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Some Electrical Seminar Abstracts
02-15-2009, 04:52 PM,
#1
Tongue  Some Electrical Seminar Abstracts

Ultra Sonic Motor

Introduction
ULTRA SONIC motor is a newly developed motor, and it has excellent performance and many useful features, e.g.: high-torque density, low speed, compactness in size, no electromagnetic interferences, and so on. USM is a kind of piezo motor. The proposed speed control scheme is assumed for these applications because they require quick and precise speed control of actuators for various load conditions. A speed control method of USM using adaptive control is proposed.

Artificial Neural Network (ANN), which follows the biological neural cells in brain, consists of a number of neurons and weighted links, and it has a good potential for control applications because it can approximate the non-linear input-output mapping of the plant. Accordingly, ANN has been applied widely in the field of power electronics control. In this paper a three layer neural network for speed controller is adopted, and the weights of the links are updated using the general back propagation in order to reduce the speed error at each sampling period. In general, the speed of USM can be controlled by driving frequency, applied voltage, and phase difference of applied voltages. This paper adopts the driving frequency as control input in order to simplify the drive system.
Automated Distribution System
Automated Distribution System

Introduction
Electric power utilities throughout the world are undergoing considerable change in structure, operation, and regulation. One of the major effects of this change is increased importance of distribution automation. With improved Distribution Automation (DA), both the reliability and the efficiency of electric power distribution can be increased. Communication system is essential to performance of automated distribution systems.

It is necessary to perform reliability assessments of communication facilities in carrying out the control functions. The paper describes an approach for reliability evaluation of the communication and control. This approach is based on the event tree methodology, and by using it sensitivity studies are performed to predict impact of communication system. It indicates that the reliable communication system is essential to the secure and reliable operation of automation system. The improvements in communication reliability can have a significant impact on the control function performance.

The results of the studies are discussed and the importance of the communication system on the reliable automation performance is demonstrated in the paper.
Fault Locating In Undegrounded And High Resistance GroundedSystems
Fault Locating In Undegrounded And High Resistance GroundedSystems

Introduction
One of the most common and difficult problems to solve in industrial power systems is the location and elimination of ground fault. Ground faults that occur in ungrounded and high resistance grounded systems do not draw enough current to trigger circuit breaker or fuse operation, making them difficult to localize.

Techniques currently used to track down faults are time consuming and cumbersome. A new approach developed for ground fault localization on ungrounded and high resistance grounded low voltage systems is described. The system consists of a novel ground fault relay that operates in conjunction with low cost indicators permanently mounted in the circuit.

The remote fault relay employs digital signal processing to detect the fault, identify the faulted phase and measure the electrical distance of the fault from the substation. The remote fault indicators are used to visually indicate where the fault is located. The resulting system provides a fast, easy, economical and safe detection system for ground fault localization.
Distribution System Relaying
Distribution System Relaying

Introduction
With the increasing loads, voltages and short-circuit duty of distribution substation feeders, distribution over current protection has become more important today than it was even 10 years ago.

The ability of the protective equipment to minimize damage when failures do occur and also to minimize service interruption time is demanded not only for economic reasons but also because the general public just expects reliable service. This publication will attempt to review some of the present distribution practices, particularly with regard to relaying, in view of some of these new developments.

It is not the purpose of this publication to settle the controversy surrounding some of the problems dealt with, but rather to give the reader a better understanding of distribution over current protection problems and some of the methods being used to solve them. Among the areas covered will be such things as: cold-load pickup, ground-fault detection, tripping methods, current-transformer (CT) connections, line burn down, and coordination between various devices. This seminars is based on distribution system over current protection. The areas includes cold load pick up, ground fault detection, tripping methods, current transformer connections, line burn down and co-ordination between various devices. In this article use of over current relays & their operations are included. Both due to economic reason and reliability service this seminars will attempt to review sum of the present distribution systems, over current protection problems and some of the methods used to solve them.
Solar Power Generation
Solar Power Generation

Introduction
Solar power generation is rapidly finding a prominence as a major part of power in the modern world. There are various problems associated with the tapping of Sunâ„¢s energy, such as movement of Sun. Researches has been going on to find new and efficient method to harness the solar power.

Commonly the solar panel is placed above the Earthâ„¢s surface facing the sun tilted at an angle of 450.But there is a problem, we can get maximum output from the panel only when the Sun comes perpendicular to the face of the panel. In late morning or afternoon, we cannot get maximum output from the panel. Thus for maximum utilization of the Sun through out the day, the panel must be kept perpendicular to the sun. This is possible only by tracking the sun In this paper, I will be dealing with Some aspects of solar power generation technique An Automatic Solar Tracking System.
Solar Hybrid PVT Systems
Solar Hybrid PVT Systems

Introduction
The tending extinction of fossil fuels has already created an awareness to look for alternative sources of energy of which solar is most promising in a topical country like ours , where it is available in abundance .

The efforts are being made to utilize solar energy in building sector to fulfill the thermal as well as electrical requirements. Various thermal systems have being developed and commercialized for space and water heating . Work is being done on projects to generate electricity through photovoltaic convert ion. The efficiency of the photovoltaic conversion is inversely proportional to the temperature.

When the temperature rises, there are occasions when the PV conversion is very adversely affected leading to the system failure. The basic idea in the development of hybrid panel is to utilize the radiations not used for photovoltaic conversion, directly for thermal purposes and all radiations falling on the photovoltaic cell, which are partially used for PV conversion and the remaining heats up the cells. A suitable heat exchanger has been designed & attached to the photovoltaic panel to extract the heat from hybrid panel to give

1. Hot water for use in buildings
2. Increased PV efficiency.

This paper deals with the results obtained from glass to glass-laminated ONGC type PV module and the initial performance evaluation test of modified module along with its instrumentation.
Conditional Monitoring
Conditional Monitoring

Introduction
Transformers are a large part of the component structure of the electricity system. Knowing the condition is essential to meeting the goals of maximizing return on investment and lowering total cost associated with transformer operation.

In order to reconcile both decreasing maintenance spending and reliable service, condition based maintenance (CBM) is often proposed. The successful application of CBM lies in obtaining information transformers, so that, on the one hand, a critical condition will be noted early enough to take measures and on the other hand, so that only minimal maintenance is being applied to transformers still in good condition.

The paper covers the following areas.
¢ General aspects of aging in transformers.
¢ An overview of condition monitoring methodology with partial discharge patterns in focus.
¢ Partial discharge measurement and diagnostics on power transformer using a multi channel digital PD detector.
Optimum VAR Control
Optimum VAR Control

Introduction
A complex method for the optimum VAR control of radial primary power distribution networks dealing with the proper selection and installation of shunt capacitors is developed here. The problem is examined both on an annual and a long-term basis.

First objective functions and relative algorithms, which determine the kind, the size, the minimum numbers the locations and the adjustments of the possibly installed standard capacitors are developed. Then all these are embodied in a complex software package, which examines all the technically acceptable VAR control solutions.

It compares them economically and finally proposes the more profitable.In this, a complex method for the optimum VAR control of a radial primary distribution network with capacitors is developed. The problem is examined both for constant and growing annual peak load buy developing relative software packages. Realistic data of the examined networks such as lateral branches, conductor sizes, load distribution and variation are taken into account. The target in every case is the determination of the kind, size, minimum number, location and possible adjustments of standard capacitors which effect the techno economically var control. This is achieved by utilizing previous considerable methods dealing with the examined problem which however are adapted to new objective functions and they are modified so as to over come their weaknesses and to optimize the necessary computing time..
The Global Voltage Regulation
The Global Voltage Regulation

Introduction
Based on closed form expressions for the power frequency voltages and currents in a typical distribution network, the voltage regulation VR at any time point during the day could be evaluated. It will depend primarily on the network configuration, the daily load curve, the load density and its power factor as well as level of the reactive power compensation.

The computed at a certain timeËœtâ„¢ can give a useful indicator for the voltage constancy over the network at that time point. The concept of ËœGlobal Voltage Regulationâ„¢ is introduced. The GVR is defined as the root mean square value of the voltage regulation over the daytime as Ëœtâ„¢ varies from 0 to 24 h. Accordingly , it takes into account the effect of both the geometrical dimensions of the distribution network and the daily temporal variation of the voltage regulation .

The theoretical value GVR =0 corresponds to the ideal case in which the voltage is constant at all nodes ,all the time. Hence GVR can be considered as a representative figure of merit describing the supply quality regarding the voltage values prevailing at the different network nodes, allover the day. The paper also addresses the identification of the optimal level of reactive power compensation (K) that will lead to the least possible GVR. Moreover the impact of both the network and load parameters on the optimal value of ËœKâ„¢ is investigated..
Synchronous Voltage Source
Synchronous Voltage Source

Introduction
The synchronous voltage source is implemented by a multi-pulse inverter using gate turnoff (GTO) thyristors . It is capable of generating internally the reactive power necessary for network compensation, and is also able to interface with an appropriate energy storage device to negotiate real power exchange with the ac system. The paper develops a of power flow control using solid - state synchronous voltage sources for shunt compensation, series compensation , and phase angle control .

It also describes the unified powerflow controller that is able to control concurrently or selectively all three network parameters(voltage, impedance, angle) determining power transmission. compensation method of employing thyristor switched capacitors and reactors shows its superior performance, uniform applicability, smaller physical size, and lower overall cost. There are clear indications that solid-state synchronous voltage sources represent the next technology for ac transmission system compensation and power flow control.

This technology offers operating features, functional performance, and application flexibility unattainable by the presently used circuit arrangements. The synchronous voltage source can be considered an ideal 60 Hz generator that has no inertia and produces an almost sinusoidal output voltage with independently variable amplitude and phase angle, thus facilitating rapid, decoupled controls for reactive and real power exchange. It can be used uniformly to control transmission line voltage, impedance, and angle by providing reactive shunt compensation, series compensation, and phase-shifting.
Gas Insulated Substations
Gas Insulated Substations

Introduction
SF6 Gas insulated Substations (GIS) are preferred for voltage ratings of 72.5KV, 145KV, 245KV, 420KV and above. In such a situation, the various equipments like circuit breakers, busbars, isolators, and load break switches; current transformers, voltage transformers, earthing switches etc. are housed in metal enclosed modules filled with SF6 gas.

The SF6 gas provides the phase to ground insulation. As the dielectric strength of SF6 gas is higher than the air, the clearances required are smaller. Hence, the overall size of each equipment and the complete substation is reduced to about 10% of conventional air “ insulated substations. As a rule GIS are installed indoor. However outdoor GIS have also been installed earlier.

The various modules of GIS are factory assembled and are filled with SF6 gas at a pressure of about 3 Kg/ cm2. Thereafter they are taken to site for final assembly. Such substations are compact and can be installed conveniently on any floor of a multi - storied building or in an underground substation.As the units are factory assembled, the installation time is substantially reduced. Such installation are preferred in cosmopolitan cities, industrial townships, etc. where cost of land is very high and higher cost of SF6 insulated switch gear (GIS) is justified by saving due to reduction in floor area requirement. They are also preferred in heavily polluted areas where dust, chemical fumes and salt layers can cause frequent flashovers in conventional outdoor air-insulated substations. The GIS has monitoring system.

The gas density in each compartment is monitored. If pressured drops slightly, the gas is automatically tapped up. With further gas leakage, the low-pressure alarm is sounded or automatic tripping or lock out occurs. By this method we can save the space required for the substation to build up. This means that gas-insulated substation can be built in any metropolitan city. Many experiments are going on the use of SF6 gas
Superconductivity
Superconductivity

Introduction
SUPERCONDUCTIVITY is the ability of certain materials to conduct electric current with no resistance and extremely low losses. This ability to carry large amounts of currents can be applied to electric power devices such as motors and generators and to electricity transmission in power lines.

For example, superconductors can carry as much as 100 times the electricity ordinary copper or aluminium wires of same size.Scientists had been intrigued with the concept of superconductivity since its discovery in the early 1900â„¢s, but the extreme low temperature the phenomenon required was a barrier to practical and low cost application.

This all changed in 1986 when a new class of ceramic super conductors were discovered that ËœSUPERCONDUCTEDâ„¢ at higher temperatures. The science of high temperature superconductivity (HTS) was born, and along with it came the prospect for an elegant technology that promises to Ëœsuperchargeâ„¢ the way energy is generated, delivered and used.At the heart of high temperature superconductivity lies a promise for the near future.

A promise for transmitting and using electricity with near perfect efficiency and much higher capacity, besides all this it also has a wide range of application like MRI scanning, maglev trains etc. This seminars shall discuss on the concepts of superconductivity, its classifications, its various properties and its applications.

ËœWe have completed the first electrical century ushered in by Thomas Edison . We are now entering a second electrical century, ushered in by High Temperature Superconductivity.â„¢.
Automatic Solar Tracker
Automatic Solar Tracker

Introduction
A new control scheme for a single “ phase diode clamped rectifier is proposed to achieve a unity power factor, balanced neutral point voltage and constant DC-bus voltage. Four power switches are used in the rectifier to generate a three-level PWM wave form on the rectifier terminal voltage.

The line current command is derived from a DC-link voltage regulator and an output power estimator. The hysteresis current Controller is used to track the line current command. To balance the neutral-point voltage, a capacitor voltage compensator is employed. The main advantages of using a three-level instead of a two-level PWM scheme are that the blocking voltage of each power switch is clamped to half the DC-bus voltage (if the off “state resistance of power switches is equal),and the voltage harmonic on the AC side of rectifier is reduced.

A novel single phase neutral point diode clamped rectifier has been proposed to achieve high power factor, low current distortion, low peak factor, and stable capacitor voltages. The proposed rectifier can be controlled to operate in two- or-three “ level PWM.

Based on the model analysis, the switching signals of the power switches can be derived from the measured line current error and the mains voltage. Experimental results show a good line current waveform with almost unity power factor and low current harmonics to meet the requirements of IEC 1000-3-2 class A. The transient response due to load change is about one cycle and voltage drop is about 5V. According to measured results the proposed rectifier has the properties of high power factor, low current distortion and fast dynamic response, based on the proposed control algorithm.
PEconomical Alternative, For CTS And PTS
Economical Alternative, For CTS And PTS

Introduction
With the increasing demand for electric power, the economics of power transmission requires the use of high transmission line voltages. This leads to escalation of cost for conventional CTs and PTs.This paper provides an economical alternative, for the use of CTs and PTs for the measurement of current and voltage. The method is an optical method using lasers. The method employs two types of devices; free path and enclosed path devices.

The basic principle of the optical method is based upon magneto-optic effect, electro optic effect and the electro gyration effect.This paper concludes with the suggestion for future development. Instead of using free path, the enclosed path method is suggested. A more highly developed version of the devices should provide a convenient, portable, large bandwidth, research tool for diagnostic use. Eventual development could lead to an acceptable instrument for long-term operational use on the power system. Such an instrument would offer the advantages of considerably improved performance over conventional devices, at much lower cost..
Reply
02-15-2009, 04:52 PM,
#2
Tongue  Some Electrical Seminar Abstracts
Ultra Sonic Motor

Introduction
ULTRA SONIC motor is a newly developed motor, and it has excellent performance and many useful features, e.g.: high-torque density, low speed, compactness in size, no electromagnetic interferences, and so on. USM is a kind of piezo motor. The proposed speed control scheme is assumed for these applications because they require quick and precise speed control of actuators for various load conditions. A speed control method of USM using adaptive control is proposed.

Artificial Neural Network (ANN), which follows the biological neural cells in brain, consists of a number of neurons and weighted links, and it has a good potential for control applications because it can approximate the non-linear input-output mapping of the plant. Accordingly, ANN has been applied widely in the field of power electronics control. In this paper a three layer neural network for speed controller is adopted, and the weights of the links are updated using the general back propagation in order to reduce the speed error at each sampling period. In general, the speed of USM can be controlled by driving frequency, applied voltage, and phase difference of applied voltages. This paper adopts the driving frequency as control input in order to simplify the drive system.
Automated Distribution System
Automated Distribution System

Introduction
Electric power utilities throughout the world are undergoing considerable change in structure, operation, and regulation. One of the major effects of this change is increased importance of distribution automation. With improved Distribution Automation (DA), both the reliability and the efficiency of electric power distribution can be increased. Communication system is essential to performance of automated distribution systems.

It is necessary to perform reliability assessments of communication facilities in carrying out the control functions. The paper describes an approach for reliability evaluation of the communication and control. This approach is based on the event tree methodology, and by using it sensitivity studies are performed to predict impact of communication system. It indicates that the reliable communication system is essential to the secure and reliable operation of automation system. The improvements in communication reliability can have a significant impact on the control function performance.

The results of the studies are discussed and the importance of the communication system on the reliable automation performance is demonstrated in the paper.
Fault Locating In Undegrounded And High Resistance GroundedSystems
Fault Locating In Undegrounded And High Resistance GroundedSystems

Introduction
One of the most common and difficult problems to solve in industrial power systems is the location and elimination of ground fault. Ground faults that occur in ungrounded and high resistance grounded systems do not draw enough current to trigger circuit breaker or fuse operation, making them difficult to localize.

Techniques currently used to track down faults are time consuming and cumbersome. A new approach developed for ground fault localization on ungrounded and high resistance grounded low voltage systems is described. The system consists of a novel ground fault relay that operates in conjunction with low cost indicators permanently mounted in the circuit.

The remote fault relay employs digital signal processing to detect the fault, identify the faulted phase and measure the electrical distance of the fault from the substation. The remote fault indicators are used to visually indicate where the fault is located. The resulting system provides a fast, easy, economical and safe detection system for ground fault localization.
Distribution System Relaying
Distribution System Relaying

Introduction
With the increasing loads, voltages and short-circuit duty of distribution substation feeders, distribution over current protection has become more important today than it was even 10 years ago.

The ability of the protective equipment to minimize damage when failures do occur and also to minimize service interruption time is demanded not only for economic reasons but also because the general public just expects reliable service. This publication will attempt to review some of the present distribution practices, particularly with regard to relaying, in view of some of these new developments.

It is not the purpose of this publication to settle the controversy surrounding some of the problems dealt with, but rather to give the reader a better understanding of distribution over current protection problems and some of the methods being used to solve them. Among the areas covered will be such things as: cold-load pickup, ground-fault detection, tripping methods, current-transformer (CT) connections, line burn down, and coordination between various devices. This seminar is based on distribution system over current protection. The areas includes cold load pick up, ground fault detection, tripping methods, current transformer connections, line burn down and co-ordination between various devices. In this article use of over current relays & their operations are included. Both due to economic reason and reliability service this seminar will attempt to review sum of the present distribution systems, over current protection problems and some of the methods used to solve them.
Solar Power Generation
Solar Power Generation

Introduction
Solar power generation is rapidly finding a prominence as a major part of power in the modern world. There are various problems associated with the tapping of Sunâ„¢s energy, such as movement of Sun. Researches has been going on to find new and efficient method to harness the solar power.

Commonly the solar panel is placed above the Earthâ„¢s surface facing the sun tilted at an angle of 450.But there is a problem, we can get maximum output from the panel only when the Sun comes perpendicular to the face of the panel. In late morning or afternoon, we cannot get maximum output from the panel. Thus for maximum utilization of the Sun through out the day, the panel must be kept perpendicular to the sun. This is possible only by tracking the sun In this paper, I will be dealing with Some aspects of solar power generation technique An Automatic Solar Tracking System.
Solar Hybrid PVT Systems
Solar Hybrid PVT Systems

Introduction
The tending extinction of fossil fuels has already created an awareness to look for alternative sources of energy of which solar is most promising in a topical country like ours , where it is available in abundance .

The efforts are being made to utilize solar energy in building sector to fulfill the thermal as well as electrical requirements. Various thermal systems have being developed and commercialized for space and water heating . Work is being done on projects to generate electricity through photovoltaic convert ion. The efficiency of the photovoltaic conversion is inversely proportional to the temperature.

When the temperature rises, there are occasions when the PV conversion is very adversely affected leading to the system failure. The basic idea in the development of hybrid panel is to utilize the radiations not used for photovoltaic conversion, directly for thermal purposes and all radiations falling on the photovoltaic cell, which are partially used for PV conversion and the remaining heats up the cells. A suitable heat exchanger has been designed & attached to the photovoltaic panel to extract the heat from hybrid panel to give

1. Hot water for use in buildings
2. Increased PV efficiency.

This paper deals with the results obtained from glass to glass-laminated ONGC type PV module and the initial performance evaluation test of modified module along with its instrumentation.
Conditional Monitoring
Conditional Monitoring

Introduction
Transformers are a large part of the component structure of the electricity system. Knowing the condition is essential to meeting the goals of maximizing return on investment and lowering total cost associated with transformer operation.

In order to reconcile both decreasing maintenance spending and reliable service, condition based maintenance (CBM) is often proposed. The successful application of CBM lies in obtaining information transformers, so that, on the one hand, a critical condition will be noted early enough to take measures and on the other hand, so that only minimal maintenance is being applied to transformers still in good condition.

The paper covers the following areas.
¢ General aspects of aging in transformers.
¢ An overview of condition monitoring methodology with partial discharge patterns in focus.
¢ Partial discharge measurement and diagnostics on power transformer using a multi channel digital PD detector.
Optimum VAR Control
Optimum VAR Control

Introduction
A complex method for the optimum VAR control of radial primary power distribution networks dealing with the proper selection and installation of shunt capacitors is developed here. The problem is examined both on an annual and a long-term basis.

First objective functions and relative algorithms, which determine the kind, the size, the minimum numbers the locations and the adjustments of the possibly installed standard capacitors are developed. Then all these are embodied in a complex software package, which examines all the technically acceptable VAR control solutions.

It compares them economically and finally proposes the more profitable.In this, a complex method for the optimum VAR control of a radial primary distribution network with capacitors is developed. The problem is examined both for constant and growing annual peak load buy developing relative software packages. Realistic data of the examined networks such as lateral branches, conductor sizes, load distribution and variation are taken into account. The target in every case is the determination of the kind, size, minimum number, location and possible adjustments of standard capacitors which effect the techno economically var control. This is achieved by utilizing previous considerable methods dealing with the examined problem which however are adapted to new objective functions and they are modified so as to over come their weaknesses and to optimize the necessary computing time..
The Global Voltage Regulation
The Global Voltage Regulation

Introduction
Based on closed form expressions for the power frequency voltages and currents in a typical distribution network, the voltage regulation VR at any time point during the day could be evaluated. It will depend primarily on the network configuration, the daily load curve, the load density and its power factor as well as level of the reactive power compensation.

The computed at a certain timeËœtâ„¢ can give a useful indicator for the voltage constancy over the network at that time point. The concept of ËœGlobal Voltage Regulationâ„¢ is introduced. The GVR is defined as the root mean square value of the voltage regulation over the daytime as Ëœtâ„¢ varies from 0 to 24 h. Accordingly , it takes into account the effect of both the geometrical dimensions of the distribution network and the daily temporal variation of the voltage regulation .

The theoretical value GVR =0 corresponds to the ideal case in which the voltage is constant at all nodes ,all the time. Hence GVR can be considered as a representative figure of merit describing the supply quality regarding the voltage values prevailing at the different network nodes, allover the day. The paper also addresses the identification of the optimal level of reactive power compensation (K) that will lead to the least possible GVR. Moreover the impact of both the network and load parameters on the optimal value of ËœKâ„¢ is investigated..
Synchronous Voltage Source
Synchronous Voltage Source

Introduction
The synchronous voltage source is implemented by a multi-pulse inverter using gate turnoff (GTO) thyristors . It is capable of generating internally the reactive power necessary for network compensation, and is also able to interface with an appropriate energy storage device to negotiate real power exchange with the ac system. The paper develops a of power flow control using solid - state synchronous voltage sources for shunt compensation, series compensation , and phase angle control .

It also describes the unified powerflow controller that is able to control concurrently or selectively all three network parameters(voltage, impedance, angle) determining power transmission. compensation method of employing thyristor switched capacitors and reactors shows its superior performance, uniform applicability, smaller physical size, and lower overall cost. There are clear indications that solid-state synchronous voltage sources represent the next technology for ac transmission system compensation and power flow control.

This technology offers operating features, functional performance, and application flexibility unattainable by the presently used circuit arrangements. The synchronous voltage source can be considered an ideal 60 Hz generator that has no inertia and produces an almost sinusoidal output voltage with independently variable amplitude and phase angle, thus facilitating rapid, decoupled controls for reactive and real power exchange. It can be used uniformly to control transmission line voltage, impedance, and angle by providing reactive shunt compensation, series compensation, and phase-shifting.
Gas Insulated Substations
Gas Insulated Substations

Introduction
SF6 Gas insulated Substations (GIS) are preferred for voltage ratings of 72.5KV, 145KV, 245KV, 420KV and above. In such a situation, the various equipments like circuit breakers, busbars, isolators, and load break switches; current transformers, voltage transformers, earthing switches etc. are housed in metal enclosed modules filled with SF6 gas.

The SF6 gas provides the phase to ground insulation. As the dielectric strength of SF6 gas is higher than the air, the clearances required are smaller. Hence, the overall size of each equipment and the complete substation is reduced to about 10% of conventional air “ insulated substations. As a rule GIS are installed indoor. However outdoor GIS have also been installed earlier.

The various modules of GIS are factory assembled and are filled with SF6 gas at a pressure of about 3 Kg/ cm2. Thereafter they are taken to site for final assembly. Such substations are compact and can be installed conveniently on any floor of a multi - storied building or in an underground substation.As the units are factory assembled, the installation time is substantially reduced. Such installation are preferred in cosmopolitan cities, industrial townships, etc. where cost of land is very high and higher cost of SF6 insulated switch gear (GIS) is justified by saving due to reduction in floor area requirement. They are also preferred in heavily polluted areas where dust, chemical fumes and salt layers can cause frequent flashovers in conventional outdoor air-insulated substations. The GIS has monitoring system.

The gas density in each compartment is monitored. If pressured drops slightly, the gas is automatically tapped up. With further gas leakage, the low-pressure alarm is sounded or automatic tripping or lock out occurs. By this method we can save the space required for the substation to build up. This means that gas-insulated substation can be built in any metropolitan city. Many experiments are going on the use of SF6 gas
Superconductivity
Superconductivity

Introduction
SUPERCONDUCTIVITY is the ability of certain materials to conduct electric current with no resistance and extremely low losses. This ability to carry large amounts of currents can be applied to electric power devices such as motors and generators and to electricity transmission in power lines.

For example, superconductors can carry as much as 100 times the electricity ordinary copper or aluminium wires of same size.Scientists had been intrigued with the concept of superconductivity since its discovery in the early 1900â„¢s, but the extreme low temperature the phenomenon required was a barrier to practical and low cost application.

This all changed in 1986 when a new class of ceramic super conductors were discovered that ËœSUPERCONDUCTEDâ„¢ at higher temperatures. The science of high temperature superconductivity (HTS) was born, and along with it came the prospect for an elegant technology that promises to Ëœsuperchargeâ„¢ the way energy is generated, delivered and used.At the heart of high temperature superconductivity lies a promise for the near future.

A promise for transmitting and using electricity with near perfect efficiency and much higher capacity, besides all this it also has a wide range of application like MRI scanning, maglev trains etc. This seminar shall discuss on the concepts of superconductivity, its classifications, its various properties and its applications.

ËœWe have completed the first electrical century ushered in by Thomas Edison . We are now entering a second electrical century, ushered in by High Temperature Superconductivity.â„¢.
Automatic Solar Tracker
Automatic Solar Tracker

Introduction
A new control scheme for a single “ phase diode clamped rectifier is proposed to achieve a unity power factor, balanced neutral point voltage and constant DC-bus voltage. Four power switches are used in the rectifier to generate a three-level PWM wave form on the rectifier terminal voltage.

The line current command is derived from a DC-link voltage regulator and an output power estimator. The hysteresis current Controller is used to track the line current command. To balance the neutral-point voltage, a capacitor voltage compensator is employed. The main advantages of using a three-level instead of a two-level PWM scheme are that the blocking voltage of each power switch is clamped to half the DC-bus voltage (if the off “state resistance of power switches is equal),and the voltage harmonic on the AC side of rectifier is reduced.

A novel single phase neutral point diode clamped rectifier has been proposed to achieve high power factor, low current distortion, low peak factor, and stable capacitor voltages. The proposed rectifier can be controlled to operate in two- or-three “ level PWM.

Based on the model analysis, the switching signals of the power switches can be derived from the measured line current error and the mains voltage. Experimental results show a good line current waveform with almost unity power factor and low current harmonics to meet the requirements of IEC 1000-3-2 class A. The transient response due to load change is about one cycle and voltage drop is about 5V. According to measured results the proposed rectifier has the properties of high power factor, low current distortion and fast dynamic response, based on the proposed control algorithm.
PEconomical Alternative, For CTS And PTS
Economical Alternative, For CTS And PTS

Introduction
With the increasing demand for electric power, the economics of power transmission requires the use of high transmission line voltages. This leads to escalation of cost for conventional CTs and PTs.This paper provides an economical alternative, for the use of CTs and PTs for the measurement of current and voltage. The method is an optical method using lasers. The method employs two types of devices; free path and enclosed path devices.

The basic principle of the optical method is based upon magneto-optic effect, electro optic effect and the electro gyration effect.This paper concludes with the suggestion for future development. Instead of using free path, the enclosed path method is suggested. A more highly developed version of the devices should provide a convenient, portable, large bandwidth, research tool for diagnostic use. Eventual development could lead to an acceptable instrument for long-term operational use on the power system. Such an instrument would offer the advantages of considerably improved performance over conventional devices, at much lower cost..
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