Functions
2.14 Automatic Reclosing System 79
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
260
The blocking applies only after reclosure in accordance with the set 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 Sequencing").
2.14.5
Zone Sequencing (not available for models 7SJ6***-**A**-)
It is the task of the zone sequence coordination to harmonize the automatic reclosure function of this device
with that of another device that forms 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 multiple reclosures, groups may also be in nested arrangement and further high-voltage fuses can
be overgraded or undergraded.
Zone sequencing functions by means of blocking certain protection functions depending on the reclosing cycle.
This is implemented by the protection elements control (see margin heading "Controlling Protection Elements").
As a special feature, changing from one reclosing cycle to the next is possible without trip command only via
pickup/dropout of 50-1 or 50N-1.
The following figure shows an example of a group reclosure at feeder 3. It is assumed that reclosure is per-
formed twice.
With fault F1 on feeder 5, protection devices in the infeed and on feeder 3 pick up. The time delay of the 50-2
element at protecting feeder 3 is set in such a way that the feeder 3 circuit breaker will clear the fault before the
fuse at feeder 5 is damaged. If the fault is cleared, all functions are reset after the restraint time has expired
and the fault is terminated. The fuse has therefore also been protected.
If the fault continues to exist, a second reclosing cycle is performed in the same way.
High speed element 50-2 is now being blocked at relay protecting Feeder 3. If the fault still remains, only the
50-1 element continues to be active in Feeder 3 which, however,
overgrades
the fuse with a time delay of 0.4
s. After the fuse operated to clear the fault, the series-connected devices 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 supposed to trip the 50-2 ele-
ments and the fuses as well. For the second reclosing, the 50-2 element also has to be blocked to give prefer-
ence to the feeder relay (50-1 element with 0.4 s). For this purpose, the device has to "know" that two reclosing
attempts have already been performed.
In this device, zone sequence coordination must be switched off: When pickup of 50-1 or 50N-1 drops out, zone
sequence coordination provokes that the reclosing attempts are counted as well. If the fault still persists after
the second reclosure, the 50-1 element, which is set to 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 sequenc-
ing enables the user to set a relatively short time period for the 50-2 elements. The 50-2 element is only used
as backup protection. If zone sequencing is not applied, the 50-1 element is to be used only with its relatively
long time period (0.9 s).
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