CHAPTER 7: PROTECTION
CONTROL ELEMENTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
335
Figure 273: Open pole detector scheme logic, sheet 2 of 2
Autoreclose
The autoreclose scheme is intended for use on transmission lines with circuit breakers
operated in both the single-pole and three-pole modes, in one or two breaker
arrangements. The autoreclose scheme provides four programs with different operating
cycles, depending on the fault type. Each of the four programs can be set to trigger up to
four reclosing attempts. The second, third, and fourth attempts always perform three-pole
reclosing and have independent dead time delays.
When used in two breaker applications, the reclosing sequence is selectable. The reclose
signal can be sent to one selected breaker only, to both breakers simultaneously or to both
breakers in sequence (one breaker first and then, after a delay to check that the reclose
was successful, to the second breaker). When reclosing in sequence, the first breaker
should reclose with either the single-pole or three-pole dead time according to the fault
type and reclose mode; the second breaker should follow the successful reclosure of the
first breaker. When reclosing simultaneously, for the first shot both breakers should reclose
with either the single-pole or three-pole dead time, according to the fault type and the
reclose mode.
The autoreclose function differs from that implemented in the UR series and needs to be
enabled. Do this setup for local/remote control on the front panel or the software.
The signal used to initiate the autoreclose scheme is the trip output from protection. This
signal can be single-pole tripping for single-phase faults and three phase tripping for
multiphase faults. The autoreclose scheme has five operating states.
Table 18: Autoreclose operating states
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State
Characteristics
Enabled
Scheme is permitted to operate.
Disabled
Scheme is not permitted to operate.
Reset
Scheme is permitted to operate and shot count is reset to 0.
Reclose in
progress
Scheme has been initiated but the reclose cycle is not finished (successful or
not).
Lockout
Scheme is not permitted to operate until reset received.
