Glossary terms beginning with G

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

A spontaneous electrochemical cell reaction in which the anode corrodes.

galvanic recycling plant

A plant designed to recover gas from equipment, compress it into storage containers through a particle pre-filter, evacuate the equipment, and process the gas through a filtration system to remove moisture and decomposition products.

gapless arrester

The maximum permissible rms value of power frequency voltage which can be applied continuously between the line and earth terminals of an arrester without exceeding the thermal rating of the arrester elements.

gas diverter

A pressure relief device.

gas flooding area

Any area, space or enclosure subject to deliberate flooding by a non-flammable gas, e.g. machine enclosures, .switchrooms, etc.

gas hazard area

The defined area or location in which leakage of a flammable gas or gas mixture into the air may cause the concentration in air of the gas or gas mixture to exceed the gas-free limit. [SR-EI April 1995].

gas recovery plant

A device for removing SF6 gas from equipment and reclaiming it by removing moisture and decomposition products (solid and gaseous) and storing the gas in integral pressure vessels or external gas cylinders.

gas turbine

A heat engine which uses the energy of expanding gases passing through a multi-stage turbine to create rotational power.

gas-free

A condition where the gas concentration is below the gas-free limit. [SR-EI April 1995].

gas-free limit

The lower of the published threshold limit value for the gas in air, or 25% of the lower explosive limit of the gas in air. [SR EI April 1995].

gas-insulated metal-enclosed switchgear

Metal-enclosed switchgear in which the insulation and arc extinction is obtained by an insulating gas, usually SF6.

gas-operated relay

A device placed in the oil line between the transformer and the conservator to detect fault conditions. A surge of oil or gas from an explosive fault will give a trip, removing the transformer from service. It will also collect gas from incipient fault or air from within the transformer and initially give an alarm, and, if it continues, a trip. A slow lowering of oil below the relay level will initially give an alarm then a trip. Buchholz is used as a generic name for this type of gas relay. (Related term: surge relay).

generating set

A group of rotating machines transforming mechanical or thermal energy into electricity. Note: For the purposes of the operating codes and the output ratings referred to, the set is taken to include the limitations of the energy source, turbine, generator, cable, set transformer and switchgear. [GOSP glossary - IEC 50 (602-02-01)].

generation

The electrical energy produced by a generator, a generating station or within a power system as a whole.  The process of producing electricity.

generator

A person who owns and/or manages one of more generating sets which are physically connected to the grid assess or to a network or to other assets connected to the grid assets.

generator ciruit-breaker

A circuit-breaker in series with a generator which interrupts output from the generator.

generator stability

The characteristic which determines a generator's normal operating envelope and its ability to regain it after a disturbance.

generator transformer

A power transformer through which the output of the generator is transmitted (usually with a step-up in voltage) for connection to the power system.

Geneva mechanism (tap-changers)

A method of operating the selector and diverter switches in the correct sequence in an on-load tap changer (OLTC).

GIS

Metal-enclosed switchgear in which the insulation and arc extinction is obtained by an insulating gas, usually SF6.

GIS switchgear group

A circuit-breaker and related disconnectors, earth switches, integral instrument transformers, SF6 bushings, wall/roof bushings, feeder cable boxes, and metal-enclosed SF6 enclosures. The relationship is determined by switchgear numbering.

GLC kit

Ground laid cable fibre optic restoration kit.

GMC

Gross maximum capacity.

good industry practice

In the case of: the grid asset owner, the exercise of that degree of skill, diligence, prudence, foresight and economic management which would reasonalbly and ordinarily be expected from a skilled and experienced asset owner engaged in the managent of a transmission network under the same or similar circumstances as apply in New Zealand at the time; and the system operator, the exercise of that degree of skill, diligence, prudence, foresight and economiuc management, as determined by reference to good international practice and which would reasonably and ordinarily be expected from a skilled and experienced system operator engaged inthe co-ordination of an integrated transmission network under the same or similar circumstances as apply in New Zealand at the time; and  a connected pary, asset owner or dispatch customer, the exercise of that degree of skill, diligence, prudence, foresight and economic management which would reasonably and ordinarily be expected from a skilled and experienced asset owner engaged in the conveyance generation or consumption of electricity (as the case may be) under the same or similar circumstances as apply in New Zealand at the time.

governor system

A mechanism for regulating the speed of a synchronous generator, during variations in input power or load.

GPS receivers

Global Positioning System receivers, refers to satellite positioning data.

gravity loads

Means vertical loads as a result of gravity acting on objects with defined mass.

gravity oil interceptor

gravity oil interceptor

greenhouse gas emissions

The Kyoto Protocol greenhouse gases accounted for within carbon footprint calculations are: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6).  The universal unit of measurement ‘CO2 equivalent’ is used. This standardises gases in terms of their global warming potential relative to carbon dioxide, and is expressed in terms of the GWP of one unit (1 kg) of CO2e.  For example, methane (CH4) has 35 times the global warming potential of CO2; therefore 1 kg of methane would be expressed as 35 kg of CO2e.

grid

That part of the New Zealand electricity transmission system, the operation of which is undertaken by the grid operator.

grid asset owner

Transpower New Zealand Limited.

grid assets

At any time, the plant, transmission lines and other facilities owned or managed by the grid asset owner which are used to interconnect all the points of connection for connected parties.

grid CBs

Circuit breakers over which the control centres have operational control.

Grid Constraint Notice

Advice issued by the grid operator in accordance with section 3.4 of the Dispatch Code.

grid controller

The control centre employee responsible for grid planning and switching operations.

grid emergency

Any of the following is considered to be a grid emergency for the purposes of the Grid Operating Security Policy:either the frequency or the voltage are markedly outside normal limits and urgent action is required either to avoid damage to equipment or to avoid a grid collapse; there is an actual imbalance between supply and demand (beyond the capacity of the frequency regulating reserves), or such an imbalance is anticipated by the grid operator; or there is a loss of communication that affects or is likely to affect the operation of the grid.

grid exit point

A point of connection where electricity may flow out of the grid.

grid injection point

A point of connection where electricity may flow into the grid.

grid interface

The equipment used to make a connection to the grid, including associated protection and communication systems. The term includes the interface between parts of the grid.

grid operator

The organisation given responsibility by the New Zealand Government for the operation of the grid (currently Transpower).

grid owner

An asset owner for part or all of the grid.

grid plan

Daily list of grid outages, includingg IT systems, detailing security implications and required actions.

grid security situation

A situation declared by the grid operator in accordance with section 5.1.3 of the Grid Security Code.

grid security warning

A warning issued by the grid operator in accordance with section 5.1.2 of the Grid Security Code.

grid support contract

Contract to support the grid such as demand response or voltage support.

grid system

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

ground

Ground defines the level at which walking or vehicle access to a structure area is normally available.

ground crew

Ground-based personnel providing support related to helicopter activities.

grouped cooling towers

Term used in TP.MS 40.08 to define the groups of cooling towers on site, as related to the item of plant the group of cooling towers is serving. (This asset is a dummy asset used to assign weekly and monthly checks done on all cooling towers as a group. The maintenance outcomes for this equipment type, as outlined in this standard, deal with the demands of water quality in the cooling towers.).

GT

A heat engine which uses the energy of expanding gases passing through a multi-stage turbine to create rotational power.

guard

Analogue tone at the normal test frequency.

GXP meter

A meter that is not a local service meter that measures, alone or in conjunction with a local service meter the energy transmitted for connected parties through a point of connection.