this is notes of metro system and engineering as per PTU

1. Metro system and
engineering
ELECTRICAL SYSTEMS
SHUBHAM SHARMA
Department of civil engineering
BGIET, SANGRUR

2. OHE system
 OHE, or Overhead Electrification, is commonly used as the electrical system in metro
systems. It consists of a network of overhead wires that supply power to the trains. The
wires, known as catenary wires, are suspended above the tracks and carry the electrical
current needed to power the trains.
 The OHE system typically uses a pantograph, which is a device mounted on top of the
train, to make contact with the catenary wires and draw power. The pantograph collects
the electricity from the wires and transfers it to the train's electrical systems, which
power the traction motors that propel the train.
 OHE systems are preferred in metro systems because they provide a reliable and
efficient method of supplying power to the trains. They eliminate the need for on-board
energy storage and allow for continuous operation of the trains without the need for
frequent recharging or refuelling.

4. How the pantograph works
 The pantograph is a device mounted on the roof of a train that allows it to collect power from the
overhead wires in the OHE system. It's like a fancy arm that reaches up and connects with the catenary
wires.
 The pantograph has a set of carbon or metal strips called collectors that make contact with the catenary
wires. When the train moves, the collectors slide along the wires, creating a connection that allows
electricity to flow from the wires to the train.
 The electricity collected by the pantograph is then transferred to the train's electrical systems, which
power the traction motors that move the train. It's like the pantograph acts as a bridge between the
overhead wires and the train, allowing the power to flow smoothly.
 The pantograph is designed to maintain a good contact with the catenary wires, even when the train is
moving at high speeds or going through curves in the tracks. It's an important part of the OHE system
that ensures the train receives a steady supply of power.

6. Types of OHE
 In metro systems, there are primarily two types of OHE (Overhead Electrification) systems
commonly used:
1. 1. Single Wire with Return Current (SWRC): This type of OHE system uses a single
catenary wire to supply power to the trains, while the return current flows through the
running rails. The catenary wire carries the positive current, while the negative or return
current is conducted through the tracks. SWRC systems are simpler in design and installation
but may have limitations in terms of power capacity.
2. Two Wire with Insulated Return (TWIR): In TWIR systems, two catenary wires are used to
supply power to the trains. One wire carries the positive current, while the other wire carries
the negative or return current. The return current is insulated from the running rails,
reducing the risk of electrical interference with other systems. TWIR systems offer higher
power capacity and better electrical performance but are more complex to install and
maintain.

7. OHE, or Overhead Electrification, offers several advantages over
other electrical systems in metro systems:
1. Cost-effective: OHE systems are generally
more cost-effective to install and maintain
compared to other electrical systems. The
overhead wires are relatively simple to install,
and the infrastructure required is less complex
than other alternatives.
2. Flexibility: OHE systems can accommodate a
wide range of train types and sizes, making
them flexible for different metro system
requirements. They can easily adapt to
changes in train technology and can be
expanded or modified as needed.
3. Energy Efficiency: OHE systems are known for
their energy efficiency. The power is supplied
directly to the trains from the overhead wires,
reducing energy losses during transmission.
This results in more efficient energy usage and
lower operational costs.
4. Reliability: OHE systems have a proven track
record of reliability. The overhead wires are
less prone to disruptions caused by weather
conditions, such as heavy rain or snow,
compared to other systems that may have
underground components.
5. Safety: OHE systems are designed with safety
in mind. The overhead wires are placed out of
reach of pedestrians and vehicles, reducing the
risk of accidents or unauthorized access to the
electrical infrastructure.

8. Traction power in metro
 Traction power is essential aspect of metro systems. Traction power refers to the electrical energy that is
supplied to the trains to power their motors and enable them to move.
 In metro systems, the traction power is typically provided through the overhead electrification (OHE)
system we talked about earlier. The catenary wires carry the electrical current, and the pantograph on top
of the train collects this power from the wires.
 The collected power is then transferred to the train's electrical systems, which include the traction motors.
These motors convert the electrical energy into mechanical energy, propelling the train forward.
 The amount of traction power required depends on various factors, such as the weight and speed of the
train, the grade of the track, and the number of passengers on board. Metro systems are designed to
ensure that there is enough traction power available to meet the demands of the trains and maintain
smooth and reliable operations. Traction power is a crucial component in keeping the trains running
efficiently and providing reliable transportation in metro systems.

10. TSS AND ASS
 In metro systems, TSS and ASS refer to important components known as traction substations and auxiliary
substations, respectively.
 Traction substations (TSS) are responsible for converting the incoming high voltage electrical power
from the power stations to the appropriate voltage and current required for the operation of the trains.
These substations step down the voltage and distribute the power to the catenary system, which supplies
the trains with traction power.
 On the other hand, auxiliary substations (ASS) provide power for various auxiliary systems and
equipment within the metro network. These systems include lighting, ventilation, escalators, elevators,
signalling systems, and other electrical components necessary for the smooth functioning of the metro
system.
 Both TSS and ASS play crucial roles in ensuring the efficient and reliable operation of metro systems by
providing the necessary power for train propulsion and auxiliary systems.

11. traction substations auxiliary substations

12. Traction substations
 Traction substations are essential components in metro systems. They play a crucial role in
supplying the required electrical power to the trains for their propulsion. Traction
substations receive high voltage electricity from the power grid and then convert it to the
appropriate voltage and current levels needed by the trains.
 These substations distribute the power through the overhead catenary system, which
allows the trains to collect the power through their pantographs. This power is then used
to drive the traction motors, enabling the trains to move along the tracks. Traction
substations are strategically located along the metro network to ensure a reliable and
efficient power supply to the trains.

13. Auxiliary substations
 Auxiliary substations, also known as ASS, are an important part of metro systems. These
substations provide power for various auxiliary systems and equipment within the metro
network. They supply electricity to systems such as lighting, ventilation, escalators,
elevators, signalling systems, and other electrical components necessary for the smooth
operation of the metro system.
 Auxiliary substations ensure that all the essential functions and services in the metro,
apart from the train propulsion, are powered effectively. They play a vital role in
maintaining the comfort, safety, and functionality of the metro system.

14. SCADA for power supply system
 The SCADA (Supervisory Control and Data Acquisition) system is an important component
of the power supply infrastructure in metro systems. It is used to monitor and control the
electrical distribution and power management within the metro network.
 The SCADA system collects real-time data from various substations, including traction and
auxiliary substations, to provide operators with a comprehensive view of the power supply
status. It allows operators to remotely monitor and control the power distribution, detect
faults, and take necessary actions to ensure uninterrupted power supply to the trains and
other auxiliary systems. The SCADA system plays a crucial role in maintaining the reliability
and efficiency of the power supply in metro systems

15. Working of SCADA
 The SCADA system works by collecting data from various sensors and devices in the power
supply system of a metro. This data includes information on voltage levels, current flow,
temperature, and other relevant parameters. The SCADA system then processes and analyses
this data, providing real-time monitoring and control capabilities to operators.
 Operators can use the SCADA system to remotely monitor the status of substations,
transformers, circuit breakers, and other components of the power supply system. They can also
control the operation of these devices, such as switching on or off certain circuits or adjusting
voltage levels.
 The SCADA system uses a network of communication channels to transmit data between the
central control station and the remote devices. This enables operators to have a comprehensive
view of the power supply system and make informed decisions to ensure its efficient and
reliable operation.

16. SCADA system

17. Standby and backup system
 In metro systems, standby and backup systems are critical for ensuring the continuous operation of essential
services. A standby system is an essential component that provides backup power in case of a primary
power failure. It ensures the continuous operation of critical systems, such as train propulsion, signalling,
ventilation, and lighting, during power outages or emergencies. The standby system typically consists of
backup generators or batteries that can supply power to the necessary systems when the primary power
source is unavailable. These backup systems are designed to automatically activate in the event of a power
failure, ensuring minimal disruption to metro operations.
 The backup system, on the other hand, encompasses a broader range of components and measures to
ensure system resilience. It includes redundant equipment, duplicate control systems, and backup
communication networks. These redundancies help mitigate the impact of failures or emergencies, ensuring
the safety and reliability of the metro system.
 Both the standby and backup systems work together to provide uninterrupted power supply and maintain
critical operations during power outages or other unforeseen events. They play a vital role in keeping the
metro system running smoothly and ensuring passenger safety.

18. Green buildings in metro systems
 Green buildings in metro systems are an exciting aspect of sustainable urban design. They focus
on incorporating environmentally friendly features and practices to reduce energy
consumption, minimize waste, and promote a healthier indoor environment.
 These green buildings in metro systems often integrate energy-efficient systems, such as solar
panels for renewable energy generation, efficient lighting and HVAC systems, and water-saving
fixtures. They may also use sustainable construction materials, implement proper waste
management strategies, and prioritize green spaces and landscaping. By incorporating green
buildings within metro systems, cities can reduce their environmental impact, improve energy
efficiency, and create healthier and more sustainable spaces for commuters and surrounding
communities.
 There are several countries who focus on green buildings in metro systems. One notable
example is the Taipei Metro in Taiwan. They have implemented green building practices in their
stations, including energy-efficient lighting, rainwater harvesting systems, and green roofs.
These features help reduce energy consumption and promote sustainability.

19.  Green buildings in metro systems contribute to sustainability in several ways. First, they
promote energy efficiency by incorporating features like solar panels, efficient lighting, and
HVAC systems. This reduces the overall energy consumption and carbon footprint of the
metro system.
 Second, green buildings prioritize water conservation through the use of water-saving
fixtures and systems. This helps reduce water consumption and promotes responsible water
management.
 Third, sustainable construction materials are used in green buildings, which are
environmentally friendly and have a lower impact on natural resources. This reduces the
depletion of resources and minimizes waste generation.
 Moreover, green buildings in metro systems often prioritize indoor air quality and occupant
comfort. They utilize proper ventilation systems, non-toxic materials, and natural lighting,
creating healthier and more pleasant spaces for commuters and employees.

20. Carbon credits
 Carbon credits can play a significant role in reducing the carbon footprint of metro systems.
Metro systems generate greenhouse gas emissions through their operations, such as energy
consumption and train operations. To offset these emissions, metro systems can participate in
carbon credit programs.
 Carbon credits are a market-based mechanism that allows organizations to invest in projects
that reduce or remove greenhouse gas emissions. By purchasing carbon credits, metro systems
can support projects that promote renewable energy, energy efficiency, or carbon sequestration.
These projects help to offset the emissions produced by the metro system, effectively
neutralizing their carbon footprint.
 Implementing carbon credits in metro systems can have multiple benefits. It not only helps to
reduce greenhouse gas emissions but also contributes to sustainable development and
supports the growth of renewable energy projects. Additionally, participating in carbon credit
programs can enhance the environmental reputation of the metro system and demonstrate a
commitment to sustainability. Overall, carbon credits provide a valuable tool for metro systems
to mitigate their environmental impact and contribute to global efforts in combating climate
change.

21.  For example, the Delhi Metro in India has been involved in carbon credit projects since
2008. They have implemented various initiatives such as regenerative braking systems, solar
power generation, and energy-efficient operations, which have helped them earn carbon
credits. Another example is the São Paulo Metro in Brazil, which has implemented projects
focused on energy efficiency, waste management, and renewable energy generation,
earning them carbon credits as well. These are just a few examples, and many other metro
systems around the world are actively working on reducing their carbon footprint through
carbon credit projects.

23. Clear air mechanics
 Clear air mechanics in the context of the metro refers to the systems and measures put in place to
ensure good air quality within the metro system. Metro systems often face the challenge of
maintaining clean and breathable air for passengers and staff. To address this, several
mechanisms are implemented. One important aspect is proper ventilation and air circulation
within the metro tunnels and stations. This involves the use of ventilation systems that supply
fresh air and remove pollutants or stale air.
 Additionally, metro systems may employ air filtration systems to remove particulate matter and
improve air quality. These filters help capture dust, allergens, and other pollutants, providing a
cleaner environment for passengers. Furthermore, some metro systems have implemented
measures to reduce emissions from trains. This includes using electric or hybrid trains, which
produce fewer pollutants compared to traditional diesel-powered trains. By reducing emissions,
metro systems can contribute to better air quality both inside the tunnels and in the surrounding
areas. So, "clear air mechanics" in the metro encompass ventilation systems, air filtration, and
emission reduction measures, all aimed at ensuring a healthier and more comfortable
environment for everyone using the metro

24. Thankyou