GL.6
SEL-751A Relay Instruction Manual Date Code 20100129
Glossary
Sequential Events Recorder—Z-Number
Sequential
Events Recorder
A relay function that stores a record of the date and time of each assertion and
deassertion of every Relay Word bit in a settable list. Provides a useful way to
determine the order and timing of events following a relay operation.
SER
Abbreviation for Sequential Events Recorder or the relay serial port command
to request a report of the latest 1024 sequential events.
Synchrophasors
The word synchrophasor is derived from two words: synchronized phasor.
Synchrophasor measurement refers to the concept of providing measurements
taken on a synchronized schedule in multiple locations. A high-accuracy
clock, commonly a Global Positioning System (GPS) receiver such as the
SEL-2407 Satellite-Synchronized Clock, makes synchrophasor measurement
possible.
Terminal
Emulation Software
Personal computer (PC) software that can be used to send and receive ASCII
text messages via the PC serial port.
Underfrequency Element
A protection element that causes the relay to trip when the measured electrical
system frequency is less than a settable frequency.
VA, VB, VC
Measured A-, B-, and C-phase-to-neutral voltages.
VAB, VBC, VCA
Measured or calculated phase-to-phase voltages.
VG
Residual voltage calculated from the sum of the three phase-to-neutral volt-
ages, if connected.
VS
Measured phase-neutral or phase-phase synchronism check voltage
VT
Abbreviation for voltage transformer. Also referred to as a potential trans-
former or PT.
Wye
As used in this instruction manual, a phase-to-neutral connection of voltage
transformers for electrical measuring purposes. Three voltage transformers are
used with one primary lead of the first transformer connected to A-phase and
the other lead connected to ground. The second and third voltage transformers
are connected to measure the voltage from B-phase and C-phase-to-ground,
respectively. This connection is frequently called “four-wire wye,” alluding to
the three phase leads plus the neutral lead.
Z-Number
That portion of the relay RID string that identifies the proper ACSELERATOR
QuickSet SEL-5030 software relay driver version when creating or editing
relay settings files.
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