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SPDC Terms T-U
TAP
An available connection which permits changing the active portion of the device in the circuit.
[STD 32–1990]
TEMPERATURE COEFFICIENT OF BREAKDOWN VOLTAGE
The ratio of the change in breakdown voltage [V(BR)] to changes in temperature. Expressed as either millivolts per degree Celsius (mV/°C) or percent per degree Celsius (%/°C).
[C62.35–1987]
The ratio of the change in breakdown voltage, V(BR), to changes in temperature. Expressed as either millivolts per degree Celsius (mV/°C) or percent per degree Celsius (%/°C) with reference to the 25 °C value of breakdown voltage.
[C62.37–1996]
TEMPERATURE DERATING
Derating with temperature above a specified base temperature, expressed as a percentage, such as may be applied to peak pulse current
[C62.37–1996]
Derating with temperature above specified base temperature, expressed as a percentage, such as may be applied to peak pulse power and peak pulse current.
[C62.35–1987]
TEMPORARY OVERVOLTAGE
An oscillatory overvoltage associated with switching of relatively long duration, which is undamped or slightly damped.
[C62.2–1987]
An oscillatory overvoltage, associated with switching or faults (for example, load rejection, single phase faults) or from non-linearities (ferro-resonance effects, harmonics) or both, of relatively long duration, which is undamped or slightly damped.
[C62.22–1991]
TERMINALS
The conducting parts provided for connecting the arrester across the insulation to be protected.
[C62.1–1989 & C62.11–1987]
THERMAL CURRENT RATING
For resistors whose rating is based on constant voltage, the initial rms symmetrical value of the current that will flow when rated voltage is applied.
[STD 32–1990]
THERMAL RESISTANCE
(RΘJL; RΘJC; RΘJA)
The effective temperature rise per unit power dissipation of a designated junction, above the temperature of a stated external reference point (lead, case, or ambient) under conditions of thermal equilibrium.
[C62.37–1996]
Junction to ambient, case, or lead temperature rise per unit input of applied power expressed as degree Celsius per Watt.
[C62.35–1987]
THERMOMETER METHOD OF TEMPERATURE DETERMINATION
The determination of the temperature by mercury, alcohol, resistance, or thermocouple thermometers, any of these instruments being applied to the hottest accessible part of the device.
[STD 32–1990]
THYRISTOR
A bi-stable semiconductor device comprising three or more junctions that can be switched from the off-state to the on-state or vice versa, such switching occurring within at least one quadrant of the principal voltage-current characteristic.
[C62.37–1996 & STD. 100-2000]
TIME TO IMPULSE SPARKOVER
The time between virtual zero of the voltage impulse causing sparkover and the point on the voltage wave at which sparkover occurs.
[C62.1–1989 & C62.11–1987]
TRANSFER TIME
The time duration of the transverse voltage.
[C62.31–1987]
TRANSIENT THERMAL IMPEDANCE
(ZΘJL (t); ZΘJC(t); ZΘJA(t))
The change in the difference between the virtual junction temperature and the temperature of a specified reference point or region (lead, case, or ambient) at the end of a time interval divided by the step function change in power dissipation at the beginning of the same time interval that causes the change of temperature-difference.
[C62.37–1996]
TRANSITION CURRENT
The current required at a given temperature and duration to cause a current-protective device to change state.
[C62.36–1991]
TRANSITION TIME
The time required for the voltage across a conducting gap to drop into the arc region after the gap initially begins to conduct.
[C62.31–1987]
TRANSVERSE (DIFFERENTIAL) MODE VOLTAGE
The voltage at a given location between two conductors of a group.
[C62.31–1987 & C62.32–1987]
TRAVELING WAVE
The resulting wave when an electrical variation in a circuit such as a transmission line takes the form of translation of energy along a conductor, such energy being always equally divided between current and potential forms.
[C62.2–1987 & C62.22–1987]
TRIBOELECTRIC CHARGING
The generation of electrostatic charges when two pieces of material are brought into intimate contact and are then separated. Also termed triboelectrification.
[C62.47–1992]
TRIBOELECTRIC SERIES
A list of substances in an order of relative positive to negative charging as a result of the triboelectric charging effect.
[C62.47–1992]
UNGROUNDED
Without an intentional connection to ground except through potential indicating of measuring devices or other very-high-impedance devices.
[STD 32–1990]
UNIDIRECTIONAL THYRISTOR SPD
A thyristor SPD that has switching characteristics in only quadrant.
NOTE-The main unidirectional thyristor SPDs are the reverse-blocking, reverse conducting and forward
conducting thyristor SPDs.
[C62.37–1996]
UNINHIBITED OIL
Mineral transformer oil to which no synthetic oxidation inhibitor has been added.
[STD 32–1990]
UNIT OPERATION
Discharging a surge through an arrester while the arrester is energized.
[C62.1–1989 & C62.2–1987 & C62.11–1987 & C62.22–1991]
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