Schweitzer Engineering Laboratories SEL-421-4 - Table 5.76 Additional Settings for Single Pole Tripping (SPT); Trip Logic

5.137
Date Code 20171021 Instruction Manual SEL-421 Relay
Protection Functions
Trip Logic
Trip Logic
Use the SEL-421 trip logic to configure the relay for tripping one or two circuit
breakers. You can apply the SEL-421 in single-pole tripping applications, three-
pole tripping applications, or both. Set the SEL-421 to trip unconditionally (as
with step distance) or with the aid of a communications channel (as with the
POTT, DCUB, DCB, and DTT schemes).
Three-Pole Tripping
The relay uses three-pole tripping logic if Relay Word bit E3PT (three-pole trip
enable SEL
OGIC control equation) equals logical 1. You can set E3PT to 1 or
assign a control input so that an external condition changes the state of this Relay
Word bit.
There are separate three-pole tripping SEL
OGIC control equations for two circuit
breakers, E3PT1 and E3PT2, respectively. When you set E3PT1 or E3PT2 to 1,
the corresponding circuit breaker trips three pole only. For details on setting
E3PT, E3PT1, and E3PT2, see Trip Logic and Reclose Sources for Single-Pole
Breaker Applications on page 6.9 and Trip Logic and Reclose Sources for Single-
Pole Breaker Applications on page 6.25 in the SEL-400 Series Relays Instruction
Manual.
Single-Pole Tripping
The relay uses single-pole tripping logic if Relay Word bit E3PT, three-pole trip
enable SEL
OGIC control equation, equals logical 0. You can either set E3PT to 0
or assign a control input so that an external condition changes the state of this
Relay Word bit.
The SEL-421 automatically single-pole trips for the following conditions when
the single-pole tripping logic is active:
➤ Zone 1 ground-distance protection asserts for a single phase-to-
ground fault
➤ Zone 2 ground-distance protection asserts for a single phase-to-
ground fault and is permitted to trip via the communications-assisted
tripping logic
➤ Any one of three SELOGIC control equations, DTA, DTB, or DTC, is
assigned to an input and asserts (per-phase direct transfer trip)
You can also set the SEL-421 to single-pole trip through the following three
options:
Table 5.76 Additional Settings for Single Pole Tripping (SPT)
Setting Prompt Selection
Z2GTSP Zone 2 Ground Distance Time Delay Single-Pole Trip Y
67QGSP Zone 2 Directional Negative-Sequence/Residual Ground
Overcurrent Single Pole Trip
Y
EWFC
a
a
In POTT and DCUB settings.
Weak-Infeed Trip SP
b
b
SP = single pole.