oSIST prEN 50121-1:2026

• Abstract:

  This document outlines the structure and the content of the whole set.; It provides information about the EMC management.; It specifies the performance criteria applicable to the whole series.; This part alone is not sufficient to give presumption of conformity to the essential requirements of the EMC-Directive and is intended to be used in conjunction with other parts of this series of standards.; The informative Annex A describes the characteristics of the railway system which affect electromagnetic compatibility (EMC) behaviour.; Phenomena excluded from the set are Nuclear EM pulse, abnormal operating conditions (e.g. fault conditions) and the induction effects of direct lightning strike.; Emission limits at the railway system boundary do not apply to intentional transmitters within the railway system boundaries.; Safety considerations are not covered by this set of standards.; The biological effects of non-ionizing radiation as well as apparatus for medical assistance, such as pacemakers, are not considered here.

• Status: Not Published
• Public Enquiry End Date: 30-Sep-2025
• ICS: 29.280 - Electric traction equipment
• ICS: 33.100.01 - Electromagnetic compatibility in general
• ICS: 45.020 - Railway engineering in general
• Technical Committee: ŽEN - Electrical applications for railways
• Current Stage: 5020 - Formal vote (FV) (Adopted Project)
• Start Date: 23-Sep-2026
• Due Date: 11-Nov-2026
• Completion Date: 28-Sep-2026
• Ref Project: FprEN 50121-1:2026 - Railway applications - Electromagnetic compatibility - Part 1: General

• Revises: SIST EN 50121-1:2017 - Railway applications - Electromagnetic compatibility - Part 1: General
• Effective Date: 09-Apr-2024

oSIST prEN 50121-1:2026 is a SIST draft standard for railway applications - electromagnetic compatibility (EMC). It is the general part of the EN 50121 series: it sets the EMC framework, the management approach, and the performance criteria used across the series for railway systems and equipment within them.

What does oSIST prEN 50121-1:2026 specify?

oSIST prEN 50121-1:2026 specifies the common structure of the railway EMC series and the performance criteria that apply to the whole set. It is intended to be used together with the other parts of EN 50121, because this part alone is not enough to give presumption of conformity to the EMC Directive.

The document is organized into five clauses and two informative annexes:

Annex	What it covers
Annex A	Railway-system characteristics that affect EMC behaviour, including coupling mechanisms, immunity and emission phenomena, traction systems, internal noise sources, and external sources of disturbance
Annex B	An EMC management plan, including an example EMC matrix and examples of compatibility planning

The scope excludes Nuclear EM pulse, abnormal operating conditions such as fault conditions, and induction effects of direct lightning strike. The railway-system boundary emission limits do not apply to intentional transmitters inside the railway system boundaries. Safety, biological effects of non-ionizing radiation, and apparatus for medical assistance such as pacemakers are outside the subject of this series.

What are the key requirements of oSIST prEN 50121-1:2026?

oSIST prEN 50121-1:2026 focuses on how EMC is managed across a railway project and how immunity test results are judged. In practice, it is a planning and evaluation document for integrators, suppliers, and project teams.

EMC management

Clause 4 requires all cases to be considered in a formal EMC management plan. The plan should be established as early as possible in the project, because railway systems combine moving sources of electromagnetic energy, tight installation spaces, and existing assemblies that can create severe environments.

For any new subsystem introduced inside the railway-system boundary, the integrator shall consider potential sources, potential victims, and the coupling mechanisms between them. In practice, this means the EMC impact of each subsystem has to be mapped, not left to late-stage testing.

Clause 4 says the EMC management plan shall reference the relevant basic EMC standards. It may be structured as an EMC matrix or another method that compares sources with victims inside the railway environment and also against the outside world.

Performance criteria

Clause 5 requires a functional description and a definition of performance criteria to be provided and recorded in the test report. This matters because the standard uses three different ways to judge immunity results, depending on the equipment and its function.

• Performance criterion A - The equipment under test (EUT) keeps operating as intended during and after the test, with no degradation below the manufacturer’s specified performance level.
• Performance criterion B - The EUT may degrade during the test, but it must operate as intended after the test and must not change operating state or stored data during the test.
• Performance criterion C - Temporary loss of function is allowed during the test if the function self-recovers or can be restored by the controls.

In practice, the manufacturer’s declared performance level, or a justified level based on the product description and expected use, has to be tied to the chosen criterion.

Railway-system context

Annex A explains why railway EMC is complex: railway systems use high power, power electronics, sliding contacts, and a mix of fixed and moving subsystems. It identifies principal coupling mechanisms and the main immunity and emission phenomena, which helps readers understand where interference comes from and why compatibility can be difficult in mixed railway environments.

Planning aids

Annex B gives a guideline and example for an EMC management plan. It describes how an EMC matrix can help show sources, victims, coupling paths, applicable EN standards, performance criteria, environments, and test-related items such as generator selection, source impedance, and frequency range.

What terms does oSIST prEN 50121-1:2026 define?

• Integrator - the party responsible for specifying and/or integrating apparatus into a system or subsystem.
• EMC - electromagnetic compatibility, the ability of equipment and systems to function acceptably in their electromagnetic environment.
• AC - alternating current.
• DC - direct current.
• RF - radio frequency.
• MRI - magnetic resonance imaging, named in the document as a sensitive external installation that may need special compatibility attention.
• EUT - equipment under test, the item whose immunity performance is being assessed.

Who uses oSIST prEN 50121-1:2026?

oSIST prEN 50121-1:2026 is used by integrators, project managers, infrastructure managers, equipment suppliers, and test teams working on railway EMC. It is relevant to rolling stock, signalling and telecommunications, and fixed power supply installations.

In practice, these users apply it when they define an EMC management plan, select the relevant parts of EN 50121, set performance criteria for tests, and judge whether a railway subsystem can coexist with other railway equipment and with the outside world.

What changed in oSIST prEN 50121-1:2026 from the previous edition?

oSIST prEN 50121-1:2026 will supersede EN 50121-1:2017. The document states these significant technical changes:

• clarification in Clause 4, Management of EMC;
• additional explanation in informative Annex A, including A.1, A.2, A.4, A.5, A.7.2, A.7.3, and A.9;
• a new informative Annex B, EMC management plan.

Which standards are used with oSIST prEN 50121-1:2026?

• IEC 60050-161:1990 - provides the EMC vocabulary used for terms and definitions.
• EN 50121-2:2025 - covers emission of the whole railway system to the outside world.
• EN 50121-3-1:2025 - covers rolling stock, train and complete vehicle.
• EN 50121-3-2:2025 - covers rolling stock apparatus.
• EN 50121-4:2025 - covers signalling and telecommunications apparatus.
• EN 50121-5:2025 - covers fixed power supply installations and apparatus.

What does the oSIST prEN 50121-1:2026 document contain?

The document contains the general framework for railway EMC, together with explanatory material on how railway systems create and receive electromagnetic disturbance. It includes a clause on EMC management, a clause on performance criteria, and informative annexes that describe railway-system characteristics and a sample EMC management plan.

Annex A summarizes coupling mechanisms, immunity and emission phenomena, traction-system types, internal sources of electromagnetic noise, and external sources such as neighbouring railway systems, radio transmitters, overhead power lines, and industrial plants. Annex B adds an EMC matrix example and shows how compatibility can be assessed by comparing source emission with victim immunity.

The document also identifies the kinds of methods and planning data that are useful for design review, EMC testing, and system integration.

SLOVENSKI STANDARD
oSIST prEN 50121-1:2025
01-september-2025
Železniške naprave - Elektromagnetna združljivost - 1. del: Splošno
Railway applications - Electromagnetic compatibility - Part 1: General
Bahnanwendungen - Elektromagnetische Verträglichkeit - Teil 1: Allgemeines
Applications ferroviaires - Compatibilité électromagnétique - Partie 1: Généralités
Ta slovenski standard je istoveten z: prEN 50121-1:2025
ICS:
33.100.01 Elektromagnetna združljivost Electromagnetic compatibility
na splošno in general
45.020 Železniška tehnika na Railway engineering in
splošno general
oSIST prEN 50121-1:2025 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 50121-1:2025
oSIST prEN 50121-1:2025
EUROPEAN STANDARD DRAFT
prEN 50121-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2025
ICS 45.020; 29.280; 33.100.01 Will supersede EN 50121-1:2017
English Version
Railway applications - Electromagnetic compatibility - Part 1:
General
Applications ferroviaires - Compatibilité électromagnétique - Bahnanwendungen - Elektromagnetische Verträglichkeit -
Partie 1: Généralités Teil 1: Allgemeines
This draft European Standard is submitted to CENELEC members for enquiry.
Deadline for CENELEC: 2025-10-24.

It has been drawn up by CLC/TC 9X.

If this draft becomes a European Standard, CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which
stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CENELEC 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.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to
provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.

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.
Project: 79747 Ref. No. prEN 50121-1:2025 E

oSIST prEN 50121-1:2025
prEN 50121-1:2025 (E)
1 Contents Page
2 European foreword . 3
3 Introduction . 4
4 1 Scope . 6
5 2 Normative references . 6
6 3 Terms definitions and abbreviations . 6
7 3.1 Terms and definitions . 6
8 3.2 Abbreviations . 6
9 4 Management of EMC . 7
10 5 Performance criteria . 7
11 Annex A (informative) The railway system . 9
12 A.1 Introduction . 9
13 A.2 General coupling mechanisms . 9
14 A.3 Principal electromagnetic phenomena for immunity . 10
15 A.3.1 Conducted low frequency phenomena . 10
16 A.3.2 Low frequency field phenomena . 10
17 A.3.3 Conducted high frequency phenomena . 10
18 A.3.4 Radiated high frequency phenomena . 10
19 A.4 Principal electromagnetic phenomena for emission . 10
20 A.5 Description of the different electric traction systems . 10
21 A.6 Components of electric traction systems . 10
22 A.7 Internal sources of electromagnetic noise . 11
23 A.7.1 General . 11
24 A.7.2 Static elements: . 11
25 A.7.3 Mobile elements: . 11
26 A.7.4 Train line: . 12
27 A.7.5 Traction return current with respect to track circuits: . 12
28 A.7.6 Trackside equipment: . 12
29 A.8 Summary of main characteristics of railway systems . 12
30 A.9 External sources of disturbance . 13
31 Annex B (informative) EMC management plan . 14
32 Bibliography . 17
oSIST prEN 50121-1:2025
prEN 50121-1:2025 (E)
34 European foreword
35 This document (prEN 50121-1:2025) has been prepared by CLC/TC 9X “Electrical and electronic applications
36 for railways”.
37 This document is currently submitted to the Enquiry.
38 The following dates are proposed:
• latest date by which the existence of this (doa) dav + 6 months
document has to be announced at national
level
• latest date by which this document has to be (dop) dav + 12 months
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) dav + 36 months
conflicting with this document have to be (to be confirmed or
withdrawn modified when voting)
39 This document has been prepared according to Decision 69/09 taken during the TC 9X meeting.
40 This document will supersede EN 50121-1:2017.
41 prEN 50121-1:2025 includes the following significant technical changes with respect to EN 50121-1:2017:
42 — clarification in Clause 4, Management of EMC;
43 — introduction of additional explanation in informative Annex A, A.1 Introduction, A.2 General coupling
44 mechanisms, A.4 Principal electromagnetic phenomena for emission, A.5 Description of the different
45 electric traction systems, A.7.2 Static elements, A.7.3 Mobile elements and A.9 External sources of
46 disturbance;
47 — introduction of new informative Annex B “EMC management plan”.
48 EN 50121, Railway applications — Electromagnetic compatibility, consists of the following parts:
49 — Part 1: General [the present document];
50 — Part 2: Emission of the whole railway system to the outside world;
51 — Part 3-1: Rolling stock — Train and complete vehicle;
52 — Part 3-2: Rolling stock — Apparatus;
53 — Part 4: Emission and immunity of the signalling and telecommunications apparatus;
54 — Part 5: Emission and immunity of fixed power supply installations and apparatus.
oSIST prEN 50121-1:2025
prEN 50121-1:2025 (E)
55 Introduction
56 The railway system EMC set of product-specific European Standards is intended, in the main, to permit
57 compliance with the EMC Directive, but also to provide a means of prescribing compatibility between internal
58 parts of the railway system. It consists of five parts described at the end of this Introduction.
59 The set of standards provides both a framework for managing the EMC for railway systems and also specifies
60 the limits for the electromagnetic (EM) emission of the railway system as a whole to the outside world and for
61 the EM emission and immunity for equipment operating within the railway system. The latter is intended to be
62 compatible with the emission limits set for the railway system as a whole and also provides for establishing
63 confidence in equipment being Fit For Purpose in the Railway environment. There are different stationary
64 emission limits set for trams/trolleybuses and for metro/mainline railway systems. The frequency covered by the
65 standards is in the range from DC to 400 GHz. No measurements need to be performed at frequencies where
66 no requirement is specified. The limits for EMC phenomena are set so that the railway system as a whole
67 satisfies the Directive on electromagnetic compatibility with the outside world, and so that EMC is achieved
68 between the various parts of the railway system. Any specific problems in complying with the limits are intended
69 to be addressed by the procedures given in the EMC Directive. Throughout the set of standards, the immunity
70 levels are chosen to ensure a reasonable level of EMC with other apparatus within the local railway environment
71 and with emissions which enter the railway system from the outside world. Limits are also placed on EM
72 emission by railway systems into the outside world.
73 The compatibility between railway system emissions and their external environment is based upon emission
74 limits from the railway systems being set by considering the results from measurements at the time that the
75 EMC Directive became enforceable. Given that the general compatibility between railway systems and their
76 environment was satisfactory at the time these measurements were made and subsequent experience of
77 applying the limits has confirmed their acceptability, compliance with this Standard has been judged to give
78 satisfactory compatibility. The immunity and emission levels do not of themselves guarantee that the railway
79 system will have satisfactory compliance with its neighbours. In exceptional circumstances, for instance near a
80 location which has unusually high levels of EM interference, the railway system can require additional measures
81 to be taken to ensure proper compatibility. Particular care should be taken when in proximity to equipment not
82 covered by the EMC Directive such as radio transmission equipment, military or medical installations. Attention
83 is particularly drawn to any magnetic imaging equipment in hospitals that can be near to urban transport. In all
84 these cases, compatibility should be achieved with consultation and co-operation between the interested
85 parties.
86 The immunity and emission levels themselves do not guarantee that integration of the apparatus within the
87 railway system will necessarily be satisfactory. The standard cannot cover all the possible configurations of
88 apparatus, but the test levels are sufficient to achieve satisfactory EMC in the majority of cases. In exceptional
89 circumstances, for instance near a location which has unusually high levels of EM interference, the system can
90 require additional measures to be taken to ensure proper operation. The resolution of this is a matter for
91 discussion between the equipment supplier and the project manager, infrastructure manager or equivalent.
92 The railway apparatus is assembled into large systems and installations, such as trains and signalling
93 operational control centres. Details are given in informative Annex A. It is not, therefore, possible to establish
94 immunity tests and limits for these large assemblies. The immunity levels for the apparatus will normally ensure
95 reliable operation, but it is important to prepare an EMC management plan to deal with complex situations or to
96 deal with specific circumstances; for example, the passage of the railway line close to a high power radio-
97 transmitter which produces abnormally high field strengths. Special conditions may have to be applied for
98 railway equipment which has to work near such a transmitter and these will be accepted as National Conditions
99 for the specification.
oSIST prEN 50121-1:2025
prEN 50121-1:2025 (E)
100 The series of standards EN 50121, Railway applications — Electromagnetic compatibility, contains the following
101 parts:
102 — Part 1: General: This part gives a description of the electromagnetic behaviour of a railway system; it
103 specifies the performance criteria for the whole set. A management process to achieve EMC at the interface
104 between the railway infrastructure and trains is referenced.
105 — Part 2: Emission of the whole railway system to the outside world: This part sets the emission limits
106 from the railway system to the outside world at radio frequencies. It defines the applied test methods and
107 gives information on typical field strength values at traction and radio frequency (cartography).
108 — Part 3-1: Rolling stock — Train and complete vehicle: This part specifies the emission and immunity
109 requirements for all types of rolling stock. It covers traction rolling stock and trainsets, as well as
110 independent hauled rolling stock. The scope of this part of the series ends at the interface of the rolling
111 stock with its respective energy inputs and outputs.
112 — Part 3-2: Rolling stock — Apparatus: This part applies to emission and immunity aspects of EMC for
113 electrical and electronic apparatus intended for use on railway rolling stock. It is also used as a means of
114 dealing with the impracticality of immunity testing a complete vehicle.
115 — Part 4: Emission and immunity of the signalling and telecommunications apparatus: This part
116 specifies limits for electromagnetic emission and immunity for signalling and telecommunications apparatus
117 installed within a Railway system. The EMC plan needs to state, if this part is also applicable for railway
118 operational equipment mounted trackside or at platforms.
119 — Part 5: Emission and immunity of fixed power supply installations and apparatus: This part applies
120 to emission and immunity aspects of EMC for electrical and electronic apparatus and components intended
121 for use in railway fixed installations associated with power supply.
122 EN 50121-1 and EN 50121-2 are product family standards which take precedence over generic standards.
123 EN 50121-3-1, EN 50121-3-2, EN 50121-4, and EN 50121-5 are product standards.
oSIST prEN 50121-1:2025
prEN 50121-1:2025 (E)
124 1 Scope
125 This document outlines the structure and the content of the whole set.
126 It provides information about the EMC management.
127 It specifies the performance criteria applicable to the whole standards series.
128 This part alone is not sufficient to give presumption of conformity to the essential requirements of the EMC-
129 Directive and is intended to be used in conjunction with other parts of this standard.
130 The informative Annex A describes the characteristics of the railway system which affect electromagnetic
131 compatibility (EMC) behaviour.
132 Phenomena excluded from the set are Nuclear EM pulse, abnormal operating conditions (e.g. fault conditions)
133 and the induction effects of direct lightning strike.
134 Emission limits at the railway system boundary do not apply to intentional transmitters within the railway system
135 boundaries.
136 Safety considerations are not covered by this set of standards.
137 The biological effects of non-ionizing radiation as well as apparatus for medical assistance, such as
138 pacemakers, are not considered here.
139 2 Normative references
140 The following documents are referred to in the text in such a way that some or all of their content constitutes
141 requirements of this document. For dated references, only the edition cited applies. For undated references, the
142 latest edition of the referenced document (including any amendments) applies.
143 IEC 60050-161:1990, International Electrotechnical Vocabulary. Chapter 161: Electromagnetic compatibility
144 3 Terms definitions and abbreviations
145 3.1 Terms and definitions
146 For the purposes of this document, the terms and definitions given in IEC 60050-161:1990 and the following
147 apply.
148 ISO and IEC maintain terminology databases for use in standardization at the following addresses:
149 — ISO Online browsing platform: available at https://www.iso.org/obp/
150 — IEC Electropedia: available at https://www.electropedia.org/
151 3.1.1
152 integrator
153 party who is responsible for the specification and/or the integration of the apparatus into a system or subsystem
154 3.2 Abbreviations
155 For the purposes of this document, the following abbreviations apply.
AC Alternating Current
CCTV Closed Circuit Television
DC Direct Current
E Electric (field)
EM Electromagnetic
oSIST prEN 50121-1:2025
prEN 50121-1:2025 (E)
EMC Electro Magnetic Compatibility
GTO Gate Turnoff (transistor)
H Magnetic (field)
IGBT Insulated Gate Bipolar Transistor
IT Information Technology
MOSFET Metal Oxide Semiconductor Field Effect Transistor
MRI Magnetic Resonance Imaging
MVA Megavoltampere
RF Radio Frequency
WIFI Wireless Fidelity
156 For the purpose of this document, definitions related to EMC and to relevant phenomena can be found in
157 IEC 60050-161:1990.
158 Other parts of this document can contain specific definitions.
159 4 Management of EMC
160 The railway system is a complex installation with moving sources of electromagnetic energy and the application
161 of the railway EMC standards is not a guarantee of satisfactory performance. There can be cases where the
162 apparatus has to be positioned in restricted spaces or added to an existing assembly,
...