GL.24
SEL-400 Series Relays Instruction Manual Date Code 20171006
Glossary
Transformer Impedance—VG
Transformer Impedance
The resistive and reactive parameters of a transformer looking in to the
transformer primary or secondary windings. Use industry accepted open-circuit
and short-circuit tests to determine these transformer equivalent circuit
parameters.
Tree Resistance
Resistance resulting from a tree in contact with a power line.
TVE
Total Vector Error. A measurement of accuracy for phasor quantities that
combines magnitude and angle errors into one quantity. Defined in
IEEE C37.118.
TXD
Transmitted data.
UCA2
Utility Communications Architecture. A network-independent protocol suite that
serves as an interface for individual IEDs.
UCA 61850-9-2LE
Guideline for implementation of IEC 61850-9-2 created by the UCAIug to
facilitate interoperability. The guideline can be considered a subset, or profile, of
the IEC 61850-9-2 standard, which defines requirements for certain parts of the
standard, including data mode implementation, data set descriptions, time
synchronization, transfer rates, and sampling rates. Also referred to as 9-2LE.
UCAIug
Utility Communications Architecture International Users Group.
Unbalanced Current
Element
Element that calculates the percentage difference between the three phase
currents.
Unbalanced Fault
All faults that do not include all three phases of a system.
Unbuffered Report
IEC 61850 IEDs can issue immediate unbuffered reports of internal events
(caused by trigger options data-change, quality-change, and data-update) on a
“best efforts” basis. If no association exists, or if the transport data flow is not fast
enough to support it, events may be lost.
Unconditional Tripping
Protection element tripping that occurs apart from conditions such as those
involving communication, switch-onto-fault logic, etc.
Ungrounded Capacitor
Bank
Capacitor bank with no intentional connection to ground. (A bank with a PT
connected between the bank’s neutral point and ground is considered
ungrounded.)
Unstable Power Swing
A change in the electrical angle between power systems for which a control
action cannot return the angular separation between systems to an angle less than
the critical angle.
Untransposed Line
A transmission line with phase conductors that are not regularly transposed. The
result is an unbalance in the mutual impedances between phases.
User ST
Region in GOOSE for user-specified applications.
VA, VB, VC
Measured A-Phase-to-neutral, B-Phase-to-neutral, 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.
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