SPDC Terms beginning with U

Terms and definitions extracted from current SPDC published documents
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ultimate mechanical strength-static (UMS-static)

The load at which any part of the surge arrester fails to perform its mechanical function.
[C62.11-2005]

ungrounded (isolated) system

A system, circuit, or apparatus without an intentional connection to ground, except through potential-indicating or measuring devices or other very-high-impedance devices.
[C62.82.1-2010]

unidirectional thyristor surge protection device (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.
[62.37-1996]

unit operation

Discharge of a surge through an arrester while the arrester is energized.
[C62.22-2009]

unit operation

A discharge of a surge through an arrester while the arrester is energized.
[C62.11-2005]

upset

Malfunction of a system because of electrical disturbances.
[C62.41.1-2002]

utilization voltage

The root-mean-square (rms) phase-to-phase or phase-to-neutral voltage at the line terminals of utilization equipment.
[C62.41.1-2002]