Automatic Reclosure Function (Optional) - Siemens siprotec 7SD5 User Manual

2 Functions
2.15

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. This means that the line can be re-
closed. Reclosure is performed by an automatic reclosure function (AR).
Automatic reclosure is only permitted on overhead lines because the option of auto-
matic extinguishing of a fault arc only exists there. It should not be used in any other
case. If the protected object consists of a mixture of overhead lines and other equip-
ment (e.g. overhead line directly connected to 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 single-phase auto-reclosure
is usually initiated for single-phase faults and a three-pole auto-reclosure for multiple-
phase faults in the network with earthed system starpoint. If the fault still exists after
automatic reclosure (arc has not disappeared, there is a metallic fault), then the pro-
tective elements will re-trip the circuit breaker. In some systems several reclosing at-
tempts are performed.
In a model with single-pole tripping, the 7SD5 allows phase-selective, single-pole trip-
ping. A single and three-pole, single and multiple shot automatic reclosure function is
integrated, depending on the ordered version.
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 protec-
tion 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.
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7SD5 Manual
C53000-G1176-C169-1