Rail Electrification Systems - Learn EVERYTHING About Them!

Summary

This video from Railways Explained offers an insightful overview of railway electrification systems, highlighting their evolution, types, and the reasons behind their diversity. It discusses the early beginnings with galvanic cells to the adoption of AC and DC systems, and the impact of electrification on train performance and the environment. The script also touches on the challenges of overhead lines and the emergence of multi-voltage locomotives for cross-border traffic, emphasizing the importance of electrification in modern rail transport.

Takeaways

• 🚂 The history of railway electrification began with the creation of the first electric locomotive in 1837 by Robert Davidson, but it was limited by the power of galvanic cells.
• 🌐 The first electric passenger train was presented by Werner von Siemens in 1879 at the Berlin Industrial Exposition.
• 🔌 Electrification development was slow due to the need to meet unique railway requirements and the lack of general electrification for households and industry.
• 🛤️ After WWI, electrification improved with the advent of large power plants and overhead power lines for high-power transmission.
• 💡 The basic electrification system includes a power supply system for the train's electric motor, with the rail track serving as a return connection for the electrical circuit.
• 🔋 There are various railway electrification systems, differing due to continuous improvements and the timing of electrification in different countries.
• 📊 European and international standards recognize six standard voltage systems for railway electrification, including both direct current (DC) and alternating current (AC).
• 🌍 The variety of systems in Europe is due to independent development within national borders and the principle of interoperability in European transport policy.
• ⚙️ The choice of AC over DC came with the development of suitable high-voltage insulating materials and the ability to use higher frequencies without overheating issues.
• 🚆 The adoption of 25 kV 50 Hz as a standard was based on the efficiency of power transmission and cost, providing an optimal balance between the two.
• 🌐 The need for multi-voltage locomotives arose from the liberalization of cross-border freight traffic and the variety of electrification systems in Europe.
• 🔌 The power supply for moving trains is facilitated by traction or feeder substations that convert electric power to the appropriate voltage, current type, and frequency for the railway.
• 🚆 Overhead lines, or catenary systems, are crucial for supplying electric traction vehicles with necessary energy under all conditions, and are irreplaceable in electrified railways.

Q & A

What was the first known primitive electric locomotive powered by galvanic cells built by?

The first known primitive electric locomotive powered by galvanic cells was built in 1837 by chemist Robert Davidson.

Who presented the first electric passenger train and when was it presented?

Werner von Siemens presented the first electric passenger train at the Berlin Industrial Exposition in 1879.

Why was the development of railway electrification slow before the First World War?

The development was slow because electric traction had yet to meet the unique requirements of railway traffic, and there was insufficient general electrification for households and industry. Additionally, steam traction had reached a high level of development that met the transport demand.

What are the two main types of current used in railway electrification systems?

The two main types of current used are Direct Current (DC) and Alternating Current (AC).

What are the advantages of using AC over DC in railway electrification?

AC allows for the use of asynchronous traction motors, which do not have the issues with high-frequency current that early DC systems faced. AC systems also enable higher train speeds, reduce the number of required substations, and are more efficient for power transmission over long distances.

What is the significance of the 15 kV and 16.7 Hz electrification system in railway history?

The 15 kV and 16.7 Hz system was the first AC system that allowed for the electrification of railways on a massive scale, starting with a locomotive built in Switzerland in 1905.

Why was the 25 kV 50 Hz system adopted as the standard in France?

The 25 kV 50 Hz system was adopted as the standard in France because it represented an optimal balance between efficiency of power transmission and the cost of high-voltage equipment.

What is a pantograph and what is its role in railway electrification?

A pantograph is a device used by trains to collect the required current from the overhead line system by pressing against the underside of the contact wire.

Why are overhead lines more efficient than third rail systems for electrified railways?

Overhead lines are more efficient because they allow for higher train speeds, reduce the number of required substations, and are safer for trespassers and track workers. They also enable more reliable and uninterrupted power supply to the train.

What are the challenges associated with maintaining overhead lines in electrified railways?

Challenges include weather impacts such as fast winds, heavy snow, and rain that can cause traffic disruptions, as well as the need for regular maintenance to prevent wear and ensure reliable power supply.

How does the introduction of multi-voltage locomotives and EMUs address the issue of different electrification systems in Europe?

Multi-voltage locomotives and EMUs are equipped to operate under various voltages, allowing them to travel across different countries with varying electrification systems without needing to change locomotives.

What is a 'neutral section' in the context of electrified railways and why is it used?

A 'neutral section' is an electrically separated portion of the overhead line that allows for maintenance and repair of faults without turning off the entire system. It can be a complete switched neutral section or a short length of non-conducting material.

What are some of the environmental benefits of electrified railways over steam or diesel trains?

Electrified railways reduce environmental pollution, enable more comfortable, quieter, and faster trains, and are generally more energy-efficient, even if the electricity is produced by fossil fuels.

What alternative to electrification has been introduced as a potential 'green solution' for railways with low traffic?

Hydrogen-powered trains have been introduced as a potential 'green solution' for railways with low traffic, as they do not require the extensive infrastructure of electrification and can be more cost-effective in such scenarios.

Outlines

00:00

🚂 Introduction to Railway Electrification Systems

This paragraph introduces the topic of railway electrification, explaining the basics and the reasons for the variety of systems in use. It begins with the history of electric locomotives, starting with Robert Davidson's 1837 model powered by galvanic cells. The script discusses the slow development of electrification due to the maturity of steam traction and the lack of developed infrastructure. It highlights the post-WWI advancements with the emergence of large power plants and overhead power lines, which facilitated the growth of electric traction motors. The paragraph concludes by explaining the fundamental components of an electrification system, including the power supply and the use of rail tracks as a return connection for the electrical circuit.

05:01

🔌 The Evolution and Classification of Electrification Systems

This section delves into the evolution of railway electrification systems, focusing on the classification based on voltage standards and types of electric current. It outlines the six standard systems recognized by European and international standards, with a particular emphasis on the development of DC and AC systems. The paragraph explains the early adoption of DC due to the limitations of AC research and the availability of high voltage insulating materials. It details the specific voltages used for trams, trolley networks, and subway systems, as well as the higher voltages used for mainline train power supply. The script also discusses the transition to AC systems with the deployment of the AC power grid and the challenges faced with early series-wound motors, leading to the adoption of 15 kV and 16.7 Hz for railway electrification.

10:07

🌐 The Global Adoption and Technical Aspects of Electrification Systems

This paragraph discusses the global adoption of electrification systems, highlighting the differences in adoption based on the timing of electrification and the available technology at the time. It covers the use of 3 kV DC in various countries and the challenges of providing sufficient current for heavy trains, especially in rural and mountainous regions. The script explains the shift to AC systems and the technical solutions developed to overcome the limitations of high-frequency current, such as the use of 15 kV and 16.7 Hz. It also discusses the adoption of 50 Hz AC systems, starting with Hungary's pioneering work with asynchronous traction and the subsequent adoption by other countries. The paragraph further explores the technical aspects of transformer weight, axle loads, track wear, and maintenance, leading to the standardization of 25 kV 50 Hz as an optimal solution for power transmission efficiency and cost.

15:08

🛠️ Infrastructure and Maintenance of Electrified Railways

This section provides an in-depth look at the infrastructure and maintenance aspects of electrified railways. It explains the role of traction or feeder substations in converting electric power for railway use and the continuous conductor running along the rail track, which can take the form of an overhead line or a third rail. The script discusses the necessity of a return conductor, the use of steel rails for this purpose, and the impact of transmission losses on the placement of substations. It also covers the use of third rail systems, their limitations in speed and application, and the advantages of overhead lines for higher speeds and efficiency. The paragraph further describes the components of an overhead line, including the pantograph, contact wire, and support structures, and the importance of maintaining the geometry and tension of the contact wire for efficient current collection.

🌍 Conclusion and Future Outlook on Railway Electrification

In the concluding paragraph, the script summarizes the importance of railway electrification in reducing environmental pollution and enabling more comfortable, quieter, and faster train operations. It acknowledges the challenges faced, such as weather impacts on overhead lines, theft of unguarded installations, and the high costs of building new infrastructure. The paragraph also introduces hydrogen-powered trains as a potential 'green solution' for areas with low traffic, suggesting an alternative to electrification. The script ends by encouraging viewers to explore previous videos on the channel and to subscribe for future content, emphasizing the educational value of the channel and its contribution to understanding the railways of the world.

Keywords

💡Railway Electrification

Railway electrification refers to the process of equipping a railway system with the necessary electrical infrastructure to power electric trains. It is central to the video's theme as it discusses the history, development, and various systems of electrification. For instance, the script mentions the first primitive electric locomotive powered by galvanic cells and the significant development of railway electrification post-World War I.

💡Electric Locomotive

An electric locomotive is a locomotive powered by electric motors, drawing electricity from overhead lines or a third rail. The video script discusses the first known electric locomotive built in 1837 and the evolution of electric locomotives with the advancement of railway electrification systems.

💡Power Supply System

A power supply system in the context of railway electrification is the infrastructure that delivers electrical energy to power the electric motors on trains. The script explains that the rail track acts as a return connection for the electrical circuit, emphasizing the importance of a stable and constant power supply for safe and reliable railway traffic.

💡Continuous Improvement

Continuous improvement in the script refers to the ongoing process of upgrading and refining railway electrification systems. The video mentions that different countries have different systems based on the time they started electrification and their continuous improvement efforts, leading to a variety of systems in use.

💡Direct Current (DC) and Alternating Current (AC)

Direct Current (DC) and Alternating Current (AC) are two types of electrical current used in railway electrification. The script explains that early systems used DC due to the limitations of AC research and high-voltage insulating materials. Later, AC systems were adopted with the development of the electric power distribution system and improvements in traction motors.

💡Traction Motors

Traction motors are electric motors that convert electrical energy into mechanical energy to propel trains. The script discusses the development of traction motors alongside the improvement of railway electrification, highlighting their importance in the operation of electric trains.

💡Overhead Line

An overhead line, also known as overhead catenary, is a system of masts, gantries, and wires used to supply power to electric trains. The script describes the components and function of the overhead line, including the use of a pantograph to collect current and the zig-zag design of the contact wire to prevent wear on the pantograph.

💡Neutral Sections

Neutral sections are electrically separated portions of the overhead line that allow for maintenance and repair without turning off the entire system. The script explains two types of neutral sections: switched neutral sections and sections with non-conducting material spliced into the contact wire.

💡Pantograph

A pantograph is a device used on electric trains to collect electrical power from the overhead line. The script describes how the pantograph presses against the contact wire and how the design of the contact wire helps to minimize wear on the pantograph.

💡Third Rail

A third rail is an additional rail used in railway electrification systems to supply electric power to trains, typically used in systems up to 1.5 kV. The script mentions that third rail systems are almost exclusively used with DC distribution and are suitable for use in smaller-diameter tunnels, such as in subway systems.

💡Interoperability

Interoperability in the context of railways refers to the ability of different systems or components to work together. The script discusses the development of multi-voltage locomotives and EMUs to address the lack of interoperability caused by the variety of electrification systems in Europe.

Highlights

Introduction to railway electrification systems, emphasizing basic principles and essential concepts.

Call to action for subscribers to increase watch time and engagement on the channel.

Historical overview starting with the first primitive electric locomotive by Robert Davidson in 1837.

Milestone of the first electric passenger train presented by Werner von Siemens in 1879.

Slow development of railway electrification due to the adequacy of steam traction and lack of electrification for households and industry.

Post-World War I improvements in railway electrification with the advent of large power plants and overhead power lines.

Recognition of electric traction's profitability over steam with high traffic density.

Explanation of the basic components of an electrification system including the power supply and the use of rail tracks as a return connection.

Differentiation of railway electrification systems based on continuous improvement and varying initial installations.

Classification of electrification systems according to voltages and types of electricity (DC and AC).

Use of DC voltages in trams, trolley networks, and subway systems, and higher voltages for primary train power supply.

Adoption of alternating current in electrified railways with the development of the AC power grid.

Introduction of 15 kV and 16.7 Hz frequency for railway electrification, overcoming issues with series-wound motors.

The choice of 25 kV 50 Hz as the standard for efficiency in power transmission and cost.

Development of multi-voltage locomotives and EMUs for cross-border traffic and interoperability.

Description of the power supply through traction or feeder substations and the use of overhead lines or third rails.

Limitations of third rail systems in terms of speed and the advantages of overhead lines for high-speed operations.

Details on the components and function of overhead lines in electrified railways.

Challenges of railway electrification including environmental impact, theft, and high infrastructure costs.

Introduction of hydrogen-powered trains as an alternative 'green solution' to electrification.

Conclusion summarizing the benefits and drawbacks of railway electrification systems.

Transcripts

Hi guys, welcome back to Railways Explained.

As our Patrons chose, today's topic will represent an overview of the railway electrification

systems.

We tried not to go too much into technical details but rather to talk about the basic

principles and essential concepts related to electrification systems, including the

reasons why there are so many different types.

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videos to watch and learn about railways.

The story of the electrification of railways starts, you guess, with the appearance of

electric locomotives.

The first known primitive electric locomotive powered by galvanic cells was built in 1837

by chemist Robert Davidson.

At the time, the limited power from batteries prevented its general use.

The first electric passenger train was presented by Werner von Siemens at the Berlin Industrial

Exposition in 1879.

The significant development of railway electrification was prolonged until the First World War.

This was because electric traction had yet to meet the unique requirements of railway

traffic.

Another reason for the slow development of the railway electrification is insufficiently

developed general electrification for households, industry, etc.

Also, steam traction reached a high level of development, and, as such, it met all the

needs of transport demand.

Only after the First World War did the railway electrification start its improvement, bearing

in mind that large power plants appeared, as well as networks of overhead power lines

for the transmission of high-power electricity over long distances.

This also gave a boost to the further development of electric traction motors.

As the use of railways grew and thus the need for more powerful locomotives, it turned out

that with sufficiently high traffic density, electric traction was actually more profitable

than steam.

At the most superficial level, the electrification system includes the power supply system that

powers the electric motor on the train.

The rail track is used as a return connection needed to complete the electrical circuit

and allow current to flow.

To enable safe and reliable railway traffic, the power supply system must be stable and

constant.

You are probably aware that there are different railway electrification systems, which are

primarily characterised by the continuous improvement.

So, in some countries, the systems that were initially installed remained, and in some

others, which entered the electrification process later, they decided to deploy the

best system available at the time.

At the same time, some countries chose to have both an initial electrification system

and to deploy another on newer railway lines.

Let s now put our focus on all those different systems,

The classification of the electrification systems is made according to several criteria.

Regarding voltages, European and international standards recognise six standard systems shown

in the table, where the division is made according to the nominal voltage and its characteristics.

Now, you can see the variety of these systems deployed in Europe with the presence of all

six classified systems.

This is the result of the fact that European railways developed independently from one

another within the borders of national countries, and on European level, with interoperability

principles included, which is nowadays one of the keywords of European transport policy

makers.

You can also notice in the previous table that there is a division according to the

type of electricity.

We have four systems based on direct current - DC and two based on an alternating current

- AC.

The earliest systems used DC since AC was not yet sufficiently researched but also high

voltage insulating material not yet widely available.

Most trams, trolley networks, and subway systems use DC voltages between 600 and 750 V. Systems

with higher voltage from 1.5 kV to 3 kV DC are mainly used as a primary train power supply.

Thus, 1,5 kV DC is used in the Netherlands, Indonesia, Ireland, partly in Japan, France,

Australia and some interurban lines in the US, New Zealand and Singapore.

3 kV DC is used in Belgium, Italy, Spain, Poland, Slovakia, Slovenia, South Africa,

Chile, the northern portion of the Czech Republic, but also the former republics of the Soviet

Union, and the Netherlands on a few kilometres between Maastricht and Belgium.

But even at 3 kV, the current needed to power a heavy train can be excessive - particularly

in rural and mountainous areas.

Thus, electrified railways adopted alternating current along with the electric power distribution

system deployment.

The deployment of the AC power grid with 50 Hz (or 60 Hz in the US) began at the beginning

of the 20th century.

But the series-wound motors of that time had problems using current with such high frequency

that caused overheating and deleterious effects at motor collectors.

This was solved by shifting the frequency slightly away from exactly ? the grid frequency,

i.e. 15 kV and 16,7 Hz.

This frequency value was arbitrarily chosen to remain within the tolerance of existing

traction motors.

The first locomotive powered at 15 kV and 16,7 Hz was built in 1905 in Switzerland.

From that moment, the electrification of railways could begin to be applied on a massive scale.

This current system was adopted in 1909 by Switzerland and Germany, in the following

year by Sweden, in 1914 by Austria, and 1922 by Norway.

By 1928, about 10,000 km of rail tracks worldwide were electrified at 15 KV, 16.7 Hz.

The use of AC with a frequency from the national power grid of 50 Hz was first successful in

Hungary when a Hungarian engineer K lm n Kand managed to design a motor that used 16 kV

50 Hz with asynchronous traction.

Although Kand 's solution showed a way for the future, railway operators outside of Hungary

lacked interest in the design.

The first railway to use 50 Hz was completed in 1936 when the Deutsche Reichsbahn deployed

a 20 kV 50 Hz AC system on the rail section between Freiburg and Neustadt.

This part of Germany was in the French zone of occupation after 1945.

As a result of examining the German system in 1951, the French Railways electrified one

line in southern France, initially at the same 20 kV but converted to 25 in 1953.

The 25 kV 50 Hz system was then adopted as the standard in France, but since a substantial

length of lines south of Paris had already been electrified at 1.5 kV DC, French Railways

also continued some major new DC electrification projects.

One of the disadvantages of 16.7 Hz locomotives compared to 50 or 60 Hz is the heavier transformer

required to reduce the voltage to the level used by these engines and their speed control

gear.

The heavier transformers also lead to higher axle loads than those of a higher frequency.

This, in turn, leads to increased track wear and increases the need for more frequent track

maintenance.

The choice of 25 kV 50 Hz was related to the efficiency of power transmission as a function

of voltage and cost, not based on a neat ratio of the supply voltage.

A higher voltage for a given power level allows for a lower current and usually better efficiency

at a higher cost for high-voltage equipment.

It was found that 25 kV was an optimal point, where a higher voltage would still improve

efficiency but not significantly about the higher costs incurred by the need for larger

insulators and greater clearance from structures.

That is why most countries which later started electrification programs electrified their

railways at the utility frequency of 50/60 Hz.

For example, despite bordering only 15 kV territory, Denmark decided to electrify their

mainline railways at 25 kV 50 Hz.

This variety of systems in Europe, as already mentioned, along with many other technical

aspects, caused a lack of interoperability.

From the 1950s onwards, the emerging formation of the European Union, and the consequent

increase in the amount of cross-border traffic, along with the addition of a 25 kV 50 Hz AC

system in France, in addition to the older 1.5 kV DC, gave rise to the need for multi-voltage

locomotives and EMUs.

Also, at the beginning of the 21st century, European railway legislation liberalised cross-border

freight traffic, creating a demand for locomotives that could work between EU countries with

different electrification systems.

That created practically a new market for multi-voltage vehicles.

Some locomotives and EMUs are equipped to operate under four voltages - 25 kV AC, 15

kV AC, 3,000 V DC and 1,500 V DC.

Modern electronics make this possible with relative ease, and cross-voltage travel is

now possible without changing locomotives.

In addition to this classification, there is also a division according to the power

supply of moving trains.

Namely, there are so-called traction or feeder substations that have the task of converting

electric power from the form provided by the electrical power industry for public utility

service to an appropriate voltage, current type and frequency.

They supply continuous conductor running along the rail track that usually takes one of two

forms: an overhead line or a third rail which further feeds the train.

To make a complete circuit, from the source of energy to the consuming item and back to

the source, a return conductor is needed to make the system function.

For this problem a simple solution is found - steel rails are used, as shown in the video.

The number and location of substations depend on the electrification system.

For example, for a 1.5 kV DC system, substations are located every 10 to 15 km, while for a

25 kV 50Hz system, they are located at a distance of 40 to 60 km.

For the 750 V system, they are placed even at a distance of 3 km.

The reason is that with DC systems, there are significant transmission system losses

as the distance between supply connections increases, which is compensated for by installing

substations more often.

The power supply system via the third rail is an option for systems up to 1.5 kV, while

all others use overhead lines.

We can safely say that third rail systems almost exclusively use DC distribution.

Also, the third rail is more compact than overhead wires and can be used in smaller-diameter

tunnels, which is a crucial factor for subway systems.

The third rail can be designed to use top contact, side contact or bottom contact, with

safety shields incorporated, carried by rail itself.

In practice, the maximum speed of trains on third-rail systems is limited to 160 km/h

(100 mph) because, above that speed, reliable contact between the train and the rail cannot

be maintained.

At this point, corrosion is always a factor to be considered in electric supply systems,

particularly DC systems.

The tendency of return currents to wander away from the running rails into the ground

can set up electrolysis with water pipes and similar metallics.

This was well understood in the late 19th Century and was one of the reasons why London's

Underground railways adopted a fully insulated DC system with a separate negative return

rail as well as a positive rail - the four-rail system.

On the London Underground, a top-contact third rail is beside the track, energised at +420

V DC and a top-contact fourth rail is located centrally between the running rails at ?210

V DC, which combine to provide a traction voltage of 630 V DC.

To enable higher train speeds, reduce the number of required substations, reduce the

risk that the third rail has on the safety of trespassers and track workers and enable

more efficient rail traffic, an overhead line was introduced, which is the name that railway

engineers use for the assembly of masts, gantries and wires found along electrified railways.

This is also called overhead catenary, overhead contact system, and overhead line equipment,

but we will stick to the term used by the International Union of Railways.

An overhead line basically has a few standard components.

To collect the required current from the system, trains use a device called a pantograph that

presses against the underside of the contact wire, which represents the point of contact

between the train and the overhead line.

As the pantograph moves under the contact wire, after a certain period of time, the

carbon insert on top of the pantograph becomes worn.

That is why the contact wire is designed and deployed in a zig-zag path to avoid wearing

a groove in the pantograph.

To achieve good high-speed current collection, keeping the contact wire geometry within defined

limits is necessary.

This is achieved by making the contact wire as stationary as possible so that power can

flow uninterrupted to the train and minimising wear of the system.

To achieve this, the contact wire is tensioned between support structures so that it can

withstand deflection by high winds and extreme temperatures.

This ensures that the current passes to the train in all weather, even at high speed.

The contact wire is suspended from vertical cables called droppers supported by a longitudinal

cable called the catenary wire.

The catenary and contact wire span between support structures, masts or steel frames.

The support structures are typically spaced approximately 50m apart depending on the alignment

of the railway line.

Catenary wires are kept in mechanical tension because the pantograph causes mechanical oscillations

in the wire, and the wave must travel faster than the train to avoid producing standing

waves that would cause wire breakage.

For medium and high speeds, the wires are generally tensioned by weights or occasionally

by hydraulic tensioners.

The task of the overhead line on the electrified railway is to supply electric traction vehicles

with the necessary energy for their movement at all times and under all conditions.

For that purpose, its role is irreplaceable.

While one electric locomotive that is broken can be replaced by another, and the power

supply of one substation that is disconnected can be taken over by neighbouring ones, until

then, the role of the overhead line cannot be taken over by any other element.

To allow maintenance and repair of faults on the overhead line without turning off the

entire system, the line is broken into electrically separated portions known as "neutral sections".

The first is a complete, switched neutral section.

This consists of separate insulated lengths of contact wire in the overlap between two

regular sections.

The insulated neutral sections are connected to the normal contact wires by switches which

are operated automatically by passing trains, thereby maintaining an unbroken electrical

supply.

The second type of neutral section is a short length of non-conducting material spliced

??into the contact wire to enable local lengths of wire to be isolated, e.g. for maintenance

work.

In any case, we hope that we managed to bring you closer to the railway electrification

system.

At least for a bit.

We could also talk about how the overhead line looks in the tunnel and other engineering

structures, the introduction of the SCADA system for the control and management of the

traction power distribution and further details.

Still, we think this is enough for now.

Anyway, electrified railways indeed reduce environmental pollution, even if electricity

is produced by fossil fuels.

It enables more comfortable, quieter and faster electric trains than steam or diesel.

Of course, there are also problems, such as the low resilience of the overhead line when

it comes to the weather impact like fast winds, heavy snow and rain, which can cause traffic

disruptions.

Some of the problems with electrification that virtually every country has, are thefts

since there are unguarded remote installations and elements of overhead line which are attractive

targets for scrap metal thieves.

In addition, electrification requires entirely new infrastructure to be built around the

existing tracks, which is of high cost.

So, there is often no justification for this investment in railways where there is not

much traffic, which is why a hydrogen-powered train has been introduced as a potential "green

solution", which is already in commercial use in some countries.

If you find this topic interesting, check out some of our previous videos, and stay

tuned for next.

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