Glossary terms beginning with T

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

The standard abbreviation for transformer when used for labelling.

tagged

Marked to indicate that an isolation point has been put into a particular state for an authorisation issue. Note: The tag is normally applied to safeguard against the unintentional operation of the equipment. Sometimes tags are applied to ensure a system remains in service to provide safety under an authorisation, eg seal oil pumps must remain in service with hydrogen-filled machines. Specially coded and coloured locks may be used as tags. [SR-EI April 1995].

tailclamp

The clamp that connects the portable earth to the station earth.

tailwater depression

The provision of forced lowering of the surface level of water in a turbine draught-tube to below the runner to enable the unit to be operated as a synchronous condenser.

tangential tension

Means the axial conductor tension at a given point in the span.

tap changer

A mechanism usually fitted to the primary winding of a transformer, to alter the turns ratio of the transformer by small discrete amounts over the defined range.

TAR

Stands for Tape Archive. This is a software utility program that allows other software to be backed up and restored from tape.

TBT

Twisted Barrell Tongue.

tee (or T) point

The point at which a branch transmission circuit is solidly and permanently connected to a main circuit, usually without switchgear. (See tee-off.).

tee-off

A branch transmission circuit which joins a main circuit and which is protected as part of the main circuit.

temporary earthing

The process of applying portable earths to de-energised high voltage equipment.

temporary earthing device

See portable earth.

tension section

Means the span or series of spans between two consecutive dead-ended or strain structures.

terminal span

The last span to the terminal tower, pole or structure in a transmission line.

terminals (circuit-breaker)

A conducting part of a circuit-breaker, provid9ed for electrical connection to external circuits.

terminals (transformers)

A conducting part of a power transformer or auxiliary circuit, provided for electrical connection to external circuits.

tertiary equipment

For the purpose of this instrument, this is the equipment which is conencted to the tertiary winding of a transformer to form a "tertiary system". Note:  The tertiary buswork between the tertiary winding and the tertiary circuit-breaker is considered part of the tertiary winding.

tertiary system

For the purpose of this instruction, this is a system which is connected to the tertiary winding of a transformer and it includes the tertiary winding itself.

tertiary winding

A transformer winding usually with a lower value of rated power compared to the secondary winding.

test liven

To apply full operating voltage to an item of power system equipment to prove its electrical insulation.

test permit (Tpt)

The authorisation for access to equipment which has been removed from service for testing where procedures are required to control hazards created by the testing. [SR-EI April 1995].

test RTU

A RTU located at SCH for monitoring and testing of the FRED Master.

test switch

A switch that enables a relay to be taken out of service for testing purposes.

The Act

Electricity Act 1992, Regulations and Codes of Practice thereunder and any amendments thereto.

the grid system

That part of the New Zealand electrical power system which electrically interconnects any or all points of service.

thermal chain

Refers to the current carrying capability of a chain of components that form a branch.

thermal image relay

A thermal electrical measuring relay which, in its operating characteristics, takes into account the thermal effects of the load and overload currents.

thermal uprate

Thermal uprating increases the operating temperature of a line to allow more current to be carried. To maintain safety clearances, this typically requires the conductors to be retensioned.

thermal uprating

Thermal uprating increases the operating temperature of a line to allow more current to be carried. To maintain safety clearances, this typically requires the conductors to be retensioned.

thermally uprate

Thermal uprating increases the operating temperature of a line to allow more current to be carried. To maintain safety clearances, this typically requires the conductors to be retensioned.

thermography

An infrared photographic method of temperature measurement.

third parties

An individual or organisation not directly contracted to provide services to Transpower.

three-terminal circuit

A transmission circuit which is controlled by circuit-breakers at three stations. Commonly referred to as a T circuit.

thyristor

A bi-stable semiconductor device (comprising three or more junctions) which can be switched from the "off-state" to an "on-state" or vice-versa.

time delay relay

A relay having an operation or resetting feature which is intentionally delayed.

time error

The difference between synchronous time and standard time. [As used in GOSP Appendix 2 Clause 2.5].

time tagging (HVDC)

All events are tagged at the time they occur, by the sequence event recorder (SER) before sending the data to the master SCADA computer. [ABB TR-LK-89-049].

top tap

The tap position of a power transformer that provides maximum number of winding turns on the HV side and therefore minimises the inrush current.

top-oil temperature

The temperature of the volume of oil between the top of a transformer winding and the top of the main tank.

torque nut

Prevailing torque nut to ISO 7040 containing a plastic locking element and used to retain a bolt or double-ended stud in position. (Known by the trade name of "Nyloc" nut.).

total recall time

The contractor’s recall time plus the time required for all operating actions required to return the equipment to service.

touch voltage

The voltage experienced by a person touching earthed metal and standing on the ground surface at a distance of 1.25 metres.

Touch voltage (Vt)

The voltage which will appear between any point of contact with uninsulated metalwork located within 2.5 metres from the surface of the ground and any point on the surface of the ground within a horizontal distance of 1.25 metres from the vertical projection of the point of contact with the uninsulated metalwork.

tower leg potential

The potential of the tower leg with respect to a copper/copper sulphate reference electrode.

TPIX

Transpower Information Exchange. A computer system containing SCADA events and energy, wholesale market prices and schedules, network model and reserve market information.

TPOIS

A computer based operational log for the Transpower control centre.

TPSN

Transpower Speech Network.  the internal telephone network, made up of interlinked Private Automatic Branch Exchanges (PABX's), or Transit Exchanges, and the bearers linking those exchanges, plus keyphone systems at smaller sites.

TR

A system fault recorder using digital technology for the recording, manipulation and conveying hte recorded fault data.

transducer

A device which converts an input signal into an output signal of another form.

transfer of control

The transfer of authority and responsibility to control power system equipment within defined boundaries.

transfer voltage hazard zone (TVHZ)

An area around a structure within which a metallic structure may not be erected, or, can only be erected or remain, if an existing structure, with appropriate mitigation measures in place.

transformer

A static electric device consisting of a winding or two or more coupled windings which transfer power by electromagnetic induction between circuits of the same frequency, usually with changed values of voltage and current. A term used in TP.MS 20.06 to include oil-immersed transformers (distribution, earthing, local service, power or generating, but excluding instrument) and oil-filled voltage regulators, reactors and associated components.

transformer circuit-breakers

The circuit-breakers located in series with each winding of a transformer. Usually designated by voltage.

transformer unit protection

Protection which will operate only for faults between the transformer CTs, for example differential protection, or faults confined to the transformer tank (for example Buchholz protection). It should not operate for faults elsewhere in the power system.

transformer: oil immersed type

A transformer where the core and windings are immersed in an insulating oil.

transformer: sealed type

A transformer which is non-breathing, that is, so sealed that there can be no significant interchange between its contents and the external atmosphere.

transient fault

A fault that is self-rectified immediately after the faulted equipment is tripped or disconnected.

transient recorder

A system fault recorder using digital technology for the recording, manipulation and conveying hte recorded fault data.

transient stability (of a power system)

A power system stability in which disturbances may have large rates of change and/or large relative magnitudes. [GOSP glossary - IEC 50 (603-03-03)].

transmission

The conveying of bulk electricity from power stations to points of supply (compared with. distribution).

transmission circuit

An electrical circuit the primary purpose of which is the transmission of electricity from one geographical location to another. [GOSP glossary].

transmission line

A series of structures carrying overhead one or more transsmission circuits.

transmission system

That part of the power system primarily intended for the conveyance of bulk electricity.

Transpower

The owner and operator of New Zealand's high voltage electricity grid.

Transpower CBs

grid CBs owned by Transpower plus Transpower owned local supply CB's, under operational control delegated to the area operator.

Transpower customer

Any person (in the legal sense) other than Transpower connected to the grid. [Output Connection Contract].

Transpower drawing folder reference

A code which defines the correct location for filing each drawing (paper print) in a set of folders. The codes define: The station to which the drawing refers. The section and subsection of the station folders in which the drawing shall be filed.

Transpower operational information system

A computer based operational log for the Transpower control centre.

Transpower representative

A person appointed by a Transpower Asset Manager who is responsible for verifying that equipment, systems and/or processes are acceptable for commissioning, for submitting "ready for commissioning" notice to the Regional Controller and for accepting commissioned equipment, systems and/or processes.

Transpower service centre

The power system service centre in the North Island (SCH) or South Island (SCC) that has operational control of the grid and dispatches generation under contract. Also commonly referred to as control centre.

Transpower station

A substation, switching station, power station switchyard or cable terminal station owned by Transpower.

treated oil

A term used in TP.MS 54.01 to describe filtered, reconditioned, reclaimed and regenerated oil.

trip

To release a lever or set free a mechanism. When used in reference to circuit-breakers, means to change the state of the circuit-breaker from closed to open.

trip circuit supervision

Protection equipment which monitors the continuity of the trip ciracuits of a circuit-breaker.

trip free (circuit-breaker)

A circuit-breaker in which the moving contacts return to and remain in the open position when the opening operation is initiated after the initiation of the closing operation, even if the closing command is maintained.

trip on close

Also known as "switch on to fault". A feature of some distance protection enabling it to trip instantaneously when its associated circuit-breaker closes on to a fault, e.g. closed earth switch.

trip time (circuit-breaker)

The interval of time between the initiation of the trip operation and the instant when the contacts separate in all poles.

tripped

The status of an item (usually a circuit-breaker) which has correctly responded to a trip command.

truck

A term used for the withdrawable circuit-breaker carriage.

turbulator (circuit-breaker)

A device sometimes provided as part of the interrupter which assists in extinguishing the arc created when the circuit-breaker current carrying contacts open under load. Also known as explosion pot, arc control chamber, cross jet pot.

TWD

The provision of forced lowering of the surface level of water in a turbine draught-tube to below the runner to enable the unit to be operated as a synchronous condenser.

type test

Performance test on a device carried out to show that the device meets the required specifications.