P.4.3
Date Code 20151029 Protection Manual SEL-411L Relay
Autoreclosing and Synchronism-Check
Autoreclosing
Single-Pole Autoreclose (79CY1)
The autoreclose logic is in a single-pole autoreclose cycle for either circuit
breaker if the following conditions are satisfied:
➤ Single-pole trip occurs
➤ Condition(s) to initiate a single-pole autoreclose cycle are
satisfied
➤ Circuit breaker(s) is in-service and ready to begin a single-pole
autoreclose cycle (that is, reset)
Three-Pole Autoreclose (79CY3)
The autoreclose logic is in a three-pole autoreclose cycle for either circuit
breaker if the following conditions are satisfied:
➤ Three-pole trip occurs
➤ Condition(s) to initiate a three-pole autoreclose cycle are
satisfied
➤ Circuit breaker(s) is in-service and ready to begin a three-pole
autoreclose cycle (that is, reset)
Lockout (BK1LO, BK2LO)
The lockout (LO) state is the default state of any circuit breaker after turn on.
Other conditions place the recloser in the LO state. The recloser has a drive-
to-lockout function that you can program for any external or internal
condition; use setting 79DTL. A circuit breaker can go to lockout by two
methods. If supervisory Relay Word bits SPnCLS or 3PnCLS do not assert
within the BKnCLSD time, or if the circuit breaker does not close within the
BKCFD time, then the circuit breaker enters the lockout state. The timer for
both supervisory Relay Word bits SPnCLS and 3PnCLS is setting BKnCLSD.
In applications using two circuit breakers, you can designate one circuit
breaker as the leader and the other circuit breaker as the follower. The relay
freezes the leader/follower decision during an autoreclose cycle unless the
autoreclose logic receives another initiation.
If the recloser receives another initiation, the logic reevaluates the leader and
follower circuit breakers to determine the number of circuit breakers in a
scheme (NBKn), the leader circuit breaker (LEADBKn), and the follower
circuit breaker (FOLBKn). This determination is based on the service status of
the circuit breakers. The logic considers a circuit breaker out of service if the
circuit breaker goes to lockout. The logic considers a circuit breaker to be in
service as soon as the circuit breaker closes and is no longer in lockout.
State Diagram
Figure 4.1 illustrates how the autoreclose logic moves from one state to
another with respect to Circuit Breaker 1. (This diagram is identical for Circuit
Breaker 2; replace the 1 in the Relay Word bits with 2.) The Relay Word bits
that correspond to each state are shown (see Table 4.1). A solid path between
two states indicates that the logic can move in only one direction. Two broken
paths between two states indicate the logic can move in either direction
between the two states. The dashed vertical line that runs through the center of
the figure indicates the states common to both circuit breakers.
Table 4.1 describes each of the five states with respect to Circuit Breaker 1,
along with the corresponding Relay Word bits.
NOTE: The relay autoreclose
function runs at once per power-
system cycle. To ensure that the logic
detects transient element state
changes that initiate closing, you
should extend the assertion time of
transient element states to 1 cycle.
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