Glossary terms beginning with M

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

Metering Administrator - as defined in TP.AP 13.02.

machine

An item of equipment capable of doing work.

MAD

This is the distance that shall beobserved by persons approaching exposed live conductors,

MADJ

Transpower's Excel workbook used to calculate an Adjustment Factor.

magnetising inrush current

A transient current which flows into the winding of a power transformer upon energising.

main circuit (circuit-breaker)

All the conducting parts of a circuit-breaker included in the main current circuit which it is designed to close or open.

main circuit (transformers)

All the high voltage conducting parts of the oil-immersed power transformers windings and bushings etc.

main contact (circuit-breaker)

A contact included in the main circuit of a circuit-breaker intended to carry in the closed position the current of the main circuit.

main distribution frame

The cabinet(s) at a communication site where all the external communication circuits are terminated.

main exciter

An exciter which supplies all or part of the power required for the excitation of a generator or synchronous condenser.

main protection

Protection equipment or system expected to have priority in initiating either a fault clearance or an action to terminate an abnormal condition in the power system. [IEC-IEV 448-01-10].

main switchboard

A switchboard used to provide the greatest degree of control of the supply of electricity to the installation.

maintained illuminance

The average illuminance over the reference surface (area) at the time maintenance has to be carried out by replacing lamps and/or cleaning the light fittings.

maintenance contractor

A company or person(s) contracted by Transpower for specified maintenance work.

maintenance distance

This is the distance from the edge of the maintenance zone to live conductors.

maintenance envelope

This is the area between the maintenance zone and live equipment into which a worker may accidentally encroach without danger.

maintenance factor

The ratio of illuminance provided by an installation in average condition of dirtiness expected in service, to the illuminance from the same installation when clean. The MF is always <1.

maintenance handle

A detachable handle or lever used to give a slow controlled closing action for contact synchronising and alignment checks on a circuit-breaker fitted with a powered closing mechanism.

maintenance loading

A multiplying factor used to adjust the cost of repairs to allow for future ongoing maintenance costs.

maintenance report

A document used by the contractor on site to record the servicing and remedial work undertaken, as well as diagnostic test results and their analysis. It also records any recommendations for any further corrective work or reinspection frequency.

maintenance switcher

A person with control of defined power system equipment operating and/or control functions to the requirements of the Security Coordinator and Grid Asset Owner.

maintenance switching time

The time required to apply/remove safety measures.

maintenance zone

This is the predetermined work area, with the boundaries, barriers and work platform positions calculated for a particular item of equipment.  Within this zone a worker not larger than the Standard Person may carry out all normal work activities safely and remain well clear of nearby live equipment.  The predetermined work area ensures that accidental reach outside the barriers will not create any electrical hazard for the workers involved.

major change

A change to the approved commissioning plan which has a major impact on delivery, control, or monitoring of Transpower's transmission services and/or security or quality of the power system.

major failure

A failure within a circuit breaker that prevents the circuit breaker from carrying out its intended function.

major insulation

The insulation between windings and core, limb barriers and the insulation between the coils and core yokes.

major oil spill

An oil spillage incident that cannot be controlled without immediate additional assistance.

major service

An invasive service which requires equipment to be removed from service and made safe and would normally also incorporate a diagnostic inspection or a minor service. Servicing work would be scheduled to correct known deterioration which occurs after a specified time interval or when certain operational parameters have been exceeded. It would also be required if diagnostic inspections indicate a potential problem or deterioration that requires investigation or repair. [MMS Service Code Document - 26 August 1996].

Management Maintenance

The computer system used by Transpower to plan, control, and record all contracted maintenance work (including purchase of materials for maintenance).

mandatory replacement

Compulsory replacement of items irrespective of condition due to their discontinuation from use for various reasons.

manual control

Control by hand, that is, not automatic.

Manual Events Log

A computer-based operational information system with keyboard entry at a service centre for operational events. This information is viewed via TPIX.

manual load shedding

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).

mapboard

Another name for a mimic diagram especially one covering more than a single station, and usually hand-dressed.

Market Data Entry

Tool to indicate to the wholesale market the security and pricing impact of outages.

master transformer

The transformer selected to initiate tap-changing for all associated parallel (follower) transformers.

master/ follower control (tap-changers)

A method of controlling the OLTCs of two or more, three-phase banks where one is selected as the master and the remaining units as followers. Each follower tap-changer is driven to the same tap as the master.

MAV

High voltage water cooled mercury arc ionic valve.

maximum continuous rating

The value assigned to an equipment parameter by the manufacturer at which the equipment may be operated for an unlimited period without damage.

maximum control level

The water level of a hydro-electric reservoir or storage lake above which the lake cannot be raised except under defined flood conditions given by the resource consent maximum design cantilever load (MDCL). Is as defined in 36B/176/CD, being the product of the applied "96 hour Average Load", divided by 1.1.

maximum demand

The peak consumption of energy (averaged over a half-hour period and expressed in watts) recorded during a given time, for example, day, week, year.

maximum design cantilever load

Means the cantilever load level above which damage to the core begins to occur and which should not be exceeded in service.  This value is specified by the manufacturer.  The bending moment and FPR core stress corresponding to the MDCL shall not produce any damage to the FPR core.

maximum design temperature

Means the maximum temperature that the conductors may reach under the influence of load current (excluding fault current), environmental conditions and solar radiation.

maximum peak load

The maximum peak load in amps that would be required to be carried on the circuit or by the equipment/component in a contingency or other abnormal system event based on the Transpower equipment rating database, or if not applicable, the actual equipment's rating.

maximum working load

The maximum load derived from worst-case site-specific design loads. These loads exclude generic factors of safety.

MCB

Moisture cured urethanes.

MCOV

The designated permissible rms voltage that may be applied continuously between the surge arrester terminals.  Often abbreviated MCOV.

MCR

The value assigned to an equipment parameter by the manufacturer at which the equipment may be operated for an unlimited period without damage.

MDCL

Means the cantilever load level above which damage to the core begins to occur and which should not be exceeded in service.  This value is specified by the manufacturer.  The bending moment and FPR core stress corresponding to the MDCL shall not produce any damage to the FPR core.

MDE

Tool to indicate to the wholesale market the security and pricing impact of outages.

MDF

The cabinet(s) at a communication site where all the external communication circuits are terminated.

MEA

Modern Equivalent Assets. Used in the Valuation process to assist in determining the optimised costs of system assets.

mean power

The average output at rated frequency of 50 Hz of a generating set over one period expressed in MW for active power, or Mvars for reactive power, as appropriate. [GOSP glossary].

MegaVoltAmpere

MVA means 1000 kVA - the flow of active power is measured in megaWatts (MW).  When compounded with the flow of reactive power, which is measured in Mvar, the resultant is measured in MegaVoltAmperes (MVA).

megger

(noun) The proprietary name for a common make of portable, hand-operated test instrument used for high voltage insulation resistance tests. (verb) To carry out insulation resistance or continuity tests using a Megger or other make of test instrument.

MEN

A system of electrical supply in which the neutral is connected to the earth at the point of supply; and at points on the supply system; and at every electrical installation connected to that system.

metal-clad switchgear

High voltage switchgear of a type that has its associated buswork totally enclosed in metal chambers or trunking.

metalclad switchgear non-withdrawable SF6 fas insulated (GIS)

Switchgear in which the circuit breaker, busbar, and feeder connections and ancilliary items are located in separate metal partitioned SF6 air insulated compartments. The circuit breakers are vacuum type and are non-withdrawable. Isolation and earthing (through the CB) is provided by a three position isolating switch.

metalclad switchgear withdrawable air insulated

Switchgear in which the circuit breaker, busbar, feeder connections and ancilliary items are located in separate metal partitioned air insulated compartments. The circuit breakers are either SF6 or vacuum type and are withdrawable for isolation purposes.

metering administrator

The Transpower person or persons or third party responsible for the revenue metering equipment interrogation.

Metering Controller

A staff member of Field Services responsible for managing revenue metering maintenance contracts.

metering equipment

Equipment used to measure the quantity of electricity conveyed at a specific point. Includes metering CTs and VTs, active and reactive energy meters and half-hour integrating pulse recorders.

Metrosil

The proprietary name for a non-linear resistor incorporated in circuits for the purpose of limiting over-voltages.

MEWP

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.

MF

The ratio of illuminance provided by an installation in average condition of dirtiness expected in service, to the illuminance from the same installation when clean. The MF is always <1.

MFL

The guaranteed lowest tensile breaking load which a component will carry before failure occurs.

MHWM

Mean High Water Mark.

micron

A unit of measurement being 1 x 10-6 of a metre. (Alternatively known as a micrometre)

mimic diagram

A schematic or single-line display on a control panel or computer monitor depicting station equipment configuration.

mimic notice

A tag attached by an operator to a control panel. Mimic notices indicate the position of safety measures and other precautions applied on equipment under an authorisation.

Minimum approach distance

This is the distance that shall beobserved by persons approaching exposed live conductors,

minimum control level

The water level of a hydro-electric reservoir or storage lake below which the lake cannot be lowered for operating purposes as defined by the resource consent.

minimum distance (basic electrical clearance)

This is the distance in air from live conductors to earth required to meet the lightning impulse withstand voltage (LIWV).  Appropriate margins must be added to allow for component or mounting flexibility, or imprecision in location, where this can occur.

minimum failing load

The guaranteed lowest tensile breaking load which a component will carry before failure occurs.

minimum flow

River flow in cumecs, set pursuant to the Resource Management Act or as defined by a resource consent or water permit, below which the flow must not fall as a result of power station operation.

minimum illuminance

The lowest illuminance occurring at any point and at any timne on the working plane in the working area.

minimum oil circuit-breaker

A circuit-breaker which uses a small quantity of oil for arc quenching and insulation. The contacts are contained in an interrupter head which is usually at the normal operating voltage.

minimum stock level

A quantity of components for use in emergency situations held by a contractor in accordance with MSL criteria set down in this standard.

minor change

A change to the approved commissioning plan can be accommodated without any impact on delivery, control, or monitoring of Transpower's transmission services and/or security or quality of the power system.

minor oil spillage

An oil spillage incident that can be controlled without additional assistance.

minor service

A non-invasive service which requires equipment to be removed from service and made safe and would also normally incorporate a diagnostic inspection. It involves servicing work to correct known deterioration which occurs after specified time intervals or after a number of operations. [MMS Service Code Document - 26 August 1996].

MMS

The computer system used by Transpower to plan, control, and record all contracted maintenance work (including purchase of materials for maintenance).

mobile elevated working

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.

MOC

Ministry of Commerce.

modern equivalent asset

A replacement asses that can be installed today and providing the same level of service as any existing asset. Required for determining the ODV value of assets.

modification

Any work done on a protection installation that involves the connections of new wiring to existing wiring, or the disconnection (either temporarily or permanently) of exisiting wiring.

MODS

A disconnector with a motor-driven operating mechanism.

modular power supply

A rack mounted power supply system comprising rectifier modules, batteries, a control module and distribution modules to make up the required supply.

momentary load

A load which can occur repeatedly but is of short duration not exceeding one minute at any occurrence.

monitored information (SCADA)

Transmitted information characterising the state, or the change in state of, equipment in a monitored station.

monobloc battery

A secondary battery in which the plate packs are fitted in a multi-compartment container. [Common monobloc voltages are 6V and 12V]. [IEC 50 (486)].

motor synchronising

Synchronising a machine by applying excitation to it after it has been accelerated to near-synchronous speed and after it has been connected to the power system.

motor-operated disconnect switch

A disconnector with a motor-driven operating mechanism.

MSDS

Material Safety Data Sheet.

MSL

A quantity of components for use in emergency situations held by a contractor in accordance with MSL criteria set down in this standard.

MTA

Maximum torque angle.

multilock

A device which has provision for a number of locks to be attached, each of which when in place will inhibit the operation of that isolation point.

multilock box

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

multilocking system

A system of locks associated with locking off safety measures.

multiple busbar station

A station having two or more busbars at the same voltage, and usually connected together at some time for operational reasons.

multiple circuit line

A transmission line carrying two or more circuits.

multiple earthed neutral

A system of electrical supply in which the neutral is connected to the earth at the point of supply; and at points on the supply system; and at every electrical installation connected to that system.

Multiplier

The Adjustment Factor multiplied by the pulse value in kWh or kW per impulse for both the data-logger and the revenue meter.

MVA

MegaVoltAmpere - the flow of active power is measured in megaWatts (MW).  When compounded with the flow of reactive power, which is measured in Mvar, the resultant is measured in MegaVoltAmperes (MVA).  MVA means 1000 kVA.

MW reserve (of a power system)

This reserve is maintained by (in approximate order of speed of response): Frequency stabilisation, Spinning reserve, Interruptible demand, Spinning reserve sharing, Automatic under frequency load shedding.