GL.3
Date Code 20020501
SEL-421/SEL-421-1 Relay
Glossary
Apparent Power, S
—
Block Trip Extension
Apparent Power, S
Complex power expressed in units of volt-amps (VA), kilovolt-amps (kVA),
or megavolt-amps (MVA). Accounts for both real (P) and reactive (Q) power
dissipated in a circuit: S = P + jQ. This is power at the fundamental frequency
only; no harmonics are included in this quantity.
Arcing Resistance
The resistance in the arc resulting from a power line fault.
ASCII
Abbreviation for American Standard Code for Information Interchange.
Defines a standard set of text characters. The SEL-421 Relay uses ASCII text
characters to communicate using front-panel and rear-panel EIA-232 serial
ports on the relay and through virtual serial ports.
ASCII Terminal
A terminal without built-in logic or local processing capability that can only
send and receive information.
Assert
To activate. To fulfill the logic or electrical requirements needed to operate a
device. To set a logic condition to the true state (logical 1) of that condition.
To apply a closed contact to an SEL-421 Relay input. To close a normally
open output contact. To open a normally closed output contact.
AT Modem Command Set
Dialing String Standard
The command language standard that Hayes Microcomputer Products, Inc.
developed to control auto-dial modems from an ASCII terminal (usually
EIA-232 connected) or a PC (personal computer) containing software
allowing emulation of such a terminal.
Autoconfiguration
The ability to determine relay type, model number, metering capability, port
ID, baud rate, passwords, relay elements, and other information that an IED
(an SEL-2020/2030 communications processor) needs to automatically
communicate with relays.
Automatic Messages
Messages including status failure and status warning messages that the relay
generates at the serial ports and displays automatically on the front-panel
LCD.
Automatic Reclose
Automatic closing of a circuit breaker after a breaker trip by a protective relay.
Automation Variables
Variables that you include in automation SEL
OGIC
control equations.
Auto-Reclose-
Drive-to-Lockout
A logical condition that drives the auto-reclose function out of service with
respect to a specific circuit breaker.
Autotransformer
A transformer with at least two common windings.
Bandpass Filter
A filter that passes frequencies within a certain range and blocks all
frequencies outside this range.
Best Choice Ground
Directional Supervision™
logic
An SEL logic that determines the directional element that the relay uses for
ground faults.
Bit Label
The identifier for a particular bit.
Bit Value
Logical 0 or logical 1.
Block Trip Extension
Continuing the blocking signal at the receiving relay by delaying the dropout
of Relay Word bit BT.
Summary of Contents for SEL-421
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