Coordinated Track Circuits

F. R. Akhmadullin

Samara State Transport University, Samara, Russia

Keywords: Rail line, track circuit, circuit, control method, rail line status control.

Abstract: The article considers a track circuit with an adaptive track receiver, which include coordinated track circuits

that are part of correlative track circuits. This article describes a method for monitoring the condition of track

sections by comparing the voltages at the inputs of track receivers of two rail lines. The described method can

be used to monitor the condition of other rail lines.The main advantage and positive quality of the considered

track circuits is that they have the ability to function with a small insulation resistance, have a much longer

length and shunt sensitivity. In addition, these track circuits are susceptible to longitudinal asymmetry and to

changes in insulation resistance, therefore they have a number of their own features according to the algorithm

of their functioning and construction. The commissioning of coordinated track circuits increases the safety of

train traffic, facilitates the working conditions of service personnel, as well as the reliability of the interval

train traffic systems themselves.

1 INTRODUCTION

When analyzing the quality of the functioning of

track circuits (TC), one of the main criteria is to

ensure the safety of train traffic. The working

conditions of the track circuits are far from normal,

taking into account the number of destabilizing

factors and interference from the traction network.

The decisive factor in the evaluation is the degree

(high) of noise immunity of the track receiver (TR).

In order to remove or minimize the destabilizing

factor affecting the operation of the TC, coordinated

track circuits (TC) are proposed for use

Taking into account the main functional purpose

of the TC, it is necessary to pay attention to the quality

characteristic of the TR – noise immunity, which can

be evaluated on the basis of the accepted elementary

discrete symbols.

When researching new concepts or upgrading

existing systems, experimental and analytical

methods are used almost everywhere

In the vast majority of variants, the

implementation of experimental research in

conditions close to natural will require significant

expenditure of both resources and time, and

sometimes such a method is not possible at all. Of

particular importance when evaluating the ITTS

channels for noise immunity, where the

communication line is track circuits (TC) and

inductive rail lines (IRL), are studies conducted on

the basis of reliable representations of both signals

and interference.

It is used for some types of interference in RL, this

is due to the fact that with one-time simultaneous

recording of the values of the characteristics of

interference and also absolutely all key conditions

that have a great impact on them, there is a need for a

special complex and expensive technique. In

addition, in the event of an accident, it will be

impossible to register interference.

Such disadvantages are absent when using

analytical methods, but they can be used only if there

is a probability to state mathematically quite clearly

all the main conditions without exception that have a

great influence in the procedure under study.

In these circumstances, one possible method of

research is considered to be simulation modeling,

implying the reconstruction of processes with the

simulation of certain and random variables that have

a direct impact on these processes.

2 MATERIALS AND METHODS

Methods based on the use of track circuits with

adaptive track receivers (ATR) are considered to be

one of the most promising ways to control the

vacancy of the track. One of the types of adaptive

196

Akhmadullin, F.

Coordinated Track Circuits.

DOI: 10.5220/0011581500003527

In Proceedings of the 1st International Scientiﬁc and Practical Conference on Transport: Logistics, Construction, Maintenance, Management (TLC2M 2022), pages 196-199

ISBN: 978-989-758-606-4

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

track circuits is considered to be coordinated TC

(CTC), which are part of the correlative track circuits

(Akhmadulin, 2006; Akhmadulin, 2007;

Akhmadulin, 2008; Akhmadulin, 2009; Akhmadulin,

F. R., 2010; Akhmadulin, 2011; Akhmadulin, 2020;

Polevoy, 2006). A significant positive quality of these

TC is considered in this case, that they have the ability

to function with a small insulation resistance, have a

much longer length and shunt sensitivity. Together

with this, such track circuits are susceptible to

longitudinal asymmetry and how quickly changes in

insulation resistance occur. The commissioning of

such TC increases the safety of train traffic, improves

the working conditions of service personnel, as well

as the reliability of the interval train traffic systems.

The monitoring of the state of rail lines of track

circuits is performed by analyzing the voltage at the

input of the receiving end with a certain set value,

constant for the entire service life.

Track circuits, in which two adjacent track circuits

(TC) are used with one common track generator (TG),

which is connected to the rail line at the boundary of

their interfaces, are called coordinated track circuits

(CTC). In such track circuits, detection and

processing of signals at the output of the rail line is

performed using difference approximation, in other

words, by analyzing the received signal values and

voltage values from the output of demodulators in

track receivers.

The algorithm of operation of the coordinated

track circuits (CTC) takes into account that during the

normal operation of the TC, it is necessary to check

two conditions when determining the

vacancy/occupancy of the track section, including the

rail breakage:

− -the magnitude of the voltages at the receiving

ends of the track circuit must be the same;

– exceeding the voltage levels of the signals at

the receiving ends of the TC of the voltage

threshold of the sensitivity of the TR for the

shunt mode of the TC.

This algorithm makes it possible to increase the

stability of establishing the vacancy of the rail track,

as well as the rail breakage in the event of a change in

the insulation resistance of the rail line.

A special specificity of the recommended concept

for the implementation of coordinated track circuits is

the use of a microelectronic element base, which

makes possible a relatively simple method

(algorithm) of decision-making (Figure 1) on the

vacancy/occupancy/breakage of the rail track in

conditions of changing the values of the insulation

resistance Z and the rail line.

Figure 1: Diagram of the decision-making structure of the

CTC.

Figure 1 shows the following values:

− the signal voltage at the output of the

demodulators of the TR of the first and second

coordinated TC, respectively, U

(t) and U

(t);

− the voltage of the shunt sensitivity threshold of

the TR of coordinated TC U

(constant value);

− a value that takes into account the natural

variation of U

1 values

(t) and U

(t) under real

operating conditions– ∆

;

− the acceptable level of the value ∆

. – ∆

tACC

The conclusion about the possibility of the CTC

operation over time and the change in the insulation

resistance of the rail line is made taking into account

the difference approximation:

1. A preliminary check of inequalities is being

developed

(t) > U

0 and U

(t) > U

;

2. The correspondence is calculated in time

∆

= U

(t) – U

(t);

3. The value of ∆

is compared with the

established norms for a particular case with the

value of ∆

tACC

Coordinated Track Circuits

197

Let's define all existing combinations of values of

these calculations:

1. There is a solution. U

(t) > U

, U

(t) > U

, ∆

= U

(t) – U

(t) and ∆

< ∆

t ACC

– we are moving

along the path 1-2-3-4-5-6-7.

2. There is a solution. ∆

≥ ∆

t ACC

– we are moving

along the path 1-2-3-4-5-6-8.

3. There is a solution. U

(t) > U

, U

(t) ≤ U

–

we are moving along the path 1-2-3-4-11.

4. There is a solution. U

(t) ≤ U

, U

(t) > U

–

we are moving along the path 1-2-3-9-10.

5. There is a solution. U

(t) ≤ U

, U

(t) ≤ U

–

we are moving along the path 1-2-3-9-8.

The algorithm presented in Figure 1 assumes the

characteristic features of the functioning of

coordinated TC with a single TG:

− analysis of voltage values of signals U

(t) and

(t) in the TR demodulator of the coordinated

TC exercising control of the 1st and 2nd

adjacent rail sections of the track occurs in

symbols 1 and 2;

− 3,4: comparison of voltage values U

(t) and U

(t) respectively with threshold values of

sensitivity U

in TR shunt mode of the TC (U

(t) > U

and U

(t) > U

) when exceeding U

(t) and U

(t) the values of U

are compared

with the values of U

(t) and U

(t) between

themselves by means of calculations according

to the formula ∆

= U

(t) – U

(t), and if U

(t)

takes values greater than U

ST,

and U

(t) is

greater than or equal to U

, then in the 11th

character a decision is made that the second

section of the rail track is occupied (P

= 0; P

= 1);

− symbol 6 is responsible for comparing the

values of the values of ∆

and ∆

t ACC

, necessary

to fulfill the conditions when controlling the

7th and 8th symbols:

− -∆

< ∆

tACC

both sections of the track control are

vacant (Р

= Р

= 0) (the decision is made in

symbol 7);

− -∆

≥ ∆

tACC

both sections of the track control are

occupied (P

= 1; P

= 1) (the decision is made

in symbol 8);

− The symbols 8 and 10 are controlled by the

symbol 9 in the case of:

− -U

(t) ≤ U

both controlled sections of the

track are occupied (P

= 1; P

= 1) (symbol 8)

− -U

(t) > U

the second of the controlled

sections is vacant, the first is occupied.

An electrical functional circuit based on and

implementing the algorithm (Figure 1) is shown in

Figure 2.

The picture shows:

− rail lines under the control of the first and

second sections of the track respectively – RL

and RL

;

− rail lines adjacent to the controlled sections of

the track – RL

1-1

and RL

2+1

;

− protection and alarm devices – PAD;

− track generator – TG;

− track receivers of the first and second CTC

respectively – TR

and TR

;

− track receivers of TC adjacent to CTC – TR

1-1

and TR

2+1

;

− decision-making device on the state of

controlled sections of the track – DD

1+2

;

− devices for making decisions (decision

devices) about the condition of the sections of

the track adjacent to the CTC– DD

(1-2)+(1-1)

and

(2+1)+(2+2)

Figure 2: Electrical functional diagram of coordinated TC.

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198

Figure 3: Replacement scheme of coordinated TC.

The device, which performs the control function

when deciding on the state of the regulated sections

of the rail-bed DD

1+2

, works based on the algorithm,

the block diagram is shown in Figure 1.

In accordance with the electrical functional

scheme, which is shown in Figure 2, a single model

of the replacement circuit for coordinated TC was

compiled (Figure 3), taking into account the concepts

of the theory of track circuits and the simulation

apparatus, it is already possible to develop a

simulation model of the coordinated TC.

3 CONCLUSIONS

Summing up, we can say that in order to establish and

assess how effective the TC is, it is necessary to

determine the ability of the track receiver to guarantee

the reception and processing of signals with a set level

of reliability under the worst operating conditions. In

addition to this, the numerical coefficient for

evaluating the efficiency of the system makes it

possible to analyze the operation and functionality of

the track circuit in different operating modes and with

different inputs, as well as, if necessary, compare the

TC with each other.

REFERENCES

Akhmadulin, F. R., 2006. Rail line status control by the

method of paired coupling. Materials of the 3rd

International Scientific and Practical Conference

«Actual problems of railway transport development»,

pp. 48-58.

Akhmadulin, F. R., 2007. Balanced track circuits. In

collection of scientific papers dedicated to the 170th

anniversary of Russian railways «Young scientists –

transport», pp. 12-14.

Akhmadulin, F. R., 2008. Nonconjugated correlative track

circuits. Scientific and technical journal «Transport of

the Urals». 4(19). pp. 67-69.

Akhmadulin, F. R., 2009. The method of control of the

correlative track circuit with paired coupling. Scientific

and Technical Journal «Bulletin of transport of the

Volga region». 4(20), pp. 31-34.

Akhmadulin, F. R., 2010. The method of monitoring the rail

line status. Materials of the II International Scientific

and Practical Conference «Science and education for

transport, dedicated to the 110th anniversary of

transport education in the Saratov region», pp. 73-76.

Akhmadulin, F. R., 2011. Nonconjugated correlative track

circuits with the control method at different input

resistances at the ends of the rail line. Materials of

scientific and technical conf. «Transport of the XXI

century: research, innovation, infrastructure,

dedicated to the 55th anniversary of USUPS: in 2

volumes», 97(180), 1, pp. 740-744.

Akhmadulin, F. R., 2020. Conjugated correlative track

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