ABB RELION REB500 Technical Manual page 148

Section 5
Bay protection functions
Dead times (t Dead1 1P to t Dead 4)
Provided the trip signal is issued before t Oper elapses, the dead time is the period between
the tripping signal (Trip CB) and the close signal (Close CB).
The required dead time must be entered separately for each reclosure cycle. This necessitates
setting the following parameters:
Provision is made for externally switching the dead times
first (fast) reclosure attempt to a second setting. The corresponding additional time period
can be set with the aid of the parameter
t1.
The second, third and fourth reclosure attempts are always three-phase.
Extended dead time (t Dead 1 Ext)
This time provides facility for extending the dead time (for example, should the
communications channel be defective or for a redundant scheme with two autoreclosure
functions). The extended dead time is enabled by the binary input Extend t1.
Maximum fault duration for a reclosure attempt (t Oper)
If a fault has persisted for some time, the probability of a successful reclosure reduces. The
likelihood of the power system becoming unstable is also greater for an unsuccessful
autoreclosure attempt following a fault which has persisted for a long period. It is for these
reasons that the time after the inception of a fault during which reclosure can be initiated is
limited. The fault duration is set using parameter
The timer for the fault duration is started by the pick-up signal from the protection function
(Start). Faults resulting in tripping after
not take place.
Should the fault duration time expire before the protection trips, autoreclosure is blocked and
the reclaim time is started.
Example:
Time T Oper < Delay(2) of the distance function means that autoreclosure only takes place for
faults in the first distance zone (Delay(1)).
This function is not required for schemes that only use current functions. The binary inputs
Start and Trip CB 3P are connected together (see
Reclaim time (t inhibit)
One purpose of the inhibit time is to permit the circuit-breaker to recover its full voltage
withstand. To this end, it disables the autoreclosure function for the time set for parameter t
inhibit after one of the following events:
• the last reclosing attempt
• a definitive trip resulting from a protection trip after the fault duration time
• a recurring trip between discrimination time and dead time (evolving fault, see output
signal Def. Trip).
Close signal duration (t Close)
The maximum duration of the circuit-breaker close signal (command output Close CB) is
determined by the parameter
overrides the close signal. A second, third or fourth reclosure attempt can only take place, if
the next trip occurs within the time
142
t Dead1 1P , t Dead1 3P , t Dead 2 , t Dead 3 and t Dead 4 .
t Dead 1 Ext and activated via the binary I/P Extend
t Oper are locked out (Def. Trip) and reclosure does
t Close . Any tripping signal which occurs during this time
t Close .
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t Dead1 1P and t Dead1 3P for the
t Oper .
Section 5.8.6.3).
Bay protection functions REB500
1MRK 505 406-UEN B
t Oper
Technical manual