GL.6
SEL-787 Relay Instruction Manual Date Code 20081022
Glossary
TFE–Z Number
TFE
A Through-Fault Event (TFE) monitor is designed to capture cumulative
mechanical stresses caused by faults that occur outside the transformer unit
protection zone.
Termin a l
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 SEL-5030 software relay driver version when creating or editing
relay settings files.
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