Railway Energy Glossary

Please click on each word to unfold the definition.

4th Railway Package

The 4th railway package aims to remove the remaining barriers to the creation of a single European rail area.

A three-way agreement on the “technical” files was reached by Parliament, the Council and the Commission in June 2015 and approved in Parliament’s Transport Committee in March 2016. The so-called “technical” pillar of the 4th railway reform package consists of proposals to amend the interoperability and safety directives and a regulation on the EU Agency for Railways (EUAR, former ERA).

The overall aim of the changes is to save train operators time and resources when submitting applications for required safety certifications and equally for rolling stock manufacturers when submitting applications for authorizations to place a vehicle on the market. Train operators wishing to operate in more than one member state, would be able submit applications to the EU Agency for Railways (EUAR) instead of several member states’ authorities, as they must do at present.

Alternating Current (AC)

Electric current in which the flow of electric charge periodically reverses direction.

AC is the form in which electric power is delivered to businesses and residences, and it is the form of electric power that consumers typically use when they plug kitchen appliances, televisions and electric lamps into a wall socket. Several power systems in Europe are AC based.

Association of Issuing Bodies

The AIB is a member association that attempts to coordinate rules, transfers and cancelations of energy tracking certificates within Europe.  They have recently introduced the AIB-inter registry hub to help facilitate the international exchange of energy certificates between all countries. Their website is linked: www.aib-net.org.

Automatic train protection (ATP)

Either of two implementations of a train protection system installed in some trains in order to help prevent collisions through a driver's failure to observe a signal or speed restriction

Balancing power

The reciprocation and revolving masses of any steam, diesel or electric locomotive need balancing, if it is to work smoothly. Revolving masses can easily be balanced by counterweights, but the balancing of reciprocating parts is a matter of compromise and judgement.

Catenary system

The overhead wire system used to send electricity to an electric locomotive or multiple unit, tram or light rail vehicle.


(European Committee for Electro technical Standardization. Founded in 1973)
Organization responsible for European standardization in the area of electrical engineering. Standards harmonised by CENELEC are regularly adopted in many countries outside Europe which follow European technical standards.


Certificates often refer to the vehicle used to carry the electricity attributes certified via an electricity tracking system.  In Europe, the primary certificate used by electricity tracking systems is the Guarantee of Origin or GO.  A certificate is often bought, sold and cancelled with prices determined by a supply and demand market.

Compiled Energy Billing Data (CEBD)

Dataset compiled by the DHS suitable for energy billing.

Conformity assessment

Activity to determine, directly or indirectly, that a process, product, or service meets relevant technical standards and fulfills relevant requirements. Assessment can include inspection and examination of a product, its design and manufacture.


Trainset. A group of rolling stock that is permanently or semi-permanently coupled together to form a unified set of vehicles. Consists are most often used in passenger train configurations. Electric Multiple Units (EMUs) and Diesel Multiple Units (DMUs) are examples of consists.

Consumption Point Identification (CPID)

Unique identifier allocated to each EMS installed on-board a traction unit. EN 50463:2012 defined a a CPID based on the EVN and a one-digit identifier for individual EMS on- board of the same vehicle. EN 50463:2017 adds the country code and the vehicle keeper marking.

Contact line

Conductor system for supplying electric energy to a traction unit through a current-collecting equipment. Metros are sometimes using a third rail mounted on isolators as contact line. Most railway lines have an overhead contact line, also referred to as catenary system. In that case the current-collecting equipment is called a pantograph.

Conversion (energy conversion)

Process of changing one form of energy to another form of energy.

A converter is an electrical device that converts alternating current to a different frequency. Converters were originally a combination of an electrical motor and generator. Modern converters use semiconductor technology instead of rotating machines.

Corridors (EU core network corridors)

9 core network corridors are identified to facilitate the coordinated implementation of the EU rail network. They bring together public and private resources and concentrate EU support, particularly to remove bottlenecks, build missing cross-border connections and promote modal integration and interoperability.

The 9 EU core network corridors are: 

1. The Scandinavian-Mediterranean Corridor

2. The North Sea-Baltic Corridor

3. The North Sea-Mediterranean

4. The Baltic-Adriatic Corridor

5. The Orient/East-Med Corridor

6. The Rhine-Alpine Corridor

7. The Atlantic Corridor 

8. The Rhine-Danube Corridor

9. The Mediterranean Corridor

Current Measurement Function (CMF)

Function of an Energy Measuring Function (EMF) measuring the current taken from and returned to the contact line by the traction unit.

Cycle braking

Making repeated service brake reductions in short succession to maintain a constant speed on short but steep grades.

Data collection system (DCS)

Data system that collects information from on-board Energy Measurement Systems and transfers this data to validation or settlement systems, like Erex. In Europe, all Data Collecting Systems (DCS) shall be able to collect data from all on-board Energy Measurement Systems (EMS), according to the protocol that will be defined in the 2017-version of the LOC&PAS TSI. All Member States shall have a Data Collection System (DCS) in 2019. Eress will offer this system towards its partners.

Data Handling System (DHS)

Energy data handling system for electrical locomotives and high speed trains that enables to collect and transmit energy data from energy meters to a Data Collection System (DCS).

Diesel multiple unit (DMU)

A set of diesel-powered self-propelling passenger rail vehicles able to operate in multiple with other such sets.

Direct Current (DC)

DC is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries, power supplies and power systems. Direct current usually flows in a conductor such as a wire, but can also flow through semiconductors and insulators, among others. The electric current flows in a constant direction, distinguishing it from alternating current (AC).

Distribution (Electric power distribution)

Final stage in the delivery of electric power; it carries electricity from the transmission system to individual consumers. Distribution substations connect to the transmission system and lower the voltage with the use of transformers.

Distributed power

A practice employed to move large trains through the mountains, where the power distribution relieves the lead units of the full weight of the train, making it easier to move on grades.

Dynamic braking

The use of a traction motors' output, working as generators, to retard train speed without relying solely on the air brakes.

EECS System

The EECS (European Energy Certificate System) is a standardization system for the European
Guarantees of Origin (GOs).  Nations that are members of the EECS system are easily able to trade GOs cross-border with no risk of double counting or claiming.

Electric multiple unit (EMU)

A set of electrically powered self-propelling passenger rail vehicles able to operate in multiple with other such sets

Electromagnetic compatibility (EMC)

Ability of a device to operate faultlessly in a prescribed electromagnetic environment. EMC aims to ensure that equipment items or systems will not interfere with or prevent each other’s correct operation.

Energy Calculation Function (ECF)

Function calculating energy data using input signals from the Voltage Measuring Function (VMF) and Current Measuring Function (CMF).

Energy Measurement Function (EMF)

Function comprising the Voltage Measurement Function (VMF), the Current Measurement Function (CMF) and the Energy Calculation Function (ECF).

Energy Measurement System (EMS)

System for measurement of electric energy taken from or returned (during regenerative braking) to the overhead contact line (OCL) by an electric train unit. EMSs are suitable for billing purposes and data provided by them shall be accepted for billing in all EU Member States.

EU Directives

Directives are prepared by the EU Commission after consultation with its own and national experts. The aim of a Directive is to achieve a common particular result. When adopted, directives give member states a timetable for the implementation of the intended outcome.

European 20-20-20 Targets

CENELEC standard to regulate Energy Measurement Systems (EMSs) and how they provide measurement and data suitable for billing and other initiatives, like energy management and energy saving.

The EN 50463 is divided into five parts:
EN 50463-1 – General
EN 50463-2 – Energy measuring
EN 50463-3 – Data handling
EN 50463-4 – Communication
EN 50463-5 – Conformity assessment

European Standard EN 50463

(This document is to be updated)
Cenelec standard to regulate Energy Measurement Systems (EMSs) and how they provide measurement and data suitable for billing and other initiatives, like energy management and energy saving.

The EN 50463 is divided into five parts:
EN 50463-1 – General
EN 50463-2 – Energy measuring
EN 50463-3 – Data handling
EN 50463-4 – Communication
EN 50463-5 – Conformity assessment

European Union Agency for Railways (ERA)

Following the entry into force of the technical pillar of the 4th EU Railway Package, the European Union Agency for Railways replaces and succeeds the European Railway Agency.

The “Agency” refers as from now to the European Union Agency for Railways. The Agency performs the revision of existing Technical Specifications for Interoperability (TSIs), keeps them up to date, and supports the sector in their application by issuing and publishing application guides and by dissemination and by training. When necessary, the Agency may also draft new TSIs, based on a mandate from the EU Commission. The development of TSIs is one of the basic tasks of the Agency.

European Vehicle Number (EVN)

Identifier for all vehicles. It is a number consisting of 12 digits.

Event recorder

Device that continuously captures analog and digital information from train systems. It stores data for a minimum of 48 hours. This data is used to evaluate incidents and accidents. Typical stored data includes speed, brake pressure, dynamic brake, horn activation, and track signal among others.

Frequency (Utility or power line frequency)

Frequency of alternating current (AC) in an electric power grid transmitted from a power plant to the end-user. In Europe the 50 Hz frequency is quite common.


Spacing of the rails on a railway track measured between the inner faces of the load-bearing rails.

All vehicles on a network must have running gear that is compatible with the track gauge.
As the dominant parameter determining interoperability, it is still frequently used for describing a railway network.


An electrical grid is an interconnected network for delivering electricity from suppliers to consumers. It consists of generating stations that produce electrical power, high-voltage transmission lines that carry power from distant sources to demand centers, and distribution lines that connect individual customers.

Guarantee of Origin

The Guarantee of Origin (GO) is the tracking certificate regulated in the European Directive 2009/28/EC. The GO is further standardized via the European Energy Certificate System (EECS). The EECS makes trade, cancelation and use of GOs standardized across Europe. The GO price is given by the supply and demand market.

Heavy haul

Heavy freight operations

High-voltage direct current (HVDC)

A high-voltage, direct current (HVDC) electric power transmission system (also called a power super highway or an electrical super highway) that uses direct current (DC) for the bulk transmission of electrical power, in contrast with the more common alternating current (AC) systems.

For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. For underwater power cables, HVDC avoids the heavy currents required to charge and discharge the cable capacity.

Hertz (Hz)

Unit of frequency defined as one cycle per second (number of vibrations, or cycles, per second). It is named for Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz are commonly expressed in kilohertz (103 Hz, symbol kHz), megahertz (106 Hz, MHz), gigahertz (109 Hz, GHz), and terahertz (1012 Hz, THz).

Intermodal freight

Moving goods by more than one type of vehicle. Intermodal freight can be transported using shipping containers which can easily be transferred among railway containers, ships, airplanes, and tractor-trailer trucks.

Interoperability Directive

Directive that defines the interoperability of the rail system within the European Union. Latest update: Directive (EU) 2016/797 of May 11 2016 

Kinetic energy

Is the energy that an object possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass to a stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes.

Main generator

The electric generator in a diesel-electric locomotive that is coupled directly to the prime mover and feeds electrical energy to the traction motors.


Science of measurement, including all its theoretical and practical aspects.

Network Statement

European Directive 2001/14/ EC describes the obligation for each Rail Infrastructure Manager to publish a Network Statement. These Network Statements present information on rail networks, in particular on commercial and legal access conditions. They aim to provide all train operators wishing to operate services on a given rail network with a single source of up-to-date, relevant information on a fair and non-discriminatory basis.

Notified body

In the European Union, a notified body is an organization that has been accredited by a member state to assess whether a product meets certain preordained standards.


A device mounted on the roof of an electric train or tram to collect power through contact with an overhead catenary wire.

Power braking

Pulling against the train brakes at the higher end of the locomotive's power output (e.g. notches five through eight on a conventional throttle). This is considered wasteful of fuel and brake shoes, and is therefore discouraged by most operating departments.

Power Purchase Agreement (PPA)

A PPA is a contract between the purchaser and supplier of energy.  The PPA contract lays out how much electricity the supplier has promised to place on the grid and how much the consumer will take off.  A PPA most often guarantees an electricity price beyond just guaranteeing the supply.  A PPA however can never deliver electricity attributes that are different from the grid-average unless a tracking certificate (like a GO) is transferred in combination with the electricity.

Railway Undertaking (RU)

Train company, Train Operator

Regenerative breaking

Energy recovery mechanism which slows a vehicle by converting its energy into a form which can be either used immediately or stored until needed. In electric railways the electricity generated is fed back into the railway electrification system (or supply system). 

In Erex system regenerated energy may be stored for each individual train or aggregated.

Remote Access (to energy measurement systems (EMSs))

Connection to the energy measurement device, through internet connection, for configuration and checking of settings and parameters.

Rolling stock

Any physical railway vehicle. If it is equipped with pantograph, it falls in the category “electric unit”.

Settlement System

System capable to receive Compiled Energy Billing Data (CEBD) from a Data Collecting System (DCS) intended to use it for billing. According to Commission Regulation 1301/2014, the on-ground settlement system shall be able to exchange data  with other settlement systems, validate the data and allocate the consumption data to the correct parties. This shall be done by taking into account the relevant legislation concerning the energy market.

Shunt (or current shunt resistor)

A shunt (which is a type of current sensor) is a low resistance precision resistor used to measure AC or DC electrical currents by the voltage drop those currents create across the resistance. Ohm's law V = I × R states that the Voltage (V in Volts) across a resistance (R in Ohms) is the product of the resistance and the current (I in Amps) flowing through the resistance.


Process of sorting items of rolling stock into complete train sets.


Parked trains are stabled. Trains might consume energy during stabling, e.g. for keeping the trains on a predefined temperature.

Technical Specifications for Interoperability (TSIs)

TSIs are the specifications by which each rail subsystem or part of it is covered in order to meet the essential requirements and to ensure the interoperability of the rail system within the European Unions’ high speed and conventional rail systems.

Traction supply

The electric source for the traction motors of electric trains

Traction unit

Electric locomotive or EMU.

Traffic Management System (TMS)

A Traffic Management System is responsible for keeping information about, i.e. the distance travelled, the time, the traffic type (cargo/passenger), the weight and the composition of traction units. This information is used by Erex system to collate metered data with train runs, and to decide whether or not to use the metered data or the reported payload for a train metering point (consumption point) in the settlement.


A group of rolling stock that is permanently or semi-permanently coupled together to form a unified set of equipment. Trainsets are most often used in passenger train configurations


A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. Transformers are used to increase or decrease the alternating voltages in electric power applications.

Transmission (Electric power transmission)

Bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines which facilitate this movement are known as a transmission network.


Technical specification for interoperability related to energy, including the functional requirements of the on ground data collection system (DCS) receiving data from on-board energy measurement system (EMS).


Technical specification for interoperability related to the ‘rolling stock — locomotives and passenger rolling stock’ subsystem of the rail system in the European Union.  
Regarding Clause On-board energy measurement system, 
TSI LOC&PAS defines the requirements of the EMS and TSI ENE defines the functional requirements of the DCS. 


UIC (International Union of Railways)

UIC is the worldwide organization for railway cooperation. It is active in all the fields involved in developing rail transport.

UIC leaflet 930

The Energy Billing Project organised by the UIC has elaborated the UIC leaflet 930 “Exchange of data for cross-border railway energy settlement”. The leaflet was published in November 2009.

The purpose of the UIC leaflet 930 is to:
 Describe the processes and protocols used for the exchange of energy consumption data between Infrastructure Managers which by respecting existing national systems thereby contribute to an improvement in European railway sector interoperability.
Define the technical requirements for the checking and verification of this data.
Allow Railway Undertakings to identify their genuine energy consumption and therefore pay exactly what is consumed; associate the consumption of each train to the bill and the energy price (including existing models) which will lead finally to energy savings.


Unbundled electricity is the delivery of both physical electricity and electricity tracking certificates coming to one end-consumer from two separate sources.  This means that the end-consumer may have a contract with an electricity supplier but also a contract with a GO supplier.  In this way the consumer is able to negotiate for the best price for both of the commodities. Most large corporations will choose for unbundled electricity products.


Difference between two points (per electric charge unit) measured in units of volts (energy that could be released if electric current is allowed to flow).

Voltage Measurement Function (VMF)

Function of an EMF measuring the voltage of the contact line.

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