Glossary of terms and definitions

The Glossary of the main definitions listed in the present work has been adapted from [4], where a comprehensive list of the terms contained in the Swissgrid Transmission Code [26] is presented.

Term Definition

Aggregate Addition of multiple values to make a new value in accordance with predefined rules.

Ancillary Ser-vices (AS)

Ancillary services that are essential for reliable grid operation.

They comprise, in particular, system coordination, balance management, primary control, black start and island opera-tion capability of generators, voltage maintenance (including a proportion of reactive energy), operational measurements and the compensation of active power losses.

Ancillary Ser-vices Provider (ASP)

Market player offering Ancillary Services to a transmission a grid operator.

Annual Power Consumption

Total electrical energy procured by the end consumer per year.

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Balance En-ergy

Volume of electricity required for each billing unit to balance the difference between the effective import (or delivery) accord-ing to metered values and the import (or delivery) accordaccord-ing to the schedule for a specific time unit to create a zero balance billing unit for the Swiss control area.

Balance Group Contract

Contract between the Transmission System Operator and the Balance Group Manager.

Balance Group Manager (BGM)

Natural person or legal entity responsible for at least one bal-ance group (BG) vis-`a-vis the TSO and all other market players.

The BGM is responsible in particular for the timely transfer of schedules and for ensuring the zero energy balance of its billing units.

Connection Point

Refers to: 1) the location at which the grid user is connected to the grid; 2) the border marking the division of responsibility between the grid operator on the one hand and grid users on the other; 3) the interface at which energy exchange is transacted.

Control Area (CA)

Smallest system unit equipped with a load-frequency control.

A control area: 1) is responsible for primary control within its area; 2) is able to maintain power exchange at a set value; 3) cooperates to maintain the frequency at its rated value in the event of a failure; 4) is responsible for billing in its area. Each control area is physically demarcated by the transition meter-ing points that supply the exchange measurement data for the secondary controller. These metering points are also used for billing purposes and for determining unintentional deviations.

Control Power Plant

Power plant that meets the technical requirements for the pro-vision of control power.

Control Power Automatic or manually retrieved electricity for maintaining the planned electricity exchange beyond the control area or control block borders and to guarantee secure grid operations by main-taining a constant supply frequency. It is made up of primary, secondary and tertiary power.

Control Re-serve

Generation capacity made available for use as control power, consisting of primary, secondary or tertiary control reserves.

Control Center (CC)

Responsible for the acceptance and validation of exchange pro-grams between the control blocks and for accepting the meter data for the interconnecting lines between the control blocks for the purpose of calculating unintentional deviations and the resulting compensation program for balancing unintentional de-viations.

Distribution System Opera-tor

Natural person or legal entity responsible for ensuring the safe and reliable operation of a distribution system and the technical quality of the power supply. The Distribution System Operator ensures, among other things, that all the necessary contracts, processes and regulations for grid connection, grid operation and grid usage are in place at all the connection points of its distribution grid.

Distribution System

High, medium or low voltage electricity grid for supplying end consumers or electricity supply companies.

Distribution Transfer of electricity over distribution systems.

Electricity Grid

System comprising numerous lines and the necessary auxil-iary systems for the transmission and distribution of electricity.

Electricity lines extending over a small area, such as on an in-dustrial site or inside a building, do not constitute an electricity grid or network.

End Consumer Consumers who purchase electricity for their own consump-tion. This does not include the electricity consumed for a power plant’s own requirements and to drive the pumps in a pumped storage hydro plant.

Final Con-sumption

Conversion of electricity to another form of energy such as light, power, heat, etc.

Generating Unit

Unit for generating active and reactive power or active and reactive energy for feeding into the grid. The generating unit is the electricity-producing equipment of a power plant, which can fall into various categories, e.g. a block-unit power plant, generation set, cogeneration unit, power plant level, an entire cascade power plant or similar. An important criterion is the geographical location of the plant: a generating unit should normally feed into the grid at a node.

Generator Natural person or legal entity which is the owner of one or more power plants or shared power plants.

Grid Access Right to use a grid to purchase electricity from a freely chosen supplier or to feed in electricity to a grid.

Grid Cost

Contribution

Amount corresponding to usage of the distribution grid, irre-spective of whether or not grid upgrades need to be made on individual grid connections. It includes a portion of the general and local distribution costs.

Grid Level Organizational breakdown of the transmission and distribution grid into different grid levels. The Swiss Grid Usage Model is based on a division into 7 grid levels (4 voltage levels and 3 transformer levels: NE1: 220 or 380 kV; NE2: transformation, NE3: 36 kV to 220 kV; NE4: transformation; NE5: 1 to 36 kV;

NE6: transformation; NE7: 0.4 to 1 kV), to which individual costs can be allocated. Each grid user is physically assigned to one of the seven levels according to their connection.

Grid Operator Private- or public-sector company which provides grid services for operating the electricity grid.

Grid Usage Contract

The grid usage contract governs the relationship between: 1) grid operators and generators; 2) grid operators and end con-sumers; 3) grid operators with any additionally connected grids;

and 4) the relationship between the grid operator and a supplier with regard to grid usage.

Grid User Market participant that feeds electricity into or draws electric-ity from the transmission or the distribution grid. The grid user is responsible in particular for concluding grid usage contracts for all of its connection points.

Grid-use Charge

or Grid-use Costs, charge levied by the grid operator for the use of its grid by third parties.

Load Manage-ment

Management of interruptible consumer installations by the Ag-gregator.

Load Profile Energy time series over which the integration of power is de-termined for each billing period.

Load Shedding Automatic or manual emergency measure for preventing the total collapse of the grid.

Power Plant Facility for providing electrical power and generating electrical energy comprising one or more generating units.

Primary Con-trol Reserve

The positive or negative part of the primary control range mea-sured from the working point prior to the occurrence of a fault up to the maximum control power, taking account of a power limiter. The concept of the primary control reserve applies to each generator, control area/block and the entire synchronous area.

Primary Con-trol

Maintains the balance between generation and demand in a grid using turbine speed regulators. It is an automatic, de-centralized function of the turbine regulator to adjust the gen-erator output as a consequence of a frequency deviation in a synchronous grid area.

Reactive En-ergy

Electrical energy required to create electrical or magnetic fields;

used for maintaining voltage stability in the grid.

Reactive Power

Electrical power required for the creation of electrical or mag-netic fields.

Reserve Power Electricity available from power plants for maintaining the planned power exchange and for guaranteeing secure operation of the grid.

Ripple Control Technical installation for controlling tariff and illumination equipment and for disconnecting and clearing specific groups of consumers.

Schedule Time series agreed in mean power values for the delivery or consumption of electricity over a specific period.

Secondary Control Power

The part of the secondary control range already activated at the working point.

Secondary Control Re-serve

The positive or negative secondary control reserve is the part of the secondary control range between the working point and the maximum or minimum value. The portion of the secondary control range already activated at the working point is called the secondary control power.

Secondary Control

Decentralized, automatic function to regulate the generation in a control area based on secondary control reserves in order: 1) to maintain the interchange power flow of the control program with all other control areas and to correct the loss of capacity in a control area affected by a power plant failure and, at the same time; 2) (in case of a major frequency deviation originating from the control area, particularly after the loss of a large generating unit) to restore the frequency in case of a frequency deviation originating from the control area to its set value in order to free the capacity engaged by the primary control and restore the primary control reserves.

Small-scale Consumer

Power consumer with small energy and power requirements.

The Distribution System Operator can set the limits for small, medium or large-scale consumers in its grid.

Stability Refers to the ability of the electrical system (grid, generators and consumers) to maintain synchronous operation of the gen-erators and to keep all of the grid operating parameters (fre-quency, voltage, electric current) within the permitted limits.

Supplier Provider of electricity to at least one end consumer. The sup-plier must be assigned the metering points of the end consumers it supplies.

System Coor-dination

Coordination of tasks which are necessary for the operation of the Swiss Transmission System and integration in the ENTSO-E interconnected grid.

Tertiary Con-trol Reserve

The power which can be connected automatically or manu-ally under tertiary control in order to provide an adequate sec-ondary control reserve. This reserve must be used in such a way that it will contribute to the restoration of the secondary control range.

Tertiary Con-trol

Any automatic, manual or scheduled change in the working points of the generating units in order to restore the secondary control reserve at the right time.

Transmission System Opera-tor (TSO)

Legal entity responsible for ensuring safe, reliable and efficient operation of the transmission grid and the control area. The TSO in Switzerland is the national grid company swissgrid. A TSO is not necessarily the owner of the transmission system.

Transmission System

Electricity grid used to transmit electricity over long distances within the home country and to connect up with foreign grids.

Transmission systems are usually operated at the 220/380 kV voltage level.

Transmission The transfer of energy via the high and very high voltage grid (Transmission System) to supply end customers or redistribu-tors. Transmission operations include both system operations, which take into consideration power flow management, system security and the provision of all necessary Ancillary Services.