Schweitzer Engineering Laboratories SEL-421-4 - Figure 6.18 DC Schematic for DCB Trip Scheme

6.80
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Applications Examples
345 kV Tapped Overhead Transmission Line Example
Trip Logic
Trip logic configures the relay for tripping. There are four trip logic settings:
➤ Trip equations
➤ Trip unlatch options
➤ Trip timers
➤ Three-pole tripping enable
Trip Equations
Set these three SELOGIC control equations for tripping:
➤ TR (unconditional)
➤ TRCOMM/TRCOMMD (communications-assisted; in this example,
use only TRCOMM)
➤ TRSOTF (Switch-Onto-Fault)
TR
The TR SELOGIC control equation determines which protection elements cause
the relay to trip unconditionally. Set TR to the Zone 1 instantaneous distance pro-
tection (Z1T), Zone 2 time-delayed distance protection, and the inverse-time
overcurrent element (51S1) for backup protection. For information on setting
51S1, see Selectable Operating Quantity Time Overcurrent Element 1 on
page 6.10.
TR := Z1T OR Z2T OR 51S1T. Trip (SELOGIC Equation)
TRCOMM
The TRCOMM SELOGIC control equation determines which protection elements
cause the relay to trip via the communications-assisted tripping scheme logic. Set
delayed Zone 2 mho phase and ground-distance protection (Z2PGS) plus delayed
Figure 6.18 DC Schematic for DCB Trip Scheme
52TC
OUT101
(3PT)
52A
START
IN101
(52AA1)
CB1 (Partial)
SEL-421 Relay
(Partial)
Carrier
(Partial)
IN103
(BT)
STOP
OUT102
(START)
OUT103
(STOP
OR 3PT)
52A
+
—
RX