Glossary terms beginning with E

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

A certificate issued by an employer to an employee which:Declares the holder as competent and having the authority to receive entry approvals; Defines the restricted areas the holder can enter;  Defines any restrictions placed on the holder.

earth connection

The conductor between equipment and the station earth grid.

earth fault

A defect in an electrical circuit or apparatus that results in a current flow to earth at the point of the defect.

earth fault factor

At a given location of a three-phase system, and for a given system configuration, the ratio of the highest rms phase-to-earth power frequency voltage on a healthy phase during a fault to earth affecting one or more phases at any point on the system to the rms value of phase-to-earth power frequency voltage which would be obtained at the given location in the absence of any such fault.

earth grid

A bonded assembly of conductors buried beneath a switchyard to provide a low impedance connection with the general mass of earth.

earth mat

A safety device in the form of a metal grating placed at ground level immediately below, and electrically bonded to, the operating mechanism of a disconnector and the earth grid.  While standing on the earth mat the operator is protected against a possible voltage difference occurring between the switch handle and earth when the disconnector is operated.

earth potential

The potential (difference) between the local earth and the earth at a (remote) point.

earth potential rise

The potential (difference)  between the local earth and the earth at a remote point due to the flow of electric current from line to earthing system to earth.

earth stick

A hand-held approved stick for use in attaching and removing portable earth headclamps.  See also insulated telescopic stick.

earth switch (ES)

A switch, which when closed provides an electrical connection between normally live equipment and earth.

earthed

Effectively connected to the general mass of earth.

earthed line work

Any work associated with a transmission line in which: A line patrol or inspection is being carried out from the ground or the air. Note: Where any helicopter, personnel or equipment supported by an aircraft are positioned within 5.0 m of live line components, that helicopter is engaged in helicopter live line work and is required to comply with TP.ML 11.09,  Safety Standards for Helicopter Live Line Work. A transmission line structure is climbed for any reason above 3.0 m from ground level, An access permit is required to be taken on a transmission circuit, Portable work site earthing is being applied to a transmission circuit, Trees are felled or trimmed to clear a transmission line, where there is any possibility of any part of the tree coming within 4.0 m of the conductor, Load-bearing components of a transmission line structure, foundation, guy wire, guy anchor, insulator set or conductor, are repaired or the loads on any of these components, are changed or altered in any way, A personnel hoist or crane is used to inspect or maintain a line, Any work is carried out on line terminations by line workers inside an outdoor substation or switchyard enclosure.

earthing (verb)

The process of making an effective conducting connection to the general mass of earth.

earthing attachments

Owner-approved devices that can be fitted by hand to a circuit-breaker to permit its use as an earthing circuit-breaker.

earthing circuit-breaker

A circuit-breaker with contacts arranged to facilitate the earthing of circuits or the busbars of metal-clad switchgear.

earthing horn

A fitting attached to high voltage equipment used for the connection of portable earth headclamps.

earthing resistor

A resistor between the neutral point of a generator or transformer and earth, designed to limit prospective fault currents.

earthing transformer

earthing transformer.

earthing truck (trolley)

An earthing device for metal-clad switchgear that is placed in the position normally occupied by a circuit-breaker.

earthquake blocking device

A device designed to detect the beginning of an earthquake and interrupt the tripping circuit of a Buchholz relay.

earths

A generic term for the apparatus used for earthing.  This includes: Work party earths: those earths applied additional to issuer applied earths, and Portable earth/temporary earths (SR-EI).

ECA (documentation)

Equipment change advice (Form TP 590).

EDI

Stands for Electronic Data Interchange. A set of standards for transferring data between two companies’ computing systems.

EDR (documentation)

Station equipment defect report (Form TP577).

effectively earthed neutral system

A system with effectively earthed neutral at a given location is a system characterised by a coefficient of earthing at this point which does not exceed 80%.

EHV cables

Cables rated 66 kV and up to 200 kV a.c. and 350 kV d.c.

electric braking

A braking action applied to a machine by causing it to produce electrical energy which is either dissipated or returned to the power system.

electrical accident

An event which involves electricity and which causes serious injury, and/or fire damage to property.

electricity distributor

An asset owner whose assets are predominantly for the distribution of electricity to customers.

electricity emissions

Emissions from electricity used in Transpower’s offices include direct (scope 2) emissions and emissions from leased assets such as lifts and some HVAC equipment.

Electricity Industry Participation Code 2010

The Code sets out participant responsibilities, including the Authority's duties and responsibilities. The Authority maintains the Code and is responsible for ensuring participants comply with the Regulations and the Code.

electricity market

The electricity market operating in New Zealand for trading in bulk electricity, including all or any specific commodity markets.

Electricity Regulations

The Code sets out participant responsibilities, including the Authority's duties and responsibilities. The Authority maintains the Code and is responsible for ensuring participants comply with the Regulations and the Code.

electro-mechanical rotor

A form of hunting in which the fluctuations are periodic variations in the speed of a synchronous machine above and belo the normal speed, resulting in periodic phase variations relative to the rest of hte power system.

electrode (liquid resistor)

One of two conductors immersed in the electrolyte and by which the fault current passes into the electrolyte and from the electrolyte to earth.

electrode arm

An element of the electrode that can be isolated for testing puposes.

electrode cell

A container designed to accommodate an electrode while immersed in an electrolyte (sea water).

electrode lines

HVDC circuits connecting the a.c./d.c. converter stations at Benmore and Haywards to their low resistance solid earthing points.  HVDC electrode lines are insulated from their supporting steel and wood pole structures and although these circuits are nominally at earth potential, electrode line voltages can increase significantly under certain loading conditions.  Special earthing procedures apply to the application of portable earthing to HVDC electrode lines.

electrode potential

The measured potential of an electrode in the soil relative to the potential of a reference electrode.

electrolyte (battery)

A liquid or solid substance containing mobile ions which renders the substance ionically conductive.  An example is the dilute sulphuric acid (H2SO4) in lead-acid batteries.

electrolytic backfill

Material surrounding and in contact with a buried anode for the purpose of maintaining or improving its performance.

electromagnetic braking

A braking action applied to a machine by causing it to produce electrical energy which is either dissipated or returned to the power system.

electromagnetic compatibility (EMC)

Electromagnetic compatibility is the ability of a device to operate faultlessly in a prescribed electromagnetic environment without at the same time affecting its surroundings in an inadmissible way (this is the generic definition from IEC-IEV adapted to the expectations of a Grid company).

elevated working platform

A general term used for scissor lift, aerial platform, or an extensible or articulating boom aerial device (either self-propelled or vehicle-mounted) used for the purpose of positioning personnel, their tools, and necessary materials to elevated work locations. Not included in this definition are ladder stands, scaffolds, or industrial trucks.

ELT

An Emergency Location Transmitter normally fixed to an aircraft and set to initiate signalling  on inadvertent impact.  It can also be activated manually.

embedded generators

Embedded generators are smaller power plants conntected to a regional electricity line business’s distribution network (as opposed to the high voltage transmission network).

EMC (Electromagnetic Compatibility)

EMC is the ability of a device to operate faultlessly in a prescribed electromagnetic environment without at the same time affecting its surroundings in an inadmissible way (this is the generic definition from IEC-IEV adapted to the expectations of a Grid company).

emergency and standby power systems

A power outage that results from the failure of a system component, requiring that it be taken out of service immediately either automatically or by manual switching operations, or an outage caused by improper operation of equipment or human error.  This type of power outage is not directly controllable and is usually unexpected.

emergency recall time

The estimated time required to return released equipment to service in a safe condition should it be requested by the service centre at any time during a release.

emergency trip device

A manually operated tripping device on or adjacent to equipment, eg  a circuit-breaker, which can be used to trip it in an emergency.

emergency under frequency limit

The frequency, below the normal frequency range, at which the grid operator is required to shed demand to minimise the risk of a grid collapse. The limit is quantified in Table 1 of the Grid Emergencies Code.

emergency under voltage

The supply low voltage level at which demand is manually shed. See TP.OG 43.01.

emissivity

The ratio of the radiant energy emitted by the surface of an object to that emitted by a black body at the same temperature.

employee

Any person who is required to work in accordance with SR-EI rules. Note:  “Employees” includes contractors and their employees.  In Section 1 of the SR-EI rules ,the “Application” paragraph lists the various categories of employees.

empty weight (E.W.) of gas cylinders

Means the weight of the cylinder complete with its value and any other fittings or appurtenances normally on the cylinder when it is being filled.

EMS

A collection of computer software applications used to monitor and control a power system.

enable

Restore the functioning of a protection and/or control system, after that system has been disabled.

end user

An entity connected to the power system for the primary purpose of consuming electricity.

end voltage

The prescribed level at the battery terminals at which a discharge is considered finished. Discharging the battery beyond this point may result in damage to the battery.

energised

Electrically livened, or connected to or containing some other source of energy e.g. steam, compressed air, hydraulic energy etc.

energy co-ordinator

The person who issues instructions based on the dispatch schedule and the real-time conditions to manage resources and meet the actual demand and the real-time condition of the grid.

energy manaement system,

A collection of computer software applications used to monitor and control a power system.

energy trader/broker

Companies that buy and sell electricity.

engineering safety

The Engineering Safety Group of the Occupational Safety and Health Service of the Department of Labour.

ensure

In the context of authorisations means to be accountable for the requirement being carried out;or to carry out the requirement personally or have it carried out by another person.

entry approval

The approval given by a person with the appropriate authority, for an employee to enter a specified facility or part of a facility.

entry approval certificate

A certificate issued by an employer to an employee which:Declares the holder as competent and having the authority to receive entry approvals; Defines the restricted areas the holder can enter;  Defines any restrictions placed on the holder.

environment code (Ec)

The code (Ec) derived from formula as noted in TP.ML. 01.01. This has the same meaning as "Tower Galvanising Age".

environmental incident

An event resulting in temporary or permanent cumulative or immediate adverse effects on the environment, eg  an oil or chemical  spillage, or release of SF6 gas.

equipment

The individual components that interconnect to form a circuit, (such as transformers, CBs, disconnectors, cables, conductors, cts, line traps) and secondary plant like a protection system. Includes all Transpower equipment, either in-service or out-out-service, and includes maintenance and storage equipment.

equipment capability statement

A document for specific equipment giving ratings and other  operating limits and data for grid operators, so that they may determine, , what the equipment can tolerate, especially in unusual conditions.

equipment inspector

A person who Is engaged by an inspection body to carry out inspection functions referred to in the PRCPR Regulations, and is the holder of a relevant certificate of competence.

equipotential (work zone)

A work zone where all equipment is electrically interconnected to provide acceptable potential differences between all parts of the zone under worst case conditions of energization.

equivalent span

Also known as the ruling span.

ER 97 design loading condition

This condition stated by regulation 66(3) of the Electricity Regulations (1997) requires repair or replacement of structures within 12 months if the asset is established as incapable of supporting the ultimate design loads.

ER 97 normal loading condition

This condition stated by regulation 66(4) of the Electricity Regulations (1997) requires repair or replacement of structures within 3 months if the asset is established as incapable of supporting the ultimate loads and the structure is located in an area where there is a risk to life or property.

ESDD

The Equivalent Salt Deposit Density. A measure of the severity of the pollution deposition at any site. Used for insulation design purposes.

ESITO

Electricity Supply Industry Training Organisation.

event list

A computer-generated and sequential record of operations, or changes of equipment status.

everyday condition

The everyday condition is the weather related loading that has a very short return period.  Apprentices F and H define the various conditions/status related to Everyday conditions.

EWP

A general term used for scissor lift, aerial platform, or an extensible or articulating boom aerial device (either self-propelled or vehicle-mounted) used for the purpose of positioning personnel, their tools, and necessary materials to elevated work locations. Not included in this definition are ladder stands, scaffolds, or industrial trucks.

excessive SF6 gas leakage rate

An excessive SF6 gas leakage rate from a circuit breaker or GIS compartment exists when 2 or more gas top-ups are required during a 3 month period.

exciter

A generator or static device which supplies all or part of the power required for the excitation of an electrical machine.

expected annual peak load

The maximum peak load in amps that can be expected to be carried within a twelve month period on the circuit or by the equipment/component based on the loading history over the previous 24 months.

explosive limits

See lower explosive limit (LEL); upper explosive limit.

extended contingent event

Those events for which, in the reasonable opinion of the grid operator, resources can be economically provided to maintain the security of the grid and power quality with the shedding of demand.

extended reserve

The reserve able to counter a contingent event or extended contingent event, the response of which is not fast enough either to limit the fall in frequency to within the limits set out in section 2 of the Power Quality Code, or to assist in the recovery of frequency to within the limits set out in section 2 of the Power Quality Code. The response is sufficient to assist in maintaining the frequency to within the limits set out in section 2 of the Power Quality Code, commencing no later than one minute after the beginning of the event and for at least a further 14 minutes thereafter.

extra high voltage (EHV)

Cables rated 66 kV and up to 200 kV a.c. and 350 kV d.c.