Understanding the Power Grid

➢ An electrical grid is a network of synchronised power providers and consumers connected by

transmission and distribution lines, operated by control centers.
➢ It includes generation stations, transmission lines (EHV AC, HVDC), substations, and various
loads (sub-transmission, primary, secondary customers).
 Evolution of Indian National Grid
Early 1960s 1
Regional grid management began,
interconnecting state grids.
2 October 1991
North East and Eastern
Grids connected.
March 2003 3
Western, Eastern and
North East regions interconnected.
4 August 2006
Northern and Eastern Grids
December 2013 5 interconnected, forming a central
grid operating at one frequency.
Southern region connected to central
grid, achieving 'one nation', 'one grid',
'one frequency'.
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 What is a Smart Grid?
Definition:
A modern electricity grid using digital technology to
monitor, control, and manage power delivery from all
sources to end-users.
It upgrades the traditional grid by integrating advanced
communication, information, and control.
Key Characteristics:
Two-way Communication: Information exchange between
utilities and consumers.
Self-Healing: Detects and responds to disturbances.
Optimized Operation: Efficient energy delivery, reduced
losses.
Renewable Integration: Seamless connection of distributed
generation.
Consumer Participation: Empowers consumers with
control.
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Why the Need for a Smart Grid?
➢ Challenges of the Traditional Grid:
▪ Aging infrastructure, inefficient delivery (high T&D losses).
▪ Limited visibility, control and vulnerability to outages/cyber threats.
▪ Difficulty integrating renewables and lack of consumer engagement.

➢ Drivers for Smart Grid Adoption:

▪ Growing energy demand, climate change and decarbonisation goals.
▪ Energy security, grid modernization and resilience needs.
▪ Advancements in IoT, AI and Big Data.
 What Makes a Grid 'Smart'?
Digital technology enabling two-way communication between utility and customers plus sensing
along transmission lines.
➢ Existing Grid ➢ Smart Grid
▪ Electromechanical ▪ Digital
▪ One-way communication ▪ Two-way communication
▪ Centralized generation ▪ Distributed generation
▪ Limited sensors ▪ Sensors throughout
▪ Manual monitoring ▪ Self-monitoring
▪ Failures & Blackouts ▪ Adaptive & Islanding
▪ Limited control ▪ Pervasive control
▪ Manual restoration ▪ Self-healing
 Key Components of Smart Grid
➢ Smart Meters: Digital, two-way
communication for real-time consumption
data.
➢ Advanced Sensing & Measurement: Sensors
(e.g., PMUs) for real-time grid status and
remote asset monitoring.
➢ Advanced Communication Infrastructure:
Fibre optics, wireless, PLC for grid-wide
data exchange. Power Line Communication (PLC) is a
technology that enables data transmission over existing electrical
power lines, allowing for simultaneous power and data transfer.

➢ Advanced Control & Automation: Automated fault detection, isolation, and restoration for
self-healing.
➢ Advanced Applications: Demand Response, Distributed Energy Resource Management,
Grid Optimization.
 Smart Grid Technologies
➢ Information & Communication Technology (ICT): Backbone for data exchange; includes sensors,
networks, data centres.
➢ Artificial Intelligence (AI) & Machine Learning (ML): For predictive maintenance, load
forecasting, anomaly detection.
➢ Internet of Things (IoT): Connects devices/sensors for real-time grid data.
➢ Big Data Analytics: Processes vast data for insights and decision-making.
➢ Cybersecurity Solutions: Protects critical infrastructure from cyber threats.
➢ Cloud Computing: Scalable data storage and processing for grid applications.
 Benefits of Smart Grid
➢ Enhanced Reliability & Resilience: Faster outage restoration, reduced impact of disasters.
➢ Improved Efficiency: Reduced transmission/distribution losses, optimized energy flow.
➢ Greater Sustainability: Facilitates renewable energy integration, reduces carbon footprint.
➢ Cost Savings: Lower utility operational costs, potential consumer bill reduction via demand
response.
➢ Consumer Empowerment: Real-time data, participation in demand response, rooftop solar
integration.
 Challenges in Smart Grid
Implementation
➢ High Initial Investment Cost: Upgrading infrastructure is expensive.
➢ Cybersecurity Risks: Interconnected systems increase attack surface.
➢ Interoperability & Standardization: Ensuring seamless communication between diverse
systems.
➢ Data Management & Privacy: Handling vast amounts of sensitive consumer data.
➢ Regulatory & Policy Frameworks: Requires supportive policies and tariff structures.
➢ Public Acceptance & Awareness: Educating consumers and overcoming resistance to new
technologies.
 Smart Grid Architecture
➢ Generation (Conventional, Renewable,
Distributed)
➢ Transmission & Distribution Networks
➢ Substations (with smart controls)
➢ Smart Meters & End-users
(homes/buildings with smart appliances,
EVs, rooftop solar)
➢ Overlying Communication Network
➢ Control Centres (SCADA, DMS, OMS)
➢ Data Analytics platforms
 Smart Meter
➢ Functionality:
▪ Real-time energy consumption measurement.
▪ Two-way utility communication.
▪ Remote reading, connection/disconnection and Time-of-Day (ToD) tariff support.
➢ Benefits:
▪ Eliminates manual reading errors, provides granular data.
▪ Facilitates demand response, improves billing accuracy.
➢ India's Progress in Smart Meter Deployment:
▪ Target: 250 million smart prepaid meters by 2025.
▪ Key Programs: Revamped Distribution Sector Scheme (RDSS) promotes smart
metering.
 Advanced Metering Infrastructure
(AMI)
➢ Definition:
▪ The comprehensive system enabling two-way communication between smart meters and
the utility's central system.
▪ Includes smart meters, communication networks and data management systems (MDMS).
➢ Components:
▪ Smart Meters: Data collection points.
▪ Communication Network: Connects meters to utility
▪ Meter Data Management System (MDMS): Collects, validates, stores, and processes
meter data.
▪ Head-End System (HES): Manages meters’ communication.
➢ Role in Smart Grid:
▪ Provides accurate, real-time data for grid operations.
▪ Enables advanced applications like outage management and demand response.
 Renewable Energy Integration
➢ Challenge: Intermittency of solar and wind sources impacts grid stability.
➢ How Smart Grid Helps:
▪ Advanced Forecasting: Better prediction of renewable generation.
▪ Real-time Monitoring & Control: Dynamic grid management for fluctuations.
▪ Distributed Energy Resource Management Systems (DERMS): Optimizes local
generation/consumption.
▪ Energy Storage: Buffers intermittent generation.
India's Renewable Energy Targets:
Target: 500 GW of non-fossil fuel energy capacity by 2030.
 EVs and Smart Grid
➢ EVs:
EVs act as both loads and potential energy storage.
Smart grid manages EV charging to optimize grid
load.
➢ Vehicle-to-Grid (V2G) Technology:
EVs can feed power back to the grid during peak
demand, acting as mobile storage.
➢ Smart Charging Infrastructure:
Optimizes charging times based on grid conditions
and prices, reducing grid stress.
➢ India's EV Movement:
Government incentives and focus on charging
infrastructure development.
Smart grid is essential for managing widespread
EV adoption.
 Demand Side Management
➢ Definition: Strategies to influence consumer electricity use, optimizing grid operation by shifting
energy from peak to off-peak periods.
➢ Key Concepts:
▪ Demand Response (DR): Incentivizes consumers to reduce/shift energy use during peak
demand.
▪ Energy Efficiency: Reduces overall consumption.
▪ Load Management: Direct control over certain loads (e.g., AC) with consent.
➢ Benefits:
▪ Reduces need for new power plants.
▪ Lowers peak hour electricity costs.
▪ Improves grid stability and reliability.
 Energy Storage System
➢ Role in Smart Grid:
▪ Grid Stability: Balances supply/demand, especially with intermittent renewables.
▪ Peak Shaving: Stores energy off-peak, releases during peak.
▪ Frequency Regulation: Helps maintain grid frequency.
▪ Backup Power: Provides resilience during outages.
➢ Types of Storage:
▪ Batteries: Lithium-ion, Flow batteries (common).
▪ Pumped Hydro Storage: Large-scale, mature.
▪ Thermal Storage: Stores heat/cold.
▪ Flywheels: For short-duration, high-power.
 Cyber Security
➢ Why it's Critical: Smart grid's interconnectedness makes it vulnerable to cyberattacks,
risking data theft, system disruption, and control manipulation.
➢ Key Threats: Malware, ransomware, Denial of Service (DoS), data breaches and physical
attacks via cyber means.
➢ Mitigation Strategies:
▪ Robust encryption, Intrusion Detection Systems (IDS).
▪ Regular audits, penetration testing, employee training.
▪ Secure by Design integration.
 Smart Grid Initiative in India
➢ Government Vision: Modernize India's power infrastructure for reliable, affordable,
sustainable power.
➢ Key Policies & Programs:
▪ National Smart Grid Mission (NSGM): Established 2015 to plan, monitor and
implement smart grid activities.
▪ Revamped Distribution Sector Scheme (RDSS): Aims to improve DISCOM
efficiencies and financial sustainability, with smart metering.
▪ Smart Cities Mission: Integrates smart grid concepts into urban development.
 India’s Smart Grid
Mission (ISGM)
➢ Establishment: Launched 2015 under the Ministry
of Power.
➢ Objectives:
▪ Accelerate smart grid deployment.
▪ Provide policy/regulatory support, develop
technical standards.
▪ Build capacity, promote R&D, facilitate
knowledge sharing.
 Pilot Programs in India
Examples of Smart Grid Pilot Projects:
▪ Puducherry: Focus on AMI, DSM, outage management.
▪ Mysore: Integration of renewables, microgrids.
▪ Kolkata: T&D loss reduction, smart metering.
▪ Ranchi: Automated distribution.
 Challenges of the Existing Grid
• Increasing Demand
1 • Huge increase in electricity demand and per capita consumption.

• Supply Shortfalls
2 • Energy gap between production and expected delivery, especially at peak.

• High Losses
3 • Overall network losses are high (22.7%), needing significant reduction.

• Aging Assets
4 • Most assets are 40-50 years old, requiring costly replacements.

• Integration of Renewables
5 • Need technology for safe and reliable integration of diverse sources.
 Roadmap for India
➢ Future Vision: A resilient, secure, efficient, and sustainable power system with high
renewable penetration and active consumer participation.
➢ Key Focus Areas:
▪ Universal Smart Metering: 100% coverage.
▪ Advanced Distribution Management Systems (ADMS): Real-time grid control.
▪ Cybersecurity Framework: Strengthening grid defences.
▪ Grid Integration of EVs: Scaling charging infrastructure and V2G.
▪ Microgrids & Distributed Generation: Promoting local energy solutions.
▪ Research & Development: Fostering innovation.
 Smart Grid Domains

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 Both central
& state govt.
involved in
power sector Discoms
Energy accumulated
produced losses
1200 Twh
20%

Energy
240 million
shortage
consumers
1.0%
Indian Power Sector- an
Overview

Peak Very High

shortage losses 23-
1.5% 25%

Low revenue
Load Growth /Per capita
6-8% use ~1010
Wh
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 Smart meter
Smart meter records consumption in intervals of 30mins or less.
communicates information at least daily back to the utility for monitoring
and billing. enable two-way communication. Provides on line update to the
user through web or in home display to help efficient energy usage and
reduce bill. Sensor for smart grid.

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Motivates: Key Drivers -Smart Metering in India

1) Power theft and losses.

2) Customer services.
3) Integration of RES.
4) Transparency.
5) 24*7 power supply.
6) Load management (DR).

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 Planning Smart Grid Reliability

Adding communication and connect/ disconnect switch

Operation Data
efficiency Analytics

Customer Asset Revenue Renewable

Service Management leakage Integration

Field Crew Demand

Metering Billing Metering Management Management
Billing

Utility operations benefited by Walk by

Utility operations benefitted by adapting Smart Metering
reading

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 Issues and Challenges
1. Lack of standard specification of meter.
2. Selection of communication technology.
3. Regulatory support missing.
4. SLA not being achieved, field issues etc..
5. All are new entrants.

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 Feeder Automation
Feeder automation system is an important part of a smart grid as it is used for
improving the efficiency, reliability, and security of the electric grid. It provides real-
time monitoring and automatic control capabilities in the power distribution network.
In smart grid technology, feeder automation is important because it allows for:
❖ Seamless integration and management of renewable energy sources.
❖ Distribution of load evenly across the network to provide load balancing.
❖ Improving the grid stability and resiliency to withstand against the faults and
disturbances.
❖ Optimizing the performance of the distribution network, etc.

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 Feeder Automation
What is a Feeder?
➢ A feeder is a type of electrical line or wire that carries power from a main
distribution point, such as a substation, to smaller distribution points or to the
end-users. The main function of a feeder is to ‘feed’ electricity to different
parts of an electrical system.
➢ Feeders are an essential component of any electrical system as they ensure
that electricity is distributed to all areas that need it. This may include
residential areas, commercial buildings, and industrial facilities. Without
feeders, it would be impossible to distribute electricity efficiently across a
wide area.
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 Feeder Automation
❑ Feeder automation is defined as a process of automating the monitoring, control, and
operations of distribution feeders. Feeder automation involves the use of intelligent
electronic devices (IEDs), digital communication networks, and automated control
systems to perform feeder operations without any need of human intervention.
❑ Feeder automation enables the utility companies to monitor the feeder operations in
real-time, and provides capabilities to control and optimize the distribution feeders for
delivering power more efficiently.

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 Feeder Automation?
Major faults occur in the feeder section of the distribution networks. Therefore, it is very
important to continuously monitor the operation of a feeder which is manually not
practical. Hence, we need an automated system that can monitor and control the feeder
operations.
Some of the key factors, which motivate for feeder automation are listed as:
1. Feeder automation is required for reducing the number of times and duration of power
outages and improving the reliability of power supply.
2. Feeder automation is also essential for predicting the failures and inefficiencies in the
distribution networks and reducing the power interruptions.
3. Feeder automation is needed for integrating and managing the renewable energy
resources. It is required because renewable energy resources like solar, wind, etc. are
intermittent in nature.
4. Feeder automation is also important for enhancing the reliability, efficiency, and
security of the power distribution networks. This helps in reducing the energy cost
and improving the consumer satisfaction.

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 Components of Feeder Automation System
1. Intelligent Electronic Devices (IEDs)
IEDs are the smart devices used for real-time monitoring and automated control of electric feeder
operations. Examples of IEDs include smart sensors, protection and control relays, digital
communication devices, smart meters, etc.
2. Communication Networks
In feeder automation, digital communication networks are used for transmitting data between different
components. Commonly used communication technologies are power line carrier, ethernet, optical fiber,
or wireless networks.
3. Distribution Management System
It is one of the key components of the feeder automation system. It is basically a centralized software
employed for collecting data from IEDs, perform their analysis, and send appropriate commands to the
control system.
4. SCADA System
Supervisory Control and Data Acquisition (SCADA) system is another software used in feeder
automation system. It is primarily used for real-time data acquisition and providing remote control of
feeder operations.
5. Automated Switches
These are the smart switches that can be operated from a remote location. The automated switches
receive commands from SCADA system and control the flow of electricity through the feeder.
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 Feeder Automation System: Operation

1) The intelligent electronic devices (IEDs) and smart sensors provided across the feeder collect the
electrical data about the feeder operation.
2) The IEDs and sensors data are transmitted to a central control system or distribution management
system for analysis.
3) The distribution management system analyzes the data to determine any issues or faults in the
feeder network. It also predicts the potential issues in the distribution network in advance.
4) Depending on the results of data analysis, the distribution management system sends commands to
the control system for taking appropriate actions.
5) A feedback loop is provided in the system for continuous monitoring of the feeder operations and
optimize the performance accordingly.
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 Feeder Automation System

1) Rapid fault detection and isolation to minimize the damages in the distribution feeders.
2) Automatic rerouting of power to reduce the power outages in unaffected areas.
3) Manage and equal distribution of electrical load across the network to provide load
balancing and minimize the chances of overloading in the feeder.
4) Keep the feeder voltage within a specified limit to improve the power quality.
5) Continuous monitoring of the distribution feeders to prevent failures and reduce the
power outages and maintenance cost.

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 Feeder Automation System: Advantages

1) Feeder automation improves the reliability of the distribution network through rapid
fault detection and isolation.
2) Feeder automation also enhances the efficiency of power distribution network through
load balancing and voltage regulation.
3) Feeder automation reduces the need of human intervention for operation and
maintenance. Hence, it also reduces the cost of operation and maintenance of feeder.
4) Feeder automation minimizes the human errors and provides rapid power restoration
service. This increases the trust of consumers and improves their satisfaction.

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 Feeder Automation System: Challenges

Feeder automation offers several advantages, but it also faces numerous challenges in the
implementation and operation:

1) The implementation of feeder automation technologies requires infrastructure

upgradation which is a cost intensive task and requires high initial cost.
2) Different technologies and devices are used for feeder automation that may have
compatibility issues.
3) Feeder automation uses digital communication networks for data transmission. Hence,
the operation of feeder automation system is vulnerable to cyber threats.
4) Feeder automation employes new technologies that require approvals from regulatory
bodies before use.
5) The installation, operation, and maintenance of feeder automation devices is a
technology intensive task that requires highly skilled personnel.

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 Wide Area Monitoring System (WAMS)
The primary function of wide area monitoring system (WAMS) is to modernize the electric
grid and to avoid power outages and blackouts.
❖ Wide Area Monitoring Systems (WAMS) represent a transformative approach in the
management and control of modern power systems. As the backbone for real-time data
collection and analysis, WAMS play a crucial role in enhancing the stability and
reliability of large interconnected power grids.
❖ WAMS empowers grid operators to verify normal oscillation behaviors. Its robust
analysis engine can quickly identify and pinpoint the precise cause of any disturbance,
enabling operators to intervene before outages occur.
❖ WAMS is an advanced measurement technology used to upgrade the existing electric
grid to the smart grid. It modernizes the power system network and avoid blackouts and
severe outages.

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 Wide Area Monitoring System (WAMS)

1) Wide Area Monitor Systems (WAMS) are basically based on the new data acquisition
technology, i.e., PMUs.

2) WAM is basically a synchro-phasor technology that employes synchronous

measurement to monitor and evaluate the state of the electric grid. It is called wide area
monitoring because it functions over a wide geographical area.

3) Monitor the state of transmission network over wide area, such that detect the faults and
stability issues and further counteracting grid instabilities.

4) The WAM system collect time-synchronized data about the grid operations. For this
purpose, it uses high-speed communication system that can report power system data 25-
50 times in a second.

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 Wide Area Monitoring System (WAMS)

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 Wide Area Monitoring System (WAMS) (PSGuard-ABB)
❖ In smart grids, the increasing technical complexity in interconnecting multiple grids
together arose the need for wide area monitoring system. This is because, the traditional
monitoring technologies are based on localized and delayed data communication, which
may lead inefficiencies in modern grid management and operation.
❖ Large-scale power grids, spread over expansive geographic areas, require a sophisticated
monitoring mechanism to detect and respond to potential disturbances promptly. This
need becomes especially critical given the growing integration of renewable energy
sources, such as solar and wind power, which are inherently variable and less predictable
than traditional energy sources.
❖ As renewable energy penetration increases and demand for electricity grows, which
results in increase of complexity in the power grid operations. Traditional grid
management systems often fall short of addressing these dynamic and multifaceted
challenges. Wide Area Monitoring Systems, equipped with technologies like Phasor
Measurement Units (PMUs) that enhance the grid’s visibility and responsiveness. These
technologies provide operators with high-resolution data, offering a comprehensive
overview of the grid’s operational status in real time.
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 Wide Area Monitoring System (WAMS)

The wide area monitoring system is employed in smart grid for the following reasons −
❖ It is fast and efficient in detecting and responding to faults and disturbances. Thus, it results in
improved reliability and stability.
❖ It reduces the impact of faults and disturbances on the system by rapidly detecting and isolating
them.
❖ It provides real-time data about grid operations and helps in better management of the grid.
❖ It improves the sustainability of the grid through the integration of renewable energy resources.
❖ WAMS facilitate the synchronized collection of data across vast regions, enabling a holistic
assessment of power system conditions.
❖ By leveraging real-time data analytics, these systems can predict potential instabilities and
incorporate preventive measures to avert power outages and system failures.

Wide Area Monitoring Systems are essential for managing the increasingly complex and demand-
intensive power grids of today. By integrating advanced monitoring technology, WAMS not only
enhance the reliability of power systems but also support the seamless incorporation of renewable
energy, paving the way for a sustainable energy future.

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 Wide Area Monitoring System (WAMS)

The main components of the wide area monitoring system (WAMS) are:
1. Phasor Measurement Unit (PMU)
2. Phasor Data Concentrator (PDC)
3. Communication System
4. Control Center

A meeting was held on March 13, 2025, at the Central Electricity Authority (CEA) office to discuss the
way forward on the draft guidelines for the placement of Phasor Measurement Units (PMUs) in the
Indian power grid.
These guidelines identify optimized locations and data signals for PMUs. The locations specified in the
guidelines are intended to provide adequate observability for the grid, and the guidelines will
standardize how and where PMUs are installed.

➢ Optimal placement of PMUs for the smart grid implementation in Indian power grid—A case study |
Frontiers in Energy.
➢ Wide Area Monitoring System (WAMS) Application in Smart Grids | IEEE Conference Publication |
IEEE Xplore
2025
 Phasor Measurement Unit (PMU)

❖ Capture precise, time-synchronized data on the voltage, current, and frequency of the
power system. The precision of PMUs is integral, as they offer a high-resolution snapshot
of electrical parameters several times per second (ms), facilitating real-time monitoring
and enhancing the stability of the grid. WAMS provides time-synchronized data every 20
ms (for a 50 Hz system) with all data timestamped.
❖ A critical enabler for the time-synchronized data collection by PMUs is Global
Positioning System (GPS) technology. GPS provides a universal time reference, ensuring
that measurements taken across vast geographical areas are accurately timestamped.
❖ This precision in timing is fundamental for phase angle comparison and for identifying
issues like oscillations or disturbances in the power system, thus maintaining the integrity
and reliability of the electrical grid.
❖ Once data is captured by PMUs, it is transmitted to Data Concentrators.

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 Phasor Data Concentrator (PDC)

❖ Continuously collects measurements from PMU

❖ correlate them and feed as a single stream
❖ Provides real-time system monitoring and control
❖ Stores measurements in a database.

PDC can receive data from at least 100 PMUs with a full resolution of 50(60) samples per
second.

Data Historians
Keep PMUs’ data in a proper sequence for further usage.
Data Visualization Applications
These are the graphical interface-based applications used for showing data to control room
operators to identify the grid conditions and issues.
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 Communication System

The communication system provides a wide range of communication protocols for

collecting and receiving synchronized phasor data from PMUs.

For example: IEEE c37.118 and IEEE 1344 communication protocols for PMU
communications.

The server may connect to other PDCs to exchange the required data in real-time with other
companies, such as ISO, transmission network, generation system, and market operators
also.

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 Feature SCADA WAMS
Data acquisition and visualization for operators; Real-time, high-resolution grid monitoring;
Purpose
supports control actions focuses on grid dynamics and stability
Measurement Devices Uses RTUs (Remote Terminal Units) Uses PMUs (Phasor Measurement Units)
Much faster: 20–60 times per second
Data Acquisition Rate Typically every 1–2s
(milliseconds-level granularity)
GPS-based strict synchronization across all
Time Synchronization No strict synchronization; timestamps can vary
PMUs
SCADA collects measurements like voltage, WAMS collects phasor (synchrophasor) data:
Data Type
current, status of breakers, etc. magnitude, phase angle, frequency, etc.

Wide geographic scale, capturing dynamic

Coverage Primarily local substations and control centers
system behavior
Monitoring, control, demand management, Dynamic stability analysis, oscillation
Use Cases
contingency operations monitoring, real-time post-event analysis
Grid operator dashboards, alarms, historical High-speed, high-resolution data for advanced
Visualization
data analytics and forecasting
May integrate with WAMS or EMS for Often integrated with SCADA/EMS for unified
Integration
enhanced control situational awareness

❖ SCADA is primarily about gathering, displaying, and controlling power systems on a slow timescale (seconds).
❖ WAMS is designed for capturing fast, synchronized, detailed measurements across broad regions for real-time insight into grid
dynamics, using data streaming many times per second and enabling dynamic analysis and stability monitoring not possible with
traditional SCADA.
 Phasor Measurement Unit (PMU)

❑ Anti aliasing filters ensure that all the analog signals have the same phase shift and attenuation, thus
assuring that the phase angle differences and relative magnitudes of the different signals are unchanged.
❑ The GPS system is used in determining the coordinates of the receiver, although for the PMUs the signal.
GPS receiver is provided in a PMU for precise time synchronization of the measurements. It receives a time
signal from GPS satellites that provides a time accuracy of better than one microsecond. The output signal
produced by the GPS receiver acts as a reference clock for synchronization of measurements across different
PMUs.
❖ Phase-Locked Oscillator: Digitalization of the
signals is synchronized with the reference clock
provided by the GPS receiver.
❖ The phasor microprocessor: Digital device that
processes the digital data to calculate the magnitude,
phase angle, frequency, rate of change of frequency,
etc. of the electrical signals.
❖ Modem is a communication device that establishes a
fast communication between the PMU and the phasor
data concentrators. It transmits the output of the
phasor microprocessor to the data concentrators for
further processing and analysis.
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 Synchro-Phasor Communication System

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 Synchro-Phasor Communication System

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 Synchro-Phasor Communication System

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 Synchro-Phasor Communication System

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 Power Transmission

An efficient transmission system is needed for transmission of power from bulk generation
units to load centres.

❖ Bulk power transmission over long distances,

❖ Low transmission losses.
❖ Less voltage fluctuations.
❖ System of interconnection.

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 High-Voltage Direct Current (HVDC)

❖ A High-Voltage Direct Current (HVDC) electric power transmission system

uses direct current (DC) for the transmission of power over long distances.
❖ With the fast development of converters (rectifiers and inverters) at higher voltages and
larger currents, DC transmission has become a major factor in the planning of the power
transmission.
❖ DC Transmission now became practical and common when long distances were to be
covered.
❖ HVDC also allows power transmission between AC transmission systems that are not
synchronized. Since the power flow through an HVDC link can be controlled
independently of the phase angle between source and load.
❖ HVDC also allows the transfer of power between grid systems running at different
frequencies, such as 50 and 60 Hz.

❖ Highest functional DC voltage for DC transmission is +/-800kV.

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 HVAC Transmission HVDC Transmission

A transmission system that transmits AC power at A transmission system that transmits DC power at a
voltage about 33 kV to 765 kV is known as HVAC voltage about 100 kV to 800 kV is known as HVDC
transmission system. transmission system.

In HVAC, transformer is used for voltage In HVDC, transformer cannot be used, because the
transformation. transformer does not work on DC.

HVAC transmission system requires at least three line HVDC system requires two conductors in bipolar
conductors. system and one conductor in a monopolar system.

The rectifier and inverter are the crucial components

HVAC does not require rectifiers and inverters.
of an HVDC system.

The voltage transformation is complex in case of

HVAC involves simple voltage transformation.
HVDC.

In HVAC, the corona loss is more. HVDC has comparatively less corona loss.

Due to uneven current density, there is skin effect in In HVDC, current density is uniform in the conductor,
HVAC system. there is no skin effect.
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 HVAC Transmission HVDC Transmission

The right of way is broader for HVAC. Right of way is

the strip of land required for installation of The right of way is narrower for HVDC.
transmission lines.

HVAC is not preferred for submarine power HVDC is preferably used for submarine power
transmission because of stray capacitance of cables. transmission.

VAC causes interference with the neighboring HVDC does not cause interference with the nearby
communication lines. communication lines.

The HVAC circuit breakers are less expensive and The HVDC circuit breakers are comparatively
have simple design. expensive and have complex design.

In HVAC system, almost 30% of conductor capacity is HVDC system utilizes full conductor capacity. It is
wasted due to AC peak ratings during the delivery of because in case of DC, the peak and average ratings
average power. are same.

In HVAC, the corona loss is more. HVDC has comparatively less corona loss.

HVAC is a less expensive system for power

HVDC system is little expensive than HVAC.
transmission.
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 Economics of Power Transmission

❖ In DC transmission, inductance and capacitance of the line has no effect on the power transfer
capability of the line and the line drop. Also, there is no leakage or charging current of the line
under steady conditions.
❖ A DC line requires only 2 conductors whereas AC line requires 3 conductors in 3-phase AC
systems.
❖ The cost of the terminal equipment is more in DC lines than in AC line.
❖ Break-even distance is one at which the cost of the two systems is the same.

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 Economics of Power Transmission

❖ In DC transmission, inductance and capacitance of the line has no effect on the power transfer
capability of the line and the line drop. Also, there is no leakage or charging current of the line
under steady conditions.
❖ A DC line requires only 2 conductors whereas AC line requires 3 conductors in 3-phase AC
systems.
❖ The cost of the terminal equipment is more in DC lines than in AC line.
❖ Break-even distance is one at which the cost of the two systems is the same.

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 Technical Performance

• Due to its fast controllability, a DC transmission has full control over transmitted power, an
ability to enhance transient and dynamic stability in associated AC networks and can limit fault
currents in the DC lines.

❖ Stability Limits
❖ The power transfer in an AC line is dependent on the angle difference between the
voltage phasors at the line ends. For a given power transfer level, this angle increases with
distance.
❖ The maximum power transfer is limited by the considerations of steady state and transient
stability.
❖ The power carrying capability of an AC line is inversely proportional to transmission
distance whereas the power carrying ability of DC lines is unaffected by the distance of
transmission.

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 Voltage Control
❖ Voltage control in AC lines is complicated by line charging and voltage drops.

❖ The voltage profile in an AC line is relatively flat only for a fixed level of power transfer
corresponding to its Surge Impedance Loading (SIL).

❖ DC converter stations require reactive power related to the power transmitted, the DC line
itself does not require any reactive power.

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 Line Compensation

❖ Line compensation is necessary for long distance AC transmission to overcome the

problems of line charging and stability limitations.

❖ The increase in power transfer and voltage control is possible through the use of shunt
inductors, series capacitors, Static Var Compensators (SVCs) and, lately, the new
generation Static Compensators (STATCOMs).

❖ In the case of DC lines, such compensation is not needed.

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 Problems of AC Interconnection

❖ The interconnection of two power systems through ac ties requires the automatic
generation controllers of both systems to be coordinated using tie line power and
frequency signals.
❖ Even with coordinated control of interconnected systems, the operation of AC ties can be
problematic due to:

1. The presence of large power oscillations which can lead to frequent tripping,
2. Increase in fault level, and
3. Transmission of disturbances from one system to the other.

❖ The fast controllability of power flow in DC lines eliminates all of the above problems.
Furthermore, the asynchronous interconnection of two power systems can only be
achieved with the use of DC links.

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 Disadvantages of DC Transmission

❖ High cost of conversion equipment.

❖ Inability to use transformers to alter voltage levels.

❖ Requirement of reactive power.

❖ Complexity of controls.

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