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GL.11
Date Code 20020501
SEL-421/SEL-421-1 Relay
Glossary
IED
—
Logical 1
IED
Intelligent electronic device.
IG
Residual current, calculated from the sum of the phase currents. In normal,
balanced operation, this current is very small or zero.
IGBT
Insulated gate bipolar junction transistor.
Independent Zone Timing
The provision of separate zone timers for phase and ground distance elements.
Infinite Bus
A constant-voltage bus.
Input Conditioning
The establishment of debounce time and assertion level.
Instance
A subdivision of a relay settings class. Group settings have several
subdivisions (Group 1–Group 6), while the Global settings class has one
instance.
Instantaneous Meter
Type of meter data presented by the SEL-421 Relay that includes the present
values measured at the relay ac inputs. The word “Instantaneous” is used to
differentiate these values from the measurements presented by the demand,
thermal, energy, and other meter types.
IRIG-B
A time code input that the relay can use to set the internal relay clock.
Jitter
Time, amplitude, frequency, or phase-related abrupt, spurious variations in
duration, magnitude, or frequency.
L/R
Circuit inductive/resistive ratio.
Latch Bits
Nonvolatile storage locations for binary information.
LED
Light-emitting diode. Used as indicators on the relay front panel.
Left-Side Value
LVALUE. Result storage location of a SEL
OGIC
control equation.
Line Impedance
The phasor sum of resistance and reactance in the form of positive-sequence,
negative-sequence, and zero-sequence impedances of the protected line.
LMD
SEL distributed port switch protocol.
LN Operator
Math SEL
OGIC
control equation operator that provides natural logarithm.
Load Encroachment
The load-encroachment feature allows setting of phase overcurrent elements
and phase distance elements independent of load levels.
Local Bits
The Relay Word bit outputs of local control switches that you access through
the SEL-421 Relay front panel. Local control switches replace traditional
panel-mounted control switches.
Lockout Relay
An auxiliary relay that prevents operation of associated devices until it is reset
either electrically or by hand.
Logical 0
A false logic condition, dropped out element, or deasserted control input or
control output.
Logical 1
A true logic condition, picked up element, or asserted control input or control
output.
Содержание SEL-421
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