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6.43
Date Code 20171021
Instruction Manual
SEL-421 Relay
Protection Applications Examples
500 kV Parallel Transmission Lines With Mutual Coupling Example
Enable Single-Pole Tripping
The relay contains both three-pole and single-pole tripping logic. The relay uses
single-pole tripping logic if the setting for E3PT, Three-Pole Trip Enable
SEL
OGIC
control equation, equals logical 0. For this example, an external reclos-
ing relay is present. Use the TOP (Trip During Open Pole) Relay Word bit and
the IN107 control input, to enable single-pole tripping. If E3PT equals logical 0
(assigned control input is deasserted), single-pole tripping is enabled.
E3PT :=
IN107 OR TOP
.
Three-Pole Trip Enable (SEL
OGIC
Equation)
Also set the appropriate three-pole tripping SEL
OGIC
control equation for Circuit
Breaker BK1 and Circuit Breaker BK2. In this example, the same three-phase
trip selection input is used for both breakers. See
Trip Logic and Reclose Sources
for Single-Pole Breaker Applications on page 6.9
Sources for Single-Pole Breaker Applications on page 6.25 in the SEL-400 Series
Relays Instruction Manual
for details on the three-pole trip enable settings.
E3PT1 :=
IN107
.
Breaker 1 3PT (SEL
OGIC
Equation)
E3PT2 :=
IN107
.
Breaker 2 3PT (SEL
OGIC
Equation)
Control Outputs
Main Board
Use SEL
OGIC
control equations to assign the control outputs for tripping.
Use the main board control outputs for tripping. The first three control outputs
trip Circuit Breaker BK1A and the next three trip circuit breaker BK1B.
OUT101 :=
TPA1
.
OUT102 :=
TPB1
.
OUT103 :=
TPC1
.
OUT104 :=
TPA2
.
OUT105 :=
TPB2
.
OUT106 :=
TPC2
.
Cross-Country Fault Identification
Fault Identification
The SEL-421 provides two means of implementing simultaneous ground fault
tripping logic for single-pole tripping applications in double-circuit tower appli-
cations. This particular example is based upon the POTT2 scheme, a 2-channel
POTT scheme. The implementation of this logic uses the simplicity and flexibil-
ity of SEL
OGIC
control equations and M
IRRORED
B
ITS
communications.
For this particular example, when a cross-country fault occurs close in to Station
R, the local line protection correctly identifies the faults as single phase-to-
ground; Line 1 protection identifies a Zone 1 A Phase-to-ground fault, while
Line 2 protection identifies a Zone 1 B Phase-to-ground fault. Tripping for both
lines at Station R is instantaneous and independent from the communications
channel.
illustrates a cross-country fault close in to Station R (that is,
beyond Zone 1 reach with respect to Station S).
Содержание SEL-421-4
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