Glossary terms beginning with L

Terms used within Transpower
Click one of the letters above to go to the page of all terms beginning with that letter.
ladder format (circuit diagrams)

A circuit diagram format where the auxiliary dc or ac supply busbars are drawn parallel and the circuits run between the busbars as the rungs of a ladder.

land electrode

An arrangement of conductors through which current can enter or leave the ground.

landowner

The owner of a block of land traversed by a Transpower transmission line.

latched

Mechanically held in a pre-set position by means of a pawl or similar device, in readiness for tripping, for example a closed circuit-breaker or a bistable relay.

LDC

A communications circuit leased from Telecom or another communications network owner that provides a dedicated, sole-use communication facility, usually a single VF channel.

lead-in cable

Non-metallic fibre-optic cable is used where the optical fibre link changes from one transmission line to another or to connect the link into terminal equipment at either end.

leased direct circuit

A communications circuit leased from Telecom or another communications network owner that provides a dedicated, sole-use communication facility, usually a single VF channel.

LEL

Lower explosive limit.

Level

A specific insulation level expressed in terms of the crest value of a standard lightning impulse. Note 1: The manufacturer of equipment will generally subject the equipment to a voltage impulse test using a standard 1.2/50 us lightning impulse with a crest value equal to the BIL or LIWL. Note 2: The older term ‘BIL’ is being gradually replaced by the term ‘LIWL’.  Standard values for LIWL are set by IEC 71-1 Insulation Co-ordination – Definitions, Principles, and Rules. Insulation co-ordination design attempts to limit lightning surges to below the LIWL of equipment.

life expectancy

The date where replacement/major refurbishment is necessary.

lifting gear

In relation to a crane is a device used: To attach the load to the hook or load handling device, or To control the load independently of the hook or load-handling device, or As a container for the load, and Includes lifting beams, lifting frames, spreaders or similar devices that are not an integral part of the crane.

Lightning Impulse Withstand

A specific insulation level expressed in terms of the crest value of a standard lightning impulse. Note 1: The manufacturer of equipment will generally subject the equipment to a voltage impulse test using a standard 1.2/50 us lightning impulse with a crest value equal to the BIL or LIWL. Note 2: The older term ‘BIL’ is being gradually replaced by the term ‘LIWL’.  Standard values for LIWL are set by IEC 71-1 Insulation Co-ordination – Definitions, Principles, and Rules. Insulation co-ordination design attempts to limit lightning surges to below the LIWL of equipment.

lightning protection

An integrated protection system at telecommunications sites which: captures the lightning on specified air terminations; conducts the lightning current safely to ground taking account of the requirements to restrict step and touch potential to safe values; dissipates the lightning current with minimum rise in ground potential; protects equipment conneced to antennas, power lines, telephone and data circuits.

line

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

line [overhead]

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

line construction work

All work associated with the construction of Transpower transmission lines listed as follows: A complete new transmission line constructed from switch yard to switch yard. A deviation of an existing line or circuits involving the construction of new access foundations and structures. Installation of additional circuits to existing structures. Resiting and re-terminating of structures /circuits into substations. Dismantling of redundant lines/circuits. Installing optical fibre ground wire (OPGW). Any other designated line construction work. [TP.ML 11.09].

line importance

Means a measure of the importance of a particular line in the overall electrical system.

line post insulator

Means composite polymer line post insulator.

line side

the telecom line side of the barrier isolation cabinet.

line trap

The term used in this standard to include power line carrier (PLC) blocking reactors and their associated tuning packs and line matching units.

lines maintenance contractor

The contractor responsible for the management of all activities in a geographic group of transmission lines.

liquid earthing resistor

A resistor which uses electrodes immersed in electrolyte. The electrolyte provides the specified resistance.

live

At a potential difference to earth. Note: The potential difference may result from connection to a voltage source or indirectly, e.g. by the effects of induction or electrostatic fields. [SR-EI April 1995].

live line glove and barrier work

A method of performing live line work on lines up to and including 33 kV, where the worker is insulated from earth and other phases by the use of insulating gloves and sleeves, insulating work platform and insulating barriers.

live line hot stick work

A method of performing live line work on lines of voltages up to 33 kV using hot stick tools and equipment.

live line minimum approach distance

An absolute minimum approach distance applicable to live line work only. Measured between a worker or conducting tools at earth potential, and an energised component; or between adjacent phases. The live line minimum approach distance is a specified reduction of the minimum approach distance, and is applicable only to work carried out in accordance with live line work standards.

live line techniques

Approved work methods which involve "bare hand" or "hot stick" work on a live conductor.

live line testing

The testing of transmission line insulators while the conductors are live.

live line work

Work performed on or near normally energised transmission circuit components, without using isolating and earthing procedures during the work, and at distances closer than the minimum approach distances specified in SR-EI Rule 703. Note: Live line work techniques may be used on isolated and earthed circuits.

live work

All work inside the relevant MAD performed on or near normally energised components of a HV transmission system without using isolating and earthing procedures during the work. Also see TP.OG 45.03. This applies but is not limited to:Load-bearing components of an energised insulator string assembly or its structure attachment are changed or have their loading altered. Live work tools are applied to energised components where the tools have less than twice the live work minimum tool insulation distances specified in subsection 12.6 of this standard. Note: Measuring conductor to ground distances with a calibrated measuring pole is not live work, provided the pole is made of fibreglass reinforced plastic or other suitable insulating material, and the conductor to worker distance is at all times greater than twice the minimum live work tool insulation distance. The use of voltage detectors is not considered live work. Energised conductors are pushed, pulled or lifted with live work tools. Crossarms, poles and equipment supporting live conductors are changed. Energised insulators are cleaned using hand held equipment with jets of water, abrasive grit or with cleaning devices mounted on hot sticks. This includes cleaning from outside the minimum approach distance. A work method is used which is defined by Transpower as live work. The clearing, trimming, pruning of vegetation and/or tree growth which has grown within the minimum approach distance to live conductors. Water blasting and painting of steel towers and equipment support steel within the minimum approach distance to the conductors. Work over live substation equipment (even though distances may be in excess of the LWMAD).

live work manual

A comprehensive manual, the function of which is to provide a wide range of information on the overall management of live work by the approved contracting company.

live work method

A fundamental technology for undertaking live line work. The three methods are hot stick, glove and barrier, and barehand.

live work minimum approach distance

The minimum approach distance applicable to live work, between a worker or conducting tools at earth potential, and energised components; or between a worker or conducting tool at energised potential, and earth or adjacent phases. The live work minimum approach distance is a specified reduction of the minimum approach distance, and is applicable only to work carried out fully in accordance with TP.SS 06.10 Live work.

live work minimum tool insulation distance

The minimum length of insulated live hot stick or rope, that can be inserted between energised components and earth or adjacent phases. The tool insulation distance may be made up of a number of jointed poles or poles containing metal inserts. In this case, the minimum tool insulation distance shall be the total of each of the lengths of insulating material not bridged by conducting components. Note: Currently the live work minimum tool insulation distance and the live work minimum approach distance are the same, and are set out in subsection 12.6 Tables 1 and 1a of this standard.

live work procedure

A documented live work unit procedure, that contains the minimum live work effort required to achieve a unit objective. Examples of live work tasks are: access a transmission conductor bare hand using live line rope, take up conductor loads on a suspension structure using hot sticks.

livening

The act of energising equipment (for example primary equipment and associated SCADA, communications equipment or protection) usually from the power system.

LIWL

Lightning impulse withstand level.

LLW

Work performed on or near normally energised transmission circuit components, without using isolating and earthing procedures during the work, and at distances closer than the minimum approach distances specified in SR-EI Rule 703. Note: Live line work techniques may be used on isolated and earthed circuits.

LMU

Line matching unit (sometimes referred to as coupling device).

load control

Types of control are: automatic under frequency load shedding.(see MW reserve of a power system), Interruptible load (see MW reserve of a power system), Manual load shedding: the forced disconnection of load by an operator/controller, Load current, The current level at which equipment normally operates (that is, not fault current).

load curve

Graphical representation of the observed or expected variation of load as a function of time.

load shedding

The forced disconnection of load, in stages. This is either manual (see load control) or automatic (see MW reserve [of a power system]).

load shedding RTU

RTU located at electricity consumer sites which monitor and control the interruptible load at the site.  The RTU reports the amount of interruptible load at the site to the FRED Master and sheds the load in response to an indication from a local under-frequency relay and /or the FRED Master.

local backup protection

A backup protection equpment or system which is energised from instrument transformers within the same substation as the corresponding main protection equipment.

local control

Control of an operation at a point on, or adjacent to, the controlled device.

local indicator

An ON/OFF indicator connected to a circuit-breaker operating mechanism which shows the closed/open status of the circuit-breaker.

local instructions

An approved document which identifies the means by which a safety rule or other management directive is applied to the local site or situation. [GSH-EI April 1995].

local service

Local a.c. supply providing power for station auxiliary services.

local service meter

A meter that measures energy used within a Transpower station where energy data are used to calculate the energy transmitted for connected parties. The data are usually subtracted from the GXP meter to give net energy through a point of connection.

local supply equipment

All the equipment required at a grid interface solely for the supply of electricity that is not owned by a line business or energy retailer.

lock off

To prevent operation by means of a lock.

lockout box

A lockable facility for holding keys, fuses etc. An example is: multilock box - a lockout box used in a multilocking system.

log (noun)

The collection of log books, log sheets, completed authorisation forms and other records including electronic and tape, which together form a complete record of operating events in a station or operating area. [SR-EI April 1995].

log book

A book designated for entering a handwritten statement of power system equipment operational events.

logged

Recorded in the log. [SR-EI April 1995].

long range plan

That part of Transpower’s MMS database which shows all known planned future outages. This plan is revised on a continual basis.

loop format (circuit diagrams)

Equivalent to ladder format circuit diagrams, but with parallel dc supply busbars near the centre of the page and circuits looped to show twisted pairs as parallel lines.

LOS

Loss of connection to the grid which results in an interruption of supply of electricity to connecting parties.

loss of communication

A sustained disruption of communications between the grid operator and the control rooms of one or more connecting parties, such that operation of the grid is affected or is likely to be affected. [GOSP glossary].

loss of supply

Loss of connection to the grid which results in an interruption of supply of electricity to connecting parties.

low voltage

Any voltage exceeding 32 V ac or 115 V dc but not exceeding 1000 V ac or 1500 V dc. [SR-EI April 1995]. In general usage within Transpower, the voltage on the secondary winding supply side of a transformer. Typically at or less than 33 kV.

low voltage limit

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

lower explosive limit

The minimum percentage of combustible gas in a mixture with air that can be ignited and will continue to burn.

LRP

That part of Transpower’s MMS database which shows all known planned future outages. This plan is revised on a continual basis.

LS or L/S

Local a.c. supply providing power for station auxiliary services.

LSD sign (lines)

Line name, structure number, danger warning sign. [TP.ML 01.09].

lumen

Is the SI unit of luminous flux, equal to the amount of light emitted per second in a unit solid angle from a uniform luminous source.

luminaire

Is a light-emitting (light giving) object/body, e.g. lamp, bulb, etc.

luminous efficacy

Is a measure of how efficiently the lamp converts electrical power (watts) to light (lumens). The higher the luminous efficacy, the more efficient the lamp.

lux

The SI unit of illuminance, equal to one lumen per square metre.

LV

Any voltage exceeding 32 V ac or 115 V dc but not exceeding 1000 V ac or 1500 V dc. [SR-EI April 1995]. In general usage within Transpower, the voltage on the secondary winding supply side of a transformer. Typically at or less than 33 kV.

LWMAD

The minimum approach distance applicable to live work, between a worker or conducting tools at earth potential, and energised components; or between a worker or conducting tool at energised potential, and earth or adjacent phases. The live work minimum approach distance is a specified reduction of the minimum approach distance, and is applicable only to work carried out fully in accordance with TP.SS 06.10 Live work.

LWMTID,

The minimum length of insulated live hot stick or rope, that can be inserted between energised components and earth or adjacent phases. The tool insulation distance may be made up of a number of jointed poles or poles containing metal inserts. In this case, the minimum tool insulation distance shall be the total of each of the lengths of insulating material not bridged by conducting components. Note: Currently the live work minimum tool insulation distance and the live work minimum approach distance are the same, and are set out in subsection 12.6 Tables 1 and 1a of this standard.