ABB RELION REX640 Technical Manual page 1232

Protection related functions
feeder. This is achieved by allowing a time-delayed overreaching zone to trip
instantaneously when a fault occurs. For this purpose, one of the DSTPDIS zones
can be configured with an independently set reach.
After the overreaching zone instantaneously trips, the autoreclosing sequence
starts. If the fault is transient, the system may get restored in the first shot of
AR. However, in case of a persistent fault only the first trip of the AR sequence
is accelerated by Zone extension logic. During the rest of the sequence, Zone
extension logic is blocked and AR initiation is performed selectively by the time-
graded distance zones.
Zone extension logic can be described using a module diagram.
Figure 700: Functional module diagram of Zone extension logic
AR control
The AR control module supervises the zone acceleration by monitoring the status
of the AR_READY and NONDIR_ST input signals. The READY output signal from
the autorecloser (AR) function, which indicates the status of the autoreclosing, is
connected to the AR_READY input. The start signal from the non-directional zone is
connected to the NONDIR_ST input. If the non-directional zone is not available for
this, then the start output from the overreaching zone with the biggest reach or
GFC can be used instead.
The permission for zone acceleration is given if AR_READY = TRUE, that is, the AR
function is ready to start a new AR sequence. If the set reclaim time of the AR
function expires before the fault is cleared, the NONDIR_ST input signal is used
to block the activation of the zone acceleration. This ensures that the accelerated
trip followed by the AR initiation is not repeated for the same fault regardless of
the reclaim time setting and the reach of the overreaching zone connected to the
EX_ACC input. Otherwise, this could lead to pumping of the circuit breaker, that
is, the repetition of the first shot without being able to complete the desired AR
sequence.
Zone acceleration
The start signal from the overreaching zone whose operation is to be accelerated
is connected to the EX_ACC input. When the EX_ACC input is activated and,
simultaneously, the AR control module gives permission for acceleration, the
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If the fault is located on the adjacent feeder or bus within the reach of
the overreaching zone, tripping and AR initiation take place in an external
fault.
EX_ACC
AR_READY
NONDIR_ST
BLOCK
The AR control module blocks the Zone acceleration module after the
initiation of the first shot until the AR sequence has been completed, that
is, until the AR_READY input signal changes its state back from FALSE to
TRUE.
Zone
AR control
acceleration
1MRS759142 F
OPR_Z_EXTN
REX640
Technical Manual