GL.15
Date Code 20020501
SEL-421/SEL-421-1 Relay
Glossary
Positive-sequence Current Supervision Pickup
—
Relay Word Bit
saturation. The a2 factor is the ratio of the magnitude of negative-sequence
current to the magnitude of positive-sequence current (I2/I1).
Positive-sequence Current
Supervision Pickup
An element that operates only when a positive-sequence current exceeds a
threshold.
Positive-Sequence
Impedance
Impedance of a device or circuit that results in current flow with a balanced
positive-sequence set of voltage sources.
POTT (Permissive
Overreaching
Transfer Trip)
A communications-assisted line protection scheme. At least two overreaching
protective relays must receive a permissive signal from the other terminal(s)
before all relays trip and isolate the protected line.
Power Factor
The cosine of the angle by which phase current lags or leads phase voltage in
an ac electrical circuit. Power factor equals 1.0 for power flowing to a pure
resistive load.
PPS
Pulse per second from a GPS receiver. PPS time mode is present when both
1k PPS and IRIG-B signals are applied to the relay Time inputs.
Protection and
Automation Separation
Segregation of protection and automation processing and settings.
Protection Settings Group
Individual scheme settings for as many as six different schemes (or instances).
Protection-Disabled State
Suspension of relay protection element and trip/close logic processing and
deenergization of all control outputs.
PT
Potential transformer. Also referred to as a voltage transformer or VT.
PTR
Potential transformer ratio.
Quadrilateral
Characteristic
A distance relay characteristic on an R-X diagram consisting of a directional
measurement, reactance measurement, and two resistive measurements.
Qualifier Code
Specifies type of range for DNP 3.0 objects. With the help of qualifier codes,
DNP master devices can compose the shortest, most concise messages.
R_TRIG
Rising-edge trigger. Boolean SEL
OGIC
control equation operator that triggers
an operation upon logic detection of a rising edge.
RAM
Random Access Memory. Volatile memory where the relay stores
intermediate calculation results, Relay Word bits, and other data.
Reactance Reach
The reach of a distance element in the reactive (X) direction in the R-X plane.
Real Power
Power that produces actual work. The portion of apparent power that is real,
not imaginary.
Reclose
The act of automatically closing breaker contacts after a protective relay trip
has opened the circuit breaker contacts and interrupted current through the
breaker.
Relay Word Bit
A single relay element or logic result. A Relay Word bit can equal either
logical 1 or logical 0. Logical 1 represents a true logic condition, picked up
element, or asserted control input or control output. Logical 0 represents a
false logic condition, dropped out element, or deasserted control input or
control output. Use Relay Word bits in SEL
OGIC
control equations.
Содержание SEL-421
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