5.140
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Functions
Trip Logic
If an external reclosing relay is being used, control signals from the reclosing
relay will typically be used to control the SEL-421 single- and three-pole tripping
sequence. Another method is to use the TOP (Trip during Open-Pole) Relay
Word bit to select a three-pole trip after a single-pole trip in the SEL-421 by mak-
ing an appropriate setting for TOPD (Trip during Open-Pole Time Delay), and
then including the TOP Relay Word bit in the E3PT setting—see Figure 5.102.
See External Recloser on page 6.10 and External Recloser on page 6.26 in the
SEL-400 Series Relays Instruction Manual for additional information. See TOPD
on page 6.41 for an application example using the TOP Relay Word bit.
Timer setting TOPD determines the period during which any subsequent single-
pole trips are converted to a three-pole trip following the original single-pole trip.
To use this feature, include the Relay Word bit TOP in the E3PT setting.
Trip Output Signals
There are seven Relay Word bits (TPA1, TPA2, TPB1, TPB2, TPC1, TPC2, and
3PT) that you can program to drive contact outputs to trip circuit breakers. Relay
Word bits TPAn, TPBn, and TPCn are phase-selective tripping signals for con-
trolling the individual poles of the circuit breakers for single-pole tripping
schemes. Use Relay Word bit 3PT (Three-Pole Trip) to trip all three poles of both
circuit breakers.
Manual Trip Logic
The SEL-421 also has additional logic for manually tripping the circuit breakers.
Use SEL
OGIC control equations BK1MTR and BK2MTR to trip the circuit
breakers manually. Use SEL
OGIC control equations ULMTR1 and ULMTR2 to
unlatch manual trips for Circuit Breaker 1 and Circuit Breaker 2, respectively.
Trip Logic Settings and Relay Word Bits
The trip logic settings are shown in Table 5.78, and the Relay Word bits are
shown in Table 5.79. Some of the settings are only required in certain situations,
as noted.
Table 5.78 Trip Logic Settings (Sheet 1 of 2)
Setting Prompt Range Default (5 A)
TR Trip SELOGIC Equation Z1P OR Z1G OR M2PT OR Z2GT
TRCOMM
a
Communications-Assisted Trip SELOGIC Equation (Z2P OR Z2G) AND PLT02
TRCOMMD Communications-Assisted Trip SEL
OGIC Equation NA
TRSOTF
b
Switch-Onto-Fault Trip SELOGIC Equation 50P1 OR Z2P OR Z2G
DTA Direct Transfer Trip A-Phase SEL
OGIC Equation NA
DTB Direct Transfer Trip B-Phase SEL
OGIC Equation NA
DTC Direct Transfer Trip C-Phase SEL
OGIC Equation NA
BK1MTR Breaker 1 Manual Trip—BK1 SEL
OGIC Equation OC1 OR PB8_PUL
BK2MTR
c
Breaker 2 Manual Trip—BK2 SELOGIC Equation NA
ULTR Unlatch Trip SEL
OGIC Equation TRGTR
ULMTR1 Unlatch Manual Trip—BK1 SEL
OGIC Equation NOT (52AA1 AND 52AB1 AND
52AC1)
ULMTR2
c
Unlatch Manual Trip—BK2 SELOGIC Equation 1
To Next Page
Loading...
