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2 Functions
Sequential faults are faults which occur during the dead time after clearance of the first
fault.
There are various ways of handling sequential faults in the 7SD610 depending on the
requirements of the network:
For the Detection of an evolving fault you can select whether the trip command of a
protective function during the dead time or every further pickup is the criterion for an
evolving fault.
There are also various selectable possibilities for the response of the internal auto-
reclose function to a detected evolving fault.
• EV. FLT. MODE Stops AutoRecl:
• EV. FLT. MODE starts 3p AR:
If reclosure is blocked due to a sequential fault without the protection issuing a three-
pole trip command (e.g. for sequential fault detection with starting), the device can
send a three-pole trip command so that the circuit breaker does not remain open with
one pole (forced three-pole trip).
Forced three-pole
If reclosure is blocked during the dead time of a single-pole cycle without a three-pole
trip
trip command having been initiated, the breaker would remain open at one pole. In
most cases, the circuit breaker is equipped with a pole discrepancy supervision which
will trip the remaining poles after a few seconds. By setting a parameter, you can
achieve that the tripping logic of the device immediately sends a three-pole trip
command in this case. This forced three-pole trip pre-empts the pole discrepancy su-
pervision of the CB because the forced three-pole trip of the device is initiated as soon
as the reclosure is blocked following a single-pole trip or if the CB auxiliary contacts
report an implausible breaker state.
When different internal protective functions initiate a single-pole trip in different
phases, the device will issue a three-pole trip command due to the tripping logic (Sec-
tion 2.16.1), independent of this forced three-pole trip. This is also true for trip com-
mands given via the direct local trip inputs (Section 2.6) or the reception of a remote
trip (Section 2.7) since these signals directly affect the tripping logic of the device.
If the device trips single-pole and if an external trip command in another phase only
reaches the device via one of the binary inputs, e.g. „>Trip L1 AR" to the internal
automatic reclosure function, this is not routed to the tripping logic. In this case, three-
pole trip is ensured only if the forced three-pole trip is effective.
The forced three-pole trip is also activated when only three-pole cycles are allowed,
but a single-pole trip is signalled externally via a binary input.
130
The reclosure is blocked as soon as a sequential fault is detected. The tripping by
the sequential fault is always three-pole. This applies irrespective of whether three-
pole cycles have been permitted or not. There are no further reclosure attempts; the
automatic reclosure is blocked dynamically (see also margin heading „Blocking re-
closure", above).
As soon as a sequential fault is detected, the recloser switches to a three-pole
cycle. Each trip command is three-pole. The separately settable dead time for se-
quential faults starts with the clearance of the sequential fault; after the dead time
the circuit breaker receives a close command. The further sequence is the same as
for single- and three-pole cycles.
The complete dead time in this case consists of the part of the dead time for the
single-pole reclosure up to the elimination of the sequential fault plus the dead time
for the sequential fault. This makes sense because the duration of the three-pole
dead time is most important for the stability of the network.
7SD610 Manual
C53000-G1176-C145-4
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