2. 1. Connection of electric traction substations on the
principle of input-output
2. Electric traction substation connected to the
nearby electric power plant

3. Connection of electric traction on the principle of input-output with two
transmission feeders equipped with three-poles switches, three-phase
busbar disconnectors and a three-pole disconnectors with earthing
blades

4. Electric traction substation connected to the
nearby electric power plant

5. There are two transformers, two transmission feeders, the two bus feeders
(high voltage and low voltage), two transformer feeders.
Each transformer has its own voltage regulator. Each feeder is fitted in same way.
The number of redundant paths, redundant equipment and devices is a basic
feature of this concept and schemes shown at figures 1 and 2. A variety of spare
delivery paths (which would be used in the case of virtually unimaginable
coincidences failures of the left feeder, right switch and transformer left) and
lots of devices make electric traction substations very complicated.

6. The solution of this problem is
illustrated by applying auxiliary bus

7. Saving three measuring transformers of 110 kV (decrease the total cost,
including installation, footages and required space).
The result: more reliable and simpler substation

8. Based on long time researching and studies, as well as broad international survey
conducted by the Committee A 50 Office for Research and testing (Office de
Recherrches et d'Essais), International Union of Railways, in singlephase
substations, surge arresters are not applied anymore.
This method of protection when the electric traction substation was built near
already protected buses of a power plant is assessed as dangerous for operational
reliability and plant staff and removed from the substations in developed
countries

9. The result: transfersally feeders are not necessary on the 110 kV side .
Scheme of electric traction substations connected via a three-phase transmission line
Transformers that are shown in the picture are without voltage regulators, which
are weak spots subjected to failures.
Result: increased plant reliability.

10. The next step of substation simplification is transformer feeder 110 kV and 25
kV feeder lacks and giving to circuit breaker in 110 kV feeder functions of
protection of transformer , as it shown in the previous figure.
In this case energy measurement is in 25 kV because there are required current
and voltage transformers for the protection.
So it is necessary to add kWh meters for measuring losses.

11. -using drawable circuit breakers in 25 kV feeders instead circuit breakers
and disconnectors which are elements of wrong manipulations;
- the application of switch-disconnectors instead circuit breakers in 25 kV
transformer feeders;
-aplication of combined instrument transformers (CT and VT in one
element) in all feeders;

12. Bypassing neutral section in separating substations with neutral section and
designing electeric traction substations with single transformer - parallel
connection of electric traction substations

13. Thyristor voltage adjustor is required to make identical voltages in catenary
in this case.

14. Distance between electric traction substations increase from
40 - 50 km to 80 - 90 km.
Peak power reduction wherein speed of trains do not decrease.

15. There are necessity for selectivity and accuracy of catenary distant relays with
power direction relay in separating substations, because two substations deliver
power to electric vehicle and ground fault.

16. Selectivity of catenary distant relays is acquired with time grading in
three zone toward sources.

17. Equivalent circuit of electric traction system 25 kV; 50 Hz for parallel
connected electric traction substations
Short circuit current:
𝑰 𝑲𝑺 =
𝑼
𝟐 ∙ 𝒁 𝑴 + 𝒁 𝑻 + 𝒁 𝒆𝒌𝒗
′
∙ 𝒍
𝑨
𝒁 𝑴 - impedance of electric network operator for two pole short circuit on
𝟏𝟏𝟎 𝒌𝑽 busbars in electric traction substation reduced on catenary voltage,
𝒁 𝑻 - impedance of single phase transformer of electric traction substations,
𝒁 𝒆𝒌𝒗
′
- equivalent impedance per unit of length of catenary

18. 𝒁 𝑴 = 𝒋 ∙
𝟏,𝟎𝟓∙𝑼 𝟐
𝑺 𝒌
𝜴
U–voltage of catenary 𝑽 ,
𝑺 𝒌 – two phase fault power on electric traction substation busbar 𝑽𝑨
𝒁 𝑻 = 𝒋 ∙
𝒖 𝒌(%)
𝟏𝟎𝟎
𝑼 𝟐
𝑺 𝑻
𝜴 ,
where: 𝒖 𝒌(%) – relative short circuit voltage % ,
𝑺 𝑻 – nominal power of transformer 𝑽𝑨
𝒁 𝒆𝒌𝒗
′
= 𝒁 𝒗
′ − 𝜺𝒁 𝒎
′ +
𝟏−𝒆−𝒌∙𝒍
𝒌∙𝒍
𝟏 − 𝜺 𝟐 𝒁Š𝑰
′ 𝜴
𝒌𝒎

19. Carson-Pollaczek formulaes:
𝒁 𝒆𝒌𝒗
′
= 𝒁 𝒗
′
− 𝜺𝒁 𝒎
′
+
𝟏 − 𝒆−𝒌∙𝒍
𝒌 ∙ 𝒍
𝟏 − 𝜺 𝟐
𝒁Š𝑰
′ 𝜴
𝒌𝒎
𝒁 𝑽
′
– impedance per unit of length of catenary
𝜴
𝒌𝒎
,
𝒁Š𝑰
′
–impedance per unit of length of returning current circuit
𝜴
𝒌𝒎
,
𝒍 – distance to electrica traction substation 𝒌𝒎 ,
𝒁 𝒎
′
– mutual impedance per unit of length catenary- returning current circuit
𝜴
𝒌𝒎
,
𝜺 =
𝒁 𝒎
′
𝒁Š𝑰
′ ,
where: 𝒌 = 𝒁Š𝑰
′
∙ 𝒈 𝒌𝒎−𝟏 - propagation coefficient of gauge
𝒈- admittance per unit of length of gauge
𝑺
𝒌𝒎

20. Impedance per unit of length of returning current circuit with two rails: 𝒁Š𝑰
′
=
𝟎, 𝟓 𝒓Š𝒂 + 𝒋 𝒙′ + 𝒙′′ + 𝝎𝑴 𝟏,𝟐
′ 𝜴
𝒌𝒎
,
where: 𝒓Š𝒂 –resistance of rails
𝜴
𝒌𝒎
,
𝒙′
- interior reactance per unit of length of rail otpor
𝜴
𝒌𝒎
,
𝒙′′
- external rail reactance per unit of length
𝜴
𝒌𝒎
,
𝝎 = 𝟐𝝅𝒇 𝒔−𝟏
- circle frequency
Internal reactance pwr unit of length of S-49 rail: 𝒙′
= 𝟎, 𝟕𝟓 ∙ 𝒓Š𝒂
External rail reactance per unit of length:
𝒋𝒙′′
= 𝟎, 𝟎𝟒𝟗𝟑 − 𝒋𝟎, 𝟏𝟒𝟒𝟔 𝟏, 𝟓𝟑 + 𝒍𝒐𝒈 𝑹Š
𝟐
∙ 𝜸
𝜴
𝒌𝒎
𝑹Š - radius of equivalent conductor: 𝑹Š =
𝑷
𝟐𝝅
𝒄𝒎 ,
where P is rail perimeter 𝒄𝒎 .
Mutual rails impedance per unit of length: 𝒋𝝎𝑴 𝟏,𝟐
′
= 𝟎, 𝟎𝟒𝟗𝟑 − 𝒋𝟎, 𝟏𝟒𝟒𝟔 𝟏, 𝟓𝟑 +

21. Dependance of catenary impedance
per unit of length on distance
for S-49 and UIC 60 rails

22. Dependance of catenary impedance arguments on
distance for S-49 and UIC 60 rails

23. Short circuit current of a single truck
Overall short circuit current on place of fault is addition of currents from
two electrical traction substations.

24. Dependance of impedance on distance
measured by distant relay

25. Short circuit impedance measured by impedance relays in separating substations
(R-X diagram)

26. CONCLUSION
The existing designs of electric traction substations in exploitation proved to be
expensive, overcomplicated and unnecessary. Consequences are too large costs of
construction and maintenance, overcomplicated facilities, lack of diagrams
clearness and problems during maintenance.
In this paper, we proposed new ways of substations designing and changes in
designs of exploited substations when the reconstruction is needed. It reduces
costs, economizes controlling, makes maintenance simplified and improves
clearness of electrical traction substations. Availability and safety of substations
remains high. Parallel connected traction substations could reduce peak power
costs and measurements of energy consumption are simpler. This paper provides
electrical calculations for protective relay adjustments in traction systems.
Calculations of impedances and short circuit currents are performed using the
Wolfram Mathematica program.