Glossary terms beginning with U

Terms used within Transpower
Click one of the letters above to go to the page of all terms beginning with that letter.
UEL

The maximum percentage of combustible gas in a mixture with air that can be ignited and will support flame.

UHF

Ultra high frequency, 300 to 3000 MHz.

ultimate tensile strength

In relation to a conductor, means the calculated breaking load (CBL).

unattended station

A station that is operated by visiting personnel who are normally located elsewhere.

under frequency limit

the frequency, below the normal frequency range, at which independent remedial action is initiated to minimise the risk of a grid collapse. The limit is quantified in Table 1 of the Grid Emergencies Code. [GOSP glossary].

uninhibited (insulating oil)

A mineral insulating oil, containing no anti-oxidant, but which may contain other additives.

unit

The combination of turbine and generator (alternator) as a device for producing electrical energy. Also includes the related boiler and unit auxiliaries in a steam power station.The term commonly used for a kilowatt-hour (kWh).

unit protection

One of the two basic classes of protection (the other is non-unit protection) whereby a precisely defined area of the primary system is protected. The protection will respond only to faults within that area.

unit transformer

A transformer that transforms the output voltage of a generator to power system voltage.

unnamed

That voltage level, above the nominal voltage at the point of connection, at which producers take independent corrective action to minimise the risk of damage to equipment. The limit is as quantified in Table 1 of the Grid Emergencies Code. [GOSP glossary].

unnamed two

A term identifying undesired or untoward operational, happenings, principally: accidents (resulting in loss), near-misses (which under slightly different circumstances could have caused loss) to people, process, equipment, material or the environment, a disturbance to the power system, a significant change in the state of the grid, equipment defects, a fire or intruder alarm operation.

unplanned operating

Operating (including that required to manage unplanned power system events) which time and/or circumstances prevent being subjected to the normal planning/approval (PROMS) process.

unplanned outage

An interruption or outage with less than 24 hours notice or no notice at all.

unscheduled work

Work that does not appear in programme windows in the annual outage plan. Includes deferred approved work, work carried out at opportune times, and approved and identified non-urgent, urgent and forced outage work.

upper explosive limit

The maximum percentage of combustible gas in a mixture with air that can be ignited and will support flame.

urgent work

Work that is not required to be done immediately, (in contrast to a forced outage), but needs to be done urgently and cannot wait for a scheduled outage. See non-urgent work.

user

Any user of a Transpower system. This is an encompasing term for Employees, Consultants and Contractors. Third parties may also apply if they use Transpower systems in any way.

UST

Ungrounded specimen test.

UTS

In relation to a conductor, means the calculated breaking load (CBL).