  $XWR 5HFORVH = $GDSWLYH 'HDG 7LPH $'7 , Section 5.1). The
addresses  and  are then of no consequence and therefore not accessible.
The detection of an evolving fault can be defined under address  (9 )/7
5(&2* with PICKUP means that, during a dead time, every fault detection ( pickup )
by a protection function will be interpreted as an evolving fault. With (9 )/7
5(&2* ZLWK 75,3 a fault during a dead time is only interpreted as an evolving fault
if it has led to a trip command by a protection function. This may also include trip
commands which are coupled in from external via a binary input or which have been
transmitted from an opposite end of the protected object. If an external protection
device operates with the automatic reclosure, evolving fault detection with pickup
requires the connection of a start signal from the external device to the 7SA6;
otherwise an evolving fault can only be detected with the external trip command even
if with PICKUP was set here.
The reaction in response to evolving faults can be selected under address . (9
)/7 02'( blocks AR means that no reclosure takes place after detection of an
evolving fault. This is always useful when only single-pole reclosure is to take place or
when stability problems are expected due to the subsequent three-pole dead time. If
a three-pole reclose cycle is to be initiated by tripping of the evolving fault, set (9
)/7 02'( = starts 3p AR . In this case a separately adjustable three-pole dead time
is started with the three-pole trip command due to the evolving fault. This is only useful
if three-pole reclosure is also permitted.
Address  76WDUW 021,725 monitors the reaction of the circuit-breaker after a
trip command. If the CB has not opened during this time (from the beginning of the trip
command), the automatic reclosure is blocked dynamically. The criterion for circuit
breaker opening is the position of the circuit-breaker auxiliary contact or the
disappearance of the trip command. If a circuit-breaker failure protection (internal or
external) is used on the feeder, this time should be shorter than the delay time of the
circuit-breaker failure protection so that no reclosure takes place if the circuit-breaker
fails.
If the reclosure command is transmitted to the opposite end, this transmission can be
delayed by the time setting in address  7 5HPRWH&ORVH. This transmission is
only possible if the device operates with adaptive dead time at the remote end
(address  $XWR 5HFORVH = $GDSWLYH 'HDG 7LPH $'7 at remote end).
This parameter is otherwise irrelevant. On the one hand, this delay serves to prevent
the remote end device from reclosing unnecessarily when local reclosure is
unsuccessful. On the other hand it should be noted that the line is not available for
Functions
6-185