Date Code 20010719 701 Motor Protection Relay
Glossary
Pickup Time–Residual Current
GL.7
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.
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 SEL
OGIC
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
â
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.
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