Sel 551 - Page 62

3.24
SEL-551 Relay Instruction Manual Date Code 20110408
Relay Elements and Logic
Reclosing Relay
Reclosing Relay
States and Settings
Changes
If a settings change is made, all of the following occur:
➤ The reclosing relay remains in the state it was in before the
settings change,
➤ The shot counter is driven to last shot (last shot corresponding
to the new settings; see discussion on last shot that follows),
➤ And the reset timer is loaded with reset time setting 79RSLD
(see discussion on reset timing that follows).
If the relay happened to be in the Reclose Cycle State and was timing on an
open interval before the settings change, the relay would be in the Reclose
Cycle State after the settings change, but the relay would immediately go to
the Lockout State. This is because the breaker is open, and the relay is at last
shot after the settings change, and thus no more automatic reclosures are
available.
If the breaker remains closed through the settings change, the reset timer times
out on reset time setting 79RSLD after the settings change and goes to the
Reset State (if it is not already in the Reset State), and the shot counter returns
to shot = 0. If the relay happens to trip during this reset timing, the relay will
immediately go to the Lockout State, because shot = last shot.
Existence or
Nonexistence of the
Reclosing Relay
If any one of the following reclosing relay settings are made:
➤ Open interval time setting 79OI1 = 0.000
➤ SELOGIC control equation setting 79RI = 0
➤ SELOGIC control equation setting 79RIS = 0
then the reclosing relay does not exist, and no automatic reclosing takes place.
These settings are explained later in this section. See also the setting sheets in
Section 4: Setting the Relay.
If the reclosing relay does not exist, the following also occur:
➤ All three reclosing relay state Relay Word bits (79RS, 79CY,
and 79LO) are deasserted to logical 0 (see Table 3.5).
➤ All shot counter Relay Word bits (SH0, SH1, SH2, SH3, and
SH4) are deasserted to logical 0 (the shot counter is explained
later in this section).
➤ The front-panel LEDs RS and LO are extinguished.
Close Logic Can Still Operate When Reclosing Relay Is Nonexistent
If the reclosing relay is nonexistent, the close logic (see Figure 3.14) can still
operate if SEL
OGIC control equation setting 52A (circuit breaker status) is set
to something other than numeral 0. Making the setting 52A = 0 defeats the
close logic and also renders the reclosing relay nonexistent.
For example, if 52A = IN1, a 52a circuit breaker auxiliary contact is
connected to input IN1. If the reclosing relay does not exist, the close logic
still operates, allowing closing to take place via the CLOSE command or
SEL
OGIC control equation setting CL (close conditions, other than auto
reclosing or CLOSE command). See Close Logic on page 3.20 for more
discussion on SEL
OGIC control equation settings 52A and CL. Also see
Optoisolated Inputs on page 3.3 for more discussion on SEL
OGIC control
equation setting 52A.
NOTE: if the reclosing relay exists,
but happens to be in the reclose cycle
state, both the RS and LO LEDs are also
extinguished.