The amount of electrical energy supplied by the electricity service utility to ultimate consumers of the network under consideration.
The amount of net electrical energy produced or directly imported from abroad by industrial or commercial concerns on the network and used directly for their own needs or to directly supply ultimate consumers.
The amount of electrical energy consumed by establishments (offices, workshops warehouses etc) of the electricity service utilities, but excluding the electricity absorbed by the auxiliaries of the power stations and the losses in the main transformers of the power stations, and that consumed for pumping and the network losses. These consumptions are commonly called "consumptions of the electricity sector" or "own" consumptions.

2.2 National electrical consumption (GWh)

The national electrical consumption is the net electrical consumption including the network losses without consumption for pumped storage.

2.3 Electrical energy supplied to the network (GWh)

The electrical energy supplied to the network is the energy, that has to be delivered, to ensure the required supply to meet the national electrical consumption.
In the special case of a national network this is equal to the sum of the net electrical energy production supplied by all power stations within the country, reduced by the amount used simultaneously for pumping and reduced or increased by exports to or imports from abroad.

2.4 Electrical energy absorbed by pumping/Consumption of pumps (GWh)

The electrical energy absorbed by the motor-pumps in raising the water into the upper reservoir for the generation of electrical energy. It should include the electrical energy consumed by the auxialiary equipment and transformer losses during pumping.

2.5 Gross electrical energy production (GWh)

The gross electrical energy production of a unit , a power station, a group of power stations, a region or a country during a given period, is the sum of the electrical energy production by all the generating sets concerned measured at the output terminals of the main generators.

2.6 Electrical energy absorbed by generating auxiliaries (GWh)

The electrical energy absorbed by generating auxiliaries is the sum of the auxiliary power consumptions for all the generator sets under consideration during both the on-load and off-load periods of the generator sets.

2.7 Losses in the main generator transformers (GWh)

The energy losses occurring in the main generator transformersduring both the on-load and off-load periods of the generator sets. The losses may be either measured or evaluated.

2.8 Net electrical energy production (GWh)

The net electrical energy productionis equal to the gross electrical energy production less the electrical energy absorbed by the generating auxiliaries and the losses in the main generator transformers.

2.9 Energy capability (GWh)

The energy capability or potential energy of a hydro-electric head installation during a given period of time is the maximum quantity of electrical energy which all the observed corrected inflows, limited to the plant capacity flow, would enable it to produce under the most favourable conditions.

Note: This theoretical definition implies that the management of the reservoirs has been carried out with the aim of optimising the efficiency whilst minimising losses with a time allowance over and above the period to which the energy capability is referred. This value should therefore not be deduced from the operating results, since the latter are the consequences of reserve management rules which comply with economic requirements that may vary over the years.

For more detailled informations the use of UNIPEDE-Terminology is recommended.

2.10 Mean energy capability (GWh)

The mean energy capability of a head installation is the average of the energy capabilities of a series of years which is as long as possible (minimum 10 years, but in the case of new installations one takes the data on which the plant was based). Different mean energy capabilities are only homogeneous and comparable with each other if they are determined by taking into account the same years and they refer to a given type of plant.

2.11 Energy capability factor of a hydro-electric region (%)

The energy capability factor of a hydro-electric region for a given period is the result obtained by dividing its given energy capability by its mean energy capability, both quantities relating to the same period and to the same installations within this region. It denotes the relative value of the corrected flows related to specific plant.
Different energy capability factors for one or more regions are only homogeneous and comparable if they are calculated with reference to the same data and hence the same plant and to a common series of years for the determination of the mean energy capabilities.

2.12 Electrical energy capability of a reservoir (GWh)

The electrical energy capability of a reservoir is the amount of electrical energy which could be produced from its own generating head installation and from all head installations downstream thereof by using its normal operating capacity in the turbines. This is assumed to be carried out without natural inflows and excluding all water losses.
In considering which power stations to take into account downstream they extend theoretically as far as the sea or the limit of the country. When practical necessity requires limitation of this extent downstream to the boundaries of the supply area or of the country, this limitation should be stated in the statistics. Generally, the less important downstream power stations may be neglected if their inclusion presents too much difficulty.

2.13 Operating electrical energy reserve of a reservoir (GWh)

The operating electrical energy reserve of a reservoir at a given moment is the electrical energy which could be produced from its own head installation and from all head installations downstream thereof by using its operating water reserve at that moment. This is assumed to be carried out without natural cumulative flows and at a rate which excludes any loss of water.

2.14 Reservoir electrical energy fullness factor (%)

The reservoir electrical energy fullness factor at a given moment is the result obtained by dividing its operating electrical energy reserve at that moment by its electrical energy capability. This concept can be extended to cover a group of reservoirs.

2.15 Imports/exports (GWh)

The imports/ exports refer to values, that take into account the physical exchanges on the cross-frontier transmission lines, but in addition also:

exchange values on lines < 110 kV outside of the interconnected transmission system.
on the other hand values resulting with regard to international contracts (water claim).

For presenting the operation of the interconnected transmission system only interconnected transmission lines, which are registered in these terms, are taken into consideration.

2.16 Exchange of physical electrical energy (GWh)

The exchange of physical electrical energy can be represented as the balance (difference imports/exports) or the volume (sum imports/exports) of the energy flows transmitted between neighbour countries.

2.17 Auto consumption (GWh)

The auto consumption of a utility is the electrical energy used for his own economic activity and derived from auto production.
This value may be equal to:

either the total auto-production of electrical energy
or the total auto-production less the electrical energy delivered to other consumers.

2.18 Network losses (GWh)

The network losses occuring in transmission and distribution networks are calculated as the difference between the electrical energy supplied to the network and the net electrical consumption.

2.19 Transmission network losses (GWh)

The losses of a transmission grid are the difference between the fed-in and the delivered energy. Own needs for the operation of the grid are included. So the losses represent all energy needed for transportation of electrical energy from the supplier (power plants and import) to customers (export and pumping).
Remark: The data on losses collected in UCTE are the losses of the 380 kV and 220 kV network, including losses of internal transformers (380 kV <--> 220 kV) and losses of transformers towards HV-networks < 220 kV. When, depending on network topology, HV-networks of a voltage < 220 kV are considered to be integral part of the transmission system, then their losses are also included.

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