Zone Sequencing (Not Available For Models 7Sj6***-**A**-) - Siemens siprotec SJ62 User Manual

2 Functions

2.14.5 Zone Sequencing (not available for models 7SJ6***-**A**-)

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50-1 and 50N-1 must obviously not be blocked (addresses 7200, 7201, 7212, 7213,
7224 and 7225).
The blocking applies only after reclosure according to the settings address. Hence, it
is possible to specify again other conditions for a third reclosure.
The blocking conditions are also valid for the zone sequence coordination, provided it
is available and activated (address 7140, see also margin heading "Zone Sequenc-
ing").
It is the task of the zone sequence coordination to harmonize the automatic reclosure
function of this device with that of another device that is part of the same power
system. It is a complementary function to the automatic reclosure program and allows
for example to perform group reclosing operations in radial systems. In case of multi-
ple reclosures, groups may also be in nested arrangement and further high-voltage
fuses can be overgraded or undergraded.
Zone sequencing works by blocking certain protective functions depending on the
reclose cycle. This is implemented by the protective stages control (see margin
heading "Controlling Protective Stages").
As a special feature, changing from one reclosing cycle to the next is possible without
trip command only via pickup/dropout of the 50-1 or 50N-1element.
The following figure shows an example of a group reclosure at feeder 3. Assume that
reclosure is performed twice.
For fault F1 at Tap Line #5, protection relays protecting the bus supply and Feeder #3
pickup. The time delay of the 50-2 element protecting Feeder #3 is set so that the
Feeder #3 circuit breaker will clear the fault before the fuse at Tap Line #5 is damaged.
If the fault was cleared, normal service is restored and all functions return to quiescent
after restraint time has expired. Thus the fuse has been protected as well.
If the fault continues to exist, a second reclosing attempt will follow in the same
manner.
High speed element 50-2 is now being blocked at relay protecting Feeder #3. If the
fault still remains, only element 50-1 continues being active in Feeder #3 which, how-
ever, overgrades the fuse with a time delay of 0.4 s. After the fuse operated to clear
the fault, the relays nearer to the fault location will drop out. If the fuse fails to clear the
fault, then the 50-1 element protecting Feeder #3 will operate as backup protection.
The 50-2 element at the busbar relay is set with a delay of 0.4 seconds, since it sup-
posed to trip the 50-2 elements and the fuses as well. For the second reclosure, the
50-2 element also has to be blocked to give preference to the feeder relay (element
50-1 with 0.4 s). For this purpose, the device has to "know" that two reclosing attempts
have already been performed.
With this device, zone sequence coordination must be switched off: When pickup of
50-1 or 50N-2 drops out, zone sequence coordination provokes that the reclosing at-
tempts are counted as well. If the fault still persists after the second reclosure, the 50-
1 element, which is set for 0.9 seconds, would serve as backup protection.
For the busbar fault F2, the 50-2 element at the bus would have cleared the fault in 0.4
seconds. Zone sequence coordination enables the user to set a relative short time
period for element 50-2. element 50-2 is only used as backup protection. If zone se-
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015