Article

Measurements and Analysis of Electromagnetic Compatibility

of Railway Rolling Stock with Train Detection Systems Using
Track Circuits
Adam Garczarek 1,2 and Dorota Stachowiak 2, *

1 Poznan Institute of Technology, Lukasiewicz Research Network, 61-755 Poznan, Poland;

adam.garczarek@pit.lukasiewicz.gov.pl or adam.garczarek@doctorate.put.poznan.pl
2 Faculty of Control, Robotics and Electrical Engineering, Poznan University of Technology,
60-965 Poznan, Poland
* Correspondence: dorota.stachowiak@put.poznan.pl

Abstract: One of the main challenges in the operation of electric traction vehicles is ensuring
safety and operational reliability. To ensure the safety of railway traffic, vehicles must
undergo a series of tests related to the investigation of disturbances generated, among
others, in the return current to the mains. This problem is further complicated by the
inability to perform such measurements under laboratory conditions. The implementation
of tests under real conditions determines the appearance of additional potential interference
sources, from power sources to improper interactions between current collectors and the
overhead contact system, and it requires strict compliance with regulatory standards and
the implementation of standardized testing procedures. This article presents issues related
to the investigation and analysis of the electromagnetic compatibility of rolling stock
with train detection systems using track circuits. The aim of these tests is to determine
the harmonic components in the traction current in relation to the permissible levels
specified in the latest editions of the European Railway Agency—ERA/ERTMS/033281
version 5.0 documents and Annex S-02 to the List of the President of the Office of Rail
Transport. The measurement methodology and test procedures are presented in detail with
respect to current legal requirements.
Academic Editor: Lionel Pichon
Keywords: rail vehicles; measurements; electromagnetic compatibility; track circuits
Received: 27 April 2025
Revised: 18 May 2025
Accepted: 20 May 2025
Published: 23 May 2025

Citation: Garczarek, A.;

1. Introduction
Stachowiak, D. Measurements The modern railway system can be thought of as a form of vast microgrid combining
and Analysis of Electromagnetic distributed active loads (trains), energy sources (renewable-based microgrids) and energy
Compatibility of Railway Rolling
storage devices [1,2]. The drive to increase energy efficiency and reduce pollution in railroad
Stock with Train Detection Systems
systems is emphasized through the implementation of smart grid and microgrid concepts.
Using Track Circuits. Energies 2025, 18,
2705. https://doi.org/10.3390/
Menicanti et al. present the use of a rail microgrid to recover energy from train braking
en18112705 and the charging infrastructure of electric vehicles [3]. Kaleybar et al. present the concept
of smart hybrid rail microgrids (H-RMGs) integrating renewable energy sources, storage
Copyright: © 2025 by the authors.
Licensee MDPI, Basel, Switzerland.
systems and electric vehicle charging stations into existing rail systems [4]. Electromagnetic
This article is an open access article interference (EMI) generated by rolling stock has the potential to affect components of
distributed under the terms and the rail microgrid, such as energy control systems, power converters, storage systems and
conditions of the Creative Commons others. Midya et al. describe how EMI generated inside the rail system or originating from
Attribution (CC BY) license
outside often disrupts the overall system performance and causes interference in nearby
(https://creativecommons.org/
civil systems. The main sources of EMI in the rail system are the rolling stock (drives, brake
licenses/by/4.0/).

Energies 2025, 18, 2705 https://doi.org/10.3390/en18112705

Energies 2025, 18, 2705 2 of 16

systems, pantograph arcing), supply substations, environmental sources (e.g., lightning)

and the track itself [5]. Traction rolling stock generates harmonics primarily resulting from
the operation of converters. The converters of the currently produced locomotives and
electric multiple units operate at frequencies in the range of 30 to 300 Hz. Static converters
usually operate at frequencies of several kilohertz; hence the most important factor is the
so-called switching noise in the range of 2–20 kHz. Occasionally, the factor influencing the
generation of electromagnetic interference is the dynamics of the pantograph. However,
this is subject to separate legal requirements, and its incorrect behavior is easier to detect
during periodic inspections. Ensuring that the electromagnetic interference generated by
these vehicles does not adversely affect the stability and safety of the microgrid and its
control elements is an important aspect of planning and operating the microgrid.
The safety of railway traffic depends, among others, on the operational reliability of
railway traffic control devices (RTCs) [6,7]. Their operation is influenced by many devices
installed on the vehicles and within the trackside infrastructure [5,8]. Interference problems
in railroad traffic control devices have been known for a long time [9]. Especially crucial is
the risk of false occupancy of the track circuit, or rather its nonexistence, as well as signal
malfunctions (the inability to detect a vehicle within the track segment). In recent years,
with the use of an increasing number of electronic devices and power electronic converter
systems, their size and variety have increased significantly, which is also reflected in the
number of publications devoted to this topic [10–12]. The harmonic and impulse influences
of the return traction current (especially on AC electrified railways) are the cause of a
significant number of track circuit failures [13]. Paper [14] points out that a second-order
passive filter can be an optimal solution for mitigating harmonic interference in railroad
signaling equipment caused by traction harmonics. On the other hand, paper [15] notes
that the use of surge protective devices and shielded incoming lines can effectively reduce
the risks of lightning damage to railway traffic control systems. In general, electromagnetic
interference generated unintentionally can adversely affect electronic protection systems,
requiring technical and organizational measures to protect against it [16]. However, there
is still a need to analyze interference due to the need to identify sources of it in order
to eliminate them. This applies especially to interference currents with frequencies that
coincide with the operating frequency of RTC devices [9,13,17]. Furthermore, with the
increasing speed of railway vehicles resulting, among others, from the modernization
of railway lines, the demand for the amount of energy supplied increases, leading to
an increasingly higher power consumption [18,19]. Current harmonics present in the
traction network directly affect infrastructure devices, particularly railway traffic control
devices [20,21]. The research carried out so far on the level of disturbances generated by
traction vehicles in the network confirms that innovative methods are required to identify
factors that generate unfavorable harmonics in the traction current [10,21,22]. Moreover, it
is assumed that the allowed margin factor characterizing the distance between the track
circuit signal causing the track relay excitation and interference should be at least 20%, and
for deexcitation 10% [17].
Electromagnetic interference from electric transport systems and rolling stock requires
precise assessment methods. The applicable standards are often considered insufficient
due to the complexity of the interference sources and the lack of sufficient research [11].
This paper presents a comprehensive and up-to-date approach to the complex problem
of electromagnetic compatibility (EMC) testing in railway applications, with particular
attention to current regulatory requirements and the specific challenges of real-world testing
scenarios. A key contribution of this work is the detailed presentation of the measurement
methodology and test procedures for the electromagnetic compatibility of rolling stock with
train detection systems using track circuits. The proposed methodology is fully aligned
Energies 2025, 18, 2705 3 of 16

with the most recent legal and normative frameworks, including ERA/ERTMS/033281
version 5.0, Annex S-02 of the List of the President of the Railway Transport Authority and
the technical specification CLC/TS 50238-2. This paper also includes a critical analysis of the
major changes introduced in the latest editions of the applicable standards. These changes
concern not only the tested frequency bands and permissible interference current levels but,
more importantly, the way in which parameter changes are evaluated. This paper highlights
important differences, such as the increase in the minimum overlap time of measurement
windows and the introduction of additional assessment criteria (permissible exceedance
duration, minimum time between consecutive exceedances), as a result of frequent updates
to the relevant documents. Additionally, this paper presents measurement results and
analyses obtained from tests conducted under actual operating conditions on a prototype
vehicle. Real-world testing poses additional challenges due to uncontrolled sources of
electromagnetic interference, which require strict compliance with applicable standards
and a rigorous implementation of measurement procedures.

2. Materials and Methods

Attempts to systematize issues related to compatibility between rolling stock and
train detection devices have been sanctioned in the CLC/TS 50238-2 specification [23],
which generally describes the methodology for its determination, as well as in subsequent
editions of the documents of the European Railway Agency ERA/ERTMS/033281 [24,25]
and in the Letter of the President of the Office of Rail Transport [26], changing the method
of measurement and the criteria for assessing the results. A common practice during tests
is to supplement them with the determination of psophometric currents based on the
relationship given in the PN-EN 50121-3-1:2017-05 standard [27] and the transient current
results from the provisions of the PN-EN 50388-1 standard [28], which allows one to obtain
a comprehensive picture of disturbances in the considered scope. The psophometric current
is an equivalent disturbance current that represents the effective disturbance of a current
spectrum in a power circuit to a communication line. The list of regulatory standards is
summarized in Table 1.

Table 1. The list of regulatory standards.

No. Standardization Document Standardized Testing Procedures

1 CLC/TS 50238-2:2020 Methodology for measuring the interference current
2 PN-EN 50121-3-1:2017-05 Psophometric current requirements and measurements
3 PN-EN 50388-1:2023-05 Transient current requirements and measurement
4 ERA/ERTMS/033281 Requirements for interference currents
5 List of the President of the Office of Rail Transport Specific Polish requirements for interference currents
6 PN-EN 15595:2019-03 Method of determining the initial adhesion coefficient
7 ILAC-G8:09/2019 Method of determining the compliance of the result with the requirements
8 Commission Regulation (EU) No 1302/2014 Introduces the requirement to measure interference currents

In order to ensure the safety of railway traffic, vehicles must undergo a number of
tests related to the examination of disturbances generated, among others, in the return
current to the mains. The requirement to carry out the above tests results from the pro-
visions of the List of the President of the Office of Rail Transport (UTK) [26], as well as
from the requirements of Commission Regulation (EU) No. 1302/2014 on the technical
specification of interoperability relating to the “Rolling stock—locomotives and passenger
rolling stock” subsystem of the railway system in the European Union [29]. However, this
problem is complicated by the inability to perform such measurements under laboratory
conditions. Carrying out tests in real conditions determines the emergence of additional
Energies 2025, 18, 2705 4 of 16

potential sources of interference, from the power source to the improper cooperation of the
current collector with the overhead contact system, and it introduces the need for rigorous
compliance with normative requirements and the application of test program standards.
The basic document that specifies the method and conditions for carrying out com-
patibility measurements between train and rolling stock detection systems is the CLC/TS
50238-2:2020 specification [23]. The tests should be carried out in accordance with the
recommendations regarding infrastructure described in point 6.2.4.3 of Annex B of the
specification [23]. Measurements of the variable and constant components of the traction
current are carried out in the main circuit, in various operating conditions of electric multi-
ple units (EMUs) and locomotives: at a standstill, when starting and stopping the vehicle,
sudden changes in speed, starts and electrodynamic braking carried out in normal and
low-traction conditions. Electrodynamic starting and braking tests are also performed with
half the traction power and with one inverter turned off as a failure simulation. Addition-
ally, measurements are recorded during starts to maximum speed and electrodynamic (ED)
braking to stop for two cases: (a) at a short distance from the power supply substation
and (b) at distance of >15 km from the substation. The tests performed are summarized in
Table 2. The test documentation should include the location of the test, e.g., by entering the
starting kilometer of the appropriate railway route.

Table 2. The list of tests performed.

No. Type of Test Speed [km/h]

1 Background -
2 Starting the vehicle -
3 Turning off the vehicle -
4 Standby (near the substation) -
5 Standby (far from substation) -
6 60 ⇒ Vmax
Changing the speed manually
7 Vmax ⇒ 60
8 60 ⇒ Vmax
Cruise control speed change
9 Vmax ⇒ 60
10 Start 0 ⇒ Vmax
100% traction power—measurement close to the substation
11 Braking Vmax ⇒ 0
12 Start 0 ⇒ Vmax
100% traction power—measurement far from the substation
13 Braking Vmax ⇒ 0
14 Start 0 ⇒ Vmax
50% of traction power—measurement close to the substation
15 Braking Vmax ⇒ 0
16 Start 0 ⇒ Vmax
50% of traction power—measurement far from the substation
17 Braking Vmax ⇒ 0
18 Start 0 ⇒ Vmax
Inverter turned off—measurement close to the substation (failure simulation)
19 Braking Vmax ⇒ 0
20 Start 0 ⇒ Vmax
Inverter turned off—measurement far from the substation (failure simulation)
21 Braking Vmax ⇒ 0
22 Start 0 ⇒ Vmax
100% traction power—limited traction (measurement close to the substation)
23 Braking Vmax ⇒ 0
24 Start 0 ⇒ Vmax
100% traction power—limited traction (measurement far from the substation)
25 Braking Vmax ⇒ 0

Furthermore, in the case of tests with reduced adhesion, according to the requirements
of the CLC/TS 50238-2 specification, the initial adhesion coefficient must be in the range of
5 to 8% [19]. The initial adhesion coefficient for tests with reduced adhesion is calculated
based on the standard PN-EN 15595:2019-03 [30] from the following relationship:

a
τ= , (1)
g
Energies 2025, 18, 2705 5 of 16

where τ is an initial adhesion coefficient, ā denotes delay value in the first interval (Figure 1),
and g is an acceleration due to gravity (constant value).

Figure 1. Determination of the initial adhesion coefficient (1—vehicle speed, 2—speed of the first
wheel set in skidding, 3—vehicle deceleration, 4—arithmetic mean of the deceleration value in the
1st interval, 5—first interval, X—time, Y—speed, delay) [30].

Measurements of the interference current Iz should be performed using two data-

processing algorithms:
1 Algorithm using the fast Fourier transform (FFT);
2 Algorithm using band-pass filters (BPFs) in accordance with the documents [24,25].
The calculated values of the Iz current refer to the requirements of Annex S-02 of the
List of the President of UTK [26], regarding permissible levels and parameters of distur-
bances for railway traffic control devices for locomotives and electric multiple units and
point 3.2.2.6. of document ERA/ERTMS/033281 [24,25]. The limit values are included in
Tables 3 and 4, highlighting the changes that have been introduced with the new edition
of the document. Analyzing the differences in the scope of the tested frequency bands
and permissible values of currents, they are small, but in terms of the method of assess-
ing the parameters of changes, there is much more; among other things, the minimum
window overlap time has been increased. Additional assessment parameters have been in-
troduced: the permissible duration of exceedance and minimum time between subsequent
exceedances. In the scope of the application of Annex S02 to the List of the President of
UTK [26], no differences were found between subsequent editions.
Figure 2 shows the permissible interference levels graphically, in red, resulting from
Annex S02 to the List of the President of UTK [26] and in brown for the limit resulting from
document [24] regarding the FFT and BPF processing algorithm. During the analysis of the
results, the extended laboratory uncertainty is considered, which is marked as Ulab (Iz).
The uncertainty value includes such factors as the uncertainties of individual elements
of the measuring system resulting from the calibration certificates, the resolution of these
devices and the resolution of the indications. Finally, the extended uncertainty, depending
on the current range Iz , is 0.53 to 78.92 mA.
The installation of a measurement system, which may contain various types of mea-
surement transducers, should be preceded by a thorough analysis of the vehicle’s drive
system. Based on the diagram of the vehicle’s main power supply circuit, it is necessary to
select the connection points for the transducers to measure current and voltage. In each case,
the equipment of the measurement system and the method of running the measurement’s
Energies 2025, 18, 2705 6 of 16

installation will depend on the specificity and construction of the vehicle being tested, and
therefore it is not possible to describe it precisely.

Table 3. Permissible interference currents from locomotives and electric multiple units—Annex S-02
to the List of the president of UTK [26].

Sensor Type Frequency [Hz] Current [A] Sensor Type Frequency [Hz] Current [A]
2–40 15 2680–2730 0.095
40–45 3.11 2740 0.044
45–48 1.85 2750–2900 0.018
Classic circuits track 48–52 1.20 2910–2950 0.044
SOT—1
52–55 1.85 2960–3030 0.108
55–60 3.11 3040–3090 0.231
1370–1400 0.396 3100–3120 0.396
1410–1440 0.231 6650–6700 0.425
1450 0.175 6710–7210 0.015
1460–1480 0.094 7220–7600 0.100
1490–1510 0.066 7610–8720 0.015
1520–1670 0.027 8730–9590 0.425
1680–1700 0.066 9600–10,500 0.022
1710–1750 0.217 SOT—2 10,510–11,650 0.425
1760–1780 0.117 11,660–12,700 0.034
1790–1910 0.032 12,710–14,040 0.425
SOT—1 1920–1930 0.095 14,050–15,290 0.037
1940–1950 0.127 15,300–16,110 0.425
1960–2060 0.207 16,120–17,590 0.021
2070–2120 0.068 17,600–17,650 0.425
2130–2270 0.018 24,300–25,100 0.425
2280–2320 0.141 25,300–27,130 0.035
2330–2370 0.076 27,140–27,690 0.425
2380–2550 0.019 EOC 27,700–29,900 0.038
2560–2570 0.050 30,000–30,300 0.425
2580–2600 0.118 30,400–32,700 0.038
2610–2670 0.189 32,800–33,000 0.425

Table 4. Permissible interference currents—ERA/ERTMS/033281 [24,25].

Frequency [Hz] Current [A]

Algorithm
[Hz] [A]
70.5–79.5 1.9
205.5–245.4 4.0
270.5–279.5 1.9
1900–2700 2.2
2700–5100 1.5 band-pass filters (BPFs)
3450–7550 1.5
4650–6360 1
9200–16,800 0.5
9320–16,755 0.33
1500–3200 0.3/3 1
FFT transform
9436–9564 2 0.3
1 —a change has been introduced in the permissible current value. 2 —a change has been introduced in the
frequency band.

A description of the measurement system, together with the specification of the

measuring equipment used, is included in the test report. The measurement results are
Energies 2025, 18, 2705 7 of 16

presented in graphical form for selected and marked samples. The charts are presented in
the frequency band 2 Hz–33 kHz, which is a reference to the frequency ranges specified in
Annex S-02 of the President’s Letter [26] and in the document ERA/ERTMS/033281 [24].

Figure 2. Current harmonic limits in the 2 Hz–33 kHz band.

3. Results and Discussion

The measurement results presented in this paper were obtained from tests carried out
on a prototype three-car electric multiple unit (EMU) supplied via a 3 kV DC overhead
catenary system. The unit is designed for a maximum operating speed of 160 km/h
and has a total installed traction power of 1.2 MW. The traction system comprises two
traction inverters, each rated at 390 kW, as well as two auxiliary inverters, each with a
nominal power output of 80 kW. The tests were carried out on a test track powered by a
traction station, the characteristics of which are known and can be taken into account when
analyzing the results. During the tests, there was no other receiver in the power supply
section that could be a potential source of additional interference.
The measuring transducers and their measuring installations are installed in places
where a high voltage is present. Therefore, it is absolutely necessary to ensure the safety of
the measurement team against electrocution and to protect the equipment used in research
against damage.
The general diagram of the measurement system for testing disturbances in the return
current to the traction network is shown in Figure 3. The actual measurement system
installed at the test facility is shown in Figure 4.

Figure 3. Connection diagram of the measuring system.

Energies 2025, 18, 2705 8 of 16

Figure 4. View of the measurement system on the actual test object.

An example set of measuring equipment in relation to Figure 3 is presented below:

(a) Measurement of the alternating component of the traction current Iz—Rogowski coil;
(b) Measurement of traction current It—current–voltage transducer;
(c) Measurement of the traction network voltage Ut—voltage transducer;
(d) Measurement of vehicle speed and deceleration v, a—VBOX device;
(e) Speed measurement v1–v4—axial sensor with 1–4 axes.
For recording the parameters listed in points a–e, it is necessary to use a digital recorder
enabling real-time calculations and the acquisition of all parameters.
Figures 5–8 show sample measurement results. The course of the fault current value
is shown in green for FFT and light green for BPF. To determine compliance with the
requirements, the principle of simple acceptance, described in point 4.2.1 of document
ILAC-G8:09/2019 [31], was used.

Figure 5. Background measurement results in the 2 Hz–33 kHz band.

Energies 2025, 18, 2705 9 of 16

Figure 6. Current harmonics in the 2 Hz–33 kHz band when starting the vehicle from 100% power to
a speed of 160 km/h—measurement close to the substation.

Figure 7. Current harmonics in the 2 Hz–33 kHz band during ED braking from 100% power to a
speed of 160 km/h—measurement close to the substation.

Frequency bands for which conditional compliance criteria were applied with a proba-
bility of 50% are marked with blue rectangles described in the legend as “Iz + Ulab(Iz)”. Fre-
quency bands for which the conditional non-compliance criteria were applied with a proba-
bility of 50% are marked with orange rectangles described in the legend as “Iz − Ulab(Iz)”.
Exceeding the permissible levels are marked with pink squares described in the legend as
“Iz − Ulab (Iz) > Limit Iz”.
Energies 2025, 18, 2705 10 of 16

Figure 8. Current harmonics in the 2 Hz–33 kHz band during ED braking from 100% power to a
speed of 160 km/h—measurement far from the substation.

Figure 5 presents the results of background measurements obtained when all power
electronic devices on the vehicle are turned off, and only the system enabling the current
collector to be lifted under the traction network is operational. Figure 6 shows the results
obtained when starting the vehicle up to the maximum speed, and Figure 7 shows the
results obtained during the braking test for the same object. It should be noted that during
braking, we are dealing with recuperation, because only on test sections that can receive
energy can such tests be performed; hence, the differences between the characteristics are
visible—Figures 6 and 7.
Figures 7 and 8 show the measurement results for the same object during full braking
from its maximum speed to stop. The visible difference in characteristics results from
the distance from the traction substation supplying a given section. The closer to the
power source, the higher the level of interference. Based on this, it can be concluded that
there are disturbances introduced by the substation itself. For a complete picture, it is
necessary to perform background measurements, complete an analysis of the harmonics of
the substation and include these results in the final characterization of the test object.
Figure 9 shows the characteristics with numerous exceedances (pink in the graph) of
the permissible values recorded during tests related to maintaining a constant speed and
then changing it in the cruise control system. The disturbances generated are related to the
operation of the automatic regulation system. During an identical test with manual control,
where the operation of the regulation system is much slower, this type of interference does
not occur.
It is also necessary to carry out some tests under conditions of limited adhesion.
Figure 10 shows the recorded current and voltage values when the vehicle loses traction
after starting. A functioning vehicle anti-lock braking system must also not have a negative
impact on the vehicle’s power system.
Power supply from the direct current traction network of electric traction vehicles
requires the use of rectifier units installed at traction substations. The substation system
includes transformers with various connection systems and rectifier systems composed
of uncontrolled diode bridges. Thanks to the multiphase nature of these transformers,
Energies 2025, 18, 2705 11 of 16

rectifier systems can be obtained with an increased number of rectified voltage pulses per
one supply voltage period. Simpler systems that are still used are six-pulse rectifier systems.
These systems are based, for example, on a three-phase transformer with a Yd connection
system and a bridge rectifier.

Figure 9. Current harmonics in the 2 Hz–33 kHz band during sudden speed changes performed by
cruise control.

Figure 10. Current, voltage and speed for starting from 100% (reduced traction).

The number of pulses in the rectified voltage depends on the converter system used.
However, the instantaneous and average value of the rectified voltage and harmonics,
apart from the structure and number of diodes in the rectifier, are influenced by many
other factors. These include, for example, the symmetry of the transformer’s structure,
the symmetry of the system’s supply voltages and their deformation from the sinusoid
and operation in the linear range of the transformer’s magnetization characteristics, as
well as, in a system consisting of a transformer and a rectifier, the nature and quality of
commutation processes [9].
Energies 2025, 18, 2705 12 of 16

Based on the technical parameters of the adopted solutions of the power supply
transformer, choke, rectifier and input filters used on the vehicle, analytical calculations of
the generated harmonics in the output voltage of an ideal substation are performed [32].
Example results of analytical calculations obtained up to the sixtieth harmonic are presented
in Table 5. However, initial harmonics, i.e., 6th, 12th, and 18th order, etc., have the highest
value but are relatively easy to identify, as they result from the specifics of the operation
of typical rectifiers at the output of a substation, 6- or 12-half traction. A problem during
analysis is caused by harmonics in the range of 24–36, where there are particularly low
values of limits for interference currents. Higher harmonics in practice cease to be important
because of their values.

Table 5. Harmonic contribution to voltage for U = 3300 VDC.

Order of Harmonic Voltage

Frequency [Hz] Share Value [%]
Harmonic n Value [V]
6 300 133.32 4.04
12 600 32.67 0.99
18 900 14.52 0.44
24 1200 8.25 0.25
30 1500 5.28 0.16
36 1800 3.63 0.11
42 2100 2.64 0.08
48 2400 1.98 0.06
54 2700 1.65 0.05
60 3000 1.32 0.04

An actual traction substation requires taking into account additional phenomena such
as a variable commutation angle depending on the current drawn from the substation or
asymmetries of the transformer and power supply system and distortion of the substation
supply voltage. In such a case, analytical calculations must be replaced by simulation cal-
culations based on an adopted model that takes into account these additional phenomena.
In order to determine the harmonics in the traction voltage and current of the substa-
tion, taking into account additional parameters that can affect the spectrum of harmonics
in the traction current, simulation analyses were carried out for the model of a six-pulse
traction substation. In the simulation model of the rectifier set, one working rectifier
transformer with a ∆/Υ | connection system + equalizing choke connected to a six-phase
|
|

rectifier was assumed, as well as their parameters based on the provided data. Two versions
of the substation were analyzed, without the smoothing device (filter) switched on and
with it switched on. The load currents and output voltages of the substation were similar to
the values during the measurement runs. The simulations assumed symmetry of the supply
and a resistive load close to the substation. In order to illustrate the different operating
conditions of the substation, calculations of harmonics in the output voltage and current
of the substation were performed for selected configurations of substation filters and for
selected load currents. The choice of the current value in the calculations was related
to the measurements carried out for the substation loads of the tested vehicle. Example
results of voltage harmonics are shown in Figure 11, while current harmonics for different
configurations are shown in Figures 12 and 13.
An analysis of the measured harmonics in the current shows typical dominant har-
monic values for the band from 50 Hz to 1000 Hz. Since the substation is the power supply
during the EZT tests, the levels of generated harmonics in the current should be related to
the requirements for the limit values of these harmonics for traction vehicles.
Energies 2025, 18, 2705 13 of 16

Figure 11. Traction voltage harmonics in the band 10 Hz–6 kHz (330 A, 3300 V, power supply
unbalance, filters off).

Figure 12. Current harmonics in the band 10 Hz–6 kHz (330 A, 3300 V, power supply unbalance,
filters included.

Figure 13. Current harmonics in the band 10 Hz–6 kHz (950 A, 2900 V, power supply unbalance,
filters off).

As mentioned in the introduction, complementary tests include the psophometric

current (equivalent to the interference current in the required frequency band) generated to
the overhead contact system. The measurement of such a current is carried out in the same
Energies 2025, 18, 2705 14 of 16

system as the previous measurements (Figure 2)—in the main circuit using an algorithm
using FFT.
The value of the psophometric current Ipso is determined based on the relationship
given in the PN-EN 50121-3-1:2017 standard [27].

1
q
Ipso =
p800 ∑(pf If )2 (2)

where If is an alternating current component with frequency f in the traction current, pf is a

psophometric weight factor [33], and p800 denotes the pf value for a frequency of 800 Hz
(p800 = 1000).
The requirements for transient current measurements result from the provisions of the
PN-EN 50388-1 [28] standard, point 11.5. The purpose of this type of measurement is to
ensure that there are no undesirable actions by the safety devices in the traction substation.
The transient current must be recorded during the vehicle starting procedure when the
quick-release switch is activated. The limit values are shown in Table 6.

Table 6. Limit values of transient current in time periods.

T [ms] Required di/dt [A/ms]

<20 di/dt < 60
>20 di/dt < 20

A comprehensive analysis should include analytical calculations, simulation calcula-

tions and an assessment of the measurement results of the traction substation. Example
elements of the analysis were performed in terms of generating disturbances, in particular,
harmonics in the substation output current. This issue is particularly important when
testing traction vehicles powered by this type of system in order to isolate interference
generated by the substation itself. Only a comparison of the obtained results will show
whether the levels of harmonics in the substation output current for the analyzed cases
of vehicle cooperation with substations do not exceed the permissible values according
to [23,24] for this parameter.

4. Conclusions
This paper presents issues related to the research and analysis of electromagnetic
compatibility with train detection systems based on track circuits, a topic that is quite
complicated and difficult to implement in practice. The complexity of the tests, including
the number of tests to be carried out under various conditions and the need to perform
them multiple times to ensure the repeatability of the results, as well as the need to take
into account so many factors affecting the results, requires a very careful approach to their
performance and, even more so, the analysis of the results obtained. The determination of
harmonic components in the traction current in relation to the permissible levels specified in
the latest and frequently updated editions of documents requires their constant supervision.
The subject of this type of measurement was discussed in detail, and, referring to the
normative requirements, the procedures for conducting research were defined. However,
from the authors’ experience, further work seems necessary to improve the ability to
identify external sources of interference affecting the obtained results.
Research on the electromagnetic compatibility of rolling stock, while focused on in-
teraction with track circuits, is part of the broader context of ensuring the stable and
trouble-free operation of evolving railroad microgrid systems. Understanding and mini-
mizing electromagnetic interference is essential for the effective planning and control and
reliable operation of these advanced systems.
Energies 2025, 18, 2705 15 of 16

Author Contributions: Conceptualization, A.G. and D.S.; methodology, A.G. and D.S.; validation,
A.G. and D.S.; formal analysis, A.G. and D.S.; investigation, A.G. and D.S.; resources, A.G.; data
curation, A.G.; writing—original draft preparation, A.G. and D.S.; writing—review and editing, A.G.
and D.S.; visualization, A.G. and D.S.; supervision, A.G. and D.S.; project administration, A.G. and
D.S.; funding acquisition, A.G. and D.S. All authors have read and agreed to the published version of
the manuscript.

Funding: This research was funded by the Ministry of Education and Science under contract
No. DWD/6/0041/2022.

Data Availability Statement: The original contributions presented in the study are included in the
article, further inquiries can be directed to the corresponding author.

Conflicts of Interest: The authors declare no conflicts of interest.

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