Railway Application - Fixed Installations - Specification for reversible d.c. substations

This Technical Report provides recommendations for DC reversible substations. These recommendations apply to systems and components that facilitate the flow of energy to and from the upstream AC grid including their related interfaces. These recommendations provide the necessary functions for the recovery of braking energy. It is intended to be used in fixed electrical installations with nominal voltage not exceeding 3 000 V DC which supply electrical power to vehicles used in public guided transport systems, i.e. railway vehicles, tramway vehicles, underground vehicles and trolley-buses It is intended to provide an overview of state-of-the-art applications, define the minimum recommendations that are presently available, and provide functional recommendations to be applied to these substations. This document focuses mainly on the substation converters and the traction transformers. Other devices such as switchgear - if they are the same as in classic substations - are not addressed here. Moreover this specification addresses performance, constraints, validation and acceptance criteria for the implementation of reversible substations. This document provides the minimum recommendations to be fulfilled. However, due to the different possible solutions and different types of existing technologies, this document does not provide technical specifications of the basic components that facilitate the functionalities described.

Bahnanwendungen - Ortsfeste Anlagen - Spezifikation rückspeisefähiger Unterwerke für Gleichstrombahnen

Applications ferroviaires - Installations fixes - Spécification pour sous-stations réversibles à courant continu

Železniške naprave - Stacionarne naprave - Specifikacija za reverzibilne d.c. podpostaje

To tehnično poročilo določa priporočila za reverzibilne d.c. podpostaje. Ta priporočila veljajo za sisteme in komponente, ki olajšajo pretok energije v omrežje AC in iz njega, vključno s povezanimi vmesniki.
Ta priporočila določajo obvezne funkcije za obnavljanje zavorne energije. Standard je namenjen za uporabo v stacionarnih električnih napravah z nazivno napetostjo, ki ne presega 3000 V DC, ki dovajajo električno energijo vozilom, ki se uporabljajo v javnih vodenih transportnih sistemih, tj. železniških vozilih, tramvajskih vozilih, podzemnih vozilih in trolejbusih.
Namenjen je zagotavljanju pregleda najsodobnejših naprav, določitvi minimalnih priporočil, ki so trenutno na voljo, in zagotavljanju funkcionalnih priporočil za uporabo pri teh postajah.
Ta dokument se osredotoča predvsem na pretvornike za podpostaje in transformatorje vleke. Druge naprave, kot so stikalne naprave (če so enake kot pri običajnih podpostajah), niso obravnavane v tem standardu. Poleg tega ta specifikacija obravnava zmogljivost, omejitve, validacijo in kriterije sprejemljivosti za izvajanje reverzibilnih podpostaj.
Ta dokument podaja minimalna priporočila, ki morajo biti izpolnjena. Vendar pa zaradi različnih možnih rešitev in različnih vrst obstoječih tehnologij ne zagotavlja tehničnih specifikacij osnovnih komponent, ki olajšajo opisane funkcije.

General Information

Status
Published
Publication Date
10-Dec-2015
Current Stage
6060 - Document made available
Due Date
11-Dec-2015
Completion Date
11-Dec-2015

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SLOVENSKI STANDARD
SIST-TP CLC/TR 50646:2018
01-oktober-2018
Železniške naprave - Stacionarne naprave - Specifikacija za reverzibilne d.c.
podpostaje

Railway Application - Fixed Installations - Specification for reversible d.c. substations

Bahnanwendungen - Ortsfeste Anlagen – Spezifikation rückspeisefähiger Unterwerke für

Gleichstrombahnen

Applications ferroviaires - Installations fixes - Spécification pour sous-stations réversibles

à courant continu
Ta slovenski standard je istoveten z: CLC/TR 50646:2015
ICS:
29.280 (OHNWULþQDYOHþQDRSUHPD Electric traction equipment
SIST-TP CLC/TR 50646:2018 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CLC/TR 50646:2018
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SIST-TP CLC/TR 50646:2018
TECHNICAL REPORT CLC/TR 50646
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
December 2015
ICS 29.280
English Version
Railway Application - Fixed Installations - Specification for
reversible d.c. substations

Applications ferroviaires - Installations fixes - Spécification Bahnanwendungen - Ortsfeste Anlagen - Spezifikation

pour sous-stations réversibles à courant continu rückspeisefähiger Unterwerke für Gleichstrombahnen

This Technical Report was approved by CENELEC on 2015-10-26.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2015 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. CLC/TR 50646:2015 E
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Contents Page

European foreword ............................................................................................................................................. 4

Introduction ........................................................................................................................................................ 5

1 Scope ...................................................................................................................................................... 6

2 Normative references ........................................................................................................................... 6

3 Terms, definitions and abbreviations ................................................................................................. 6

3.1 Terms and definitions ........................................................................................................................... 6

3.2 Abbreviations ........................................................................................................................................ 7

4 General ................................................................................................................................................... 8

4.1 Application of reversible substation ................................................................................................... 8

4.2 Energy efficiency analysis ................................................................................................................... 8

4.3 System architecture .............................................................................................................................. 8

4.4 Braking safety ..................................................................................................................................... 10

5 Standard performances ...................................................................................................................... 10

5.1 General recommendations ................................................................................................................. 10

5.2 Performance of the system ................................................................................................................ 10

5.2.1 Power rating ........................................................................................................................................ 10

5.2.2 Energy efficiency ................................................................................................................................ 10

5.2.3 Harmonics and reactive power compensation ................................................................................ 10

5.2.4 Additional recommendations............................................................................................................. 11

5.2.5 Safety .................................................................................................................................................... 11

5.2.6 Availability ........................................................................................................................................... 11

6 Constraints .......................................................................................................................................... 11

6.1 Climatic environment .......................................................................................................................... 11

6.2 Electromagnetic compatibility ........................................................................................................... 11

6.3 Harmonic content ................................................................................................................................ 11

6.4 Interfaces with operational environment .......................................................................................... 11

6.4.1 General ................................................................................................................................................. 11

6.4.2 Installation ........................................................................................................................................... 11

6.4.3 Power supply and distribution .......................................................................................................... 12

6.4.4 Monitoring ............................................................................................................................................ 12

6.4.5 Rolling stock ........................................................................................................................................ 12

6.4.6 Operation ............................................................................................................................................. 12

7 Functional aspects .............................................................................................................................. 12

7.1 General ................................................................................................................................................. 12

7.2 Energy regeneration ........................................................................................................................... 13

7.3 Power quality ....................................................................................................................................... 13

7.3.1 General ................................................................................................................................................. 13

7.3.2 Substation voltage and load balancing ............................................................................................ 14

7.3.3 Harmonic compensation .................................................................................................................... 14

7.3.4 Reactive power optimization.............................................................................................................. 14

7.4 Protection functions ........................................................................................................................... 14

7.5 Automatic converter configuration ................................................................................................... 15

7.6 Substation control and monitoring ................................................................................................... 15

7.7 Centralized control function .............................................................................................................. 16

8 System simulation and equipment sizing ........................................................................................ 16

8.1 General ................................................................................................................................................. 16

8.2 Energy consumption computation .................................................................................................... 17

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8.3 Rating of equipment ........................................................................................................................... 17

9 Further standardization needs .......................................................................................................... 18

Bibliography ...................................................................................................................................................... 20

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European foreword

This document (CLC/TR 50646:2015) has been prepared by CLC/SC 9XC “Electric supply and earthing

systems for public transport equipment and ancillary apparatus (Fixed installations)”.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights.

This document has been prepared under a mandate given to CENELEC by the European Commission and the

European Free Trade Association.
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Introduction

This document originates from the Technical Specification issued by UIC/UNIFE on the same topic, and was

offered as a CENELEC Technical Report. The purpose of this Technical Report is to provide recommendations

for reversible DC substations.

Reversible substations are capable of feeding the train regenerative braking energy (up to 100 %) back to the

AC high voltage distribution network, while maintaining the capability of exchanging energy between trains on

the DC line. A substantial amount of energy can be saved for DC systems which operate electric trains fitted

with regenerative braking, on commuter services or operating on steep gradient lines. The system receptivity

can be improved by feeding the excess regenerative braking energy to the upstream AC network (e.g. AC

railway network or national grid) at a higher voltage level.

This document provides recommendations if DC Reversible Traction Substations are installed to improve line

receptivity of DC power supply networks. This document is suitable for newly manufactured traction substations

as well as for upgrading and renewal of existing lines. This technical recommendation aims at improving the

energy efficiency of the DC transport system, reducing energy consumption, and contributing to a greener

environment.
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1 Scope

This Technical Report provides recommendations for DC reversible substations. These recommendations apply

to systems and components that facilitate the flow of energy to and from the upstream AC grid including their

related interfaces.

These recommendations provide the necessary functions for the recovery of braking energy. It is intended to be

used in fixed electrical installations with nominal voltage not exceeding 3 000 V DC which supply electrical

power to vehicles used in public guided transport systems, i.e. railway vehicles, tramway vehicles, underground

vehicles and trolley-buses

It is intended to provide an overview of state-of-the-art applications, define the minimum recommendations that

are presently available, and provide functional recommendations to be applied to these substations.

This document focuses mainly on the substation converters and the traction transformers. Other devices such

as switchgear - if they are the same as in classic substations - are not addressed here. Moreover this

specification addresses performance, constraints, validation and acceptance criteria for the implementation of

reversible substations.

This document provides the minimum recommendations to be fulfilled. However, due to the different possible

solutions and different types of existing technologies, this document does not provide technical specifications of

the basic components that facilitate the functionalities described.
2 Normative references

The following standards, in whole or in part, are normatively referenced in this document and are essential for

its application. For dated references, only the cited edition applies. For undated references the latest edition of

the referenced document (including any amendment) applies.

EN 50160, Voltage characteristics of electricity supplied by public electricity networks

EN 50163, Railway applications — Supply voltages of traction systems

EN 50327, Railway applications — Fixed installations — Harmonisation of the rated values for converter groups

and tests on converter groups

EN 50328:2003, Railway applications — Fixed installations — Electronic power converters for substations

EN 50329, Railway applications — Fixed installations — Traction transformers

EN 50388, Railway Applications — Power supply and rolling stock — Technical criteria for the coordination

between power supply (substation) and rolling stock to achieve interoperability

IEC 60050, Electropedia: The World's Online Electrotechnical Vocabulary ("IEV Online")

3 Terms, definitions and abbreviations
3.1 Terms and definitions

For the purpose of this document, the terms and definitions given in IEC 60050 and the following apply.

3.1.1
contact line

conductor system for supplying electric energy to vehicles through current-collecting equipment

[SOURCE: IEC 60050-811-33-01:1991]
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3.1.2
dynamic braking

use of the electrical machine of the traction unit as a generator during the braking phase in order to achieve

speed reduction and thus convert the kinetic energy of the traction unit during its braking phase into electrical

energy
3.1.3
electronic power converter

operative unit for power conversion comprising one or more sets of semiconductor devices

[SOURCE: IEC 60050-551-12-01:1998, modified – The definition was shortened and the Note and figure

contained in the original definition are not reproduced here.]
3.1.4
minimum threshold voltage
thi

lower limit of the DC output voltage range within which Reversible Substation can work in inverter mode

3.1.5
regenerative braking energy
net energy coming from the dynamic braking and injected into the contact line
Note 1 to entry: It does not include on board losses and auxiliary load.
3.1.6
reversible substation
RSS

traction substation that allows the flow of energy from the contact line to the upstream grid (railway network or

national grid)
3.1.7
semiconductor device

device whose essential characteristics are due to the flow of charge carriers within a semiconductor

[SOURCE: IEC 60050-521:2002, 521-04-01]
3.1.8
vehicle
single item of rolling stock

Note 1 to entry: Examples of a single item of rolling stock include a locomotive, a coach and a wagon.

[SOURCE: IEC 60050-811-02-02:1991]
3.2 Abbreviations
AC: Alternating Current
DC: Direct Current
EMC: Electro-Magnetic Compatibility
EMI: Electro-Magnetic Interference
IGBT: Insulated Gate Bipolar Transistor
RSS: Reversible Substation
TSI ENE: Technical Specification for Interoperability for Energy subsystem
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4 General
4.1 Application of reversible substation

Existing standards provide requirements for the power supply system at the interface between traction units and

fixed installations: EN 50163 for feeding voltages and frequency levels and their variations in different situations

and EN 50388 for technical criteria for coordination between rolling stock and power supply to achieve

interoperability.

These standards consider the aspect of vehicle regenerative braking energy that can be reused as follows:

• on-board for auxiliary devices or heating/ventilation/air-conditioning functions; the on-board demand is

usually far too low to absorb all the braking power supplied;

• other trains: energy is used by other trains taking power in the vicinity. This depends on traffic density,

headways, and the profile of line voltage.

In classic DC systems, if the energy is not fully recovered by the above means, the energy will be lost and

dissipated into brake resistors, generally on-board, or in mechanical braking, contributing to energy waste and

thermal losses. Besides being energy inefficient, if used in a confined environment (such as tunnels and

underground passenger stations), it can significantly increase the temperature of that environment and affect

the air quality caused by brake pad dust.

If the DC railway system is fitted with energy storage systems (on-board or trackside) and/or with reversible

substations (RSS), the wasted energy can be reused or in the case of RSS, fed back into the upstream AC

railway network, in the same way as that for AC electric traction systems.

The reversible substation allows the transfer of regenerative braking energy - combination of kinetic and gravity

energy for steep gradient lines - to the upstream network. Furthermore, the amount of regenerative energy that

is transferred is not limited by the upstream network.

The TSI ENE requires the use of traction unit regenerative braking capability as a service brake, in AC or in DC

systems, to promote energy efficiency. Additionally, the interoperability billing system encourages Railway

Undertakings to be charged in the future for the net energy consumption of their trains.

4.2 Energy efficiency analysis

The technical analysis of energy savings shows that the optimum use of dynamic braking on DC lines can

achieve the following:

• improving the line receptivity on DC networks to nearly 100 % in normal and degraded mode as it is the

case for AC power supply system,
• minimizing system losses,
• giving priority to energy exchange between vehicles,

• suppressing rheostat braking without transferring the additional load onto the mechanical braking which will

reduce heat dissipation, mass and volume of on-board equipment.

Additionally, by implementing appropriate technology, balancing the loads of paralleled substations can

optimize energy flow, thereby improving energy efficiency. To achieve some or all of these objectives, one of

the architectures described in 4.3 should be adopted.
4.3 System architecture

Converters with power semiconductors in bridge circuits are used to convert three-phase AC to DC. They can

be classified as line-commutated converters (uncontrolled or controlled type) or self-commutated converters.

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Substations intended for feeding only are commonly designed as uncontrolled line-commutated converters (i.e.

diode rectifier).

Beside diode rectifiers, controlled line-commutated converters and self-commutated converters can also be

used for rectification purposes. Both technologies are not commonly used in today’s DC substations because

cost-efficiency and reliability of diode rectifiers so far exceed the advantages of these converters. However, a

main advantage of these technologies is the control of DC feeding voltage which enables these types of

converters to be used for load management between substations and to reduce energy losses in the contact

line.

Controlled line-commutated converters and self-commutated converters can also be used for inverting

purposes. However, while a single bridge self-commutated inverter is able to support energy flow in both

directions (rectification and inversion), a line-commutated converter needs two anti-parallel bridges to operate.

Generally, but not exclusively, the following main converter technologies can be realized:

a) reversible substation with uncontrolled rectifier:

1) uncontrolled rectifier and controlled inverter (diode rectifier and thyristor inverter);

2) uncontrolled rectifier and self-commutated inverter (diode rectifier and IGBT Inverter);

b) reversible substation with controlled rectifier or self-commutated converter:

1) controlled rectifier and controlled inverter (thyristor rectifier and thyristor inverter);

2) controlled rectifier and self-commutated inverter (e.g. thyristor rectifier and IGBT inverter);

3) self-commutated converter (IGBT single bridge converter).

For upgrading existing substations, where the transformer-rectifier-set is still in a good condition, options a) 1)

and a) 2) above are usually the easiest technologies to deploy.

In case of new construction of substations, any of the options b) 1) to b) 3) can be taken into consideration to

avoid restrictions for the inversion function (in relation to the no-load voltage of uncontrolled rectifiers).

The main advantage of b) 1) to b) 3) is to decrease the no-load voltage during inversion. This function enables

the inverters to improve the collection of braking energy from different vehicles that are distributed in the

system.

Options a) 2) and b) 2) allow operation of the self-commutated inverter when the rectifier is active (in parallel to

the rectifier). This can be used for reactive current compensation, active filtering of harmonics or to operate as a

booster during load peaks.

From the converter topology point of view, b) 3) represents a simple configuration, because one bridge allows

energy flow in both directions. However, in this configuration the high thermal load of the semiconductors

should be taken into account.
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4.4 Braking safety

Dynamic braking is not a fail-safe system. Furthermore, dynamic braking fades away at very low speeds.

Therefore, braking safety requires the installation of additional on-board mechanical brakes either to

complement the dynamic brakes or to be used as a main brake to bring the train to a complete stop and also to

stop in an emergency situation. Thus, there is no mandatory requirement for dynamic braking performance to

provide a guaranteed safe level of stopping distance performance for rolling stock.

5 Standard performances
5.1 General recommendations

All RSS installations should be compliant with general and functional recommendations in relation to the chosen

architecture.

Safety, health, environmental protection and the technical compatibility aspects should comply with the

applicable standards and regulations.
5.2 Performance of the system
5.2.1 Power rating

The following standards should be used as a reference for specifying the power ratings¸ wherever suitable and

as detailed in Clauses 8 and 9: EN 50327, EN 50328 and EN 50329. For controlled inverter architecture, refer

to the deviations described in Clauses 8 and 9 of this document.

The converter loading and load cycles can be assessed for a given application using simulations. The

simulations should consider the most severe operating conditions, e.g. minimum headway for normal operation

and first-level outage mode. The rating current, overload current and short-term overload current values or other

values related to a customized duty class X should be determined in relation to the results of the simulations

stated above, taking into account the protection and overload capabilities provided by the converters.

In cases where more than one unit is required in the same substation, a current balancing strategy should be

taken into account regarding the ratings.
5.2.2 Energy efficiency

In considering the efficiency improvement of the system, attention should be given to the efficiencies of

individual components, taking into account that the energy is flowing in both directions between the contact line

and the grid.

For the electronic power converters, the current state of the art allows the following minimum efficiencies to be

reached:

• efficiency of substation converter > 0,97 in rectifier mode at the rated power;

• efficiency of substation converter > 0,96 in inverter mode at the maximum power of the duty cycle.

The efficiency is defined in EN 50328 and the losses to be considered are listed in EN 50328:2003, 3.3.2.

5.2.3 Harmonics and reactive power compensation

Self-commutated converters in cases a) 2) and b) 2) and 3) of 4.3 can be used for AC harmonic filtering and

reactive power compensation on the AC side. In cases a) 2) and b) 2), the inverter acts as a compensator in

parallel with the rectifier.

The impact of compensation functions should be taken into account in determining the power rating of the

converter.
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5.2.4 Additional recommendations

In the case of a fault, it is necessary to isolate the faulty converter and reconfigure the supply. For this purpose,

the appropriate disconnectors should be selected. The substation should be designed to achieve selectivity in

fault detection and clearing hierarchy. In case of upgrading of existing substations, the additional components

should not adversely affect the existing protections selectivity.
5.2.5 Safety

The safety level of the power supply system should not be affected by the energy recovery carried out by

reversible DC substations.
Safety may be demonstrated according to CLC/TS 50562.
5.2.6 Availability

The availability of the power supply system should not be affected by reversible DC substations in both power

feeding and recovering modes.
6 Constraints
6.1 Climatic environment

EN 50125-2 and EN 50328 should be used as a reference. Specific conditions should be indicated per

application.
6.2 Electromagnetic compatibility
EN 50121-2 and EN 50121-5 should be used as a reference.

With respect to compatibility with rolling stock, signalling equipment, and the associated power and control

cables, the admissible EMC levels are also governed by local regulations.
6.3 Harmonic content

There is no standardized limit value with which every electric item would have to comply individually. Where

reversible substations are directly connected to a public network, compliance with local regulations from the

electricity provider is mandatory.
See also 7.3.1.
6.4 Interfaces with operational environment
6.4.1 General

Reversible DC substations should be fully compatible with other subsystems on the railway transport system.

6.4.2 Installation

Reversible DC substations should comply with the rules of safety and integration required by railway electrical

substations as stated in the relevant standards.

Due to the technology using static and controlled converters with power semiconductor devices, thermal losses

should be dissipated in the environment via an appropriate cooling system, adapted to the power rating of the

equipment.
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6.4.3 Power supply and distribution

In order to measure the energy which is sent back to the network or the grid, a bidirectional energy meter

should be installed at the point of connection to the upstream grid.

Upgrading equipment of existing installations should minimize the interfaces, additional space and additional

equipment. Reversible DC substations should be compatible with the adjacent substations and the rolling stock.

6.4.4 Monitoring

Monitoring and maintenance diagnostic data of reversible DC substation control equipment should be available

in the substation and should allow for remote control. The following functions are recommended:

• real-time information on equipment status,
• tracking and recording of faults,

• real-time energy monitoring, normally on the AC side (e.g. Energy consumption recording with appropriate

average period according to railway operator or energy provider requirements)
• data for maintenance purpose (e.g. operating hours, switching cycles),

• power quality criteria as required (e.g. harmonic distortion and power factor), see 7.3.

As an option, a real time energy diagnostic system in the Operation Control Centre can be provided to operate

an energy management system to interface with th
...

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