Parameter: 79 Common > Sequence Fail Timer
•
Default setting: 60 s
An autoreclose sequence will start if the circuit‑breaker was closed, a trip has occurred and the protection
element is configured as an autoreclose trigger. The autoreclose will remain in the Sequence in
Progress state until the circuit‑breaker is open and the protection pickup has reset. It will then progress
to the dead time state. If this does not occur within the 79 Sequence Fail Timer the autoreclose
will go to the Lockout state. This prevents autoreclose being primed indefinitely.
Parameter: 79 Common > Sequence Co-ord
•
Default setting: Enabled
When set to Enabled the relay will co-ordinate its sequence and shot count such that it automatically
keeps in step with downstream devices as they advance through their sequence. The relay detects that a
pickup has operated but has dropped-off before its associated time delay has expired. It then increments
its shot count and advances to the next stage of the autoreclose sequence without issuing a trip. This is
repeated as long as the fault is being cleared by the downstream device such that the relay moves
through the sequence bypassing the inst trips and moving on to the delayed trip to maintain grading
margins.
When the advanced instantaneous and delayed protection sequence is applied with more than one
device installed in series on a network it is important that all devices co-ordinate the advance through
their own ARC sequences even though the protection does not operate. The operation of a downstream
protection can be detected by the upstream device by an element pickup even though this does not
result in a trip or reclose. This is termed Sequence Co-ordination and prevents an excessive number
of recloses as each successive relay attempts to clear the fault in isolation. For this reason each relay in an
ARC scheme must be set with identical instantaneous and delayed sequence of trips.
[dw_7SR5_function79ApplicationAndSettingNotes1, 1, en_US]
Figure 7-8 Sequence Co-ordination
The relay closest to the fault (D) would step through its instantaneous trips in an attempt to clear the
fault. If unsuccessful, the relay would move to a delayed trip sequence.
The other relays in the network (A, B and C) would recognize the sequence of pickup followed by current
switch-off as ARC sequences. They would therefore also step to their delayed trip to retain co-ordination
with the respective downstream devices. The next trip would be subject to current grading and Lockout
the ARC sequence such that the fault is cleared by the correct CB.
When set to Enabled the relay will co-ordinate its sequence and shot count such that it automatically
keeps in step with downstream devices as they advance through their sequence. The relay detects that a
pickup has operated but has dropped-off before its associated time delay has expired. This indicates that
a downstream protection device has operated to clear the fault. The relay increments its shot count and
advances to the next stage of the autoreclose sequence without a trip being issued so that its shot
number is kept in alignment with that of the downstream device. This is repeated as long as the fault is
being cleared by the downstream device such that the relay moves through the sequence bypassing the
inst trips and moving on to the delayed trip at the same time as the downstream device to maintain
grading margins when the delayed protection is applied.
The Sequence Co-ordination feature should generally be considered when more than 1 device with
autoreclose are connected in series with overlapping protection.
Parameter: 79 Common > Cold Load Action
•
Default setting: Off
Control Functions
7.3 79 Automatic Reclosing
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual 427
C53000-G7040-C014-1, Edition 11.2019
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