Functions
2.17 Automatic Reclosure Function (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
318
2.17
Automatic Reclosure Function (optional)
Experience shows that about 85% of the arc faults on overhead lines are extinguished automatically after being
tripped by the protection. The line can therefore be re-energised. Reclosure is performed by an automatic
reclose function (AR).
Automatic reclosure function is only permitted on overhead lines because the possibility of extinguishing a fault
arc automatically only exists there. It must 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.
If the circuit breaker poles can be operated individually, a 1-pole automatic reclosure is usually initiated in the
case of 1-phase faults and a 3-pole automatic reclosure in the case of multi-phase faults in the network with
earthed system star point. If the fault still exists after reclosure (arc not extinguished or metallic short-circuit),
the protection issues a final trip. In some systems several reclosing attempts are performed.
In the model with 1-pole tripping the 7SD5 allows phase-selective 1-pole tripping. A 1- and 3-pole, one- and
multi-shot automatic reclosure is integrated depending on the order variant.
The 7SD5 can also operate in conjunction with an external automatic reclosure device. In this case, the signal
exchange between 7SD5 and the external reclosure device must be effected via binary inputs and outputs.
It is also possible to initiate the integrated auto reclose function by an external protection device (e.g. a backup
protection). The use of two 7SD5 with automatic reclosure function or the use of one 7SD5 with an automatic
reclosure function and a second protection with its own automatic reclosure function is also possible.
2.17.1
Functional Description
Reclosure is performed by an automatic reclosure circuit (ARC). An example of the normal time sequence of
a double reclosure is shown in the figure below.
Figure 2-156
Timing diagram of a double-shot reclosure with action time (2nd reclosure successful)
The integrated automatic reclosing function allows up to 8 reclosing attempts. The first four reclose cycles may
operate with different parameters (action and dead times, 1-/3-pole). The parameters of the fourth cycle apply
to the fifth cycle and onwards.
