Protection against overvoltage
overvoltage
causes of overvoltage
lightning
types of lightning strokes
harmful effect of lightning
protection against lightning
Here are the steps to solve this problem:
1. Given:
Conductor diameter (d) = 10.4 mm
Spacing between conductors (s) = 2.5 m
Air temperature (T) = 21°C = 294 K
Air pressure (P) = 73.6 cm of Hg = 9.6 kPa
Irregularity factor (K) = 0.85
Surface factor for local corona (K1) = 0.7
Surface factor for general corona (K2) = 0.8
2. Critical disruptive voltage (Vc) = 28√(sdP/K)
= 28√(10.4×10-3×2.5×
This document discusses different types of insulators used in overhead power lines. It describes pin insulators, suspension insulators, strain insulators, and shackle insulators. Suspension insulators consist of multiple porcelain discs connected in series by metal links. The voltage is not uniformly distributed across the discs of a suspension insulator string due to shunt capacitances. Methods to improve string efficiency include using longer cross arms, grading insulators with different capacitances, and adding a guard ring. The document also provides sample one mark and 12 mark questions related to insulators.
The document discusses protection of alternators from various faults. It describes 7 types of faults that alternators require protection from: (1) failure of prime mover, (2) failure of field, (3) overcurrent, (4) overspeed, (5) overvoltage, (6) stator winding faults, and (7) unbalanced loading. It then provides details on differential protection and the Merz-Price circulating current scheme, which is commonly used to protect against stator winding faults. It also discusses limitations of this scheme and modified schemes for protection in other situations.
This document provides an overview of air blast circuit breakers. It discusses that air blast circuit breakers use compressed air to extinguish arcs during opening of contacts. The document classifies air blast circuit breakers into axial blast, cross blast, and radial blast types based on the direction of the air blast. It also describes the construction, operation, advantages, disadvantages, applications, and future perspectives of air blast circuit breakers.
This document discusses power quality issues such as voltage sags, interruptions, spikes, swells, and harmonics. It explains the causes and consequences of each issue. Solutions discussed include improving the electric grid, using distributed energy resources like generators and energy storage, following standards, installing enhanced interface devices, and making equipment less sensitive. The key is preventing power quality problems through various measures to avoid losses.
The document discusses protection schemes for transformers. It describes faults that can occur in transformers such as open circuits, overheating, and winding short circuits. It then discusses different protection systems for transformers including Buchholz relays, earth fault relays, overcurrent relays, and differential protection systems. Differential protection systems operate by comparing currents from current transformers on both sides of the transformer and tripping the circuit breaker if a difference is detected, indicating an internal fault. The combination of protection schemes provides comprehensive protection for transformers.
The document discusses electromagnetic relays used in power systems. It describes two main operating principles for electromagnetic relays: electromagnetic attraction and electromagnetic induction. Electromagnetic attraction relays operate using an armature attracted to magnet poles, and include attractor-armature, solenoid, and balanced beam types. Electromagnetic induction relays operate on induction motor principles using a pivoted disc and alternating magnetic fields, and include shaded-pole, watt-hour meter, and induction cup structures. The document also defines important relay terms like pick-up current, current setting, and time-setting multiplier.
Protection against overvoltage
overvoltage
causes of overvoltage
lightning
types of lightning strokes
harmful effect of lightning
protection against lightning
Here are the steps to solve this problem:
1. Given:
Conductor diameter (d) = 10.4 mm
Spacing between conductors (s) = 2.5 m
Air temperature (T) = 21°C = 294 K
Air pressure (P) = 73.6 cm of Hg = 9.6 kPa
Irregularity factor (K) = 0.85
Surface factor for local corona (K1) = 0.7
Surface factor for general corona (K2) = 0.8
2. Critical disruptive voltage (Vc) = 28√(sdP/K)
= 28√(10.4×10-3×2.5×
This document discusses different types of insulators used in overhead power lines. It describes pin insulators, suspension insulators, strain insulators, and shackle insulators. Suspension insulators consist of multiple porcelain discs connected in series by metal links. The voltage is not uniformly distributed across the discs of a suspension insulator string due to shunt capacitances. Methods to improve string efficiency include using longer cross arms, grading insulators with different capacitances, and adding a guard ring. The document also provides sample one mark and 12 mark questions related to insulators.
The document discusses protection of alternators from various faults. It describes 7 types of faults that alternators require protection from: (1) failure of prime mover, (2) failure of field, (3) overcurrent, (4) overspeed, (5) overvoltage, (6) stator winding faults, and (7) unbalanced loading. It then provides details on differential protection and the Merz-Price circulating current scheme, which is commonly used to protect against stator winding faults. It also discusses limitations of this scheme and modified schemes for protection in other situations.
This document provides an overview of air blast circuit breakers. It discusses that air blast circuit breakers use compressed air to extinguish arcs during opening of contacts. The document classifies air blast circuit breakers into axial blast, cross blast, and radial blast types based on the direction of the air blast. It also describes the construction, operation, advantages, disadvantages, applications, and future perspectives of air blast circuit breakers.
This document discusses power quality issues such as voltage sags, interruptions, spikes, swells, and harmonics. It explains the causes and consequences of each issue. Solutions discussed include improving the electric grid, using distributed energy resources like generators and energy storage, following standards, installing enhanced interface devices, and making equipment less sensitive. The key is preventing power quality problems through various measures to avoid losses.
The document discusses protection schemes for transformers. It describes faults that can occur in transformers such as open circuits, overheating, and winding short circuits. It then discusses different protection systems for transformers including Buchholz relays, earth fault relays, overcurrent relays, and differential protection systems. Differential protection systems operate by comparing currents from current transformers on both sides of the transformer and tripping the circuit breaker if a difference is detected, indicating an internal fault. The combination of protection schemes provides comprehensive protection for transformers.
The document discusses electromagnetic relays used in power systems. It describes two main operating principles for electromagnetic relays: electromagnetic attraction and electromagnetic induction. Electromagnetic attraction relays operate using an armature attracted to magnet poles, and include attractor-armature, solenoid, and balanced beam types. Electromagnetic induction relays operate on induction motor principles using a pivoted disc and alternating magnetic fields, and include shaded-pole, watt-hour meter, and induction cup structures. The document also defines important relay terms like pick-up current, current setting, and time-setting multiplier.
This document discusses the history and development of high voltage engineering. It begins with early experiments with static electricity by ancient Greeks. Key figures who contributed include Franklin, Faraday, Tesla, and Edison. Faraday's law established that a magnetic field can induce current in a wire. Advances allowed longer distance power transmission. Challenges included developing high voltage insulation. Numerical methods like finite element analysis are now used to model electric field distributions in complex high voltage components.
Protection of transmission lines(encrypted)Rohini Haridas
This document discusses protection methods for transmission lines. It describes:
1. Transmission lines require more protective schemes than other equipment due to their long lengths and exposure, making faults more common.
2. Key methods of transmission line protection include time-graded overcurrent protection, differential protection, current-graded overcurrent protection, and distance protection.
3. Distance protection uses impedance relays that can discriminate between faults along the line and those near the end, providing more selective operation than overcurrent protection alone. It describes implementations using simple impedance, reactance, and mho relays.
Representation of power system componentsPrasanna Rao
This document discusses the representation of power system components in circuit models for analysis. It introduces the key components of a power system, including generators, transmission lines, and distribution systems. It then covers circuit models for representing synchronous machines, transformers, transmission lines, and static and dynamic loads. The rest of the document discusses additional modeling techniques like one-line diagrams, impedance diagrams, per-unit systems, and calculating base values for analysis.
Surge arresters are devices used to protect electrical equipment from lightning and switching surges. There are several types including rod arresters, horn gap arresters, multigap arresters, and modern metal oxide arresters. Surge arresters work by limiting high voltages from lightning strikes or other surges to safe levels before they reach equipment like transformers. They do this using a metal oxide varistor that acts as an insulator under normal voltages but conducts at higher surge voltages, diverting excess energy to ground. This protects equipment downstream from potential damage.
POWER SYSTEM PROTECTION
Protection Devices and the Lightning,. protection,
Lightning protection, Introduction
Air Break Switches
Disconnect switches
Grounding switches
Current limiting reactors
Grounding transformers
Co-ordination of protective devices
Grounding of electrical installations
Electric shock
Lightning protection
Lightning Arrestor
Surge arrestors are protective devices that limit voltage spikes and surges from damaging electrical equipment. They work by diverting excess current during events like lightning strikes or power faults to ground. When voltage increases, the resistor inside the arrestor decreases in resistance, allowing extra current to drain out and prevent voltage from increasing in protected equipment. Surge arrestors are installed at substations and near transformers to shield sensitive equipment from voltage transients. They parallel arrangement allows surges to be discharged without propagating through the system.
This presentation discusses the key protection devices used in electrical substations. It introduces current transformers and potential transformers, which reduce current and voltage levels for protection relays. Relays detect faults by measuring currents and voltages. When a fault is detected, relays signal circuit breakers to isolate the faulty component. Other protection devices discussed include lightning arresters, isolators, and surge diverters. The objective of the substation protection system is to isolate only faulty parts of the network while keeping the rest operational.
To sense/detect the fault occurrence and other abnormal conditions at the protected equipment/area/section.
To operate the correct circuit breakers so as to disconnect only the faulty equipment/area/section as quickly as possible, thus minimizing the damage caused by the faults.
To operate the correct circuit breakers to isolate the faulty equipment/area/section from the healthy system in the case of abnormalities like overloads, unbalance, undervoltage, etc.
To clear the fault before the system becomes unstable.
To identify distinctly where the fault has occurred.
This PPT explains about the circuit breaker, and its types. Then about the need and purpose of the circuit breaker. And finally the testing and types of testing of circuit breakers.
This document provides an overview of sulfur hexafluoride (SF6) circuit breakers. It discusses that SF6 circuit breakers are commonly used in modern power systems for their safety and protection. The document describes the types and working principles of SF6 circuit breakers, including how the SF6 gas is able to quench arcs that form when contacts open or close under fault conditions. It also outlines the physical and chemical properties of SF6 that make it suitable for use in circuit breakers, as well as the advantages and disadvantages of SF6 circuit breakers. The document concludes by noting limitations in the use of SF6 and potential alternatives being researched.
This document discusses corona phenomenon in overhead transmission lines. It defines corona as the ionization of air surrounding power conductors, which causes a faint violet glow. Critical disruptive voltage and factors affecting corona such as atmospheric conditions, conductor size and spacing are explained. Methods to reduce corona loss include increasing conductor size, using bundled or hollow conductors, corona rings, and increasing spacing. While corona causes power loss and interference, it also reduces voltage surges and electrostatic stresses.
A protective relay is a device that detects abnormal conditions in an electrical circuit, such as a fault, and triggers a circuit breaker to disconnect the faulty part of the circuit. There are several types of relays including definite time, differential, solid state, electromechanical, backup, current, voltage, and frequency relays. A differential relay compares currents on both sides of a power transformer to detect faults. Solid state relays have no moving parts, allowing for high-speed operation. Electromechanical relays use a spring, armature, electromagnet and contacts to close the circuit when energized. Protection schemes use primary and backup relays, with primary relays clearing faults fastest and backup relays removing more of
The document discusses power system stability, including classifications of stability (steady state, transient, and dynamic) and factors that affect transient stability. It also covers topics like the swing equation, equal area criterion, critical clearing angle, and multi-machine stability studies. Some key points:
1) Power system stability refers to a system's ability to return to normal operating conditions after disturbances like faults or load changes.
2) Transient stability depends on factors like fault duration and location, generator inertia, and pre-fault loading conditions.
3) The equal area criterion states that a system will remain stable if the accelerating and decelerating area segments on the power-angle curve are equal.
4)
This document discusses different methods of grounding electrical systems, including solid grounding, resistance grounding, reactance grounding, and resonant groundings using a Peterson coil. Solid grounding directly connects the neutral point to earth, holding it at earth potential but allowing high fault currents. Resistance grounding limits fault current by connecting through a resistor. Reactance grounding uses an inductor instead of resistor. Resonant grounding with a Peterson coil adjusts the inductance to balance capacitive currents and prevent arcing faults.
1. Surge arresters are selected with voltage ratings of 336kV, 360kV, 372kV or 390kV to account for temporary overvoltages during faults.
2. Condition monitoring techniques like third harmonic resistive current monitoring are effective for detecting failures in surge arresters due to moisture ingress or degradation.
3. Investigations found moisture entry through faulty seals or gaskets led to failures in many surge arresters, accelerated by manufacturing defects. Improved sealing methods using O-rings instead of flat gaskets and routine dip testing were implemented.
The document discusses lightning concepts, including:
1. How cloud-to-ground lightning occurs due to charge separation in clouds and the equalization of charge potential between clouds and the earth.
2. The sequence of events in a lightning strike, where stepped leaders from clouds meet upward streamers from the earth's surface to form a discharge path.
3. Conventional lightning protection systems are dependent on a low-impedance ground, but facility grounding systems are often poorly maintained and insufficient, limiting the effectiveness of passive and active protection devices.
4. A new solution is introduced to overcome the shortcomings of conventional systems and provide reliable protection against all forms of lightning damage.
Transient over-voltages can be caused by lightning, switching operations, or resonance effects. Lightning is a large spark that produces voltages of 200 MV with currents of 40 kA that stresses insulation. Switching can cause voltages from changes in circuit conditions like breaking inductive circuits. Resonance can produce very high voltages between capacitive and inductive elements. Proper insulation coordination and lightning protection devices like rod gaps, horn gaps, and arresters are required to coordinate insulation levels and protect equipment from transient over-voltages.
This document discusses the history and development of high voltage engineering. It begins with early experiments with static electricity by ancient Greeks. Key figures who contributed include Franklin, Faraday, Tesla, and Edison. Faraday's law established that a magnetic field can induce current in a wire. Advances allowed longer distance power transmission. Challenges included developing high voltage insulation. Numerical methods like finite element analysis are now used to model electric field distributions in complex high voltage components.
Protection of transmission lines(encrypted)Rohini Haridas
This document discusses protection methods for transmission lines. It describes:
1. Transmission lines require more protective schemes than other equipment due to their long lengths and exposure, making faults more common.
2. Key methods of transmission line protection include time-graded overcurrent protection, differential protection, current-graded overcurrent protection, and distance protection.
3. Distance protection uses impedance relays that can discriminate between faults along the line and those near the end, providing more selective operation than overcurrent protection alone. It describes implementations using simple impedance, reactance, and mho relays.
Representation of power system componentsPrasanna Rao
This document discusses the representation of power system components in circuit models for analysis. It introduces the key components of a power system, including generators, transmission lines, and distribution systems. It then covers circuit models for representing synchronous machines, transformers, transmission lines, and static and dynamic loads. The rest of the document discusses additional modeling techniques like one-line diagrams, impedance diagrams, per-unit systems, and calculating base values for analysis.
Surge arresters are devices used to protect electrical equipment from lightning and switching surges. There are several types including rod arresters, horn gap arresters, multigap arresters, and modern metal oxide arresters. Surge arresters work by limiting high voltages from lightning strikes or other surges to safe levels before they reach equipment like transformers. They do this using a metal oxide varistor that acts as an insulator under normal voltages but conducts at higher surge voltages, diverting excess energy to ground. This protects equipment downstream from potential damage.
POWER SYSTEM PROTECTION
Protection Devices and the Lightning,. protection,
Lightning protection, Introduction
Air Break Switches
Disconnect switches
Grounding switches
Current limiting reactors
Grounding transformers
Co-ordination of protective devices
Grounding of electrical installations
Electric shock
Lightning protection
Lightning Arrestor
Surge arrestors are protective devices that limit voltage spikes and surges from damaging electrical equipment. They work by diverting excess current during events like lightning strikes or power faults to ground. When voltage increases, the resistor inside the arrestor decreases in resistance, allowing extra current to drain out and prevent voltage from increasing in protected equipment. Surge arrestors are installed at substations and near transformers to shield sensitive equipment from voltage transients. They parallel arrangement allows surges to be discharged without propagating through the system.
This presentation discusses the key protection devices used in electrical substations. It introduces current transformers and potential transformers, which reduce current and voltage levels for protection relays. Relays detect faults by measuring currents and voltages. When a fault is detected, relays signal circuit breakers to isolate the faulty component. Other protection devices discussed include lightning arresters, isolators, and surge diverters. The objective of the substation protection system is to isolate only faulty parts of the network while keeping the rest operational.
To sense/detect the fault occurrence and other abnormal conditions at the protected equipment/area/section.
To operate the correct circuit breakers so as to disconnect only the faulty equipment/area/section as quickly as possible, thus minimizing the damage caused by the faults.
To operate the correct circuit breakers to isolate the faulty equipment/area/section from the healthy system in the case of abnormalities like overloads, unbalance, undervoltage, etc.
To clear the fault before the system becomes unstable.
To identify distinctly where the fault has occurred.
This PPT explains about the circuit breaker, and its types. Then about the need and purpose of the circuit breaker. And finally the testing and types of testing of circuit breakers.
This document provides an overview of sulfur hexafluoride (SF6) circuit breakers. It discusses that SF6 circuit breakers are commonly used in modern power systems for their safety and protection. The document describes the types and working principles of SF6 circuit breakers, including how the SF6 gas is able to quench arcs that form when contacts open or close under fault conditions. It also outlines the physical and chemical properties of SF6 that make it suitable for use in circuit breakers, as well as the advantages and disadvantages of SF6 circuit breakers. The document concludes by noting limitations in the use of SF6 and potential alternatives being researched.
This document discusses corona phenomenon in overhead transmission lines. It defines corona as the ionization of air surrounding power conductors, which causes a faint violet glow. Critical disruptive voltage and factors affecting corona such as atmospheric conditions, conductor size and spacing are explained. Methods to reduce corona loss include increasing conductor size, using bundled or hollow conductors, corona rings, and increasing spacing. While corona causes power loss and interference, it also reduces voltage surges and electrostatic stresses.
A protective relay is a device that detects abnormal conditions in an electrical circuit, such as a fault, and triggers a circuit breaker to disconnect the faulty part of the circuit. There are several types of relays including definite time, differential, solid state, electromechanical, backup, current, voltage, and frequency relays. A differential relay compares currents on both sides of a power transformer to detect faults. Solid state relays have no moving parts, allowing for high-speed operation. Electromechanical relays use a spring, armature, electromagnet and contacts to close the circuit when energized. Protection schemes use primary and backup relays, with primary relays clearing faults fastest and backup relays removing more of
The document discusses power system stability, including classifications of stability (steady state, transient, and dynamic) and factors that affect transient stability. It also covers topics like the swing equation, equal area criterion, critical clearing angle, and multi-machine stability studies. Some key points:
1) Power system stability refers to a system's ability to return to normal operating conditions after disturbances like faults or load changes.
2) Transient stability depends on factors like fault duration and location, generator inertia, and pre-fault loading conditions.
3) The equal area criterion states that a system will remain stable if the accelerating and decelerating area segments on the power-angle curve are equal.
4)
This document discusses different methods of grounding electrical systems, including solid grounding, resistance grounding, reactance grounding, and resonant groundings using a Peterson coil. Solid grounding directly connects the neutral point to earth, holding it at earth potential but allowing high fault currents. Resistance grounding limits fault current by connecting through a resistor. Reactance grounding uses an inductor instead of resistor. Resonant grounding with a Peterson coil adjusts the inductance to balance capacitive currents and prevent arcing faults.
1. Surge arresters are selected with voltage ratings of 336kV, 360kV, 372kV or 390kV to account for temporary overvoltages during faults.
2. Condition monitoring techniques like third harmonic resistive current monitoring are effective for detecting failures in surge arresters due to moisture ingress or degradation.
3. Investigations found moisture entry through faulty seals or gaskets led to failures in many surge arresters, accelerated by manufacturing defects. Improved sealing methods using O-rings instead of flat gaskets and routine dip testing were implemented.
The document discusses lightning concepts, including:
1. How cloud-to-ground lightning occurs due to charge separation in clouds and the equalization of charge potential between clouds and the earth.
2. The sequence of events in a lightning strike, where stepped leaders from clouds meet upward streamers from the earth's surface to form a discharge path.
3. Conventional lightning protection systems are dependent on a low-impedance ground, but facility grounding systems are often poorly maintained and insufficient, limiting the effectiveness of passive and active protection devices.
4. A new solution is introduced to overcome the shortcomings of conventional systems and provide reliable protection against all forms of lightning damage.
Transient over-voltages can be caused by lightning, switching operations, or resonance effects. Lightning is a large spark that produces voltages of 200 MV with currents of 40 kA that stresses insulation. Switching can cause voltages from changes in circuit conditions like breaking inductive circuits. Resonance can produce very high voltages between capacitive and inductive elements. Proper insulation coordination and lightning protection devices like rod gaps, horn gaps, and arresters are required to coordinate insulation levels and protect equipment from transient over-voltages.
This document discusses overvoltage protection in distribution substations. It describes how lightning is a major cause of overvoltage and can damage electrical equipment if not protected. The Dagon East substation in Myanmar uses DynaVar station class and intermediate lightning arresters rated at 72kV and 10kA to protect its equipment from overvoltage. The arresters help limit transient voltages and protect the substation during lightning strikes and faults, helping to prevent damage and ensure reliable power supply.
This document discusses earthing and grounding in electrical systems. It defines earthing as connecting electrical equipment or systems to earth, usually soil, to prevent accidents and damage. There are two types: equipment earthing, which connects non-current metal parts; and system earthing, which connects parts of the electrical system. Neutral earthing connects the neutral point in a star system to earth. The document outlines the advantages of neutral earthing, such as keeping voltages stable and eliminating high voltages from arcing grounds, allowing for better protection and safety. Methods of neutral earthing include direct earthing or earthing through a resistor or reactor.
PROTECTION AGAINST OVER VOLTAGE AND GROUNDING Part 1Dr. Rohit Babu
The document discusses protection against overvoltages and grounding in power systems. It defines external and internal overvoltages, describes how lightning causes overvoltages, and explains the mechanisms of direct and indirect lightning strokes. It also covers topics like wave shapes of lightning voltages, overvoltage protection of transmission lines using overhead ground wires, and measurement of surge voltages using a klydonograph.
Over voltages can be caused by internal factors like switching operations or insulation failures, or external factors like lightning. Lightning arrestors protect equipment by diverting high voltage surges to ground. They break down temporarily during over voltages and regain insulation at normal voltages. Insulation coordination determines equipment insulation strength to withstand normal operating voltages and temporary over voltages based on factors like highest system frequency, temporary over voltages, and transient surges. Equipment is tested and rated with a basic insulation level to ensure it can withstand impulse voltages above that level.
The document defines and describes different types of overvoltages that can occur on power systems, including temporary, transient, lightning, and switching overvoltages. It explains that overvoltages are caused by both internal factors like switching and insulation failures, as well as external lightning strikes. The mechanism of lightning is then described in detail, including how charge separation in storm clouds leads to the formation of stepped leaders and streamers, completing an ionized conductive path between the cloud and earth.
The document provides information about high voltage engineering. It discusses various topics related to over voltages in electrical power systems and dielectric breakdown.
Some key points include:
1) Corona critical disruptive voltage is the voltage at which conductors glow faintly violet due to corona effect, producing ozone and power loss.
2) Overhead transmission line protections include ground wires, ground rods, counterpoise wires and protective devices.
3) Dielectric breakdown depends on factors like gas pressure, gap distance, and insulation material properties as per Paschen's law and Townsend's coefficients.
4) High voltage generation techniques include impulse generators, trigatron gaps, and voltage multiplier circuits like C
The document is a catalog describing ABB hélita® lightning protection systems. It provides information on lightning mechanisms, protection technologies like early streamer emission air terminals and meshed cages, standards, and installation procedures. Lightning protection systems aim to provide a preferred path for lightning to be conducted safely to ground to prevent damage to structures. Early streamer emission technology enhances the formation of upward streamers to better intercept downward lightning leaders. Meshed cages divide the lightning current over multiple conductors.
This document describes a computer-based model for selecting lightning arresters for a 132/33kV substation. The model uses MATLAB with a GUI interface to calculate key parameters for lightning arrester specification, including voltage rating, impulse sparkover voltage, power frequency sparkover voltage, discharge current rating, and protection level. It performs these calculations based on inputs of line voltage, frequency, and earthing system effectiveness. The model was used to select arresters with ratings of 116kV and 29kV for the 132kV and 33kV lines respectively of the substation. The document outlines the methodology and considerations for properly selecting and installing lightning arresters to provide adequate protection for electrical equipment.
The document discusses lightning arresters, including their working principle, types, and advantages/disadvantages. Lightning arresters protect electrical equipment by diverting high voltage surges from lightning strikes or nearby objects to ground. They break down at a preset voltage to provide a path of least resistance to ground. Common types include rod gap, sphere gap, horn gap, and metal oxide arresters. Lightning arresters help reduce property damage and protect outdoor substation equipment and power lines from damage from lightning strikes. However, they require more space and have a higher installation cost than some alternatives.
This document discusses safety practices regarding earthing and protection in electrical installations. It notes that approximately 12 people die every day and 42% of total fires occur due to electrical sources in India. Proper earthing and use of protective devices is important for safety. Factors like lack of maintenance, supervision, knowledge and negligence can lead to accidents. The document discusses causes of arcing faults and lightning accidents. It emphasizes the importance of proper earthing for safety, maintenance of voltage levels, and operation of protection devices. Earthing reduces touch and step voltages to safe levels.
The document provides information on electrical safety practices related to power distribution systems. It discusses hazards like electrocution and electrical fires that occur daily due to unsafe electrical installations. It emphasizes the importance of following safety procedures during electrical work and mentions common accident causes like improper tools, lack of protective devices, or poor supervision. The document also contains technical details on electrical topics like arcing faults, earthing systems, surge arrestors, and substation design standards to help ensure safe and reliable power distribution.
Substation design involves considering many factors to ensure safety, reliability, maintainability and the ability to expand the system over time. Key components in a substation include circuit breakers, transformers, busbars, isolators, current and potential transformers, surge arrestors, shunt reactors, and capacitors. The functions of this equipment include switching, voltage transformation, power transfer, protection, insulation and surge protection. Associated systems that support substation function include earthing systems, lighting, protection relays, control cables, and fire suppression systems.
The document discusses the concept of earthing in electric power system engineering. It defines earthing as connecting electrical equipment to the earth or ground for safety and proper system operation. There are two main types of earthing discussed: neutral or mains earthing, which connects the star point of power lines to ground; and equipment earthing, which grounds all non-current carrying metal parts. Solidly grounding the neutral point provides the best protection but causes high fault currents, while resistance or impedance earthing limits fault current but displaces voltages. The document recommends using chemical earthing rods for lower earth resistance and periodic inspection and testing of earthing systems to ensure safety.
1) Lightning strikes on power lines cause steep voltage surges that can damage equipment if not protected. The waveforms of lightning surges rise very quickly over 1-5 microseconds.
2) There are two main categories of overvoltages: internal causes like switching operations and insulation failures, and external causes like lightning strikes. Lightning discharge occurs when the potential gradient in air due to charged clouds builds up and causes a pilot leader streamer that travels toward the ground.
3) Different types of lightning arrestors like rod gaps, sphere gaps, horn gaps, and modern valve/thyrite/lead oxide types are used to protect equipment by diverting lightning surges to ground.
This document provides information on OPR lightning protection systems, including:
- An overview of lightning mechanisms and how different lightning protection systems work.
- Descriptions of early streamer emission air terminals, single rod air terminals, meshed cages, and stretched wires.
- Details on how to perform risk analysis and technical studies to design a lightning protection system.
- The procedure for measuring the early streamer emission of air terminals according to industry standards.
- Information on surge protection devices to protect against indirect lightning effects.
- The importance of equipotential bonding and maintaining separation distances between the lightning protection system and building components.
The document discusses lightning arresters, which are devices used to protect electrical equipment from voltage surges. It provides details on the different types of lightning arresters, including rod gap arresters, horn gap arresters, multi-gap arresters, expulsion arresters, valve arresters, and metal oxide varistor arresters. The key functions of lightning arresters are to limit surge voltages from lightning or faults and divert excess energy to ground to prevent equipment damage. Proper installation and maintenance of lightning arresters is important to ensure reliable protection.
High voltages can cause overvoltage events that exceed the design limits of electrical systems. There are two main types of overvoltage: lightning overvoltage from natural sources, and switching overvoltage caused by changing loads on a system. Lightning overvoltage occurs when a lightning strike induces high voltage in a system. Switching overvoltage happens when large inductive or resistive loads are connected or disconnected, causing voltage spikes. Both types of overvoltage can damage equipment and should be controlled through various techniques like resistors, phase control, and reactors. Uncontrolled overvoltages present a danger, so protection methods are important for system reliability and safety.
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
ACEP Magazine edition 4th launched on 05.06.2024Rahul
This document provides information about the third edition of the magazine "Sthapatya" published by the Association of Civil Engineers (Practicing) Aurangabad. It includes messages from current and past presidents of ACEP, memories and photos from past ACEP events, information on life time achievement awards given by ACEP, and a technical article on concrete maintenance, repairs and strengthening. The document highlights activities of ACEP and provides a technical educational article for members.
6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
Low power architecture of logic gates using adiabatic techniquesnooriasukmaningtyas
The growing significance of portable systems to limit power consumption in ultra-large-scale-integration chips of very high density, has recently led to rapid and inventive progresses in low-power design. The most effective technique is adiabatic logic circuit design in energy-efficient hardware. This paper presents two adiabatic approaches for the design of low power circuits, modified positive feedback adiabatic logic (modified PFAL) and the other is direct current diode based positive feedback adiabatic logic (DC-DB PFAL). Logic gates are the preliminary components in any digital circuit design. By improving the performance of basic gates, one can improvise the whole system performance. In this paper proposed circuit design of the low power architecture of OR/NOR, AND/NAND, and XOR/XNOR gates are presented using the said approaches and their results are analyzed for powerdissipation, delay, power-delay-product and rise time and compared with the other adiabatic techniques along with the conventional complementary metal oxide semiconductor (CMOS) designs reported in the literature. It has been found that the designs with DC-DB PFAL technique outperform with the percentage improvement of 65% for NOR gate and 7% for NAND gate and 34% for XNOR gate over the modified PFAL techniques at 10 MHz respectively.
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1. Protection Against Overvoltage
QUAID-E-AWAM UNIVERSITY
OF ENGINEERNG SCIENCE AND TECHNOLOGY NAWABSHAH,
SINDH, PAKISTAN.
DEPARTMENT OF ELECTRICAL ENGINEERING
PRESENTED BY: Muhammad Arif(17EL49 )
Roll No Name
17EL27 Tarique Sahito (GL)
17EL49 Muhammad Arif (AGL)
17EL99 Syed Hussain Ali
17ELO7 Allah bux
17EL17 Ali kichi
Group Details
PRESENTED TO: Dr Aslam Pervez Memon
Date : 20/08/2020
2. What are Overvoltages?
According to IEEE standard for Insulation Coordination, Overvoltage is defined
as:
“ Voltage between one phase and ground or between two phases, having a
crest value exceeding the corresponding crest of maximum system voltage.”
Overvoltages may be classified by shape and duration as either temporary or
transient.
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3. What are Overvoltages?
Temporary Overvoltage:
An Oscillatory phase-to-ground or phase-to phase overvoltage that is at a
given location of relatively long duration(seconds, even minute) and that is
undamped or only weakly damped.
Temporary overvoltage usually originate from switching operation or faults
(e.g load rejection, single-phase fault, fault on a high-resistance ground or
ungrounded system) or from nonlinearities (Ferro resonance, harmonics), or
both.
They are characterized by the amplitude, the oscillation frequencies, the
total duration or the decrement.
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4. What are Overvoltages?
Transient Overvoltage:
A short-duration highly damped, oscillatory, or non oscillatory overvoltage,
having duration of few milliseconds or less.
Transient overvoltage is classified as one of the following types:
Lightning Overvoltage
Switching Overvoltage
Very fast front, short duration overvoltage
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5. Transient Overvoltage:
Lightning Overvoltage:
A type of Transient voltage in which a fast front voltage is produced by
lightning or fault.
Such overvoltage is usually unidirectional and of very short duration.
A typical waveform is shown in figure.
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6. Transient Overvoltage:
Switching Overvoltage:
A transient overvoltage in which a slow front, short-duration, unidirectional
or oscillatory, highly damped voltage is generated (usually by switching or
fault).
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7. Transient Overvoltage:
Very fast front, short-duration overvoltage:
A transient overvoltage in which a short duration, usually unidirectional,
voltage is generated (often by GIS disconnect switch operation or when
switching motor).
High frequency oscillation or often superimposed on the unidirectional wave.
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9. 1) Internal Causes
(i) Switching surges:
Switching Operations on Unloaded Line:
A switching operation produces a sudden change in the circuit conditions.
When an open-ended line is connected to a source of voltage, travelling
waves are set up which rapidly charge the line.
On reaching the open end of the line, these waves are totally reflected
without change of sign, thereby producing voltage-doubling at that end.
These reflected waves travel back to the supply end, giving rise to further
reflections.
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10. 1) Internal Causes
(i) Switching surges :
Sudden Opening of Loaded Line:
If a line carrying load is suddenly opened,
A transient voltage of value given by e = i Z0 is set up,
Where i is the instantaneous value of the current at the instant of opening
of line,
And Z0 is the natural or surge impedance of the line.
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12. 1) Internal Causes
(ii) Insulation Failure:
The insulation failure in a power system may take place in various ways
such as:
Between the conductors of an overhead line.
The cores of an insulated cable.
Between one conductor.
Or core, and earth.
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13. 1) Internal Causes
(iii) Arcing Grounds:
it is experienced in insulated neutral system.
Consider an alternator, whose one phase has been connected to a long line
which has got distributed inductance and capacitance to earth,
As shown in Fig. The alternator winding can be imagined to be connected to
earth through its capacitance.
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14. 1) Internal Causes
(iv) Resonance:
Resonance in an electrical circuit implies that the impedance of the circuit
is purely resistive and the power factor is unity.
Thus at resonance the inductive reactances and capacitive reactances cancel
out.
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15. 2) External Causes:
Lightning Phenomenon:
Lightning is a discharge of electrical energy.
It may occur:
Between cells in the same storm as Inter cloud Lightning or within a cloud
as Intra cloud Lightning (80%)
Cloud to Air (1%)
Cloud to Ground (19%)
The strong negative charge at the base of the thunderstorm induces a positive
charge at the surface by repulsion of electrons
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16. 2) External Causes
Lightning Phenomenon:
If the electric field, or the difference between the negative and positive
charge regions, is large enough.
The insulator between the charge regions (the air) “breaks down” and the
lightning discharge can occur between the regions of positive and negative
charge.
The break down voltage for air is about 10,000 Volts/meter.
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17. Lightning Phenomenon:
The lightning stroke begins when the electric fields exceed the break down
voltage.
Initially streams of electrons surge from the cloud base toward the ground in
steps of 50 to 100 m.
Start and stop steps as the stepped leader progresses toward ground.
This occurs over a few microseconds and is relatively invisible.
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18. More On Lightning Phenomenon:
Streamer:
When the stepped leader gets near the ground within 100 m or so...
Positive charge moves from the ground up toward the stepped leader --
these are called streamers.
The streamers may come from almost any pointed object on the ground:
Trees Antennas Grass
Flagpoles Telephone Poles People
Really Tall Towers
Electric fields are stronger around pointed objects.
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19. More On Lightning Phenomenon:
Stroke:
An electrical current of about 20,000 Amps flows, depositing the electrons
on the ground.
The current generated over the short time interval heats the surroundings
to approximately 3000 K (The sun’s surface ~ 6000 K).
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20. Methods of Protection Against Lightning
These are mainly three main methods generally used for protection against
lightning. They are
Earthing screen.
Overhead earth wire.
Lightning arrester or surge dividers.
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21. Earthing screen
Earthing screen is generally used over electrical substation.
In this arrangement a net of GI( Galvanized Iron ) wire is mounted over the
sub-station.
The GI wires, used for earthing screen are properly grounded through
different sub-station structures.
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22. Earthing screen(cont..)
This network of grounded GI wire over electrical sub-station, provides very
low resistance path to the ground for lightning strokes.
This method of high voltage protection is very simple and economic but the
main drawback is, it can not protect the system from travelling wave which
may reach to the sub-station via different feeders.
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23. Overhead Earth Wire
This method of over voltage protection is similar as earthing screen.
The only difference is, an earthing screen is placed over an electrical sub-
station,
whereas, overhead earth wire is placed over electrical transmission network.
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24. Overhead Earth Wire(cont..)
One or two stranded GI wires of suitable cross-section are placed over the
transmission conductors.
These GI wires are properly grounded at each transmission tower.
These overhead ground wires or earth wire divert all the lightning strokes to
the ground instead of allowing them to strike directly on the transmission
conductors.
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25. Lightning Arrester
The previously discussed two methods, i.e. earthing screen and over-head
earth wire are very suitable for protecting an electrical power system from
directed lightning strokes but system from directed lightning strokes but
these methods can not provide any protection against high voltage travelling
wave which may propagate through the line to the equipment of the sub-
station.
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26. Lightning Arrester(cont..)
The lightning arrester is a devices which provides very low impedance path to
the ground for high voltage travelling waves.
The concept of a lightning arrester is very simple. This device behaves like a
nonlinear electrical resistance. The resistance decreases as voltage increases
and vice-versa, after a certain level of voltage.
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27. Lightning Arrester(cont..)
The functions of a lightning arrester or surge dividers can be listed as below.
Under normal voltage level, these devices withstand easily the system voltage
as electrical insulator and provide no conducting path to the system current.
On occurrence of voltage surge in the system, these devices provide very low
impedance path for the excess charge of the surge to the ground.
After conducting the charges of surge, to the ground, the voltage becomes to
its normal level. Then lightning arrester regains its insulation properly and
prevents regains its insulation property and prevents further conduction of
current, to the ground.
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28. Lightning Arrester(cont..)
There are different types of lightning arresters used in power system, such as
rod gap arrester, horn gap arrester, multi-gap arrester, expulsion type LA,
value type LA.
In addition to these the most commonly used lightning arrester for over
voltage protection now-a-days gapless ZnO lightning arrester is also used.
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29. Review Questions
Q. What are the types of over voltages?
Ans. (i) External Over voltages
(ii) Internal Over voltages
Q. How are they caused?
Ans. External over-voltages are caused due to:
(i) Direct lightning strokes
(ii) Electro-magnetically induced over-voltages due to lightning discharge
taking place near the line, called as 'Side Stroke'
Internal Over-voltages are due to:
(i) Switching operation or fault condition
(ii) Sudden release of load in the network.
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30. Review Questions (Cont…)
Q. What is lightning phenomenon?
Ans. The discharge of the charged cloud to ground is called lightning
phenomenon.
Q. What is magnetic link?
Ans. It is an instrument for the measurement of surge currents due to
lightning.
Q. What is a Surge Absorber?
Ans. Surge absorber or Surge modifier is a device which absorbs energy
contained in a travelling wave and reduces the amplitude of the Surge and
steepness of its wave front. Ferranti Surge Absorber is an example.
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31. Review Questions (Cont…)
Q. What is arcing ground?
Ans. During a Line to Ground fault on an ungrounded system, till the fault is
cleared, there will be intermittent discharges to ground thro' the capacitance
between the healthy phases and ground. This phenomenon is called 'arcing
ground'.
Q. On what factor, does the effectiveness of Overhead Ground wires depend
upon?
Ans. The tower footing resistance is the factor on which the effectiveness of
the overhead ground wire depends upon.
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