ABB REL650 Applications Manual page 339

1MRK 506 334-UUS A
Application manual
types of faults is also widely accepted in completely meshed power systems. In
transmission systems with few parallel circuits, single-phase reclosing for single-phase
faults is an attractive alternative for maintaining service and system stability.
Auto-reclosing open times, dead times
Three-phase shot 1 delay: For three-phase High-Speed Auto-Reclosing (HSAR) a typical
open time is 400 ms. Different local phenomena, such as moisture, salt, pollution etc. can
influence the required dead time. Some users apply Delayed Auto- Reclosing (DAR) with
delays of 10 s or more. The delay of reclosing shot 2 and possible later shots are usually
set at 30 s or more. A check that the CB duty cycle can manage the selected setting must
be done. The setting can in some cases be restricted by national regulations. For multiple
shots the setting of shots 2-5 must be longer than the circuit breaker duty cycle time.
Extended t1 and tExtended t1
Extended auto-reclosing open time for shot 1.
The communication link in a permissive (not strict) line protection scheme, for instance
a power line carrier (PLC) link, may not always be available. If lost, it can result in delayed
tripping at one end of a line. There is a possibility to extend the autoreclosing open time
in such a case by use of an input to PLCLOST, and the setting parameters. Typical setting
in such a case: Extended t1 = Enabled and tExtended t1 = 0.5 s.
tTrip , Long trip pulse
Usually the trip command and initiate auto-reclosing signal reset quickly as the fault is
cleared. A prolonged trip command may depend on a CB failing to clear the fault. A trip
signal present when the CB is reclosed will result in a new trip. Depending on the setting
Extended t1 = Disabled or Enabled a trip/ initiate pulse longer than the set time tTrip will
either block the reclosing or extend the auto-reclosing open time. At a setting somewhat
longer than the auto-reclosing open time, this facility will not influence the reclosing. A
typical setting of tTrip could be close to the autoreclosing open time.
tInhibit , Inhibit resetting delay
A typical setting is tInhibit = 5.0 s to ensure reliable interruption and temporary blocking
of the function. Function will be blocked during this time after the tInhibit has been
activated.
timetReset , Reset time
The Reset 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 reclosing cycle.
One may consider a nominal CB duty cycle of for instance, O-0.3 s CO- 3 min. – 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 of the fault level and breaker duty cycle.
Section 11
Control
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