Siemens siprotec 7SA522, User Manual

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Functions
6-151
7SA522 Manual
C53000-G1176-C119-2
6.11 Automatic reclosure function
Experience shows that about 85 % of the arc short-circuits on overhead lines
extinguish automatically after being tripped by the protection. The line can therefore
be reclosed. Reclosure is performed by an automatic reclosure circuit (ARC).
An example of the normal time sequence of a double reclosure is shown in Figure
6-82.
If the circuit-breaker poles can be operated individually, a single-pole short interruption
is usually initiated in the case of single-phase faults and a three-pole interruption in the
case of multi-phase faults in the network with earthed system star point. If the short-
circuit is still present after reclosure (arc not extinguished or metallic short-circuit), the
protection issues a final trip. Several reclosure attempts are made in some networks.
Automatic reclosure is only implemented on overhead lines because automatic
extinguishing of a short-circuit arc is not possible on cables and transformers. It should
not be used in any other case. If the protected object consists of a mixture of overhead
lines and other equipment (e.g. overhead line in block with a transformer or overhead
line/cable), it must be ensured that reclosure can only be performed in the event of a
fault on the overhead line.
In the version with single-pole tripping, the 7SA522 allows phase-selective, single-
pole tripping. A single and three-pole, single and multiple shot automatic reclosure
function is integrated, depending on the ordered version.
The 7SA522 can also be implemented with an external automatic reclosure device. In
this case the signal exchange between 7SA522 and the external reclosure device
must take place via the binary inputs and outputs.
It is also possible to have the integrated automatic reclosure circuit initiated by an ex-
ternal protection (e.g. second protection). The use of two 7SA522 with automatic
reclosure function or the use of one 7SA522 with an automatic reclosure function and
a second protection with its own automatic reclosure function are equally possible.
Fig. 6-82 Timing diagram of a double reclosure with action time (2nd reclosure successful)
starting
trip
command
close
command
action
reclaim
dead time
1st reclosure
dead time
2nd reclosure
reclaim
aborted
2nd reclosure successful, no further
tripping during reclaim time
1st reclosure unsuccessful; further
tripping during reclaim time
reclosure active start with 1st trip command
aborted
aborted