Glossary terms beginning with A

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

Internal relay or control device component which is used for converting an analogue signal to a digital signal.

A/F

Across flats.  This refers to the dimension between the flat, inner faces of a hexagonal die used for compressing compression fittings.

ABCB

A circuit breaker of the type that utilises a blast of high pressure air between its opening contacts to interrupt the current flow.

abnormal operating condition

A condition whereby a rating or design parameter of a piece of equipment is exceeded.  Examples are overloads and under or over voltages. Note:  The above is a general definition, but for the purpose of DG 30.01 Electric and magnetic field design parameters for ac 50 Hz transmission lines, substations and underground cables, a specific definition is given in that document.

AC

Alternating Current. An electric current that reverses directions at regular intervals. In New Zealand’s electricity system this occurs 50 times a second.

ACB

A circuit-breaker in which the contacts open and close in air at atmospheric pressure.

Acceleration Protection Scheme

A protection method which speeds up a relay operation at one end of a transmission circuit with a signal sent from the relay at the other end, with the objective to trip the circuit-breakers at each end of the circuit in minimum time, simultaneously.

access device

Cardax keytags and keys for accessing Transpower controlled and/or restricted areas.

Access Permit

The authorisation for access to equipment which has been removed from service, for work other than testing requiring a test permit. Note: This term has replaced clearance with the implementation of the Safety Rules - Electrical Industry.

Access Platform

Any power-operated elevating work platform where the height of the platform may be adjusted by powered means using articulation, scissors mechanism, telescoping boom or tower, or any combination of these.

Accumulator

A pressure vessel for storing energy by means of compressed gas, eg. nitrogen, the energy transfer medium usually being hydraulic oil.

Acknowledgement (of a circuit-breaker trip)

The action of issuing an “open” command to a circuit-breaker after it has been tripped by a protection operation, to disarm the auto-reclose (if fitted) and cancel the tripped indication when switching from mimic panels.

ACSR (lines)

Aluminium conductor steel reinforced.

ACSR/AC (lines)

Aluminium conductor steel reinforced aluminium-clad core wire.

ACSR/GC

Transmission line conductor: aluminium core steel reinforced, galvanised steel wire core.

Active Power

The product of the voltage and the in-phase component of alternating current, expressed in watts (W).

Actual reserve or carry over

The time period for which the battery/d.c supply can maintain the discharge duty cycle following failure of the 125 V charger/rectifier. i.e. from mains failure until minimum equipment distribution voltage (22.5 V)/station battery  voltage (90 V), is reached.

Actuator (circuit-breaker)

An electric, hydraulic, mechanical or pneumatic device, or combinations of these, that will provide a predetermined mechanical movement.

AD wrapped cable

An all-dielectric fibre optic cable wrapped onto conductors.

Adjustment Factor

The calculated adjustment required to adjust for the instrument transformer errors of the metering installation.

ADSS

An all-dielectric self-supporting optical fibre cable system.

Aeolian Vibration

Vertical vibration of conductors caused by the steady laminar flow of air across the conductors.

Aerial Cable

Means any insulated or covered conductor or assembly of cores with or without protective covering, which is placed above ground, in the open air and is suspended between two or more supports.

Aerial Conductor

Means any bare conductor that is placed above ground, in the open air and is suspended between two or more supports.

AEXS

Term used in TP.MS 40.08 to define an air exhaust system consisting of the following major components: air intakes or grilles, in-line exhaust fans and air outlet cowls or diffusers. This system may include ancillary equipment such as controls, sensors and fire dampers.

AFC

An automatic means of controlling oscillator frequency to hold it stable.

After-cooler (compressor)

A heat exchanger for cooling air discharged from compressors. It provides the most effective means of removing moisture from compressed air and gases.

AGS

Armour Grip Suspension (Assembly).

AHC

A certificate issued by an employer to an employee which provides personal identification; defines which authorisations the employee is competent to hold; defines any limits on the type of work which can be carried out by the employee; defines any limits on the places where the AHC applies. Note: The standards for assessing competence are set by the equipment owner, and a certificate is valid only for a specified time. [SR-EI April 1995].

AHU

Term used in TP.MS 40.08 to define a ventilation system consisting of the following major components (some being enclosed within an enclosure or casing): air intakes, filters, fans, electric heating coils, connected ductwork and components, fire and control dampers, electric reheat boxes, air diffusion equipment, electrical connections, power supplies, distribution boards and control systems. The AHU ventilation system may or may not include the following additional items: direct expansion or chilled water cooling coil, refrigerant storage and pump systems and packaged air cooled refrigerant condensers or connections to a separate chilled water supply system (see CHILL), and electric steam humidifiers.

AIA

Accident Incident Announcement.

air and vehicle travel

Emissions from air travel include domestic and international air travel. Vehicle travel includes emissions from rental cars, taxis, fleet vehicles and staff use of private vehicles for business purposes.

Air Blast Circuit Breaker

A circuit breaker of the type that utilises a blast of high pressure air between its opening contacts to interrupt the current flow.

Air Circuit Breaker

A circuit-breaker in which the contacts open and close in air at atmospheric pressure.

Air Crew

Airborne personnel providing support from within a helicopter.

Air Exhaust System

Term used in TP.MS 40.08 to define an air exhaust system consisting of the following major components: air intakes or grilles, in-line exhaust fans and air outlet cowls or diffusers. This system may include ancillary equipment such as controls, sensors and fire dampers.

Air Handling Unit

Term used in TP.MS 40.08 to define a ventilation system consisting of the following major components (some being enclosed within an enclosure or casing): air intakes, filters, fans, electric heating coils, connected ductwork and components, fire and control dampers, electric reheat boxes, air diffusion equipment, electrical connections, power supplies, distribution boards and control systems. The AHU ventilation system may or may not include the following additional items: direct expansion or chilled water cooling coil, refrigerant storage and pump systems and packaged air cooled refrigerant condensers or connections to a separate chilled water supply system (see CHILL), and electric steam humidifiers.

Alpha 90 (HVDC)

Alpha 90 is ordered by the sequences in the inverter to bring the direct voltage to zero for pole shutdown. The function controls the firing angle by ramping the maximum limit of the current control amplifiers towards 90 degrees.

Alpha Max Limiter (HVDC)

The alpha max function calculates a firing angle in order to achieve nominal gamma based on the actual values of UdiO, dX and current order.

Alternate Meter

A metering system that can be used when the GXP or class 0.2S (MARIA category 5) meter(s) is not available e.g. when CTs are bypassed or the VT is disconnected. An alternate meter must have all its primary equipment located separately from the GXP meter primary equipment and an independent output to the Transpower data logger or to another data logger suitable for interrogation by the Data Administrator. The alternate metering system may be of lower accuracy than the GXP or class 0.2S (MARIA category 5) metering system.

Alternator

An alternating current generator.

Annual Outage Plan

That part of the long range plan which is in the current financial year. This plan is republished monthly. Compilation of windows for routine maintenance and planned project / IT windows for the next financial year ahead from 1 July to 30 June.

Anode Capacity

The current which can be produced by a stated weight of anode material is usually expressed in Ampere hours per kilogram (Ahkg-1 ).

Anode(1)

An electrode through which direct current enters the soil around the grillage causing oxidation reactions to take place.

Anode(2)

An electrode through which a principal stream of electrons leaves the inter-electrode space (Part of the mercury valve).

Anti-oxidant (insulating oil)

An additive incorporated in an insulating liquid to reduce or delay its degradation by oxidation.

Anti-pump Relay (circuit-breaker)

A device which prevents a circuit-breaker being repeatedly opened and closed while both open and close signals are applied at the same time.

API Oil Interceptor

An American Petroleum Institute gravity-type oil water separator that has an oil-in-water effluent between 20 and 150 ppm.

API Oil Separator

An American Petroleum Institute gravity-type oil water separator.

Approved

Agreed to in writing by a suitably authorised person in Transpower.

Approved contracting company (lines)

A contracting company approved in writing by Transpower, in accordance with the standard on carrying out live line work.

Approved Disconnector

An approved disconnector, in the context of TP.OG 41.06, is one which may be used to interrupt a specified type of current, up to a specified maximum magnitude, at a specified location only (as listed in Appendix A to TP.OG 41.06). An approved disconnector can be used to interrupt only the type of current for which it is approved (as listed in Appendix A to TP.OG 41.06).

Approved Earthing Device

A device for temporarily earthing equipment for work, of appropriate rating and design for the conditions of use, proven by appropriate type test, and of a type either provided or endorsed for use by the industry or any industry sector.

Approved Work Procedures (lines)

A step-by-step written procedure proven by actual trial on earthed lines and formally approved by the contracting company, for using live line tools and techniques to enable a specific task to be accomplished safely. Procedures may be standard for routine tasks, or specially written or modified to undertake an unusual or one-off type of task. Written procedures are mandatory for all level L2 and L3 work and may be required by Transpower for some level L1 work depending on the complexity of the task.

AR

The automatic reclosure of a circuit-breaker after a predetermined time following a fault tripping.

Arc

A discharge of electricity through gas (normally air).

Arc Length

The actual length of the irregular path of an arc.

Arc Reach

The distance from a point midway between the arc extremities to the most remote point of the arc at the time of its maximum length.

Arc Through

An HVDC mercury arc valve fault, where the valve conducts in the forward direction when it should conduct in the reverse. Effects range from insignificant to severe; the most severe is an inverter by pass valve arc through. This fault is cleared by a control action.

Arcback

A transient HVDC mercury arc valve fault caused when a valve fails to withstand the reverse voltage step, resulting in a transient reverse current flow in the valve. It causes a transient two- phase a.c. short circuit, cleared by control action.

Arcback Protection

Instantaneous temporary blocking after detecting phase-to-phase short circuit within the protective zone. Back-up protection is provided by the existing valve group ac overcurrent protection.

Arcing Contact (circuit-breaker)

A contact on which the arc is intended to be established and extinguished.

Area Operating Centre

A centre designated to manage the operating activities of an operating area. Includes power company control rooms.

arresters

The power frequency current which flows through an arrester following the passage of discharge current.

AS Wire

Aluminium-clad steel wire.

ASAP

Alarm Status Annunciator Panel.

ASR

Alarm Status Reporting equipment.

Asset Manager

The person responsible for the management and welfare of the grid operating asset type.

Asset owner

The entity that legally owns specific equipment.

associated authorisation

A collective term for the access permit and test permit. Under an authorisation, the recipient’s work party is allowed temporary access to defined equipment which has been removed from service and which is in a defined state, to enable work to be undertaken. Note: Entry approval is not an authorisation as defined above.

Assurance

A statement made by an operator/controller controlling an equipment isolation point which is not controlled by the issuer; to the issuer of an authorisation; confirming the safety measures applied by that operator/controller. Note: The assurance system applies only where equipment has isolation points which are not all under the control of the issuer.

Asynchronous operation of a synchronous machine

The non-synchronous operation of a synchronous machine in which the asynchronous generating torque is equal to the prime mover torque or in which the asynchronous motor torque is equal to the motor shaft torque.

Authorisation (auth’n)

A collective term for the access permit and test permit. Under an authorisation, the recipient’s work party is allowed temporary access to defined equipment which has been removed from service and which is in a defined state, to enable work to be undertaken. Note: Entry approval is not an authorisation as defined above.

Authorisation area

A defined area within which an access permit or test permit is in force and which is marked out where practicable using authorisation rope and authorisation area notices.

Authorisation area entry notice

A notice posted at the entrance to an authorisation area, defining the type of authorisation which applies within the area, the name of the recipient of the authorisation and basic safety information. Form 569 is supplied for this purpose.

Authorisation area notice

A standard portable sign with a background colour of safety green carrying the words AUTHORISATION AREA in white lettering.

authorisation area,

A collective term for the access permit and test permit. Under an authorisation, the recipient’s work party is allowed temporary access to defined equipment which has been removed from service and which is in a defined state, to enable work to be undertaken. Note: Entry approval is not an authorisation as defined above.

Authorisation holder's certificate

A certificate issued by an employer to an employee which provides personal identification; defines which authorisations the employee is competent to hold; defines any limits on the type of work which can be carried out by the employee; defines any limits on the places where the AHC applies. Note: The standards for assessing competence are set by the equipment owner, and a certificate is valid only for a specified time. [SR-EI April 1995].

authorisation holder’s

A collective term for the access permit and test permit. Under an authorisation, the recipient’s work party is allowed temporary access to defined equipment which has been removed from service and which is in a defined state, to enable work to be undertaken. Note: Entry approval is not an authorisation as defined above.

Authorisation rope

Yellow and green stranded rope used at stations solely for the purpose of defining the boundaries of access permit and test permit authorisation areas.

Auto-reclose

The automatic reclosure of a circuit-breaker after a predetermined time following a fault tripping.

Auto-synchronise

Automatic connection of alternators, synchronous condensers and/or sources of supply following an automatic process of checking that satisfactory conditions for synchronism exist.

Auto-transformer starting

The process of starting an a.c. motor at reduced voltage by connecting the primary winding initially to an auto-transformer and reconnecting the winding directly to the supply at rated voltage for the running condition.

Automatic frequency control (communications)

An automatic means of controlling oscillator frequency to hold it stable.

Automatic gain control (communications)

A process or device by which the gain of an amplifier is automatically adjusted, generally with the object of minimising changes in the level of the output signal with changes in the level of the input signal.

Automatic generation control (AGC)

The function of an EMS application that automatically adjusts generation to meet the load.

Automatic under frequency load shedding

The automatic disconnection of customers for severe or prolonged under frequency. Implemented on relays installed within the distribution network or at Transpower’s substations, which trip customers in two, nominally, 20% groups.

Automatic voltage regulator

A device that continuously monitors the voltage at a voltage regulating point on the system (generator, condenser, transformer etc.) and automatically initiates corrective action to maintain that voltage within pre-set limits.

Auxiliary circuit

Ancillary low voltage circuits, other than control circuits and the main current circuit, providing indication, protection, power supplies etc.

Auxiliary connections

Auxiliary connections.

Auxiliary contact

A contact included in an auxiliary circuit and mechanically operated by the circuit-breaker or disconnector.

Auxiliary equipment

Station equipment which supports the operation of primary equipment, for example exciters, oil pumps, compressors, fans. (Compare with primary equipment, secondary equipment).

Auxiliary transformer

Auxiliary transformer.

Availability

The number of hours per year the network or part thereof is in service. Unavailability is the opposite of availability, e.g. hours per year the network or part thereof is not providing service.

Available for service

A declaration made by the regional centre controller to the Security Co-ordinator that defined grid system equipment is available for service.

AVR

A device that continuously monitors the voltage at a voltage regulating point on the system (generator, condenser, transformer etc.) and automatically initiates corrective action to maintain that voltage within pre-set limits.