Glossary
SIMPRO-100
234 PRIM-2400C
Phase Rotation
The sequence of voltage or current phasors
in a multi-phase electrical system. In an ABC
phase rotation system, the B-phase voltage
lags the A-phase voltage by 120°, and the
C-phase voltage lags B-phase voltage by
120°. In an ACB phase rotation system, the
C-phase voltage lags the A-phase voltage by
120°, and the B-phase voltage lags the
C-phase voltage by 120°.
Pickup Time
The time measured from the application of an
input signal until the output signal asserts.
The time can be user settable, as in the case
of a logic variable timer, or can be a result of
the characteristics of an element algorithm,
as in the case of an overcurrent element
pickup time.
Pinout
The definition or assignment of each electrical
connection at an interface. Typically refers to
a cable, connector, or jumper.
Power Factor
The cosine of the angle by which phase
current lags phase voltage in an ac electrical
circuit. Power factor equals 1.0 for power
flowing to a resistive load.
PT
Abbreviation for potential transformer. Also
referred to as a voltage transformer or VT.
Q
R
RAM
Abbreviation for Random Access Memory.
Volatile memory where the relay stores
intermediate calculation results, Relay Word
bits, and other data that is updated every
processing interval.
Reactive Power Element
A motor protection element that can trip the
protected motor if the measured reactive
power exceeds a user settable threshold.
Relay Word
The collection of relay element and logic
results. Each element or result is represented
by a unique identifier, known as a Relay Word
bit.
Relay Word Bit
A single relay element or logic result that the
relay updates once each processing interval.
A Relay Word bit can be equal to either
logical 1 or logical 0. Logical 1 represents a
true logic condition, picked up element, or
asserted contact input or contact output.
Logical 0 represents a false logic condition,
dropped out element, or deasserted contact
input or contact output. You can use Relay
Word bits in control equations to control relay
tripping, event triggering, and output contacts,
as well as other functions.
Remote Bit
A Relay Word bit whose state is controlled by
serial port commands, including the
CONTROL command, binary Fast Operate
command, or Modbus
®
command.
Residual Current
The sum of the measured phase currents. In
normal, balanced operation, this current is
very small or zero. When a motor ground fault
occurs, this current can be large.
RMS
Abbreviation for Root-Mean-Squared. Refers
to the effective value of the sinusoidal current
and voltage measured by the relay,
accounting for the fundamental frequency
and higher order harmonics in the signal.
ROM
Abbreviation for Read-Only Memory.
Nonvolatile memory where the relay firmware
is stored.
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