Calculation Model of the Effectiveness of Electromagnetic Field

Protection: Using the Example of a Train Dispatcher's Workplace

Kh. M. Kamilov

, O. T. Aliyev

and I. I. Gavrilin

Tashkent State Transport University, Tashkent, Uzbekistan

Ural State University of Railway Transport, Yekaterinburg, Russia

Keywords: Electromagnetic fields, uninterruptible power supply, shielding, electrical, dielectric and magnetic

conductivity, protective casing and shield, design scheme and model.

Abstract: An increase in the number and increase in the power of various artificial sources (radio communication, VDT

and personal computer, uninterruptible power supply, etc.) lead to a significant increase in the level of

electromagnetic radiation in the workplace, which create an additional artificial electromagnetic field that

adversely affects human health. One of the most reliable ways to protect against the electromagnetic field is

to shield these equipment. The article develops a computational model for calculating the effectiveness of the

screen from the effects of electromagnetic fields at the workplace of a train dispatcher.

1 INTRODUCTION

The emission of harmful and dangerous factors at the

workplace of a train dispatcher is formed in

connection with the indicators of technical means.

The electromagnetic field at the workplace of a train

dispatcher is mainly created by VDT and personal

computers that dispatchers regularly use in their

work, as well as electromagnetic waves emitted by an

uninterruptible power supply (Eliseeva, 2005;

Kudryashov, 2005).

The measurements that were carried out during

the certification of workplaces for working conditions

showed that the voltage of the electromagnetic field

in the workplace of the train dispatcher mainly creates

an uninterruptible power supply that provides power

to the VDT and personal computers at the workplace.

The uninterruptible power supply is located inside the

desktop cabinet, and the chair on which the dispatcher

sits is placed next to it, due to the need for constant

monitoring of data from monitors (Sulaymanov,

2019).

One of the most reliable ways to protect against

the electromagnetic field is to shield these

equipment. When creating structures that protect

against the intensity of the electromagnetic field,

various materials (metal or dielectric) are used,

which have the property of absorbing or repelling

the electromagnetic field in a certain frequency

range (Lynkov, 2004; Rakhimbekov, 2017;

Odinaev, 2015; Gichev, 1999).

The absorption efficiency of the electromagnetic

field is determined by the electrical, dielectric and

magnetic properties of the material used for

shielding. Due to such properties of the material,

electromagnetic energy is absorbed due to dielectric,

magnetic and conduction losses. Shielding allows to

reduce the level of electromagnetic field intensity to

a safe level (Bespalova, 2015).

2 MAIN PART

The shielding is divided into magnetic, electric and

electromagnetic fields. Almost always the same

dielectric medium is placed on both sides of the

screen, and in this case the efficiency of the screen is

written as follows (Ovcharenko, 2008):

𝑒=20𝑙𝑔

𝑐ℎ𝑘ℎ

+ 20𝑙𝑔1 + 0,5

𝑧



𝑧



𝑧



𝑧



𝑡ℎ𝑘ℎ, (1)

where ℎ− screen thickness, mm; 𝑘−propagation

coefficient, mm

-1

;

𝑧



− resistance of the medium to the

electromagnetic field, Ohms;

𝑧



− the resistance of the screen material to the

electromagnetic field, Ohms.

Kamilov, K., Aliyev, O. and Gavrilin, I.

Calculation Model of the Effectiveness of Electromagnetic Field Protection: Using the Example of a Train Dispatcherâ

Zs Workplace.

DOI: 10.5220/0011577200003527

In Proceedings of the 1st International Scientiﬁc and Practical Conference on Transport: Logistics, Construction, Maintenance, Management (TLC2M 2022), pages 42-44

ISBN: 978-989-758-606-4

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

However, the resistance 𝑧



in the induction zone

depends not only on the type of the main component

of the electromagnetic field, but also on the shape of

the screen structure.

Taking into account the shape of the screen, the

resistance𝑧



is written as follows (Ovcharenko,

2008):

When shielding an electric field (Ovcharenko,

2008):

𝑧



𝜔𝜀



𝑟

∗

𝑚

(2)

When shielding a magnetic field (Ovcharenko,

2008):

𝑧



=𝜔𝜇



𝑟

∗

𝑚, (3)

Where m=2 at 𝑟

∗





for a flat screen, m=1 at 𝑟

∗

𝜌 for a cylindrical screen, and 𝑚=



√



at 𝑟

∗

=𝑟for a

spherical screen (Ovcharenko, 2008).

When shielding a magnetic field, it is necessary to

take into account the individuality of the material

from which the screen is made. Usually for magnetic

materials (steel, permalloy, ferrite)

, and for

non-magnetic materials (copper, aluminum, lead)

. In the case that at relatively low

frequencies of the electromagnetic field

(

𝑓<



𝐻𝑧

)

𝑘ℎ<<1,𝑐ℎ𝑘ℎ≈1,𝑡ℎ𝑘ℎ≈𝑘ℎfor

protective devices made of magnetic metals, the

shielding efficiency is calculated by the formula

(Ovcharenko, 2008):

𝑒=20𝑙𝑔 1 +

2𝑚

∙

𝜇



𝜇



∙

ℎ

𝑟

∗

 (3)

It does not depend on the frequency of the field.

For protective devices made of non-magnetic

metals, the shielding efficiency is calculated by the

formula (Ovcharenko, 2008):

𝑒=10𝑙𝑔 1 +

𝑚

∙𝜔𝜇



𝜎



𝑟

∗

ℎ (4)

This efficiency depends on the frequency and at

the frequency

0→

also tends to zero.

In the region of relatively high frequencies10



𝑓,Гц < 10



, it is convenient to determine the

screening efficiency by the formula (Ovcharenko,

2008):

𝑒=8,686



𝜔𝜇



𝜎



ℎ + 20𝑙𝑔 



𝜎



𝜔𝜇



𝑧



 (5)

In the microwave region covering decimeter,

centimeter and millimeter waves (

109

10...10≥f

Hz), the wavelength

is commensurate with the

diameter of d screen, i.e.𝜆≥𝑑, and the shielding

efficiency is oscillatory (Ovcharenko, 2008).

If there are holes or cracks in the screen, which

arise as a result of imperfections in its design and

production technology, the screening efficiency

decreases. In this case, it can be determined by the

formula (Ovcharenko, 2008):

𝑒=10𝑙𝑔



2𝑧



𝑧



 + 𝐴 + 8,686𝐵 (6)

where the resistance

is determined by the

formulas (2) (Ovcharenko, 2008):

𝑧



=



𝜔𝜇



𝜎



 (7)

The summand A and the multiplier B take into

account the leakiness of the screen (Ovcharenko,

2008):

𝐴=20𝑙𝑔 

2𝜋

𝑘



𝑟

∗







∙

(

1 − 0,5𝑘



𝑙

)



 (8)

𝐵=

2𝜋ℎ

𝑙

, (9)

where 𝑟

∗

≈0,62𝑣





the equivalent radius of the

screen of any geometric shape (v is the internal

volume of the screen, mm

), mm;

l is the largest size of the hole (crack) in the screen,

mm;

𝑘



=𝜔



𝜇



𝜀



(10)

When developing a scheme for calculating the

effectiveness of the protective shield, it was based on

a convenient technical layout of the dispatcher's

workplace and theoretical formulas for calculating

the effectiveness of the above-mentioned means of

protection against electromagnetic fields

(Sulaymonov, 2021).

The working surface of the train dispatcher's

workplace consists of two parts, one of which is

equipped with a work desk with train schedules.

Monitors are installed on the rest of the desktop to

track information. An uninterruptible power supply is

placed inside the desktop cabinet, consisting of a

mini-transformer and a rectifier, which regularly

supplies power to VDT and personal computers.

Despite the low power of the uninterruptible power

Calculation Model of the Effectiveness of Electromagnetic Field Protection: Using the Example of a Train Dispatcherâ

Zs Workplace

supply, it is very close to the place where the

dispatcher is located. Therefore, it should be noted

that the voltage of the electromagnetic field

propagating from it is much higher than the

permissible voltage level of the electromagnetic field.

It is known that the shielding of an uninterruptible

power supply as a means of protection against the

effects of electromagnetic field strength is a simple

and inexpensive uncomplicated device (Sulaymonov,

2021).

The reduction of the electromagnetic field

strength of the uninterruptible power supply can be

achieved by covering its body with protective casings

and shielding the inner surfaces of the walls of the

desktop cabinet (Sulaymonov, 2021).

The efficiency of the screen and casing in

shielding was evaluated according to the formula (4)

given above.

The developed computational model is two-

dimensional, and the shape of the casing and the

screen differs from each other. The casing has a semi-

cylindrical shape. The inner surfaces of the walls of

the table stand are flat. When mathematically

expressing the effectiveness of the calculation model,

it is necessary to take into account the design

parameters, the shape of the protective equipment

(cylindrical casing and flat screen). Taking into

account the logarithmic expression of efficiency, it is

recommended to use the following mathematical

expression based on formula (4) to evaluate the

overall effectiveness of the protective casing and

screen:

𝑒



=10𝑙𝑔 1 +

𝑚

𝜔𝜇



𝜎



𝑟

∗

ℎ

+ 10𝑙𝑔1 +

𝑚

𝜔𝜇



𝜎



𝑟

∗

ℎ,(11)

where 𝑚

– sphere shape coefficient; 𝜔=2𝜋𝑓–

circular frequency, s

-1

; 𝜇– absolute magnetic

permeability, Gn/m; 𝜎– specific conductivity of the

medium, Cm/m; 𝑟

∗

– equivalent radius of the screen of

any geometric shape, mm; ℎ– screen thickness, mm;

𝑚

– flat shape coefficient.

3 CONCLUSION

Thus, the use of screens (cylindrical casing and flat

screen) to reduce the level of electromagnetic field

intensity, i.e., the opening of the source provides an

increase in the effectiveness of the means of

protection.

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