Combined zero-sequence cutoff protection is used extensively in high voltage power networks. It consists of an overcurrent relay responding to zero-sequence current and a directional relay determining fault current direction. The protection operates based on zero-sequence current and voltage measurements. It provides selective protection for lines with two transformers supplying each end, as the sensitivity of the voltage relay is higher than the current relay under minimum fault conditions. The operating currents and voltages are selected based on calculations of maximum and minimum zero-sequence currents and voltages during different fault scenarios. Combined zero-sequence cutoff protection reliably protects circuits with two-end supply but has some disadvantages like long time delays and insufficient sensitivity with large loads.
This document provides an overview of advanced power system protection topics including differential protection, busbar protection, linear couplers, and pilot wire protection.
It discusses the principles and applications of differential protection including Merz-Price and balanced voltage schemes. It also covers special considerations for differential protection such as phase shift, tap changing transformers, and inrush current.
The document then summarizes busbar protection and how it uses a pure earth fault system to measure fault current flowing from the switchgear to earth. Finally, it examines linear couplers and how they are used in differential protection systems as well as the performance of pilot wire protection schemes that can employ either balanced voltage or circulating current principles.
This document discusses system earthing in industrial and commercial electrical systems. It covers:
1. Reasons for earthing systems, including carrying fault currents safely and preventing electric shock.
2. Factors that influence earth resistance, such as soil moisture content and electrode depth.
3. Thresholds for body current that can cause adverse health effects like fibrillation.
4. Concepts of touch and step voltages caused by potential differences in earthed systems.
5. Calculation of maximum earth fault currents and factors like ground resistivity and grid geometry that influence potential rises.
6. Types of earth electrodes and equations for calculating resistance and potential gradients around hemispherical and spherical electrodes
The document discusses power system protection. It defines the objectives of power system protection as detecting and isolating faults instantaneously while minimizing the number of circuits isolated and restoring the system quickly. It also discusses criteria for proper protection systems, including reliability, selectivity, speed of operation, and discrimination. Detection methods like current transformers and potential transformers are explained. Common protection relays like electromagnetic attraction, balance beam, and electromagnetic induction types are also summarized.
A Study of SVC’s Impact Simulation and Analysis for Distance Protection Relay...IJECEIAES
This paper focuses on analyzing and evaluating impact of a Static Var Compensator (SVC) on the measured impedance at distance protection relay location on power transmission lines. The measured impedance at the relay location when a fault occurs on the line is determined by using voltage and current signals from voltage and current transformers at the relay and the type of fault occurred on the line. The MHO characteristic is applied to analyze impact of SVC on the distance protection relay. Based on the theory, the authors in this paper develop a simulation program on Matlab/Simulink software to analyze impact of SVC on the distance protection relay. In the power system model, it is supposed that the SVC is located at mid-point of the transmission line to study impact of SVC on the distance relay. The simulation results show that SVC will impact on the measured impedance at the relay when the fault occurs after the location of the SVC on the power transmission line.
This document discusses switchgear technology, specifically focusing on different types of circuit breakers (CBs). It describes:
1. The basic physics of arcs in CBs and how they are controlled through insulating materials, arc chutes that confine and cool arcs, and contact arrangements.
2. How air circuit breakers (ACBs) and air blast CBs interrupt arcs naturally or through injected air, while oil circuit breakers (OCBs) rely on oil to cool arcs.
3. SF6 and vacuum breakers, which use insulating gases and high vacuum respectively to rapidly deionize arcs at current zero.
The International Journal of Engineering and Science (The IJES)theijes
The document compares a conventional full bridge buck DC-DC converter and an LCL-T type buck DC-DC converter through simulation. Simulation results show that the proposed 4-switch LCL-T buck converter has higher efficiency than the conventional full bridge converter. Key advantages of the LCL-T converter include reduced switching losses due to zero-voltage switching, improved electrical performance from the front-end LCL-T connection, and multi-output capability from associating one or two capacitors for resonant operation. The LCL-T converter is well-suited for low voltage, low power applications.
The document summarizes key aspects of transmission line design and components. It discusses the methodology for designing transmission lines, including gathering design data, selecting reliability levels, and calculating loads. It also covers the selection and design of various transmission line components such as conductors, insulators, towers, and grounding systems. Design considerations include voltage levels, safety clearances, mechanical requirements, and optimization of costs.
This document provides an overview of advanced power system protection topics including differential protection, busbar protection, linear couplers, and pilot wire protection.
It discusses the principles and applications of differential protection including Merz-Price and balanced voltage schemes. It also covers special considerations for differential protection such as phase shift, tap changing transformers, and inrush current.
The document then summarizes busbar protection and how it uses a pure earth fault system to measure fault current flowing from the switchgear to earth. Finally, it examines linear couplers and how they are used in differential protection systems as well as the performance of pilot wire protection schemes that can employ either balanced voltage or circulating current principles.
This document discusses system earthing in industrial and commercial electrical systems. It covers:
1. Reasons for earthing systems, including carrying fault currents safely and preventing electric shock.
2. Factors that influence earth resistance, such as soil moisture content and electrode depth.
3. Thresholds for body current that can cause adverse health effects like fibrillation.
4. Concepts of touch and step voltages caused by potential differences in earthed systems.
5. Calculation of maximum earth fault currents and factors like ground resistivity and grid geometry that influence potential rises.
6. Types of earth electrodes and equations for calculating resistance and potential gradients around hemispherical and spherical electrodes
The document discusses power system protection. It defines the objectives of power system protection as detecting and isolating faults instantaneously while minimizing the number of circuits isolated and restoring the system quickly. It also discusses criteria for proper protection systems, including reliability, selectivity, speed of operation, and discrimination. Detection methods like current transformers and potential transformers are explained. Common protection relays like electromagnetic attraction, balance beam, and electromagnetic induction types are also summarized.
A Study of SVC’s Impact Simulation and Analysis for Distance Protection Relay...IJECEIAES
This paper focuses on analyzing and evaluating impact of a Static Var Compensator (SVC) on the measured impedance at distance protection relay location on power transmission lines. The measured impedance at the relay location when a fault occurs on the line is determined by using voltage and current signals from voltage and current transformers at the relay and the type of fault occurred on the line. The MHO characteristic is applied to analyze impact of SVC on the distance protection relay. Based on the theory, the authors in this paper develop a simulation program on Matlab/Simulink software to analyze impact of SVC on the distance protection relay. In the power system model, it is supposed that the SVC is located at mid-point of the transmission line to study impact of SVC on the distance relay. The simulation results show that SVC will impact on the measured impedance at the relay when the fault occurs after the location of the SVC on the power transmission line.
This document discusses switchgear technology, specifically focusing on different types of circuit breakers (CBs). It describes:
1. The basic physics of arcs in CBs and how they are controlled through insulating materials, arc chutes that confine and cool arcs, and contact arrangements.
2. How air circuit breakers (ACBs) and air blast CBs interrupt arcs naturally or through injected air, while oil circuit breakers (OCBs) rely on oil to cool arcs.
3. SF6 and vacuum breakers, which use insulating gases and high vacuum respectively to rapidly deionize arcs at current zero.
The International Journal of Engineering and Science (The IJES)theijes
The document compares a conventional full bridge buck DC-DC converter and an LCL-T type buck DC-DC converter through simulation. Simulation results show that the proposed 4-switch LCL-T buck converter has higher efficiency than the conventional full bridge converter. Key advantages of the LCL-T converter include reduced switching losses due to zero-voltage switching, improved electrical performance from the front-end LCL-T connection, and multi-output capability from associating one or two capacitors for resonant operation. The LCL-T converter is well-suited for low voltage, low power applications.
The document summarizes key aspects of transmission line design and components. It discusses the methodology for designing transmission lines, including gathering design data, selecting reliability levels, and calculating loads. It also covers the selection and design of various transmission line components such as conductors, insulators, towers, and grounding systems. Design considerations include voltage levels, safety clearances, mechanical requirements, and optimization of costs.
This document provides an introduction to switched-mode power supplies (SMPS). It discusses the basic components of regulated power supplies, including linear and SMPS types. SMPS circuits convert unregulated DC input to regulated DC output using a high-frequency DC-to-DC converter and transformer, allowing for improved efficiency over linear supplies. Example problems are provided to demonstrate calculating capacitor sizing for ripple reduction and transformer turns ratios for voltage stepping in power supply circuits.
Lecture 4 b signalconditioning_ac bridgeMuhamad Azwan
This document discusses various types of AC bridges used to measure inductances and capacitances, including their operating principles and examples. It describes AC bridges such as the basic AC bridge, Maxwell bridge, Hay bridge, Schering bridge, Wien bridge, and the use of Wagner ground connection to reduce stray capacitances in bridge circuits. The key applications of AC bridges are measuring inductances, capacitances, frequencies, and characterizing capacitors.
Frequency dependency analysis for differential capacitive sensorjournalBEEI
A differential capacitive sensing technique is discussed in this paper.
The differential capacitive sensing circuit is making use of a single power supply. The design focus for this paper is on the excitation frequency dependency analysis to the circuit. Theory of the differential capacitive sensor under test is discussed and derivation is elaborated. Simulation results are shown and discussed. Next, results improvement has also been shown in this paper for comparison. Test was carried out using frequency from 40 kHz up to 400 kHz. Results have shown output voltage of Vout=0.07927 Cx+1.25205 and good linearity of R-squared value 0.99957 at 200 kHz. Potential application for this capacitive sensor is to be used for energy harvesting for its potential power supply.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Effect of change in burden and power factor on CTsManish Sadhu
This document discusses the effects of burden and power factor on the ratio and phase angle errors in current transformers. It explains that burden is the load imposed on the secondary winding, and errors depend on the impedance connected, known as burden. An increase in burden impedance causes ratio error to increase and phase angle to shift to more positive values. The errors also decrease with increasing primary current. The power factor and frequency of the secondary burden circuit can also impact ratio and phase angle.
This document analyzes how various phenomena can affect distance protection settings and measurements. It examines the impact of fault impedance, changes in ground resistivity affecting zero sequence impedance, mutual zero sequence impedance between parallel lines, and infeed effects. The analyses were performed on a real 115kV system using simulation software. Fault impedance can cause apparent impedance measurements to shift into different zones. Changes in ground resistivity can result in underreach if not accounted for. Mutual coupling and infeed effects can also distort impedance measurements if not considered in protection settings.
The document describes a zero-voltage switching and zero-current switching full-bridge converter that utilizes the leakage inductance of a transformer. It presents the concept and methodology of the converter, which uses series resonance to achieve lossless switching. Simulation results are shown that demonstrate the switching currents achieving zero-voltage switching turn-on and zero-current switching turn-off, as intended with the design. The document also proposes a modification to the converter by incorporating a bridge rectifier at the transformer secondary.
The document describes an experiment to measure the tangent of the dielectric loss angle (tan δ) of an unknown capacitor using a Schering bridge. Key steps include: connecting components like the analog board, function generator and power supply; adjusting the frequency to 1 kHz; balancing the bridge by minimizing sound from the speaker as the potentiometer R2 is adjusted; recording readings; and calculating the unknown capacitance, effective resistance, and dissipation factor using provided equations. The aim is to study measurement of capacitance, resistance, and losses using a Schering bridge circuit.
Tertiary interbus transformer and alternative protectionSouvik Dutta
This document summarizes a literature study on the condition of tertiary bushings in interbus transformers and alternative protection schemes. It discusses how directly earthing the delta-connected tertiary winding raises the voltage stress on bushings, potentially reducing their lifetime. Online monitoring data is presented showing abnormalities in bushing parameters like tan δ. Literature suggests continuously operating bushings at 1.571 times rated voltage could reduce lifetime to around 2.5 years. The document evaluates direct earthing and floating schemes for protecting the tertiary winding.
Design & Implementation of Zero Voltage Switching Buck ConverterIJERA Editor
Zero voltage switching (ZVS) buck converter is more preferable over hard switched buck converter for low power, high frequency DC-DC conversion applications. In Zero voltage switching converter, turn on & turn off of a switch occurs at zero voltage that results in lower switching losses. In this converter soft switching is achieved by using resonant components. The optimal values of resonant components are determined by using electric functions derived from circuit configuration. This type of soft switched resonant converter offers very low electromagnetic interference (EMI).This study presents the circuit configuration with least components to realize highly efficient zero voltage switching resonant converter. It’s feasibility is confirmed with the developed proto type model and experimental results are verified.
The document discusses AC bridges and the Schering bridge. AC bridges are used to measure inductance and capacitance and are based on the Wheatstone bridge circuit. The Schering bridge specifically measures insulating properties with phase angles close to 90 degrees. It consists of an arm with a capacitor and is used to find the equivalent series resistance and capacitance of an unknown impedance at null. An example problem demonstrates using the Schering bridge equations to calculate the unknown Rx and Cx values.
This document summarizes several types of AC bridges used to measure resistance, inductance, and capacitance. It describes Maxwell's inductance bridge, which uses two known impedances and two pure resistances to measure an unknown inductance. It also discusses Hay's bridge, a modification of Maxwell's bridge that can measure higher quality factor inductors. The document outlines Schering bridge, which measures capacitance and loss of a capacitor using a loss-free standard capacitor. Finally, it briefly introduces Wien's parallel bridge, a ratio bridge used in audio-frequency R-C oscillators to measure capacitance ratios.
This document discusses power transmission from generation stations to substations. Electricity is generated at power stations and transmitted through high voltage transmission lines to primary substations. The transmission lines have series capacitors to offset the lines' inductive reactance, and shunt resistors to limit fault currents. At substations, the voltage is reduced through transformers before distribution to customers.
This document provides an overview of basic electrical concepts and circuit analysis for engineering students. It covers topics like voltage and current sources, Kirchhoff's laws, Thevenin's and superposition theorems, AC circuits including power calculations, and three-phase systems. The key points are:
1) It defines fundamental electrical terms and describes different types of sources and circuit analysis methods like mesh and nodal analysis.
2) Kirchhoff's laws are introduced for analyzing circuits using the concepts of current law and voltage law.
3) Thevenin's and superposition theorems are summarized as techniques for simplifying circuits with multiple sources.
4) Single-phase AC circuits are covered including definitions
This document provides an overview of transmission line basics and concepts. It discusses key transmission line parameters like characteristic impedance, propagation delay, per-unit-length capacitance and inductance. It covers transmission line equivalent circuit models and relevant equations. It also discusses transmission line structures, parallel plate approximations, reflection coefficients, and discontinuities. The goal is to understand transmission line behavior and analysis techniques.
Method Of Compensation Instability Of Frequency Modulators In The Absence Of ...theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
This document provides an introduction to three-phase circuits and power. It defines key concepts like real power, reactive power, and power factor for sinusoidal voltages and currents. It describes how to calculate real and reactive power from rms voltage, current, and phase angle. Balanced three-phase systems are introduced, and how they allow more efficient power transmission compared to single-phase systems. Equations for solving problems involving three-phase circuits are also presented.
This document discusses several types of AC bridges used to measure unknown resistances, capacitances, and inductances. The Maxwell's inductance bridge uses two known impedances on one side and two pure resistances on the other to measure an unknown impedance. The Maxwell's capacitance bridge can measure unknown inductance by compensating the positive phase angle of inductance with the negative phase angle of capacitance. The Anderson bridge precisely measures unknown inductance over a wide range by using a known capacitance and resistance.
The document discusses different types of AC bridges used to measure inductance and capacitance. It describes 6 AC bridges: 1) Similar-Angle Bridge, which measures the impedance of a capacitive circuit. 2) Maxwell-Wein Bridge, which measures unknown inductances with a capacitance standard. 3) Opposite Angle Bridge, where the balance conditions depend on the measurement frequency. 4) Wein Bridge, which can measure either series or parallel components of an impedance. 5) Scherning Bridge, useful for measuring high phase angle insulating properties. Examples are provided to demonstrate calculations for determining unknown impedance values using the bridge equations.
This document discusses Matlab/Simulink implementation for reducing motor derating and torque pulsation of an induction motor using a matrix converter. It provides background on how non-sinusoidal supply from traditional inverters causes harmonic losses and torque pulsation in induction motors. The document summarizes simulation results showing that a matrix converter can provide a pure sinusoidal supply, reducing harmonic losses and torque pulsation. Simulations of a matrix converter driving an induction motor in Matlab/Simulink are presented, showing sinusoidal voltage/current waveforms and reduced torque pulsation at steady state.
This document discusses research on using extrusion honing (EH) to improve the surface finish of Inconel 625 fabricated by electric discharge machining (EDM). EH involves flowing an abrasive-laden polymer media over a material's surface to deburr, polish, and remove defects. The study investigated the effect of EH process parameters on the surface roughness of square Inconel 625 samples. Results showed that EH significantly improved surface finish by removing microcracks and recast layers from EDM. Surface roughness decreased dramatically in the first few EH passes then continued to gradually improve up to the 11th pass. Scanning electron microscope images confirmed that EH successfully removed defects from EDM.
This document discusses cross-cloud testing strategies for cloud computing applications. It proposes building an application prototype that can perform cross-cloud testing on multiple cloud platforms. The key aspects of existing approaches are that they do not test cloud-based software applications across different cloud environments. The proposed approach aims to develop a system that can test applications deployed on multiple independent cloud infrastructures to provide more flexibility and avoid vendor lock-in. Experimental results show the proposed approach can efficiently protect data during cross-cloud testing.
This document provides an introduction to switched-mode power supplies (SMPS). It discusses the basic components of regulated power supplies, including linear and SMPS types. SMPS circuits convert unregulated DC input to regulated DC output using a high-frequency DC-to-DC converter and transformer, allowing for improved efficiency over linear supplies. Example problems are provided to demonstrate calculating capacitor sizing for ripple reduction and transformer turns ratios for voltage stepping in power supply circuits.
Lecture 4 b signalconditioning_ac bridgeMuhamad Azwan
This document discusses various types of AC bridges used to measure inductances and capacitances, including their operating principles and examples. It describes AC bridges such as the basic AC bridge, Maxwell bridge, Hay bridge, Schering bridge, Wien bridge, and the use of Wagner ground connection to reduce stray capacitances in bridge circuits. The key applications of AC bridges are measuring inductances, capacitances, frequencies, and characterizing capacitors.
Frequency dependency analysis for differential capacitive sensorjournalBEEI
A differential capacitive sensing technique is discussed in this paper.
The differential capacitive sensing circuit is making use of a single power supply. The design focus for this paper is on the excitation frequency dependency analysis to the circuit. Theory of the differential capacitive sensor under test is discussed and derivation is elaborated. Simulation results are shown and discussed. Next, results improvement has also been shown in this paper for comparison. Test was carried out using frequency from 40 kHz up to 400 kHz. Results have shown output voltage of Vout=0.07927 Cx+1.25205 and good linearity of R-squared value 0.99957 at 200 kHz. Potential application for this capacitive sensor is to be used for energy harvesting for its potential power supply.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Effect of change in burden and power factor on CTsManish Sadhu
This document discusses the effects of burden and power factor on the ratio and phase angle errors in current transformers. It explains that burden is the load imposed on the secondary winding, and errors depend on the impedance connected, known as burden. An increase in burden impedance causes ratio error to increase and phase angle to shift to more positive values. The errors also decrease with increasing primary current. The power factor and frequency of the secondary burden circuit can also impact ratio and phase angle.
This document analyzes how various phenomena can affect distance protection settings and measurements. It examines the impact of fault impedance, changes in ground resistivity affecting zero sequence impedance, mutual zero sequence impedance between parallel lines, and infeed effects. The analyses were performed on a real 115kV system using simulation software. Fault impedance can cause apparent impedance measurements to shift into different zones. Changes in ground resistivity can result in underreach if not accounted for. Mutual coupling and infeed effects can also distort impedance measurements if not considered in protection settings.
The document describes a zero-voltage switching and zero-current switching full-bridge converter that utilizes the leakage inductance of a transformer. It presents the concept and methodology of the converter, which uses series resonance to achieve lossless switching. Simulation results are shown that demonstrate the switching currents achieving zero-voltage switching turn-on and zero-current switching turn-off, as intended with the design. The document also proposes a modification to the converter by incorporating a bridge rectifier at the transformer secondary.
The document describes an experiment to measure the tangent of the dielectric loss angle (tan δ) of an unknown capacitor using a Schering bridge. Key steps include: connecting components like the analog board, function generator and power supply; adjusting the frequency to 1 kHz; balancing the bridge by minimizing sound from the speaker as the potentiometer R2 is adjusted; recording readings; and calculating the unknown capacitance, effective resistance, and dissipation factor using provided equations. The aim is to study measurement of capacitance, resistance, and losses using a Schering bridge circuit.
Tertiary interbus transformer and alternative protectionSouvik Dutta
This document summarizes a literature study on the condition of tertiary bushings in interbus transformers and alternative protection schemes. It discusses how directly earthing the delta-connected tertiary winding raises the voltage stress on bushings, potentially reducing their lifetime. Online monitoring data is presented showing abnormalities in bushing parameters like tan δ. Literature suggests continuously operating bushings at 1.571 times rated voltage could reduce lifetime to around 2.5 years. The document evaluates direct earthing and floating schemes for protecting the tertiary winding.
Design & Implementation of Zero Voltage Switching Buck ConverterIJERA Editor
Zero voltage switching (ZVS) buck converter is more preferable over hard switched buck converter for low power, high frequency DC-DC conversion applications. In Zero voltage switching converter, turn on & turn off of a switch occurs at zero voltage that results in lower switching losses. In this converter soft switching is achieved by using resonant components. The optimal values of resonant components are determined by using electric functions derived from circuit configuration. This type of soft switched resonant converter offers very low electromagnetic interference (EMI).This study presents the circuit configuration with least components to realize highly efficient zero voltage switching resonant converter. It’s feasibility is confirmed with the developed proto type model and experimental results are verified.
The document discusses AC bridges and the Schering bridge. AC bridges are used to measure inductance and capacitance and are based on the Wheatstone bridge circuit. The Schering bridge specifically measures insulating properties with phase angles close to 90 degrees. It consists of an arm with a capacitor and is used to find the equivalent series resistance and capacitance of an unknown impedance at null. An example problem demonstrates using the Schering bridge equations to calculate the unknown Rx and Cx values.
This document summarizes several types of AC bridges used to measure resistance, inductance, and capacitance. It describes Maxwell's inductance bridge, which uses two known impedances and two pure resistances to measure an unknown inductance. It also discusses Hay's bridge, a modification of Maxwell's bridge that can measure higher quality factor inductors. The document outlines Schering bridge, which measures capacitance and loss of a capacitor using a loss-free standard capacitor. Finally, it briefly introduces Wien's parallel bridge, a ratio bridge used in audio-frequency R-C oscillators to measure capacitance ratios.
This document discusses power transmission from generation stations to substations. Electricity is generated at power stations and transmitted through high voltage transmission lines to primary substations. The transmission lines have series capacitors to offset the lines' inductive reactance, and shunt resistors to limit fault currents. At substations, the voltage is reduced through transformers before distribution to customers.
This document provides an overview of basic electrical concepts and circuit analysis for engineering students. It covers topics like voltage and current sources, Kirchhoff's laws, Thevenin's and superposition theorems, AC circuits including power calculations, and three-phase systems. The key points are:
1) It defines fundamental electrical terms and describes different types of sources and circuit analysis methods like mesh and nodal analysis.
2) Kirchhoff's laws are introduced for analyzing circuits using the concepts of current law and voltage law.
3) Thevenin's and superposition theorems are summarized as techniques for simplifying circuits with multiple sources.
4) Single-phase AC circuits are covered including definitions
This document provides an overview of transmission line basics and concepts. It discusses key transmission line parameters like characteristic impedance, propagation delay, per-unit-length capacitance and inductance. It covers transmission line equivalent circuit models and relevant equations. It also discusses transmission line structures, parallel plate approximations, reflection coefficients, and discontinuities. The goal is to understand transmission line behavior and analysis techniques.
Method Of Compensation Instability Of Frequency Modulators In The Absence Of ...theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
This document provides an introduction to three-phase circuits and power. It defines key concepts like real power, reactive power, and power factor for sinusoidal voltages and currents. It describes how to calculate real and reactive power from rms voltage, current, and phase angle. Balanced three-phase systems are introduced, and how they allow more efficient power transmission compared to single-phase systems. Equations for solving problems involving three-phase circuits are also presented.
This document discusses several types of AC bridges used to measure unknown resistances, capacitances, and inductances. The Maxwell's inductance bridge uses two known impedances on one side and two pure resistances on the other to measure an unknown impedance. The Maxwell's capacitance bridge can measure unknown inductance by compensating the positive phase angle of inductance with the negative phase angle of capacitance. The Anderson bridge precisely measures unknown inductance over a wide range by using a known capacitance and resistance.
The document discusses different types of AC bridges used to measure inductance and capacitance. It describes 6 AC bridges: 1) Similar-Angle Bridge, which measures the impedance of a capacitive circuit. 2) Maxwell-Wein Bridge, which measures unknown inductances with a capacitance standard. 3) Opposite Angle Bridge, where the balance conditions depend on the measurement frequency. 4) Wein Bridge, which can measure either series or parallel components of an impedance. 5) Scherning Bridge, useful for measuring high phase angle insulating properties. Examples are provided to demonstrate calculations for determining unknown impedance values using the bridge equations.
This document discusses Matlab/Simulink implementation for reducing motor derating and torque pulsation of an induction motor using a matrix converter. It provides background on how non-sinusoidal supply from traditional inverters causes harmonic losses and torque pulsation in induction motors. The document summarizes simulation results showing that a matrix converter can provide a pure sinusoidal supply, reducing harmonic losses and torque pulsation. Simulations of a matrix converter driving an induction motor in Matlab/Simulink are presented, showing sinusoidal voltage/current waveforms and reduced torque pulsation at steady state.
This document discusses research on using extrusion honing (EH) to improve the surface finish of Inconel 625 fabricated by electric discharge machining (EDM). EH involves flowing an abrasive-laden polymer media over a material's surface to deburr, polish, and remove defects. The study investigated the effect of EH process parameters on the surface roughness of square Inconel 625 samples. Results showed that EH significantly improved surface finish by removing microcracks and recast layers from EDM. Surface roughness decreased dramatically in the first few EH passes then continued to gradually improve up to the 11th pass. Scanning electron microscope images confirmed that EH successfully removed defects from EDM.
This document discusses cross-cloud testing strategies for cloud computing applications. It proposes building an application prototype that can perform cross-cloud testing on multiple cloud platforms. The key aspects of existing approaches are that they do not test cloud-based software applications across different cloud environments. The proposed approach aims to develop a system that can test applications deployed on multiple independent cloud infrastructures to provide more flexibility and avoid vendor lock-in. Experimental results show the proposed approach can efficiently protect data during cross-cloud testing.
This document discusses the development of a novel pattern detection processor using an adaptively divisible dual-port BiTCAM (binary ternary content-addressable memory) to achieve high-throughput, low-power and low-cost pattern detection for mobile devices. The proposed dual-port BiTCAM architecture uses a dual-port AND-type match-line scheme with dual-port active AND gates. This allows for shared storage spaces to reduce power consumption through improved storage efficiency. The divisible BiTCAM also provides flexibility to regularly update the virus database.
The document summarizes research on using ant colony optimization (ACO) to solve the travelling salesman problem (TSP). It provides background on TSP, describes how ACO was applied to find optimal routes between cities. The researchers tested their ACO approach on sample problems with 5 cities/ants and 8 cities/ants, finding the optimal route in 31 steps. They conclude ACO provides relatively good results in a short time, making it useful for practical applications where exact methods require too much computation time.
This document discusses the force analysis of a Geneva wheel and face cam used in an automat machine. The automat is used in the insulator pre-assembly line of spark plug manufacturing. It contains details of the components, their geometry, material properties, forces acting on them, and the methodology for analyzing the stresses using CAD, FEA, and simulation software. Specifically, it calculates the tangential forces on the Geneva wheel at its minimum and maximum positions during drum indexing. It also calculates the tangential forces on the face cam during workpiece carrier indexing, as well as the effective force and torque acting on the cam. The results and discussions section presents the material properties, mesh details, boundary conditions, and loading cases considered for the F
This document summarizes research on discovering and preventing discrimination in data mining. It discusses how data mining models derived from historical data can unintentionally discriminate based on sensitive attributes like gender, race, or religion. Three main approaches for preventing discrimination are described: preprocessing data to remove biases, modifying algorithms to avoid discriminatory results, and postprocessing results to remove discrimination. The document reviews several existing techniques for each approach and discusses open challenges, including how to measure discrimination removal and extend methods to multiple classes.
This document proposes a frame-based adaptive compressed sensing technique for speech signals. It divides speech sequences into non-overlapping frames and processes each frame independently. It then classifies frames based on the correlation between the current and previous frames. Depending on the classification, different sampling strategies are applied - fewer measurements for highly correlated frames and more measurements for frames with more new information. Experimental results show the proposed adaptive technique provides better speech reconstruction quality compared to non-adaptive compressed sensing.
This document summarizes a study on the effects of adding inulin and beta-glucan fibers on the physicochemical, rheological, and sensory properties of Barbari bread, a traditional Iranian bread. Flour was treated with inulin at levels of 2%, 2.5%, and 3% and with beta-glucan at levels of 1%, 1.5%, and 3%. Tests were performed to analyze moisture, protein, ash and other flour properties as well as dough rheological properties using a Farinograph and Extensograph. Sensory evaluation was also conducted. The results showed that dough and bread with 3% inulin and 1.5% beta-glucan had better characteristics according to
This document summarizes an experimental study on heat transfer characteristics of a shell and tube heat exchanger using hiTRAN wire matrix turbulators as tube inserts. The study found that using the hiTRAN inserts increased turbulence in the tube side flow, reducing the boundary layer and increasing heat transfer coefficients by 120-130% compared to a plain tube. While the inserts increased pressure drop, the significant increase in heat transfer outweighed this effect. The main applications of hiTRAN inserts are in laminar and transitional flow regimes where they are most effective at enhancing heat transfer, but they can also provide benefits in turbulent flow regimes.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document presents the design of an ultrahigh-speed electrical drive system capable of operating at 500,000 rpm with an output power of 100 W. A permanent magnet machine with a slotless winding is used to achieve low inductance and a high fundamental frequency. Three power electronic topologies are experimentally tested - a voltage source inverter with external inductors, a voltage source inverter with block commutation, and a current source inverter with external capacitors. The voltage source inverter with block commutation and additional DC-DC converter is selected as it results in the lowest system volume due to lower switching losses and a simpler control implementation.
This document discusses optimization of MapReduce for Hadoop-based big data applications. It notes that while Hadoop is effective for large data volumes, its performance could be improved through MapReduce optimization. Specifically, it proposes a multilayered scheduling approach where an initial MapReduce with sample data generates outputs to optimize a final MapReduce processing. This could reduce execution time for exploring large datasets. The document also suggests optimization through techniques like predictive load scheduling, pre-fetching, pre-shuffling, and uniform load distribution across nodes. Overall improvements to MapReduce scheduling are argued to enhance resource utilization and quality of service for big data applications on Hadoop frameworks.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document describes the development of an air hockey game application for Android using the Native Development Kit (NDK). It discusses defining the structure of the air hockey table using vertices, building the table geometry, mapping colors, adding textures, touch interaction, and collision detection. The goal is to create a basic 3D air hockey game that demonstrates graphics capabilities when programming for Android with C/C++ code via the NDK. It also proposes areas for future extension, such as adding physics engines and artificial intelligence. The document serves as a case study for how to build a simple 3D game application with native code on the Android platform.
Analysis of Modeling of Current Differential ProtectionIJPEDS-IAES
Analysis of transients in longitudinal differential protection schemes is given
basing on results obtained by simulation. Simulation diagram for modeling
differential protection with current transformers with non-linear cores is
proposed. Main shortcomings of using current transformers as measuring
transducers are shown. Solutions of the problem revealed are proposed.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Consideration of Three Phase Faults on Transmission Line with Distance Protec...ijtsrd
In a modern power system, electrical energy from the generating station is delivered to the consumers through a network of transmission and distribution. Transmission lines are also important elements of electric power system and require attention of protecting for safety against the possible faults occurring on them. The detection of a fault and disconnection of a faulty section or apparatus can be achieved by using fuses or relays in conjunction with circuit breakers. Distance relay has the ability to detect a fault within a distance along a transmission line or cable from its location. Distance relay protection is the most widely used in case of high voltage and extra high voltage in the transmission line. In this paper discussion about how to protect the long transmission line with distance relay. June Tharaphe Lwin | Christ Tine Lin "Consideration of Three Phase Faults on Transmission Line with Distance Protection" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd28013.pdfPaper URL: https://www.ijtsrd.com/engineering/electrical-engineering/28013/consideration-of-three-phase-faults-on-transmission-line-with-distance-protection/june-tharaphe-lwin
Dynamic Performance of Distance Relayson Series Compensated Transmission Line...Premier Publishers
Series compensation is installed in power system networks to increase power transfer capacity, improve the system stability, reduce system losses, improve voltage regulation and for achieving flexible power flow control. Distance relays are widely used as main or backup protection of transmission lines including series-compensated transmission lines. The performance of conventional distance relays is affected by series capacitors and cause certain protection issues. This paper briefly discusses the problems like voltage inversion, current inversion, overreach and under reach during the fault conditions specific to series compensated lines. The behavior of capacitor protection techniques is discussed with simulations performed using Real Time Digital Simulator (RTDS) simulator for a typical 400 kV system having series compensation. The analysis is based on Transmission Line fault simulations, internal and external to the 400-transmission line where the Fixed Series Compensation (FSC)is installed.
This paper proposed a new sparce matrix converter with Z-source network to provide unity voltage transfer ratio. It is an ac-to-ac converter with diode-IGBT bidirectional switches. The limitations of existing matrix converter like higher current THD and less voltage transfer ratio issues are overcome by this proposed matrix converter by inserting a Z-source. Due to this Z-source current harmonics are totally removed. The simulation is performed for different frequencies. The simulation results are presented to verify the THD and voltage transfer ratio and compared with the existing virtual AC/DC/AC matrix converter. The experimental output voltage amplitude can be varied with the variable frequencies.
This document presents a new voltage sag compensation scheme that uses a pulse width modulation (PWM) switched autotransformer. The proposed scheme aims to maintain the rated voltage at critical load terminals during voltage sag events. It consists of an IGBT switch and autotransformer connected in series with the load. During normal operation, the thyristors bypass the compensator and supply power directly to the load. During a sag, the IGBT is controlled by PWM pulses to inject the missing voltage and regulate the load voltage. Simulation results in MATLAB/Simulink show the performance of the three-phase compensator under different sag and swell conditions. The proposed approach has fewer switching devices and good compensating capability compared to other common compensators.
Simulation of SPWM based Z-Source InverterIOSR Journals
1) The document presents a simulation of a SPWM based Z-source inverter. Z-source inverters can boost or buck the output voltage from a DC supply, overcoming limitations of traditional voltage source inverters.
2) MATLAB/Simulink models were developed for a Z-source inverter feeding resistive, inductive, and motor loads. Simulation results validated that the Z-source inverter has lower total harmonic distortion than traditional voltage source and current source inverters.
3) The Z-source inverter topology was analyzed and its operating principle explained. Sinusoidal pulse width modulation was used for switching control. Simulation results showed improved performance of the Z-source inverter over
Impact of Thyristor Controlled Series Capacitor Insertion on Short-circuit Ca...IJAPEJOURNAL
This research paper presents a study on phase to earth fault short-circuit calculation with fault resistance on a single transmission line 400 kV in eastern Algerian transmission networks at Algerian Company of Electricity and Gas (Sonelgaz Group) compensated by series Flexible AC Transmission System (FACTS) i.e. Thyristor Controlled Series Capacitor (TCSC) installed in midline. The facts are used for controlling transmission voltage, power flow, reactive power, and damping of power system oscillations at high power transfer levels. The direct impacts of TCSC insertion on the total impedance, active power and reactive power a electrical transmission line and also parameters of short-circuit : symmetrical currents, line currents, symmetrical voltages and line voltages are carried out. More the effects of injected voltage by TCSC for three case studies are presented.
Parasitic consideration for differential capacitive sensorjournalBEEI
Parasitic integration for a single supply differential capacitive sensing technique is presented in this paper. In real capacitive sensor measurement, parasitic impedance exists in its measurement. This paper objective is to study the effect of capacitive and resistive parasitic to the capacitive sensor circuit. The differential capacitive sensor circuit derivation theory is elaborated first. Then, comparison is made using simulation. Test was carried out using frequency from 40 kHz up to 400 kHz. Result is presented and have shown good linearity of 0.99984 at 300 kHz, R-squared value. This capacitive sensor is expected to be used for energy harvesting application.
Design of Three-Phase Three-Switch Buck-Type Rectifier for Pre-Charging Appli...IAES-IJPEDS
The main objective of a pre-charging circuit in variable frequency drives is to
pre-charge the DC-bus capacitor without any voltage and current overshoot
within the specified time. In exisiting variable frequency drives seperte precharging
circuits (or) thyristor bridges were used due to this drives power
density, cost becomes high and control technique becomes complex. This
paper presents about the design of three-phase three-switch buck-type
rectifier for pre-charging application used in variable frequency drives which
elimates the disadvantages of existing techniques. In this paper we will
discuss about design procedure of pre-charging circuit of an 800KW
converter with dc-link output voltage of 775V at an input ac voltage of 550V,
60Hz, selection of power and passive components, voltage and current stress
of power transistors. In the final this paper discusses about loss distribution
of the components and comparison of new converter technique with existing
pre-charging techniques.
Implementation of FC-TCR for Reactive Power ControlIOSR Journals
This document discusses the implementation of a Fixed Capacitor Thyristor Controlled Reactor (FC-TCR) system for reactive power control. FC-TCR is a type of Static VAR Compensator (SVC) that can inject or absorb reactive power to control voltage. It consists of a fixed capacitor in parallel with a thyristor controlled reactor. The reactor current is controlled by varying the firing angle of thyristors, allowing both lagging and leading reactive power. MATLAB simulation results show that reactive power output from the FC-TCR increases as the reactor inductance increases while keeping the capacitor constant, demonstrating effective reactive power control.
Applications of power electronic device to power systemswathiammu7
This presentation summarizes power electronic devices used in power systems, including the SCR and TRIAC. It describes the introduction, structure, operating modes, characteristics and applications of the SCR. The SCR's applications include motor starters and regulators. It also discusses the TRIAC's structure, operating quadrants, VI characteristics and applications such as LED drivers for street lighting. The presentation concludes with noting that power systems are networks for supplying, transferring and using electrical power to homes and industry.
This document provides an overview of power system engineering concepts related to unbalanced system analysis. It begins with an introduction to symmetrical and unsymmetrical faults on three-phase systems. It then discusses percentage reactance and base KVA, the steps for symmetrical fault calculations, and an introduction to symmetrical components and sequence impedances. The document proceeds to explain single line-to-ground faults, line-to-line faults, and double line-to-ground faults. It provides examples of calculating fault currents and sequence components. In summary, the document covers fundamental concepts for analyzing faults in three-phase power systems, including symmetrical and unsymmetrical faults, sequence components, and example calculations.
1) Differential protection compares currents flowing into and out of a protected zone. A difference indicates an internal fault. Modern relays use microprocessors to compare currents.
2) Differential protection is applied to transformers by taking the transformation ratio into account. Ratios of current transformers (CTs) on the high voltage and low voltage sides must match the transformer ratio.
3) Restricted earth fault protection monitors residual current to protect transformer windings against earth faults, providing coverage where overcurrent protection is insufficient.
This document describes various principles of relay operation used in power systems. It discusses several categories of relays including level detection relays, magnitude comparison relays, differential relays, phase angle comparison relays, distance relays, pilot relays, harmonic content relays, and frequency sensing relays. It also describes some common relay designs such as plunger-type electromechanical relays and their operating characteristics. Relay principles can be based on detecting changes in current, voltage, phase angles, harmonic components, or frequency during fault conditions.
Mitigation of switching overvoltage by application of surge arrester on capac...IAEME Publication
This document summarizes a study on mitigating switching overvoltages when de-energizing capacitor banks. [1] A MATLAB simulation was created based on an existing 33kV, 14.7MVAR capacitor bank. [2] Three surge arrester arrangements were tested: phase to phase, phase to ground, and phase to neutral. [3] The results show that connecting surge arresters limited overvoltages to acceptable levels and reduced the probability of circuit breaker restrikes that could damage equipment.
Mitigation of switching overvoltage by application of surge arrester on capac...IAEME Publication
This document summarizes a study on mitigating switching overvoltages when de-energizing capacitor banks. [1] A MATLAB simulation was created based on an existing 33kV, 14.7MVAR capacitor bank. [2] Three surge arrester arrangements were tested: phase to phase, phase to ground, and phase to neutral. [3] The results show that connecting surge arresters limited overvoltages to acceptable levels and prevented circuit breaker restrikes that could damage equipment.
A Study on Protection of Cables by Solkor Differential Protection Relay with ...IJERA Editor
This paper intends to briefly compare the protection of buried three phase high voltage cable with Solkordifferential protection relay using metallic pilot wires orfibre optic pilot wires. Dielectric property of the fiber optic provides complete electrical isolation as well as interference free signaling. This provides total immunity from GPR (ground potential rise), longitudinal induction, and differential mode noise coupling andhigh-voltage hazards to personnel safety. So Fibre optic provides great advantage for Solkor differential protection relaying.
A Study on Protection of Cables by Solkor Differential Protection Relay with ...
K046016266
1. Zorica Bogićević Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 6( Version 1), June 2014, pp.62-66
www.ijera.com 62 | P a g e
An Investigation of the Ability of Combined Zero – Sequence Cutoff Protection in Line High Voltage Slobodan Bjelić1, Zorica Bogićević2, 1Faculty of Technical Sciences, Kosovska Mitrovica, Serbia 2Advanced High Technical School, Zvecan, Serbia ABSTRACT Zero-sequence cutoff protection has found extensive use in 110-400 kV power networks. Level of value protection settings a starting over-current relay is selected from the requirement of its adjustment out against three zero-sequence current on the end of protected line. Sensitivity of zero-sequence cutoff protection on line is function of equivalent zero-sequence impedance reduction to point bus-bars with disposition protection. Owing to availability of transformers with earthed neutrals at each substation of a 110-400 kV network which are the source of a zero-sequence current, the possibility exists of wide use of zero-sequence cutoffs and stepped zero-sequence protections practically on all lines of medium and large length. From these reasons propose is the use ``cutoff``` protection.
Keywords – cutoff, substation, simulation, protection, voltage
I. INTRODUCTION The protection consists of over-current relay CR responding to an earth fault, power-directional relay CP determining the direction of the fault power flow, and time relay TR introducing a time delay into the protection operation needed according to the selectivity requirement, Fig 1. The starting current relay and the current winding of the power-directional relay are connected into the neutral wire of the current transformers for current 3I0 [9,13] where as the polarizing (voltage) winding of the power relay is fed with voltage 3V0 from the broken delta connection of the voltage transformer [3,4]. The starting element of the zero-sequence protection features high sensitivity as it is not necessary to adjust the element out against load currents. To speed up the clearance of faults to earth in circuits with solidly earthed neutral, use is made of cutoffs which respond to a zero-sequence current. Their operating principle is the same as that of the cutoffs responding to a phase current. Zero-sequence cutoffs are available in plain current and directional versions, with and without time delay.
II. DESCRIPTION OF COMBINED OVER CURRENT ZERO-SEQUENCE CUTOFF PROTECTION The operating current of the starting relays of a zero-sequence over-current protection is selected from two condition: -the requirement of reliable action of the protection in the event of a fault at the end of the adjacent (second) circuit section and -from the requirement of its adjustment out against unbalance currents. It is in this aspect that the directional cutoff fundamentally differs from the non-directional cutoff. The operating current of the directional cutoff is smaller than that of the non-directional one. That is why the zone of action of the first cutoff is much greater than that of the second zone. As a power relay features a dead zone, the directional cutoff should be used only in those cases when the plain cutoff fails to satisfy the sensitivity condition [6,7,8]. The directional instantaneous cutoff scheme differs from directional over-current protections, Fig. 1. in that it lacks a time relay. Combined over-current zero- sequence cutoff protection a) with voltage transformer, b) voltage transformer is absent, Fig. 1. a. and 1.b.). The sensitivity of the zero-sequence protections can be small therefore. When a fault appears the zero-sequence impedance can be grows concerned with impedance under normal service, where zero-sequence of current grows, for examples a include line or transformer (or autotransformer) with neutral point.. This sensitivity can be grows bat widely used combined zero-sequence protection consist of two relays schemes [9,10]: zero-sequence over-current relay and zero-sequence voltage relay. Three schemes is represent in (Fig.1.a, b, c). The circuit is assumed to be a no-load circuit.
RESEARCH ARTICLE OPEN ACCESS
2. Zorica Bogićević Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 6( Version 1), June 2014, pp.62-66
www.ijera.com 63 | P a g e
Fig.1: Combined overcurrent zero-sequence cutoff
protection a) with voltage transformer, b) voltage
transformer is absent, c). shows some cases of
equivalent zero-sequence circuit current flow in
certain parts of the circuit.
II.I. CALCULATION AND ANALYSIS
Fig 1.c, shows some cases of equivalent
zero-sequence circuit current flow in certain parts of
the circuit. The operating current of the directional
zero-sequence cutoffs are adjusted out against current
3I0max in the event of an earth fault (phase to ground
or two-phase to ground fault) Line L on the busbars
of the opposite substation (point) K according to the
expression similar. It is assumed to include two
transformer (PT1, PT2) with neutral point and current
is:
. . 0.max I k 3I op pr A r (1)
0.max I maximum value of flowing zero-sequence
current inside a line in considere transient conditions
service substation in the event of an earth fault (phase
to ground or two-phase to ground fault) line L on the
starting busbar in point K and where PT2 transformer
is include (conditions of maximum current).
When is used combined zero-sequence
cutoff protection bay diagram 1.a a) with voltage
transformer and two relays: current relay CR and
voltage relay VR it is necessary selected value of
operating voltage relay of zero-sequence voltage VR
to relation ( because 1 2 Z , Z are parallel
connection):
1 2
1 2
. . 0.max 3
Z Z
Z Z
U k I op pr A VR
(2)
1 2 Z ,Z zero-sequence impedance power
transformers (PT1, PT2) in equivalent scheme zero-sequence,
Fig.1.c).
The current operating of the current relay
zero-sequence CR, represent in Fig. 1.a.,b. bay part a)
it is needed from condition are adjusted out against
current 3I0 in the event of an fault (phase to ground or
two-phase to ground fault) Line Lon the busbars of
the opposite substation (point) K according to the
expression similar and assumed it is off duty one
transformer, exemple PT2 with neutral point.
3 .
op. pr.A r 0.min.out putPT 2 I k I (3)
0.min.out putPT 2
I maximum value of flowing zero-sequence
current inside a line in considere transient
conditions service substation in the event of an earth
fault (phase to ground or two-phase to ground fault)
line L on the starting busbar in point K and where
PT2 transformer is off duty (coditions of minimum
current).
Estimation of combined zero-sequence
cutoff protection can by made with comparation
under transient condition of a minimum value current
and of a maximum value current in a fault scheme.
If a value operating current combined zero-sequence
is considere from relation (3) small
concerned magnitude operating current zero-sequence
is considere from relation (1) should be
coordinated so that the opera ting currents with
sensitivity voltage relay kvr combined zero-sequence
protection. It is clear ,under transient condition of
maximum value of current in bouth equivalent
schemes on a combined zero-sequence cutof
protection the operating current of current relay and
operatin voltage of voltage relay thei have equal
sensitivity. The operating curren t of a current relay
and operating voltage of a voltage relay calculate
from one equivalent scheme (under transient
conditions where are include both transformers
[2,3,4].
Under transient conditions of minimum
value of current the sensitivity of voltage relay is
bigger, bay relation (4),
. . 0
0 . .
3
3
U I
U I
k
k
op pr A
op pr A
SC
SV
=
2
1 2
1 2
1 2
0 . .
0 1 . .
3
3
Z
Z Z
Z Z
Z Z
I I
I Z I
op pr A
op pr A
(4)
Under transient conditions of minimum
value of current the voltage relay have (Z1+Z2)/Z2
time selectivity then current relays, bay circuit
equivalent Fig. 1. c.
III. EVALUATION OF THE DIFFERENT
COMBINED ZERO-SEQUENCE CUTOFF
PROTECTION
The operating principle of protection is sim-ple
and reliable, which enables circuits with two-end
supply to be protected selectively. A combination of
combined cutoffs protection with a directional over-current
protection provides a protection which in
3. Zorica Bogićević Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 6( Version 1), June 2014, pp.62-66
www.ijera.com 64 | P a g e
many cases provides fairly fast clearance of faults
and sensitivity. Analyze and the service practice
shows that the combined protection functions reliably
[11,12,14].
The disadvantages of the protection are:
-long time delays, near the sources of supply in
particular;
-insufficient sensitivity in circuits with large loads
and relatively small fault current multiples;
- a dead zone in the event of three-phase faults;
-the possibility of the incorrect choice of the direction
with the voltage circuit, feeding the power-directional
relay, being damaged.
The directional over current protection is
widely used as the main protection in networks up to
35 kV with two-end supply. In 110- and 220-kV
networks, the classic directional overcurrent
protection finds its application as a back-up
protection, but sometimes, when combined with a
cutoff, as the main protection.
The selection of operating current
op pr I . according to the first requirement is made in
the same way as for the over current protection, pro-ceeding
from the considerations set forth , by formula
[1,3,4]:
rst
sa st mah
op pr K
k k I
I 1
. (5)
The maximum value of current Imax should
be determined from the most severe but possible in
service conditions. In ring circuits and in radial
circuits with two-end supply (see Fig. 2.a and b)
maximum loads develop on the lines upon
disconnection them. For instance, if line LII is
disconnected in the circuit shown in Fig. 2..b, the
load current on line LI reaches its maximum.
In this case, the phases of the voltages
applied to the protection are distorted and therefore
the power-directional relay can close its contacts
enabling the protection to operate even if the power
flow is towards the busbars of the substation.
According to the second requirement the operating
current of the protection is derived from the formula:
[2,3], :
op pr saf h ph I k I . . (6)
where h ph ld sh c I I kI . [3,4] , and safety factor
ksaf is taken as 1.15 to 1.30 depending on how
accurately the value of Ih.ph is evaluated.. Taken as
the final value of Iop.pr is the greater magnitude
derived from expressions (5) and (6).
As for protections in a circuit with small
earth fault current (where h ph ld I I . ) and
protections in a circuit with solidly earthed neutral
which are interlocked in the case of earth faults, the
operating current of starting relays is selected
according to the first requirement only, i.e., by
formula (5).
To provide selectivity, the sensitivity of the
protections operating in one direction should be
coordinated so that the operating currents grow as the
power source is approached. Such coordination
prevents the non-selective operation of the protection
in the event of a fault current close in value to the
operating currents of the protections. The aforesaid is
illustrated by Fig.2.b. When a fault appears near the
feeding busbars at point K1 the ratio of fault currents
IKA and IKB is inversely proportional to
impedance 1 ` K z and 1 "K z , i.e.,
1
1
`
"
K
K
KB
KA
z
z
I
I
(7)
Fig. 2. Calculation of over current cutoff on
parallel lines. Design schemes for selection of
operating current of zero-sequence cutoffs on
parallel lines (a, b, c) and nature of current I01
variation in the case of fault on parallel line L2
disconnected on one side (d)
Consequently,, the operating current of a
directional overcurrent cutoff is adjusted out against
fault currents flowing from the busbars of the
substation.
Under these conditions the impedance of
operative line L1 is reduced by mutual inductance
due to current I02, which involves an increase in
design current I01 and voltage. Three schemes is
represent in (Fig.2.c). (see simulation Fig.4.a,b,c).
Certain combinations of reactances xo of
parts of the network under consideration may be
responsible for a maximum current rise in line L1 not
due to a fault on the busbars at point K1 but on the
parallel line at point K when this line is disconnected
on one side (Fig.2.c). (see simulation Fig.4.a,b,c.)
Although the fault at point K2 is more
distant than that at K1 current I01 in line L1 may now
happen to be greater in value due to a change of'
current flow in the parallel branches of the network
because of a reduction in the impedance of line L1
caused by the strong mutual inductance from line L2.
Figure 2.d shows current I01 and full current Iok at the
point of a fault plotted against the location of the
4. Zorica Bogićević Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 6( Version 1), June 2014, pp.62-66
www.ijera.com 65 | P a g e
fault I0cal is represented by the greater of the
obtained values of I01 . Zero-sequence currents
should be calculated for that kind of an earth fault
wherein their value is greatest.
It is known from the fault current calculation
theory that with equal total positive- and negative-sequence
reactances of the equivalent circuit
1 2 x x current (1,1)
0
(1)
0 I I if 0 1 x x .
After calculation and correlation of x0with
x1we find the calculated form of the fault (single-phase-
or two-phase-to-earth faults).
IV. ANALYSIS OF THE SIMULATION RESULTS
The Distributed Parameter Line block
implements an N-phase distributed parameter line
model with lumped losses. The model is based on the
Bergeron's traveling wave method usedb y the
Electromagnetic transient program (EMTP) [2,5].
The breaker block implements a circuit
breaker where the opening and closing times can be
controlled either from an external Simulink signal
(external control mode), or from an internal control
timer (internal control mode). The arc extinction
process is simulated by opening the breaker device
when the current passes through 0 (first current zero
crossing following the transition of the Simulink
control input from 1 to 0). Specifies the number of
phases, N=3, of the model.
Specifies the frequency used to compute the
modal resistance R, inductance L, and capacitance C
matrices of the line model. The resistance R per unit
length, as an N-by-N matrix in ohm/km. For a 2-
phase or three-phase continuously transposed line,
you can enter the positive and zero-sequence
resistances [R1 R0]. For a symmetrical six-phase line
you can enter the sequence parameters plus the zero-sequence
mutual resistance [R1 R0 R0m]. For
unsymmet rical lines, you must specify the complete
N-by-N resistance matrix. The inductance L per unit
length, as an N-by-N matrix in henries/km (H/km).
For a symmetrical line, you can either specify the N-by-
N matrix or the sequence parameters. The
capacitance C per unit length, in farads/km (F/km).
For a symmetrical line, you can either specify the N-by-
N matrix or the sequence parameters. For a 2 or 3
phase continuously transposed line possible positive
and zeo sequence (C1, C0). The line length, in km.
(100km).
Measurements: Select Phase-to-ground voltages to
measure the sending end and receiving end voltages
for each phase of the line model. Multi-meter block
in model to display the selected measurement during
the simulation. This model does not rep- resent
accurately the frequency dependence of RLC
parameter of real power lines, because of skin effects
in the conductor and ground, the R and L matrice
exhibit strong frequency dependence, causing an
attenuation of the high frequencies.
Example of simulation influence parallel line I and
II.
The psbmonophaseline.mdl illustrate as a
100 km line connected on a pu(1), 50 Hz infinite
source The line deenergized and reenenrgized after 2
cycles.The simulation is performed simultaneously
with the distributed parameters line block in Fig. 3.
Fig. 3: The receiving end voltage obtained with
distributed Parameter Line block. Phase (deg) 0,
The influence phase (A) line I on phase (A) line II,
closed Breaker 1 and 2
Fig. 4. a) Phase (deg) 0, simulation of influence
phase (A) line I upon phase (A) line II, open
Breaker 2 , AI-yellow, AII-pink., b) Phase (deg)
+120, simulation of influence phase (A) line I upon
phase (B) line II, open Breaker 2. A- pink, B
yellow, c) Phase (deg) +120, simulation of
influence phase (A) line I upon phase (C) line II,
open Breaker 2. , A- pink, C yellow.
5. Zorica Bogićević Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 6( Version 1), June 2014, pp.62-66
www.ijera.com 66 | P a g e
V. CONCLUSION
From increase sensitivity of protection in in protection from phase-to ground fault and two-phase to ground fault the combined zero-sequence cutoff protection is widely used as the main protection in network 110-400 kV. Consequently,, the operating parameters of a current and voltage relays in combined zero- sequence directional overcurrent cutoff is adjusted out against fault currents flowing from the busbars of the opposite substation. It is clear , from analysis, where is realized combined zero-sequence directional over-current and voltage cutoff is adjusted out against fault currents flowing from the busbars of the other lines with conditions selectivity of current and voltage relay. The zero-sequence cutoff protection is widely used as the main protection in network 110- 400 kV From increase of sensitivity in protection from phase-to ground fault and two-phase to ground fault. The operating principle of directional combined zero-sequence cutoff protection is simple and reliable, which enables circuits with two-end supply to be protected selectively.
REFERENCES
[1] S Bjelic, Z Bogićevic, Computer Simulation of Theoretical Model of Electromagnetic Transient Processes in Power Transformers, International Journal of Information Technology and Computer Science, (IJITCS)6, no. 1(2013): 1.
[2] Dommel, H, Digital Computer Solution of Electromagnetic Transients in Single and Multiple Networks, IEEE Transactions on Power Apparatus and Systems, Vol. PAS- 88, No. 4, April, 1969.
[3] J. Lewis Blackburn Thomas J. Domin: ``Protective Relaying Principles and Applications``,Third Edition, 2006 by Taylor&Francis Group, LLC., : 416-428.
[4] Bjelic S. Overcurrent protections of distribution electrical networks / Prekostrujne zaštite distributivnih električnih mreža, 2009, UDK 621.313(075.8) SITOPRINT Niš, (2010), COBISS.SR-ID 512270494,
[5] MATLAB SIMULINK Sim Power System, Copyright 1984-2002 the Math Works, Version 6.5.0, 180913a, June 2, 2000.
[6] Bjelic S., Jelic N., Automatic Secondary VAR Control: A Multivariable Approach , ★★★★★ , 1995 01/01, German National Library of Science and Technology (GetInfo) BL CP.
[7] Antonin Veverka: TECHNIKA VYSOKÝCH NAPĚTÍ SNTL/ALFA, DT621.3027.3: 621.315.31:II, Elektrickě
razově jevy ve vinutih transforma torů a točivýh strojů, Praha, 1982.
[8] Bjelic, S.,Mladenovic, V, Algorithm and possible method of emergency control electrical network View in Scopus | Show abstract, 9th Symposium on Neural NetworkApplications in ElectricalEngineering,NEUREL2008Proceeding,pp. 69
[9] Markovic, N., Bjelic, S., Bogicevic, Z, Graphical zero-sequence cut-offs method of determining of fault to earth in electrical lines, View in Scopus | Show abstract, 9th Symposium on Neural Network Applications in Electrical Engineering, NEUREL 2008 Proceedings , pp. 73
[10] S Bjelić, U Jakšić, N Marković., Informatical Model of the System of Automatic Breakdown Control in Energetic Systems ELEKTRONIKA IR ELEKTROTECHNIKA, Vol. 1, 2011, p. 87–92.
[11] N Marković, S Bjelić, M Vujičić Development of new measuring systems based on symmetric components in electric networks- Electronics and Electrical Engineering.–Kaunas:,2010 Journal Arhive Kaunas University Lituania, ISSN 1392- 1215,Electronics&electrical engineering, T120,No 8(104), 2010, p.57–62.
[12] S Bjelic, Z Bogicevic, N Kreckovic… - cired.net, estimation of curents flow, loss of power and voltage fall down in distributive networks by using pdm kmp, q program , Cite, 19 International Conference of Electrical Distribution, Paper 0907, Block 4.2, Method and tools, Cired, Wien, 2007.
[13] T Jagan Mohan Rao, P Anil Kumar, Ch. Krishna Rao, Voltage Source Inverter/Converter for the Improvement of Power Quality Using Fuzzy Logic Controller, Int. Journal of Engineering Research and Applications, ISSN : 2248- 9622, Vol. 4, Issue 5( Version 1), May 2014, pp.46-50
[14] Marković, N., Bjelić, S., Živanić, J., Jakšić, U. Numerical simulation and analytical model of electrical arc impedance in the transient processes | Symulacje i analiza modelu impedancji łuku elektrycznego w stanach nieustalonych, 2013, View in Scopus | Show abstract, Przeglad Elektrotechniczny 89 (2 A) , pp. 113, .