GL.9
Date Code 20090715 SEL-421 Relay
Glossary
Electromechanical Reset—Fast Operate
Electromechanical Reset
Setting of the relay to match the reset characteristics of an electromechanical
overcurrent relay.
End-Zone Fault
A fault at the farthest end of a zone that a relay is required to protect.
Energy Metering
Energy metering provides a look at imported power, exported power, and net
usage over time; measured in MWh (megawatt hours).
Equalize Mode
A procedure where substation batteries are overcharged intentionally for a
preselected time in order to bring all cells to a uniform output.
ESD
(Electrostatic Discharge)
The sudden transfer of charge between objects at different potentials caused
by direct contact or induced by an electrostatic field.
Ethernet
A network physical and data link layer defined by IEEE 802.2 and IEEE
802.3.
Event History
A quick look at recent relay activity that includes a standard report header;
event number, date, time, and type; fault location; maximum fault phase
current; active group at the trigger instant; and targets.
Event Report
A text-based collection of data stored by the relay in response to a triggering
condition, such as a fault or ASCII TRI command. The data show relay
measurements before and after the trigger, in addition to the states of
protection elements, relay inputs, and relay outputs each processing interval.
After an electrical system fault, use event reports to analyze relay and system
performance.
Event Summary
A shortened version of stored event reports. An event summary includes items
such as event date and time, event type, fault location, time source, recloser
shot counter, prefault and fault voltages, currents, and sequence current, and
M
IRRORED BITS
®
communications channel status (if enabled).
The relay sends an event report summary (if auto messaging is enabled) to the
relay serial port a few seconds after an event.
EXP Operator
Math SELOGIC control equation operator that provides exponentiation.
F_TRIG
Falling-edge trigger. Boolean SELOGIC control equation operator that triggers
an operation upon logic detection of a falling edge.
Fail-Safe
Refers to an output that is open during normal relay operation and closed
when relay power is removed or if the relay fails. Configure alarm outputs for
fail-safe operation.
Falling Edge
Transition from logical 1 to logical 0.
Fast Hybrid Control
Output
A control output similar to, but faster than, the hybrid control output. The fast
hybrid output uses an insulated gate bipolar junction transistor (IGBT) to
interrupt (break) high inductive dc currents and to very rapidly make and hold
the current until a metallic contact operates, at which time the IGBT turns off
and the metallic contact holds the current. Unlike the hybrid control output,
this output is not polarity sensitive; reversed polarity causes no misoperations.
Fast Meter
SEL binary serial port command used to collect metering data with SEL
relays.
Fast Operate
SEL binary serial port command used to perform control with SEL relays.
Courtesy of NationalSwitchgear.com
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