ABB REB670 Applications Manual page 327

1MRK 505 337-UUS -
Application manual
, Number of reclosing shots
In power transmission 1 shot is mostly used. In most cases one reclosing shot is sufficient
as the majority of arcing faults will cease after the first reclosing shot. In power systems
with many other types of faults caused by other phenomena, for example wind, a greater
number of reclose attempts (shots) can be motivated.
First shot and reclosing program
There are six different possibilities in the selection of reclosing programs. The type of
reclosing used for different kinds of faults depends on the power system configuration and
the users practices and preferences. When the circuit-breakers only have three-phase
operation, then three-phase reclosing has to be chosen. This is usually the case in
subtransmission and distribution lines. Three-pole tripping and reclosing for all 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
Single-phase auto-reclosing 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 WYE with a neutral reactor
improves the arc extinction.
Three-phase shot 1 delay: For three-phase High-Speed Auto-Reclosing (HSAR) a typical
open time is 400ms. Different local phenomena, such as moisture, salt, pollution, can
influence the required dead time. Some users apply Delayed Auto-Reclosing (DAR) with
delays of 10s or more. The delay of reclosing shot 2 and possible later shots are usually set
at 30s 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.
and , 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 auto-reclosing 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 = On and tExtended t1 = 0.8 s.
tSync , Maximum wait time for synchronismcheck
The time window should be coordinated with the operate time and other settings of the
synchronism check 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 reclosing.
Section 12
Control
321