GL.6 Glossary
Terminal Emulation Software–Z-Number
SEL-787 Relay Instruction Manual Date Code 20150130
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
voltages, if connected.
VT
Abbreviation for voltage transformer. Also referred to as a potential
transformer or PT.
Volts/Hz
The ratio of voltage to frequency is a measure of transformer excitation and
the Volts/Hz element protects against overexcitation.
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 relay driver version when creating or editing relay settings files.
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