7th Sem Electrical Energy Distribution & Utilisation PDF

# Electrical Energy Distribution & Utilisation ## Unit-1: Substation ### Selection & Location Of Site Selecting a substation site requires consideration of multiple factors to ensure efficient operation, safety, and minimal environmental impact. Here are some key considerations: - **Accessibili...

# Electrical Energy Distribution & Utilisation ## Unit-1: Substation ### Selection & Location Of Site Selecting a substation site requires consideration of multiple factors to ensure efficient operation, safety, and minimal environmental impact. Here are some key considerations: - **Accessibility:** Easy access for maintenance crews, large equipment delivery, and emergency services. - **Electrical Infrastructure:** Proximity to existing electrical infrastructure, such as power lines and transmission grids, can reduce costs and simplify connection. - **Land Availability:** Sufficient land area is needed to accommodate substation equipment, access roads, and safety clearance. - **Environmental Impact:** Avoid environmentally sensitive areas, such as wetlands or wildlife habitats. EMF emissions are also a concern, especially near residential areas. - **Geotechnical Considerations:** Assess soil stability and foundation requirements to ensure the site can support equipment weight and withstand environmental factors like earthquakes or flooding. - **Security:** The site must be easily securable and not prone to unauthorized access or vandalism. - **Zoning and Planning Regulations:** Ensure compliance with local zoning regulations, land use plans, and permitting requirements. - **Future Expansion:** Anticipate future growth in power demand and potential grid expansion. - **Community Consideration:** Engage with local communities and stakeholders to address concerns and gain support. - **Cost:** Consider land acquisition costs, construction costs, and ongoing operational expenses. - **Detailed Engineering Studies & Approvals:** Once the site is selected, detailed engineering studies, environmental impact assessments, and regulatory approvals are needed before construction begins. ### Classification Of Substation Substations can be classified based on: - **Voltage Level:** - **High Voltage Substation:** Voltage levels above 69 kV. - **Medium Voltage Substation:** Voltage levels ranging from 2.4 kV to 69 kV. - **Low Voltage Substation:** Voltage levels below 2.4 kV. - **Function:** - **Transmission Substation:** Connects two or more transmission lines or circuits. - **Distribution Substation:** Receives power from transmission lines and distributes it to consumers. - **Converter Substation:** Converts power from AC to DC or vice versa, often used in HVDC (High Voltage Direct Current) systems. - **Switching Substation:** Primarily for switching and controlling the flow of electricity. - **Layout:** - **Indoor Substation:** Housed within a building or structure. - **Outdoor Substation:** Equipment often mounted on support structures in an open area. - **Hybrid Substation:** Combines elements of indoor and outdoor substations. - ** Construction:** - **Conventional Air-Insulated Substation (AIS):** Uses air as the primary insulating medium. - **Gas-Insulated Substation (GIS):** Employs sulfur hexafluoride (SF6) or other gasses for smaller footprint and environmental protection. - **Hybrid Gas-Insulated Substation:** Combines GIS and AIS elements for optimized performance. - **Specialized Substations** - **Mobile Substation:** Transportable substations for temporary purpose or during emergencies. - **Renewable Energy Substation:** Designed to integrate power from renewable sources like wind or solar. **Note:** Substation classifications may overlap, and further categorizations can be applied based on specific requirements or technological advancements. ### Major Equipment Of Substation Substations are crucial components of electrical power systems, where the voltage is transformed for transmission or distribution purposes: - **Transformers:** Change the voltage level of electricity for transmission or distribution. - **Circuit Breakers:** Interrupt the flow of electricity in case of a fault or overload, protecting the electrical system from damage. - **Disconnect Switches:** Isolate equipment for maintenance or emergencies. - **Busbars:** Conductors that serve as common connection points, carrying electric current between components. - **Capacitors and Reactors:** Improve power factor and control voltage. - **Voltage Regulators:** Ensure voltage stays within acceptable limits, addressing fluctuations in the electrical grid. - **Switchgear:** Includes various types of equipment used for switching, controlling, and protecting electrical circuits. - **Protection Relays:** Monitor the electrical system for abnormal conditions, sending signals to circuit breakers to isolate faults. - **Control Panels:** Provide operators with information about the status of equipment and allow adjustments as needed. - **Battery Banks and Chargers:** Provide backup power for critical systems, especially in the event of a power outage. - **Instrument Transformers:** Measure voltage and current in the electrical system. - **Grounding System:** Safely dissipates fault currents into the ground, protecting equipment and personnel. ### Graphical Symbols For Substation Apparatus & Circuit Elements - **Transformer:** Represents a transformer, which steps voltage up or down. - **Circuit Breaker:** Represents a device used to protect an electrical circuit from damage due to overload or short circuit. - **Disconnect Switch:** Represents a switch used to isolate a circuit or equipment for maintenance. - **Busbars:** Represents a set of electrical conductors used for collecting and distributing electrical power. - **Lightning Arrestor:** Represents a device used to protect electrical equipment from lightning strikes. - **Isolator:** Represents a switch used for isolating a circuit or equipment from the power supply. - **Capacitor Bank:** Represents a bank of capacitors used for power factor correction or voltage support. - **Current Transformer (CT):** Represents a device used to measure alternating current. - **Voltage Transformer (VT):** Represents a device used to measure voltage. - **Grounding (Earthing):** Represents a connection to earth for safety and electrical protection. ### Types Of Bus-Bar Arrangements - **Single Bus-Bar Arrangement:** The simplest arrangement with one bus-bar for power distribution. Economical, but offers no redundancy. - **Double Bus-Bar Arrangement:** Two bus-bars in parallel, one in operation, the other as a standby. Provides maintenance and redundancy. - **Main and Transfer Bus-Bar Arrangement:** A main bus-bar for normal operation, with a transfer bus-bar for maintenance or when the main bus-bar fails. - **Sectionalized Bus-Bar Arrangement:** The bus-bar is divided into sections, each with its own isolator switch. Provides maintenance capability without affecting the rest of the system. - **Ring Main Unit (RMU):** Bus-bars are configured in a ring, providing redundancy and multiple pathways for power flow. Enhances reliability and fault tolerance. - **Duplex Bus-Bar Arrangement:** Similar to the double bus-bar arrangement, but with additional redundancy. - **Zonal Interlocking Bus-Bar Arrangement:** Employs interlocking mechanisms to ensure only one section can be energized at a time, enhancing safety during maintenance. ### Substation Earthing Substation earthing (grounding) is crucial for safety: - **Safety:** Provides a low-resistance path for fault currents to flow to the earth, preventing dangerous voltages from building up in equipment and structures. - **Grounding Systems:** Common types include solid grounding, resistance grounding, and reactance grounding. - **Design Considerations:** Factors to consider include soil resistivity, fault currents, step and touch potentials, and the layout of the substation. - **Components:** Typically include grounding electrodes (rods or plates), conductors, ground grids, and connections to equipment and structures. - **Maintenance:** Regular maintenance and testing of earthing systems are necessary to ensure effectiveness. - **Standards and Regulations:** Ensure compliance with relevant standards, such as those specifying grounding resistance, step and touch potentials, and safety practices. ### Introduction To Gas-Insulated Substations (GIS) GIS substations offer several advantages over conventional AIS (air-insulated substations): - **Compact Design:** GIS substations occupy significantly less space, making them ideal for installations in densely populated areas or locations where land is limited. - **Improved Reliability:** Encapsulating critical components within a sealed environment protects them from external environmental factors like moisture, dust, and pollution. - **Enhanced Safety:** The use of SF6 gas as an insulating medium reduces the risk of electrical arcing, fires, and explosions. The sealed enclosures are designed to withstand high mechanical stresses, further enhancing safety. - **Reduced Environmental Impact:** While SF6 is a potent greenhouse gas, the sealed design of GIS prevents it from being released into the atmosphere during normal operation. - **Higher Voltage Ratings:** GIS technology allows for the construction of substations operating at higher voltages compared to AIS. - **Challenges:** GIS systems can be costly and require specialized maintenance procedures due to the complexity of the system. ### Unit-2: Power Distribution System -I #### Primary and Secondary Distribution - **Primary Distribution** involves delivering electricity from power plants or substations to end-users. - **High Voltage Transmission:** Typically done at voltages ranging from 69 kV to 765 kV, depending on distance and power requirements. High voltages reduce energy losses during long-distance transportation. - **Step-Down Transformers:** Reduce voltage to a lower level suitable for local distribution at substations closer to end-users. - **Primary Distribution Lines:** Carry the stepped-down electricity through overhead power lines or underground cables. - **Distribution Transformers:** Further reduce the voltage to levels suitable for use in homes, businesses, and other facilities. - **Secondary Distribution:** - **Low Voltage Distribution Lines:** Carry electricity from distribution transformers to individual buildings, residences, and businesses. These lines are typically lower in voltage and are often overhead lines or buried underground. - **Service Drop or Service Lateral:** Final connection from the secondary distribution line to a building. - **Panelboards and Circuit Breakers:** Distribute electricity within a building, providing protection from overloads and faults. - **Branch Circuits:** Carry electricity from panelboards to power outlets, lights, and appliances. #### Key Differences Between Primary and Secondary Distribution - **Voltage Level:** - **Primary Distribution:** Higher voltages (typically above 600 volts). - **Secondary Distribution:** Lower voltages (typically below 600 volts). - **Infrastructure:** - **Primary Distribution:** Larger lines designed long-distance transmission. - **Secondary Distribution:** Smaller lines designed for localized distribution. - **Transformers:** - **Primary Distribution:** Step-up transformers at power plants or substations and step-down transformers at distribution substations. - **Secondary Distribution:** Distribution transformers at the neighborhood level. #### Types Of Conductors In Distribution Systems - **Overhead Conductors:** - **Bare Conductors:** Aluminum, copper, or steel, with no insulation. Used in overhead power lines. - **Covered Conductors:** Insulated with weather-resistant materials like thermoplastic or rubber. - **Underground Conductors:** - **Insulated Conductors:** Copper or aluminum covered with PVC or XLPE. - **Shielded Conductors:** Have additional layers of shielding to prevent electromagnetic interference. - **Submarine Conductors:** Specifically designed for underwater transmission lines. - **High-Temperature Conductors:** Designed to withstand higher operating temperatures. - **Composite Conductors:** Made of a combination of materials, offering a balance between strength, conductivity, and weight. - **Superconductors:** Exhibit zero electrical resistance when cooled to extremely low temperatures. ### Comparison Of Distribution Systems: Radial - **Radial Distribution System:** A tree-like structure where power flows in one direction only. - **Advantages:** Simplicity, cost-effectiveness, easy to maintain. - **Disadvantages:** Vulnerable to single point failures, limited flexibility. - **Ring Main Distribution System (Ring Network):** A closed loop with multiple pathways for power flow. - **Advantages:** Increased reliability, redundancy, better load balancing. - **Disadvantages:** More complex design, higher costs. - **Parallel Feeder Distribution System:** Multiple feeders running parallelly from the source to the load. - **Advantages:** Improved reliability, fault tolerance, easy to expand. - **Disadvantages:** Higher initial cost, requires more feeders. - **Mesh Distribution System:** Multiple interconnected pathways, providing high redundancy and reliability. - **Advantages:** Extremely high reliability, minimal disruption during failures. - **Disadvantages:** Complex design, very high initial investment, maintenance costs. ### Parallel and Ring Main - **Parallel Circuit:** Components are connected in such a way that there are multiple paths for the current to flow. Voltage across each component is the same, but current varies depending on resistance. Commonly used in homes and buildings, allowing devices to operate independently. - **Ring Main:** A continuous loop of cable runs from the consumer unit to various outlets and then back to the consumer unit. Provides redundancy. ### Economics Of Feeder Design - **Material Cost:** Optimization of materials used in feeder cables and associated equipment. - **Installation Cost:** Consider labor costs, equipment rental, and other expenses. - **Maintenance Costs:** Design for minimal labor needs and long-lasting components. - **Energy Losses:** Minimize losses due to resistance in cables and other components. - **Voltage Drop:** Minimize voltage drop along feeder cables. - **Capacity Planning:** Account for current and future load requirements to ensure proper feeder sizing. - **Reliability and Downtime Costs:** Enhance feeder reliability to reduce downtime costs. - **Regulatory Compliance:** Meet or exceed regulatory requirements. - **Lifecycle Cost Analysis:** Evaluate total cost of ownership over time, considering initial capital expenses, operating costs, maintenance, etc. ### Unit-3: Power Distribution System II #### Methods For Reduction Of Line Losses In Distribution System - **Proper Sizing and Layout Of Conductors:** Use larger conductors with lower resistance to decrease power dissipated as heat and reduce line losses. - **Voltage Regulation:** Maintain optimal voltage levels by using effective voltage regulation techniques, reducing resistive losses. - **Improving Power Factor:** Correcting low power factors (ratio of real power to apparent power) with capacitor banks can reduce reactive power losses. - **Balancing Loads:** Rebalancing loads across phases or sections of the distribution network can reduce losses in specific areas. - **Selecting Efficient Transformers:** Use transformers with higher efficiency ratings to reduce losses associated with transformer operation. - **Implementing Smart Grid Technologies:** Use advanced metering infrastructure (AMI), distribution automation, and real-time monitoring systems for better control and management, helping optimize operations and reduce losses. - **Distribution Automation:** Automation of system operations allows for real-time monitoring and control of various parameters. - **Energy Storage Systems:** Integrate energy storage systems into the network to mitigate voltage fluctuations, balance loads, and improve reliability. - **Minimizing Theft and Unauthorized Usage:** Implement measures to prevent electricity theft and unauthorized usage, reducing losses associated with non-payment and illegal connections. - **Regular Maintenance and Upgradation:** Perform scheduled maintenance and periodic upgrades to keep the system in optimal condition, reducing line losses over time. #### Introduction To High Voltage Distribution Systems (HVDS) - **Higher Voltage Levels:** HVDS operates at higher voltage levels (e.g., 66 kV to 132 kV) compared to conventional distribution system (e.g., 11 kV or 33 kV). - **Reduced Line Losses:** The higher voltage levels result in lower current flows, leading to reduced resistive losses in distribution lines. - **Improved Voltage Regulation:** HVDS systems typically incorporate advanced voltage regulation mechanisms (e.g., automatic voltage regulators and capacitive voltage transformers) to help maintain stable voltage levels under varying load conditions. - **Enhanced Reliability:** HVDS systems are more reliable due to using higher voltage levels, reducing the likelihood of voltage drops, power interruptions, and equipment failures. - **Better Safety:** HVDS systems are designed with safety considerations in mind, with greater clearance distances between conductors, advanced protection features to detect and isolate faults quickly, and a focus on optimized network designs. ### Distribution Automation: Need For Distribution Automation - **Reliability Improvement:** Rapid detection and isolation of faults reduces the frequency and duration of power outages, improving restoration speed and reducing customer downtime. - **Cost Savings:** Automated systems reduce operational costs associated with manual inspections, maintenance, and repairs, optimizing energy distribution and reducing waste. - **Increased Efficiency:** Monitor and control distribution systems in real-time, optimizing energy flow, balancing loads, and regulating voltage. - **Safety Enhancement:** Automated systems enhance worker and public safety by minimizing the need for manual interventions in hazardous conditions. - **Integration of Renewable Energy**: Manage variability and unpredictability from sources like solar and wind power. - **Data-Driven Decision Making:** Analyze data to make informed decisions about upgrades, maintenance, and future investments. - **Support For Smart Grid Initiatives:** Distribution automation is a key component of broader smart grid deployments. - **Overall:** Distribution automation is essential for modernizing and optimizing electrical distribution systems to meet the evolving needs of utilities, customers, and society as a whole. ### Feeder Automation - **Feeder Automation Systems:** Use intelligent devices and communication systems to monitor, control, and optimize the distribution of electricity through feeders, which are the circuits that deliver power from substations to consumers. - **Monitoring:** Continuously monitors voltage, current, power factor, and frequency along feeder lines. - **Control:** Remotely manages switches, breakers, and other devices to isolate faults, reconfigure the network, or reroute power. - **Fault Detection and Localization:** Identify and locate faults like short circuits or overloads. - **Self-Healing:** Automatically reconfigure the network without human intervention to restore power to affected areas, improving reliability. - **Integration With SCADA:** Feeder automation systems are often integrated with supervisory control and data acquisition (SCADA) systems, providing centralized monitoring and control. - **Communication:** Use various wired or wireless communication technologies, such as fiber optics, radio frequency, or cellular networks. ### Communication Requirements For Distribution Automation - **Reliability:** Ensure continuous operation of distribution automation functions through redundancy in communication paths. - **Low Latency:** Rapid response to changing network conditions to allow for timely control and coordination of distribution automation devices. - **Scalability:** Expand to accommodate future growth in the number of devices and data traffic. - **Security:** Implement robust security measures to protect against cyber threats, unauthorized access, and data breaches. - **Interoperability:** Ensure seamless communication between devices and systems from various vendors. - **Bandwidth:** Provide sufficient bandwidth to transmit data from sensors, meters, and control devices throughout the distribution network. - **Coverage:** Ensure adequate coverage across the entire distribution grid, including remote areas. - **Adaptability:** Accommodate future technological advancements. - **Cost-Effectiveness:** Balance performance with cost considerations. - **Fault Detection and Diagnostics:** Support FDD capabilities to detect and diagnose faults quickly, enabling proactive maintenance and restoration. - **Integration with SCADA Systems:** Integrate seamlessly with SCADA systems to facilitate centralized monitoring, control, and data management. - **Resilience:** Ensure communication systems can handle environmental factors such as electromagnetic interference, harsh weather conditions, and physical damage. ### Remote Terminal Unit (RTU) - Introduction To SCADA Systems - **Remote Terminal Unit (RTU):** An intermediary device between field devices (sensors, actuators), and the central SCADA system. - **Functionality:** Collect data from field devices and send control commands. - **Data Acquisition:** Collect data from sensors and equipment. - **Control:** Send control commands to actuators, valves, switches, etc. - **Communication:** Establish communication links with the central SCADA system using communication protocols like Modbus. - **Local Processing:** Perform data processing tasks like scaling sensor readings, filtering data, or performing logic. - **Redundancy and Reliability:** Implement redundant power supplies and communication links to ensure reliability. - **Security:** Protect data and control commands from unauthorized access or tampering. - **Supervisory Control and Data Acquisition (SCADA) Systems:** - **Definition:** SCADA systems are a combination of hardware and software components that monitor and control processes and infrastructure remotely. - **Components:** - **RTUs/PLCs:** Acquire data from field devices and control them. - **Master Terminal Unit (MTU):** The central unit that collects data from RTUs, displays it to operators, and sends control commands. - **Human-Machine Interface (HMI):** Software used by operators to monitor processes and interact with the SCADA system. - **Communication Infrastructure:** Networks that connect RTUs/PLCs with the MTU, using wired or wireless communication technologies. - **Applications:** - **Utilities:** Monitoring and controlling water distribution, electricity generation, and distribution. - **Manufacturing:** Process control in factories and assembly lines. - **Transportation:** Managing traffic control systems, railways. - **Oil and Gas:** Monitoring pipelines, drilling operations. - **Benefits Of SCADA Systems:** - **Increased Efficiency:** Real-time monitoring and optimization of processes. - **Improved Safety:** Early detection of issues allows for preventive actions. - **Cost Savings:** Reduce downtime, energy consumption, and maintenance costs. - **Regulatory Compliance:** Helps industries comply with regulatory requirements by maintaining accurate records and data. - **Challenges Of SCADA Systems:** - **Security:** Vulnerabilities to cyber threats demand robust security measures. - **Integration:** Compatibility issues can arise when integrating new components or systems. - **Reliability:** Ensuring continuous operation, especially in critical infrastructure. - **Understanding RTUs and SCADA systems is crucial for industrial operations seeking to automate processes while maintaining reliability and security.**