GL.4
SEL-421/SEL-421-1 Relay
Date Code 20020501
Glossary
Blocking Signal Extension
—
Commissioning Testing
Blocking Signal Extension
The blocking signal for the DCB (directional comparison blocking) trip
scheme is extended by a time delay on dropout timer to prevent unwanted
tripping following current reversals.
Bolted Fault
A fault with essentially zero impedance or resistance between the shorted
conductors.
Boolean Logic Statements
Statements consisting of variables that behave according to Boolean logic
operators such as AND, NOT, and OR.
Breaker Auxiliary Contact
An electrical contact associated with a circuit breaker that opens or closes to
indicate the breaker position. A form-a breaker auxiliary contact (ANSI
Standard Device Number 52A) closes when the breaker is closed and opens
when the breaker is open. A form-b breaker auxiliary contact (ANSI Standard
Device Number 52B) opens when the breaker is closed and closes when the
breaker is open.
Breaker-and-a-half
Configuration
A switching station arrangement of three circuit breakers per two circuits; the
two circuits share one of the circuit breakers.
Category
A collection of similar relay settings.
CCVT
Coupling-capacitor voltage transformer that uses a capacitive voltage divider
to reduce transmission voltage to a level safe for metering and relaying
devices. See CVT.
Checksum
A method for checking the accuracy of data transmission involving
summation of a group of digits and comparison of this sum to a previously
calculated value.
CID
Checksum identification of the firmware.
Circuit Breaker
Failure Logic
This logic within the SEL-421 Relay detects and warns of failure or
incomplete operation of a circuit breaker in clearing a fault or in performing a
trip or close sequence.
Circuit Breaker
History Report
A concise circuit breaker event history that contains as many as 128 events.
This breaker history report includes circuit breaker mechanical operation
times, electrical operation times, interrupted currents, and dc battery monitor
voltages.
Circuit Breaker Report
A full report of breaker parameters for the most recent operation. These
parameters include interrupted currents, number of operations, and
mechanical and electrical operating times among many parameters.
Class
The first level of the relay settings structure including Global, Group, Breaker
Monitor, Port, Report, Front Panel, DNP settings, Protection SEL
OGIC
control
equations, Automation SEL
OGIC
control equations, and Output SEL
OGIC
control equations.
Cold Start
Beginning a system from power up without carryover of previous system
activities.
Commissioning Testing
Testing that serves to validate all system ac and dc connections and confirm
that the relay, auxiliary equipment, and SCADA interface all function as
intended with your settings. Perform such testing when installing a new
protection system.
Summary of Contents for SEL-421
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