R.2.10
SEL-421 Relay Reference Manual Date Code 20111215
Auto-Reclosing and Synchronism Check
Two-Circuit-Breaker Auto-Reclosing
These settings connect the internal SEL-421 recloser for both three-pole
reclosing and single-pole reclosing. Enter enable settings ESPR1 and E3PR1
as appropriate for your application.
The SEL-421 is a single-pole tripping relay; if E3PT and E3PT1 are logical 0,
the relay is enabled for single-pole tripping. Conversely, if E3PT and E3PT1
are logical 1, the relay is enabled for three-pole tripping only.
Relay Word bits R3PTE and R3PTE1 are logical 1 for any of the following
conditions when the setting NUMBK (Number of Breakers in Scheme) is
logical 1 and SPLSHT (Single-Pole Last Shot) is asserted (see Figure 2.8):
➤ BK1TYP := 3, (Breaker 1 Trip Type)
➤ NSPSHOT := N, (Number of Single-Pole Reclosures)
External Recloser
If reclosing is performed by an external relay, assert SELOGIC control
equations E3PT and E3PT1 via a control input (for example):
E3PT := NOT IN104 Three-Pole Trip Enable (SELOGIC Equation)
E3PT1 := NOT IN104 Breaker 1 3PT (SELOGIC Equation)
Connect the external recloser single-pole trip output signal to IN104. Other
external recloser signals are required; consult the external recloser
documentation for interconnection with the SEL-421.
Two-Circuit-Breaker Auto-Reclosing
Two Circuit Breaker
Auto-Reclose Modes
The SEL-421 auto-reclose logic operates in three modes:
➤ Single-pole mode (SPAR)
➤ Three-pole mode (3PAR)
➤ Single- and three-pole mode (SPAR/3PAR)
Relay settings ESPRn (Single-Pole Reclose Enable—BKn) and E3PRn
(Three-Pole Reclose Enable—BKn) determine the auto-reclose mode (see
Recloser Mode Enables on page R.2.24). These settings are inputs to the
recloser initiation Relay Word bits SPARC (Single-Pole Reclose Initiate
Qualified) and 3PARC (Three-Pole Reclose Initiate Qualified); see Figure 2.8
and Figure 2.9. SPARC asserts when all necessary conditions to begin a
single-pole auto-reclose cycle are satisfied (ESPRn, for example) and the
recloser receives a single-pole reclose initiation SPRI (see Figure 2.8). Relay
Word bit 3PARC asserts when all necessary conditions to begin a three-pole
auto-reclose cycle are satisfied (E3PRn, for example) and the recloser receives
a three-pole reclose initiation 3PRI (see Figure 2.9).
Other recloser settings include the initial recloser settings (see Enable Auto-
Reclose Logic for One Circuit Breaker on page R.2.8) and the trip logic enable
settings E3PT, E3PT1, and E3PT2. When SEL
OGIC control equations E3PT,
E3PT1, and E3PT2 are deasserted, a single-pole reclose follows a single-pole
trip; when these SEL
OGIC control equations are asserted, only three-pole
tripping and reclosing result (see Trip Logic and Reclose Sources on
page R.2.26).
NOTE: In the following discussion,
n is 1 or 2 for Circuit Breaker BK1 or
BK2.
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