generation, transmission and distribution,
transmission and distribution
transmission or distribution of electrical energy for supply to third parties. It may also have as an objective the combined production of electrical energy and heat for supply to third parties.

4.1.1.2 Autonomous generator

An autonomous generator may be classified as an utility.
An autonomous generator is an undertaking whose principal activity is to produce electrical energy with the sole intention of sale to distributors or, via third party systems, to costumers.

4.1.2 Auto-producers

An auto-producer is an undertaking which in addition to its main activities generates electrical energy wholly or partially for its own use.

4.2 Stages during construction of a power station

The overall construction period of a power station may be divided into different periods during which specific events occur. The following definitions relate to these periods and events.

4.2.1 Planning phase

4.2.1.1 Consents received

All the necessary public/statutory consents have been received to permit the start of main site construction.

4.2.1.2 Preliminary works

Preparatory work on the site and adjacent areas including demolition, site levelling, provision of access roads, etc, prior to placing the main civil works contract(s).

4.2.1.3 Placing main contracts

Entry into a major financial commitment by placing an order for main equipment and/or major site work.

4.2.2 Under construction

Before a power station or part of a power station is classified as being under construction all the following conditions must have been met:

all consents have been received for the given site; and
preliminary work on site has commenced; and
placing main constracts has happened

4.2.3 First synchronized to the network

A generator set is first synchronized to the network when it supplies electrical energy generated from its own steam supply system, hydraulic turbine or equivalent.

4.2.4 Post-synchronising operation

If a generator set has been first synchronized to the network, but it has not yet been accepted into commercial operation then it should be classified as being in post-synchronizing operation.

4.2.5 Commercial operation

A power station or part of a power station enters from post-synchronising operation into commercial operation when full ownership and control passes to the operators.
These detailled phases concern especially thermal power stations. If a list of power stations taken into service is demanded, in general the date of the first synchronising is the fixed day.

4.3 Classification of hydro-electric head installations

Hydro-electric head installations are classified according to the use that can be made of the cumulative flow that they receive, depending on whether the cumulative flow must be used within a short period of time or whether it can be retained for a certain period. This criterion is based on the reservoir filling period "D" calculated using the annual characteristic mean flow.

4.3.1 Run-of-river head installations

These head installation normally operate on base load and use the cumulative flow continuously.

Filling period D < 2 hours

4.3.2 Storage head installations

Hydro-electric head installations storing their cumulative flows wholly or partly in their retaining works in order to generate during hours of higher demand.
According to the filling period of a reservoir it can be defined as follows:

Pondage: 2 hours < D < 400 hours

Reservoir: D > 400 hours
These head installations are normally operated in such a way as to allow load following. By extension, when the operationof a head installation is directly related to that of a reservoir upstream and the intermediate inflows are negligible, these head installations must be considered to belong to the same category as the one which governs them.

4.3.3 Different types of head installations with pumping

Pumped storage head installation or head installation with pumping are those in which water can be raised by means of pumps and stored, to be used later for the generation of electrical energy.
The basic differences between the various types of pumped storage head installation arise from the way in which the turbines and pumps are arranged in the hydraulic circuits.
In all types of pumped storage stations, the pumps and turbines are connected to one or several interconnected upper reservoir(s).
When the pumps and turbines are connected to the same lower reservoir or to reservoirs which are themselves connected, the pumping cycle can be repeated many times. A distinction must be made according to whether the upper reservoir is fed by significant natural flows.

Note: If, on the other hand, the pumps and turbines are connected to physically separate lower reservoirs without a hydraulic connection between them except by way of an upper reservoir, there can be no pump/turbine cycle as such, and the pumps have only the role of pumping into the upper reservoir the contribution of water acquired at their level. A station having this latter configuration is known by the term "station with contributory pumping".

This head installations are classified in the categories referred to in definitions above, according to the filling period of the reservoir "D"

4.3.4 Pure pumped storage head installation

A pure pumped storage head installation is one without significant natural cumulative flow into the upper reservoir.

Note: The natural cumulative flow into the upper reservoir, in an average year, permits a utilisation period of the maximum electrical capacity in the turbine mode less than or equal to 250 hours (average value in Italy and France).

4.3.5 Mixed pumped storage head installation

A mixed pumped storage head installation is one with significant natural cumulative flow into the upper reservoir.

Note: The natural cumulative flow into the upper reservoir, in an average year, permits a utilisation period of the maximum electrical capacity in the turbine mode of more than 250 hours (average value in Italy and France).

4.4 Classification of thermal power stations and other sources

A thermal power station is a power station in which the primary energy is converted to electrical energy using a thermodynamic process.

4.4.1 Conventional thermal power stations

The conventional thermal power stations comprise steam-operated generating plants with condensation (with or without extraction) or with back-pressure turbines and plants using internal combustion engines or gas turbines.

Note: In the UCTE statistics also geothermal plants and waste-fired power stations are included.

Steam turbines:
Non condensing (open cycle), also often called back-pressure turbines, as well as condensing turbines (closed cycle). Steam turbines can be fuelled by all forms of fossil fuels.
Gas turbines:
Gas turbines use high-temperature, high pressure gas as fuel and, in which part of the heat supplied by the gas is converted into rotational energy. Fuel can be natural gas, coal gases, or liquid fuels.
Diesel-type engines:
The internal combustion engine referred to here is based on the Diesel cycle, which works on the compression ignition principle. Diesel-type engines can use a variety of fuels ranging from natural gas to liquid fuels.
Combined cycle systems:
A combined cycle power station is an electrical generating installation comprising one or more gas turbines whose exhaust gases are fed to a waste-heat boiler, which may or may not be supplied with supplementary fuel. The steam raised in the boiler is used to drive a turbine coupled to a generator.
Cogeneration power station (combined heat and power):
A cogeneration power station is a thermal installation in which the energy released from fuel is transmitted to an intermediate fluid. This intermediate fluid is normally directed in its entirety to electrical generator sets, designed and equipped in such a way that energie is partly used for driving the generator sets to produce electrical energy and partly to supply heat for various purposes: industrial uses, district heating etc....

4.4.2 Nuclear power stations

A nuclear power station is a thermal power station in which the energy in nuclear fuel is converted to electrical energy.

4.4.3 Other power sources

The category other power sources includes among others wind power and photovoltaics.

4.5 Classification of fuels

Solid fuels:
Solid fuels comprise hard coal, brown coal and other solid fuels. Hard coal refers to all grades of anthracite and bituminous coal with a gross calorific value greater than 23.865 kJ/kg on ash-free but moist basis. Hard coal includes coking coal, anthracite, coke-oven coke and lignite coke.Brown coal includes sub-bituminous coal, lignite, brown coal briquette and peat briquettes.Other solid fuels comprise all fuels such as peat, wood, etc.
Liquid fuels:
Liquid fuels comprise crude oil, NGL and petroleum products, including petroleum coke, liquified petroleum gases and refinery gas.
Gaseous fuels:
Consist mainly of methane occuring naturally in underground deposits and in colliery gas, blast furnace gas, coke-oven gas and gas from municipal gas plants.
Waste and biomass:
Comprise among others wood waste, vegetable waste, industrial waste, municipal waste and sulphite lies or "black liquor".

4.6 Closed power stations (MW)

Two types can be distinguished:

A closed power station is a power station, the installations of which have been dismantled. Fixed day is the date of the definitive separation from the network.
Long term reserve capacity: Long term reserve capacity which is placed in reserve for long periods, in excess of one year. Its maximum electrical capacity is not declared as part of maximum electrical capacity of the system.

4.7 Circuit of an electrical line or cable

A circuit of an electrical line or cable is a number of electrically inseparable conductors forming a 3-phase or other system and capable of conveying electrical energy from one point to another.

4.8 Circuit length of an electrical line or cable (km)

The circuit length of an electrical line or cable is the actual length of any one of its conductors or the mean of the lengths of the conductors if there is any appreciable difference in their lengths.

4.9 Operating transmission lines

An operating transmission line is an internal 400 kV network connection of a country and/or an interconnected line > 110 kV. These network connnections are the only ones considered by the collect.

4.10 Interconnection

An interconnection is a connection (lines, cables and equipment, including transformers, etc) that may be used to convey electrical energy in either direction between networks, between power stations, or between power stations and networks.
An interconnection may exist within the limits of a single or between several undertakings, within one or between several geographical areas, within one or between several countries.
The expression interconnected network comprises all interconnected lines included in the limits mentioned above, without regard to voltage.
The expression interconnected line indicates a line providing an interconnection as defined above.
The expression interconnected countries indicates countries that are linked together by one or more interconnection(s).
The definition of interconnection and the above comments remain valid whether the connections considered are reserved exclusively for that purpose or are also used to supply consumers on their route without using an intermediate distribution network.
The term networks in parallel is reserved for interconnected networks functioning in synchronism, which is the usual condition.

4.11 Conventional transmission capacity of cross-frontier tie-lines

The conventional transmission capacity of cross-frontier tie-lines is based upon parameters standardised within UCTE for the calculation of the thermal load capability of each line.
For aerial lines these are: ambient temperature of +35°C, wind velocity of 0,56 m/s at a right angle to the line as well as the voltage value (stated in column 10 or 11 in the table T9 of the Statistical Yearbook). The conditions relevant to system operation in various countries at various time of the year can strongly differ from those above. Because the real allowable load capability of the line depends on many other factors, such as load flow distribution, upholding of voltage, real ambient conditions, limits of stability, n-1 security, etc., the conventional transmission capacity has no relevance from the point of view of system operation or economics but allows just a comparison of order of magnitude of the various lines.
Adding together the conventional transmission capacity of several tie-lines does not allow to infer on the real total transmission capability and leads to irrelevant results from the point of view of system operation

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