I stumbled across some information on: http://www.ipassoc.co.uk/publications_article12.htm
It is reproduced below as the page has a colourful background making it a bit difficult to read:
This paper describes how the Transmission and Distribution Grids have been defined in various European and FSU countries. For each country wherever possible we have detailed:
1. The voltage levels of the national transmission networks grouped into EHV, HV, MV and LV categories being:
¬∑ EHV = 220 kV,
¬∑ 35 kV = HV <220 kV,
¬∑ 1kV = MV < 35 kV,
¬∑ LV<1 kV.
2. How transmission (as opposed to distribution) is defined and what assets are included in the transmission grid (voltage levels of lines, functional criteria or geographical context to define transmission within the electricity grids).
The paper does not cover every country in each region; it concentrates on those which have implemented reform of their power sector around a horizontally split industry with the separation of generation, transmission and distribution.
Transmission voltages: EHV: 275 kV, 400 kV with some 132 kV (in Scotland and some generator circuits).
Distribution: HV: 132 kV; MV: 33kV, 20 kV (only used in one area), 11 kV; LV: 400V.
Some earlier voltages still exist: HV: 66 kV; MV: 25 kV, 22 kV, 6.6 kV, 3 kV.
The transmission network is owned by the transmission businesses of NGC, Scottish Power and Scottish Hydro-Electric (now part of Scottish and Southern Electricity) i.e. all 275 kV, 400 kV networks, and for SP and SHE all 132 kV. NGCs network only includes the 132 kV lines which form part of Scottish interconnector and dedicated lines to nuclear generators. NGC also owns reactive compensation equipment that is installed at 132 kV.
Transmission businesses are limited to defined geographic areas.
Transmission consists of 400kV, 150kV and a small amount of 66kV. Distribution generally consists of lines below 150 kV.
EHV: 380 and 220 kV.
HV: 120 (residual), 132 (northern part of the Country) and 150 kV.
Some 60-80 kV lines are still present as historical grids mainly relevant to hydro generation in mountainous areas.
MV: 10, 15, 20 kV and other residual voltages.
LV: (phase to phase voltage), 380 V.
Transmission is defined by a combination of a voltage and a functional criterion.
All lines at EHV are included in Transmission. Lines at voltage levels between 120 kV and 220 kV are included in Transmission according to the following functional criteria:
Lines connecting generation sites with installed capacity above 10 MVA, selected with the minimum distance (open-air distance) criterion to the nearest EHV substation;
Lines connecting generation sites with installed capacity above 10 MVA, serving as reserve lines to the primary circuit as identified above;
Lines potentially used in emergency conditions and for any security requirements of the national transmission grid;
Lines interconnecting the national transmission grid with foreign transmission networks (excluding possible direct lines).
The following assets are also included in Transmission:
Substations connecting the EHV with HV level, excluding the connection sites with:
- Distribution networks;
- Generation sites (including autoproducers);
- Customer sites.
Equipment necessary to (physically) operate network assets, excluding those used for the system operation (supervision and control, data acquisition, etc.);
Networks or parts of networks under construction or already authorised, which necessarily comply with the functional conditions in Item 1.
EHV: 380 and 220 kV.
HV: 150, 110 and 50 kV.
MH: 25, 20, 12.5, 10, 6, 5 and 3 kV.
LV: 400 V.
Transmission is not clearly defined.
All lines at EHV and HV are considered transmission lines. Sometimes lines at 25 kV or lower are also considered transmission lines.
EHV: 420 kV, 320 kV, 220 kV.
HV: 132 kV, 66 kV, 45 kV.
MV: 22 kV and 11 kV.
LV: 230 V and 400 V.
The National Transmission Grid (NTG) is defined as a combination of voltage level and a functional criterion. The National Transmission Grid shall:
Connect generation and distribution in different parts of the country.
Include cross-border interconnectors.
Provide grid connection points in all main regions.
Give all actors access to a common marketplace.
NTG includes all EHV lines (except radial lines that only connects generation or industrial consumers) and some 132 kV lines in regions where 132 kV is the highest voltage level.
HV lines (except 132 kV lines included in NTG) are regarded as Regional Networks. There are more than 100 regulated regional network owners that are very diversified in their size and structure. Several different regional network owners can operate in the same geographical area. About 50% of generation capacity is connected to the regional networks.
In accordance with the Portuguese Legislation, the following voltage level rating is applied in Portugal:
VHV: greater than 110 kV.
HV: greater than 45 kV and lower than or equal to 110 kV.
MV: greater than 1kV and lower than or equal to 45 kV.
LV: lower than or equal to 1 kV.
The following list refers to the voltage level available in the National transmission or distribution grids according to the required rating:
EHV: 400 and 220 kV.
HV: 150, 132 (residual) and 60 kV.
MV: 30, 15, 10 kV and other residual voltage levels (6 and 5 kV- centre and north regions).
Transmission is defined by a combination of voltage and functional criteria. All EHV lines are included in the transmission grid. The 150 kV lines and the 132 kV interconnection line (Lindoso-Conchas) belong to the transmission grid. The remaining 132 kV lines, which constitute a residual grid, belong to the distribution grid.
All 60 kV lines belong to the distribution grid. Lines connecting the transmission grid with binding and non-binding generation sites, binding and non-binding customers, and binding distributors sites are property of the entity, which operates them.
The following assets are included in Transmission:
Substations connecting the EHV with all the other voltage levels;
Equipment necessary to physically operate the grid assets, including the system operator facilities and associated assets;
Grids or parts of grids under construction or already authorised.
REPUBLIC OF IRELAND
EHV: 400 and 220 kV. One 275 kV double circuit interconnecting the Republic of Ireland (ROI)) and Northern Ireland.
HV: 110 and 38 kV.
MV: 20 and 10 kV.
LV: 220 V.
Transmission is defined by a combination of a voltage criterion and functional criteria.
All EHV lines, cables, switchgear and associated equipment is defined as Transmission. All lines, cables, switchgear and associated equipment at 110 kV voltage are part of the transmission system except certain radial feeds, summing to [243 km] out of [3886 km]. In the case of "Tail" stations from the 110 kV system to a Distribution substation, the Transmission boundary is at the remote feeding station at the line terminal of the outgoing line disconnect.
110 kV circuits and substations within the Dublin area are designated as forming part of the Distribution system, with all other 110 kV circuits and stations forming part of the transmission system.
The transmission grid is defined as including:
"Lines, equipment units, transformers and other electrical elements with voltages equal to or above 220 kV and any other installations, regardless of their voltage, whose functions include transmission or international interconnection and, where applicable, interconnections with Spanish electric power systems located on islands or outside the peninsula".
Lines with voltages equal to or above 220 kV;
International interconnections, regardless of their voltage;
Substation with voltages equal to or above 220 kV;
400/220 kV transformers;
Active and Reactive power control elements, connected to the 400 kV and 220 kV lines, and those connected to the tertiary windings of the transformers of the transmission grid;
Interconnections between the insular systems and the peninsular system, and the interconnections between the insular systems;
Those installations, regardless their voltage, that the Ministry in charge of Energy, as a result of the process of planning of the transmission grid, deems to perform a transmission function;
Any assets involving communication, protection, control, auxiliary services, land, buildings and other auxiliary items, whether electrical or not, which are required for the proper operation of specific transmission grid installations; and
The transmission control centres.
The transformers of generation groups, the connecting installations of these groups to the transmission grid, customer's installations for their exclusive use and dedicated lines are not deemed to be part of the transmission grid.
The electricity distribution grid is made up of all electrical installations below 220 kV excluding those included in the "Transmission Grid" (see above).
EHV: 400 and 220 kV.
HV: 30-130 kV.
MV: mainly 20 kV.
LV: (phase to phase voltage), 400 V.
Transmission is defined by a combination of a voltage and a functional criterion.
All lines at 400 and most at 220 kV (see below) are included in Transmission. Also included in the transmission system are:
Lines interconnecting the national transmission grid with foreign transmission networks.
EHV switching stations and substations between EHV voltages.
The EHV part of substations connecting EHV to HV, except transformers.
Equipment necessary to (physically) operate the network assets, excluding those used for the system operation (supervision and control, data acquisition, etc.).
Networks or parts of networks under construction or already authorised at EHV level or which necessarily comply with the functional conditions in Item 1.
GERMANY AND DENMARK
The power network in Germany and Denmark is owned and operated by vertically integrated regional power companies with distribution in the hands of the individual municipalities. This is a different model of ownership to that of a national transmission network serving local distribution companies and is not relevant to the comparisons in this paper.
In the newly restructured industry, post privatisation, Distribution has been set to include all lines of 110 kV and below. Transmission include all lines greater than 110kV.
The transmission network in Hungary includes the following lines: 750 kV, 400 kV, 220 kV, and 120 kV. Distribution is below 120 kV. In recent years, the Hungarian power system has become integrated into the power system of Western Europe. The connection of the Hungarian system to the West-European UCPTE system was completed in 1995. A 400 kV interconnection was put into operation between Hungary and Croatia in November 1999.
In the newly restructured industry, Transmission will be 110kV and above (330kV), with the boundary on the high voltage side of the transformer. This has been done to put the 110kV transformers with the privatised Distribution businesses, who should be able to raise capital for refurbishment/replacement more easily than the Transmission business. In the UK, the boundary would be on the low voltage side. This has been a subject of many debates in Lithuania and there is still the potential for this to change.
The high voltage transmission network comprises all electricity generated and fed into the system on the 440 kV and 220 kV level as well a limited portion of energy produced by local electricity generators connected to the 110 kV system.
Moldova has an extensive power transmission and distribution system, but much of the equipment is obsolete and poorly maintained. The high voltage transmission system has 400kV, 330kV, and 110 kV. One 400 kV interconnection with Bulgaria exists, as well as three 110 kV interconnections with Romania, and five 330 kV interconnections and nine 110 kV interconnections with Ukraine. In addition, there is also a 750 kV line passing through Moldova to connect Ukraine with Romania and Bulgaria, but this line is not directly connected into the Moldovan power system.
Under the 1997 restructuring, electric transmission and dispatch were assigned to Moldtranselectro, the state-owned company which owns the high voltage lines. The five distribution companies are Chisinau, North Western, Northern, Central, and Southern. They have lines and serve customers at the level of 35 kV down to 400 volts.
Historically transmission lines include all those of 35kV and above, including 110kV, 220kV and 500 kV. Distribution lines include 0.4 kV, 6kV and 10kV.
The Ministry of Fuel and Energy is in the process of reforming the multiple local distribution networks which have been in Municipal ownership into the East and West distribution companies, to complement the privatised network in Tblisi. As part of this all 35kV and 110kV non-systemic lines will belong to the distribution companies.
The transmission system in Kyrgyzstan operates electricity lines with the voltage from 110 kV to 1150 kV and substations. Distribution includes all lines < 110kV.