SIST EN 50122-2:2022/A1:2025
(Amendment)Fixed installations for railway applications - Electrical safety, earthing and the return circuit - Part 2: Provisions against the effects of stray currents caused by DC traction systems
Fixed installations for railway applications - Electrical safety, earthing and the return circuit - Part 2: Provisions against the effects of stray currents caused by DC traction systems
This document specifies requirements for protective provisions against the effects of stray currents, which result from the operation of DC electric traction power supply systems.
As several decades' experience has not shown evident corrosion effects from AC electric traction power supply systems, this document only deals with stray currents flowing from a DC electric traction power supply system.
This document applies to all metallic fixed installations which form part of the traction system, and also to any other metallic components located in any position in the earth, which can carry stray currents resulting from the operation of the railway system.
This document applies to all new DC lines and to all major revisions to existing DC lines. The principles can also be applied to existing electrified transportation systems where it is necessary to consider the effects of stray currents.
This document does not specify working rules for maintenance but provides design requirements to allow maintenance. The range of application includes:
a) railways,
b) guided mass transport systems such as:
1) tramways,
2) elevated and underground railways,
3) mountain railways,
4) magnetically levitated systems, which use a contact line system, and
5) trolleybus systems,
c) material transportation systems.
This document does not apply to
a) electric traction power supply systems in underground mines,
b) cranes, transportable platforms and similar transportation equipment on rails, temporary structures (e.g. exhibition structures) in so far as these are not supplied directly from the contact line system and are not endangered by the electric traction power supply system,
c) suspended cable cars,
d) funicular railways.
Ortsfeste Anlagen für Bahnanwendungen - Elektrische Sicherheit, Erdung und Rückleitung - Teil 2: Schutzmaßnahmen gegen Streustromwirkungen durch Gleichstrombahnen
Installations Fixes pour applications ferroviaires - Sécurité électrique, mise à la terre et circuit de retour - Partie 2: Mesures de protection contre les effets des courants vagabonds issus de la traction électrique à courant continu
Fiksni postroji za železniške naprave - Električna varnost, ozemljitev in povratni tokokrog - 2. del: Zaščitni ukrepi proti učinkom blodečih tokov, ki jih povzročajo enosmerni sistemi vleke - Dopolnilo A1
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-2025
Fiksni postroji za železniške naprave - Električna varnost, ozemljitev in povratni
tokokrog - 2. del: Zaščitni ukrepi proti učinkom blodečih tokov, ki jih povzročajo
enosmerni sistemi vleke - Dopolnilo A1
Fixed installations for railway applications - Electrical safety, earthing and the return
circuit - Part 2: Provisions against the effects of stray currents caused by DC traction
systems
Ortsfeste Anlagen für Bahnanwendungen - Elektrische Sicherheit, Erdung und
Rückleitung - Teil 2: Schutzmaßnahmen gegen Streustromwirkungen durch
Gleichstrombahnen
Installations Fixes pour applications ferroviaires - Sécurité électrique, mise à la terre et
circuit de retour - Partie 2: Mesures de protection contre les effets des courants
vagabonds issus de la traction électrique à courant continu
Ta slovenski standard je istoveten z: EN 50122-2:2022/A1:2025
ICS:
29.120.50 Varovalke in druga Fuses and other overcurrent
nadtokovna zaščita protection devices
29.280 Električna vlečna oprema Electric traction equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD EN 50122-2:2022/A1
NORME EUROPÉENNE
EUROPÄISCHE NORM August 2025
ICS 29.120.50; 29.280
English Version
Fixed installations for railway applications - Electrical safety,
earthing and the return circuit - Part 2: Provisions against the
effects of stray currents caused by DC traction systems
Installations fixes pour applications ferroviaires - Sécurité Ortsfeste Anlagen für Bahnanwendungen - Elektrische
électrique, mise à la terre et circuit de retour - Partie 2: Sicherheit, Erdung und Rückleitung - Teil 2:
Mesures de protection contre les effets des courants Schutzmaßnahmen gegen Streustromwirkungen durch
vagabonds issus de la traction électrique à courant continu Gleichstrombahnen
This amendment A1 modifies the European Standard EN 50122-2:2022; it was approved by CENELEC on 2025-06-23. CENELEC
members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this amendment the
status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This amendment exists in three official versions (English, French, German). A version in any other language made by translation under the
responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the same status as
the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 50122-2:2022/A1:2025 E
Contents Page
European foreword . 3
1 Modification to the Title . 3
2 Modification to Clause 2, Normative references . 4
3 Modification to Clause 4, Identification of hazards and risks . 4
4 Modification to 5.1, General . 4
5 Modification to 5.2, General Criteria for the protection of the tracks . 4
6 Modification to 5.3, Criteria for systems with steel reinforced concrete or metallic
structures . 5
7 Modification to 6.2.3, Track system . 5
8 Modification to 6.2.6, Electrical separation between the return circuit and system parts with
earth-electrode effect . 5
9 Modification to 7.3, Adjacent pipes or cables. 6
10 Modification to 7.4, Voltage limiting devices . 6
11 Modification to Clause 8, Protective provisions applied to metallic structures . 6
12 Modification to A.1, Rail resistance . 6
13 Modification to A.2, Conductance per length between running rails and steel reinforced
structures . 7
14 Modification to A.3, Conductance per length for track sections without civil structure . 7
15 Modification to A.4, Local conductance per length for track sections without civil structure
........................................................................................................................................................ 8
16 Modification to A.5, Insulated rail joints . 8
17 Modification to B.1, Repetitive measurements of the rail potential to monitor the
conductance . 8
18 Modification to C.1, Estimation of the stray currents passing from the running rails to the
earth . 9
19 Modification to C.2, Estimation of the longitudinal voltage in steel reinforced structures . 9
20 Modification to D.1, General . 9
21 Modification to D.2.1, General . 9
22 Modification to D.2.2, Initial test . 9
23 Modification to D.2.3, Heat Aging .10
24 Modification to D.2.4, Influence of winter weather and rain .10
25 Modification to D.2.5, Evaluation .10
26 Modification to Bibliography .10
European foreword
This document (EN 50122-2:2022/A1:2025) was prepared by SC 9XC, “Electric supply and earthing systems
for public transport equipment and ancillary apparatus (fixed installations)”, of CLC/TC 9X, “Electrical and
electronic applications for railways”.
The following dates are fixed:
• latest date by which this document has to be (dop) 2026-08-31
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) 2028-08-31
conflicting with this document have to be
withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a Standardization Request addressed to CENELEC by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
Any feedback and questions on this document should be directed to the users’ national committee. A complete
listing of these bodies can be found on the CENELEC website.
1 Modification to the Title
Modify the first part of the title to read:
“Fixed installations for railway application - Electrical safety, earthing and the return circuit - Part 2: Provisions
against the effects of stray currents caused by DC traction systems”
2 Modification to Clause 2, Normative references
Add the following standard:
“EN ISO 21857:2021, Petroleum, petrochemical and natural gas industries - Prevention of corrosion on pipeline
systems influenced by stray currents (ISO 21857:2021)”
3 Modification to Clause 4, Identification of hazards and risks
Replace the first paragraph with the following:
DC electric traction power supply systems can cause stray currents, which can adversely affect railway
infrastructure as well as third party structures, if the feed and return circuits are not sufficiently insulated from
earth.
Replace the first line of the second paragraph with the following:
“Where current leaves the structure through an electrolytic path such as concrete or soil the major effects of
such stray currents can be corrosion.”
Replace the sixth paragraph with the following:
“The railway system design shall be completed before key parameters for stray current effects are decided. This
includes parameters such as substation locations, track formations, bonding, insulated rail joint positions and
civil structure designs (e.g. overhead contact line system, including foundations, bridges, viaducts, tunnels).
See also 5.4 and Clause 6.”
4 Modification to 5.1, General
Replace the first paragraph with the following:
“The magnitude and extent of stray currents depends on the overall system design of the electric traction power
supply system. Stray currents leaving the return circuit through an electrolytic path can affect the return circuit
itself and neighbouring installations, see Clause 4.”
Replace the NOTE 2 with the following:
“NOTE 2 Stray currents from DC railway systems are, by their nature, dynamic, and adherence to the guidelines in
Clause 5 does not always ensure that the corrosion risk to third party infrastructure does not exist.”
Replace the last sentence of the last paragraph with the following:
“The corrosion risk to the railway system can be assessed using the guidelines in this document.”
After the last paragraph, add the following new NOTE 3:
“NOTE 3 The responsibility for the assessment of the corrosion risk to third-party structures lies with the owners of those
structures. EN ISO 21857 provides guidance for pipelines and can be used for other structures as well. EN ISO 21857
recommends joint committees to assess the stray current corrosion risks, e.g. railway infrastructure managers and other
involved parties.”
5 Modification to 5.2, General Criteria for the protection of the tracks
Replace the first paragraph with the following:
“Experience over more than three decades has proven that the corrosion damage to the tracks including their
fixings over this period is acceptable, if the average stray current per length does not exceed the following
value”:
Replace the third paragraph with the following:
“The given value of I’ indicates a time averaged stray current leakage per length of one track.”
max
In the seventh paragraph, replace “life-time” with “lifetime”.
Replace Formula (3) and the Key below with the following:
I '
max
“ G ' ≤ (3)
RE
ΔU
RE
where
I’ is 2,5 mA/m per track or the value coming from the investigation in 5.4;
max
G’ is the conductance per length, in siemens per kilometre (S/km, whereby 1 S/km = 1/Ωkm);
RE
∆U is the average positive rail potential shift, in volts (V).”
RE
In the thirteenth paragraph (after the Key list of Formula) replace “G’ < 0,5 S/km” with “G’ < 0,5 S/km per
RE RE
track”.
Replace the fourteenth paragraph with the following:
“If the average positive rail potential shift combined with the conductance per length does not meet the criteria
of I’ = 2,5 mA/m per track, the electric traction power supply system should be optimized.”
max
6 Modification to 5.3, Criteria for systems with steel reinforced concrete or metallic
structures
In the first sentence of the third paragraph, replace “EN 50162:2004” with “EN ISO 21857:2021”.
Replace the last sentence of the third paragraph with: “Both requirements shall comply with
EN ISO 21857:2021.”
After the third paragraph add the following NOTE:
“NOTE An applicable assessment method is described in EN ISO 21857:2021, Annex J. For railway structures case a) is
applicable.”
Replace the third sentence of the last paragraph with the following:
“Clause C.2 shows an example calculation.”
Delete the last sentence of the last paragraph.
7 Modification to 6.2.3, Track system
In the end of the second paragraph, add the following sentence:
“Annex D and Annex E provide guidelines to test insulating materials.”
In NOTE 1, replace “without” with “without moisture”.
In the first bullet of EXAMPLE 2, delete the second part of the sentence.
8 Modification to 6.2.6, Electrical separation between the return circuit and system
parts with earth-electrode effect
Replace the title of subclause 6.2.6 with the following:
“Electrical separation between the return circuit and parts not insulated from earth”
9 Modification to 7.3, Adjacent pipes or cables
In the second paragraph, add
...
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