tReset: The reclaim time sets the time for resetting the function to its original state, after
which a line fault and tripping will be treated as an independent new case with a new auto
reclosing cycle. One may consider a nominal CB duty cycle of for instance, O – 0.3sec –
CO – 3min – CO. However the 3 minute (180 s) recovery time is usually not critical as
fault levels are mostly lower than rated value and the risk of a new fault within a short time
is negligible. A typical time may be tReset = 60 or 180 s dependent on the fault level and
circuit breaker duty cycle.
tSync: Maximum wait time for fulfilled synchrocheck conditions. The time window
should be coordinated with the operate time and other settings of the synchrocheck
function. Attention should also be paid to the possibility of a power swing when reclosing
after a line fault. Too short a time may prevent a potentially successful auto reclosing.
tCBClosedMin: A typical setting is 5.0 s. If the circuit breaker has not been closed for at
least this minimum time, an auto reclosing start will not be accepted.
tSuccessful: If the circuit breaker closing command is given and the circuit breaker is
closed within the set time interval tUnsucCl, the SUCCL output is activated after the set
time interval tSuccessful.
tUnsucCl: The reclaim timer, tReset, is started each time a circuit breaker closing
command is given. If no start occurs within this time, the auto recloser will reset. A new
start received in “restart time” status will reenter the auto recloser to “in progress” status
as long as the final shot is not reached. The auto recloser will reset and enter “inactive”
status if a new start is given during the final restart time. This will also happen if the circuit
breaker has not closed within set time interval tUnsucCl at the end of the reclaim time.
This latter case is controlled by setting UnsucClByCBChk. The auto reclosing sequence is
considered unsuccessful for both above cases and the UNSUCCL output is activated.
DeadTime settings
NoOfShots: In power transmission one shot is mostly used. In most cases one auto
reclosing shot is sufficient as the majority of arcing faults will cease after the first auto
reclosing shot. In power systems with many other types of faults caused by other
phenomena, for example wind, a greater number of auto reclosing attempts (shots) can be
motivated.
t1 1Ph, t1 2Ph, t1 3Ph: There are separate settings for the first shot for single-, two- and
three-phase auto reclosing dead times.
Single-phase auto reclosing dead time: A typical setting is t1 1Ph = 800ms. Due to the
influence of energized phases the arc extinction may not be instantaneous. In long lines
with high voltage the use of shunt reactors in the form of a star with a neutral reactor
improves the arc extinction.
Section 15 1MRK 506 369-UUS -
Control
678 Line distance protection REL670 2.2 ANSI
Application manual
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