Application of XLPE Cables in Electric Networks

Supplying DC Traction Loads

Andrey Kryukov

1,2 a

, Konstantin Suslov

1,3 b

, Aleksandr Cherepanov

, Quoc Hieu Nguyen

and Ilya Shushpanov

Department of Power Supply and Electrical Engineering, Irkutsk National Research Technical University, Irkutsk, Russia

Department of Transport Electric Power, Irkutsk State Transport University, Irkutsk, Russia

Department of Hydropower and Renewable Energy, National Research University “Moscow Power Engineering

Institute”, Moscow, Russia

Shandong Women’s University, China

Keywords: Electricity Supply to the DC Traction Substations, Cable Power Transmission Lines, Modeling.

Abstract: The connection of railway traction substations (TS) to high-voltage networks of electric power systems

relies on overhead power transmission lines. This approach has several downsides: considerable width of

the protection zone; potential for damage during strong winds, and the accumulation of ice and frost depos-

its. Additionally, there is a risk of injury to both people and animals caused by step voltages resulting from

wire breakage. The noted negative consequences can be forgotten when using 110 kV cable lines (CL) with

cross-linked polyethylene (XLPE) insulation for connecting traction substations. The study presented in this

paper aims to develop digital models for determining power flows in direct current traction power supply

systems (DC TPSS) with power supply to converter substations via cable line. Multiphase modeling meth-

ods are used alongside the Fazonord software product, specifically version 5.3.5.0–2024. The obtained re-

sults allow us to draw the following conclusions: the use of cable lines leads to an increase in the minimum

three-minute voltages of 2 to 3.5%, while active power losses in the main power transmission line decrease

by 8 to 14%. DC traction substations do not create some noticeable levels of unbalance in the adjacent net-

works. However, any unbalance in a three-phase system has a negative effect on power consumers, espe-

cially on widely used induction electric motors. The use of XLPE cables allows reducing unbalance factors

by 11-22 times. In the presence of overhead lines (OL), the levels of harmonic distortions on the 110 kV

buses of traction substation (TS) 2 and TS 3 exceed the normally permissible values. Replacing the over-

head lines with cable lines makes it possible to reduce the indicators by approximately 60%. The factors of

certain harmonics are reduced by 37...100%. The developed digital models can be used to design and oper-

ate DC TPSS. The method for power flow determination is universal and can be used to make calculations

for external power supply systems of any configuration and traction networks of various designs.

https://orcid.org/0000-0001-6543-1790

https://orcid.org/0000-0003-0484-2857

https://orcid.org/0000-0002-7712-9537

https://orcid.org/0000-0002-6969-8369

https://orcid.org/0000-0001-7121-7651

1 INTRODUCTION

Overhead power lines are traditionally used to con-

nect railway traction substations (TS) to 110-220 kV

networks. This approach has some disadvantages:

• a significant area of the protection zone;

• the potential for damage from strong winds and

the accumulation of ice and frost deposits;

• the risk of injury to people and animals caused

by step voltages when wires break.

These negative effects can be eliminated by using

110-220 kV cables with cross-linked polyethylene

(XLPE) insulation in external systems of power

106

Kryukov, A., Suslov, K., Cherepanov, A., Nguyen, Q. H. and Shushpanov, I.

Application of XLPE Cables in Electric Networks Supplying DC Traction Loads.

DOI: 10.5220/0013285700003953

Paper published under CC license (CC BY-NC-ND 4.0)

In Proceedings of the 14th International Conference on Smart Cities and Green ICT Systems (SMARTGREENS 2025), pages 106-113

ISBN: 978-989-758-751-1; ISSN: 2184-4968

supply to TS. Cable lines differ from overhead

lines in a small area of the protection zones, protec-

tion from the effects of powerful winds and ice, a

lower risk of electrical injuries, increased capacity

with compensation for inductive loads, and others.

In some cases, despite the high cost, CLs may be

preferable to overhead lines.

The issues of energy efficiency, quality and reli-

ability of equipment and power transmission lines

have been considered in many studies by research-

ers (Asainov, 2024; Rzazade, 2023, Bulatov, 2020).

Modern methods and mathematical models are

used in the research (Rogalev, 2022;

Klyuev, 2022;

Monakov, 2023, Zlatov, 2014, Genbach, 2020, Bu-

latov 2017).

Many studies examine the problems of deter-

mining the power flows of DC TPSS, which under-

scores their significance. For example, algorithms

for modeling the electrical interference of 24 kV

DC traction network on adjacent lines are presented

in (Marikin, 2019). The method for considering the

conductivity of the earth when determining the

power flows of DC TPSS is described in (Lesni-

kov, 2020). The specific features of traction net-

work calculations are explored in (Gavrilin, 2012).

The problem of enhancing the energy efficiency of

TPSS by using storage devices located at section-

ing points is solved in (Cheremisin, 2015). The

method for assessing the effect of magnetic inter-

ference of 3 and 24 kV DC traction networks on

adjacent communication lines is presented in

(Mushkov, 2021). The results of fault analysis

based on modeling the DC TPSS of the metro un-

der various operating conditions are presented in

(Luo, 2022). The characteristics of DC TPSS under

short-circuit conditions are investigated in (Xia,

2020). An algorithm for determining the equivalent

load of TPSS is implemented in (Lu, 2021). An

AC/DC converter applicable in the DC TPSS and

intended for high-speed trains is presented in

(Sokol, 2019). The results of modeling the dynamic

distribution of the earth fault current in the DC

TPSS are given in (Yan, 2022). The reliability and

service life of the DC TPSS are assessed consider-

ing load characteristics in (Chen, 2021). A new DC

TPSS is described in (Chen, 2015). The influence

of the metro DC TPSS on the harmonics of the

power grid is studied in (Aoyang, 2017). A method

for improving the efficiency of feeder protection in

the DC TPSS is proposed in (Wei, 2019). The

structural diagram and control strategy of the en-

hanced DC TPSS are considered in (Kang, 2022).

A comprehensive strategy for improving the quali-

ty of electric power for the TPSS is developed in

(Song, 2023). Modeling the DC TPSS for high-

speed rail transport is explored in (Simiyu, 2021).

The results of studying the new TPSS for a com-

prehensive improvement of the electric power qual-

ity are discussed in (Chen, 2015). A probabilistic

method for calculating the metro traction load

based on the Monte Carlo method is proposed in

(Chang, 2020). The hardware emulator of the DC

TPSS for determining the rail potential is described

in (Wang, 2018). A new hybrid transformer for the

metro TPSS is modeled and simulated in (Wang,

2022).

2 METHODOLOGY

The analysis of the publications indicates that they

address numerous significant aspects of the DC

TPSS modeling. However, the problem of deter-

mining the power flows of DC TPSS, which in-

clude cable lines with insulation made of cross-

linked polyethylene, remains unsolved. TPSSs have

a number of features that significantly distinguish

them from general-purpose electrical networks.

These include (Zakaryukin, 2005): a highly varia-

ble and nonlinear traction load; the structural diver-

sity of subsystems resulting from single-phase DC

traction networks and three-phase external power

supplies in DC TPSS; notable spatial distribution;

and mobility of electricity consumers such as elec-

tric locomotives. The listed factors complicate

modeling the DC TPSS operating conditions char-

acterized by significant harmonic distortions. This

problem – significant for both theory and practice –

can be solved using the methods, algorithms, and

the Fazonord software described in (Zakaryukin,

2005; Zakaryukin, 2023; Suslov, 2023; Kryukov,

2024; Kryukov, 2024).

The constant EMF method used for modeling is

described in detail in (Wang, 2018). The calcula-

tions of the DC TPSS power flows were carried out

using diacoptic methods. In this case, the electro-

motive forces and their internal resistances were

assumed to be constant and were determined by the

idle parameters of the converter.

The TPSS power flows were determined using

the commercial software Fazonord. The current

5.3.5.0–2024 version of this software implements

the DC network modeling technology described in

detail in (Zakaryukin, 2023).

Application of XLPE Cables in Electric Networks Supplying DC Traction Loads

107

3 RESULTS OF MODELING

Below are the calculation results for the power sup-

ply system of a DC railway section (Figure 1). The

TPSS includes three substations and two inter-

substation areas, 20 km long. Modeling is carried out

for two options that differ in the design of the external

network. The first option considers lines implemented

on the basis of XLPE cables, and the second option

employs overhead power transmission lines.

The power flows arising during the movement of

trains weighing 3 884 tons were calculated. The co-

ordinates of the location of the live parts are shown

in Figure 2.

The modeling results are shown in Table 1 and

Figures 3-12. Figures 3 and 4, along with Table 1

present data characterizing the voltage levels U on

the current collectors of electric locomotives. As

seen in the Figures, the use of cable lines leads to an

increase in the minimum three-minute voltage of 2

to 3.5%. It is also seen that these parameters are sta-

bilized, for example, the standard deviation U for the

first down train decreases by 7%.

DC traction network of a double-track section

CL 1

CL 2 CL 3

TDN-16000

TDP-12500

TS 1

TS 2 TS 3

110 kV

10 kV

3 kV

30 +j15 MV·A

Figure 1: Electrical network diagram.

Figures 5 - 7 show graphs characterizing the en-

ergy efficiency of the external network of the TPSS.

As seen in the Figures, power losses in the main

power transmission line are reduced by 8 to 14%

when cable lines are used.

)

Figure 2: Coordinates of live parts: a – cable centers; b – overhead line wires.

)

Figure 3: Voltage on pantographs of electric locomotives.

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108

)

Figure 4: Comparison of cable lines and overhead lines: a – voltage changes for electric locomotive 2; b – minimum three-

minute voltages; ERS – electric rolling stock.

)

Figure 5: Power losses (a) and flows (b) for the case of cable lines.

)

Figure 6: Power losses (a) and flows (b) for the case of overhead power lines.

Figure 7: Comparison of power losses in transmission lines.

Application of XLPE Cables in Electric Networks Supplying DC Traction Loads

109

Table 1: Minimum three-minute voltage at the current

collectors.

Power line

types

Electric locomotive number

1 2 3 4

Cable line 3 2.85 3 2.85

Overhead line 2.9 2.79 2.9 2.79

Direct current traction substations do not create

noticeable levels of unbalance in adjacent networks.

However, any unbalance of a three-phase system

affects negatively power consumers, especially

widely used induction motors. The use of XLPE

cables decreases the levels of unbalance by 11 to 22

times, as illustrated in Figure 8.

Figures 9-11 demonstrate the determined non-

sinusoidal conditions generated by the converter

units of the traction substation. They indicate that in

the presence of an overhead line, the levels of har-

monic distortion on the 110 kV buses of TS 2 and

TS 3 exceed the normally permissible values. The

replacement of an overhead line with a cable line

diminishes the total harmonic factor by 60%. The

indicators kU(n) for individual harmonics decrease

by 37 to 100%, as shown in Figure 11.

Figure 12 illustrates the results of determining the

magnetic field strengths along the railway axis at a

height of 1.8 m. As seen in the Figure, the maximum

values H

max

of the amplitudes do not exceed the

permissible values for the considered calculation

options. For cable lines, however, the maximum

value of H

max

is 28% higher than this indicator for

overhead lines.

Figure 8: Unbalance on 110 kV buses of TS 3: for illustration purposes, the k2U values for the cable line are increased ten-

fold.

)

Figure 9: Harmonic distortion factors for voltage (a) and current (b) on 110 kV TS3 buses of (phase A)

)

Figure 10: Harmonic distortion factors for voltage on 110 kV TS buses (phase A): a – average values; b – maxima.

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110

Figure 11: Harmonic spectra of voltage on 110 kV TS3 buses.

Figure 12: Amplitudes of magnetic field strengths along the power transmission line axis at a height of 1.8 m.

4 CONCLUSIONS

The use of XLPE cables in external power supply

systems of DC railways provides the following posi-

tive outcomes: it substantially narrows the required

protection zone; mitigates damage from severe

winds, as well as the buildup of ice and frost; and

reduces the risk of injury to people and animals

caused by step potentials when wires break. In addi-

tion, the modeling results indicate that utilizing

XLPE cables increases the minimum three-minute

voltages by 2 to 3.5%, decreases active power losses

in the main power transmission line by 8 to 14%,

and brings down unbalance factors by 11 to 22

times. By replacing the overhead line with XLPE

cables, we can achieve a reduction of approximately

60 % in harmonic distortions on the 110 kV buses of

the traction substation.

The developed digital models can be used to de-

sign and operate DC TPSS. The methodology for

determining the power flows is highly adaptable and

can be used in calculating the power flows of exter-

nal power supply systems of any configuration and

traction networks of various designs.

The research was funded by the Russian Science

Foundation (project No. 25-29-00937).

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