Schweitzer Engineering Laboratories SEL-421-4, Instruction Manual

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6.3
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Autoreclosing
Autoreclosing States
Three-Pole Autoreclose (79CY3)
The autoreclose logic is in a three-pole autoreclose cycle for either circuit breaker
if all of 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 state is the default state of any circuit breaker after startup. Other
conditions place the recloser in the LO state. The relay 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. The circuit
breaker enters the lockout state if either of the following occur:
➤
Supervisory Relay Word bits SP n CLS or 3P n CLS do not assert
within the BK n CLSD time
➤
The circuit breaker does not close within the BKCFD time
The timer for both supervisory Relay Word bits SP n CLS and 3P n CLS is setting
BK n CLSD. Setting BK n CLSD = OFF disables the BK n CLSD delay timer,
requiring either SP n CLS or 3P n CLS to assert before transitioning to the next
state.
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 fol-
lower circuit breakers to determine the number of circuit breakers in a scheme
(NBK
n ), the leader circuit breaker (LEADBK n ), and the follower circuit breaker
(FOLBK n ). This determination is based on the service status of the circuit break-
ers. 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
NOTE:
The autoreclose function runs
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.
Figure 6.1 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 6.1 ). 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 6.1 describes each of the five states with respect to Circuit Breaker 1, along
with the corresponding Relay Word bits.