ABB RER670 - Page 230

which are transient by nature. When the power line is switched off by the operation
of line protection and line breakers, the arc de-ionizes and recovers its ability to
withstand voltage at a somewhat variable rate. Thus, a certain dead time with a de-
energized line is necessary
. Line service can then be resumed by automatic
reclosing of the line breakers. The dead time selected should be long enough to
ensure a high probability of arc de-ionization and successful reclosing.
For individual line breakers, auto reclosing equipment, the required circuit breaker
dead time is used to determine the “dead time” setting value. When simultaneous
tripping and reclosing at the two line ends occurs, line dead time is approximately
equal to the auto recloser “dead time”. If the auto reclosing dead time and line
“dead time” differ then, the line will be energized until the breakers at both ends
have opened.
Open
Closed
Operate time
Line
protection
Circuit
breaker
Break time
Trip command
Contacts separated
Arc extinguishers
Fault duration Circuit breaker open time
Fault duration
Resets
Instant of fault
Operates
Break timeClosing time
Operate time
Fault
Operates
Resets
Close command
Contact closed
Set AR dead time Reclaim time
Auto-reclosing
function
Start AR
Reclosing
command
AR reset
IEC04000146-3-en.vsd
IEC04000146 V3 EN-US
Figure 70: Single-shot automatic reclosing at a permanent fault
Automatic reclosing can be performed with or without the use of synchrocheck.
For the individual line breakers and auto reclosing equipment, the auto reclosing
dead time expression is used. This is the dead time setting for the auto recloser.
During simultaneous tripping and reclosing at the two line ends, auto reclosing
dead time is approximately equal to the line dead time. Otherwise these two times
may differ as one line end might have a slower trip than the other end which means
that the line will not be dead until both ends have opened.
Section 12 1MRK 506 375-UEN A
Control
224 Railway application RER670 2.2 IEC
Application manual