Glossary
A
- AC
Alternating Current. An electric current that reverses directions at regular intervals. In New Zealand’s electricity system this occurs 50 times a second.
B
- Backbone projects
Backbone projects typically increase the capacity on Transpower's main 220 kV network.
C
- Commerce Commission
The regulatory body with responsibility for regulating Transpower’s operational and capital expenditure.
- Committed project
A committed project is one which has received Commerce Commission approval (if necessary) or is the subject of a signed agreement between Transpower and one of its customers.
- Conductors
Conductors (or wires) carry the electricity along the transmission line. They are made of copper or steel-reinforced aluminium.
- Cost band
- A:up to $5 million
- B:$5 - $10 million
- C:$10 - $20 million
- D:$20 - $50 million
- E:$50 - $100 million
- F:$100 - $300 million
- G:$300 million plus
D
- DC
Direct Current. An electric current that does not reverse and flows in only one direction.
- Designation
A designation is a provision in a district plan which provides notice to the community of an intention by a requiring authority (like Transpower) to use land in the future for a particular work or project. Once a site is designated for a particular purpose, the requiring authority is able to proceed with the specific work and control activities that occur on the site. The requiring authority can apply to the Minister of Lands to compulsorily purchase or lease all or part of the land under the Public Works Act 1981. The landowner can also apply for an order obliging the requiring authority to enter a purchase or lease arrangement.
- Distribution Network
The companies that own and maintain the local electricity lines and cables that deliver power to homes and businesses. There are 28 lines companies in New Zealand.
E
- Easement
An easement is a written agreement under which one party receives a right and benefit from another. In the case of a transmission line easement, it conveys the right of Transpower to construct, operate, maintain and upgrade a transmission line over a strip of land, which is defined in an easement transfer. The landowner retains the right to use the easement land subject to some restrictions related to operation of the transmission line.
- Electric Fields
Electric fields can occur naturally or be man made. Electric fields are produced by the voltage on a wire. The higher the voltage, the stronger the electric field. The strength of an electric field is measured in thousands of volts per metre (kV/m). Electric fields are strongest close to their source and drop off quickly as we move away from the source. All Transpower's new lines are designed and operated so that they comply with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines for electric and magnetic fields.
- Electricity Authority
The body set up to oversee and administer the Electricity Industry Participation Code.
- Electricity Commission
Between 2003 and 2010 the government appointed body with responsibility for managing rules and regulations governing the operation of the electricity sector. From 1 November 2010, governance of the industry passes to the Commerce Commission and the Electricity Authority.
- EMF
With regard to transmission lines EMFs are strongest close to the wires and become weaker further away from the wires. Electric and magnetic fields (EMFs) are present wherever there is electricity – including in the home, office and worksite.
G
- Grid Planning Process
Forms the foundation of Transpower's grid planning activities. It includes a generic part common across all projects (such as consideration of the Energy and Grid Development Strategies) and a part specific to individual projects (such as the process for identifying a need and options).
H
- HVDC
High Voltage Direct Current. The main advantage of direct current over alternating current is a reduction in transmission losses. However, it is expensive to convert normal AC power to DC power and back again. HVDC is generally only cost-effective if moving more than 500 MW further than about 500 km.
I
- Indicative Cost
- see Cost band
K
- Kilowatt Hour
- The use of 1,000 watts of electricity for one full hour
- 1 kWh = ten 100 watt bulbs all burning at the same time for one hour
- 10 bulbs x 100 watts each x 1 hour = 1,000 watts hours or 1kWh
- 1000 kWh = 1 MWh (Megawatt hour)
- 1,000,000 kWh = 1 GWh (Gigawatt hour).
L
- Lines Company
- see Distribution Network
M
- Magnetic Fields
Magnetic fields can occur naturally or be man made. Magnetic fields are produced by the flow of electric current through a wire. The higher the current, the stronger the magnetic field. The strength of a magnetic field is measured in micro tesla (mT). When a piece of electrical equipment is switched off, there is no flow of current so there is no magnetic field. Magnetic fields are strongest close to their source and drop off quickly as we move away from the source. Unlike Electric Fields the strength of a magnetic field is not influenced by the voltage on the wire at all. All Transpower's new lines are designed and operated so that they comply with the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines for electric and magnetic fields.
- Maximum Approval Cost
The maximum amount that the Commerce Commission has approved for this project.
N
- N-1
A reliability standard for transmission planning. A transmission network planned to n-1 will continue to supply load uninterrupted when a single asset (circuit, transformer, generator) disconnects from the power system.
- N-g-1
A reliability standard for transmission planning. A transmission network planned to n-g-1 will continue to supply load uninterrupted when both a transmission asset and the single largest generator disconnect from the power system.
- Notice of Requirement
The document that lets a Local Authority know that a designation is required under the Resource Management Act 1991 (RMA). It must also contain an Assessment of Environmental Effects (AEE). A notice of requirement must go through a public notification, recommendation and decision making process before it is confirmed as a designation in the authority's district plan.
P
- Pole 1
The name of the converter systems of an HVDC link that convert the voltage from AC to DC and back again.
- Poles or Towers
Poles and Towers are support structures that have crossarms to hold the conductors clear of the ground. Towers are sometimes referred to as pylons.
- Proposed project
A proposed project is one which has been proposed to the Commerce Commission but has not yet been approved.
R
- Regional projects
Regional projects are often site-specific projects, or otherwise involve the lower capacity and regional 110 kV networks.
- Requiring Authority
Transpower is a requiring authority under the Resource Management Act. Only requiring authorities can require that land be designated, by lodging a notice of requirement to the relevant Local Authority.
T
- Thermally Uprate
Thermal uprating increases the operating temperature of a line to allow more current to be carried. To maintain safety clearances, this typically requires the conductors to be retensioned.
- Transformer
A device that raises or lowers the voltage or force of AC electricity.
- Transmission Circuit
Each transmission line carries one or two transmission circuits (and on rare occasions, three or four). Each circuit comprises a set of three conductors (wires) and is an electrical connection between two substations.
V
- Volt
A unit for measuring the force used to produce an electric current; the push or force that moves electric current through a conductor. 1 Kilovolt = 1000 volts.
- Voltage Support
Voltage is the electromotive force (pressure) that transfers power along transmission lines. In long transmission lines, this force may reduce too much by the time it reaches its destination, increasing the risk of voltage collapse. Equipment like capacitors, static var compensators and synchronous condensers are installed to provide reactive support by "propping up" the voltage to within an acceptable range.
W
- Watt
A unit for measuring electric energy.
- 1 Kilowatt = 1000 watts
- 1 Megawatt = 1,000,000 watts
- 1 Gigawatt = 1,000,000,000 watts.
- Wires
- see Conductors
