Chapter 01- High Voltage Engineering Introduction
9 likes8,833 views
This document discusses the history and development of high voltage engineering. It begins with early experiments with static electricity by ancient Greeks. Key figures who contributed include Franklin, Faraday, Tesla, and Edison. Faraday's law established that a magnetic field can induce current in a wire. Advances allowed longer distance power transmission. Challenges included developing high voltage insulation. Numerical methods like finite element analysis are now used to model electric field distributions in complex high voltage components.
Chapter 01- High Voltage Engineering Introduction
- 1. High voltage Engineering Dated : 25-10-2017
- 2. • During power blackouts we realise our dependence on the power system and high voltage in particular. How did it happen that we became so dependent upon electricity something that is actually invisible. • The natural phenomena were there, just waiting to be tamed by geniuses of the kind of Michael Faraday, the Father of Electricity. In this process each inventor or scientist built on the work of others.
- 3. • It all started in ancient Greece. The Greek philosopher Thales of Miletus in 600 B.C described the phenomenon of static electricity which was already known to the Greeks. • The Dutchman Pieter van Musschenbroek invented the Leyden jar, the first electrical capacitor, in 1745. Shortly afterwards, William Watson proved, using a Leyden jar, that a discharge of static electricity is actually an electric current.
- 4. • In June 1752 Benjamin Franklin, the American statesman, performed his famous dangerous kite experiment during a thunder storm and showed that lightning is associated with the flow of a large electric current. • The research of two Italians, Luigi Galvani (1737 – 1798) and Alessandro Volta (1745 – 1827) on the interaction between metal electrodes and a chemical electrolyte was the forerunner of the electric battery. It was however not Chemistry that would furnish the main source of electricity, but Physics.
- 5. • Faraday was born in 1791 near London as the son of a poor blacksmith and received only a few years’ formal education. Only 13 years old, he started to work at a bookbinder’s shop in London. • He started experimenting with electricity and may rightly be regarded as the inventor of the main principles that form the basis of the generation, transmission and utilization of electricity: the generator, the transformer and the electric motor.
- 6. • His major contribution was Faraday’s Law, which states that, when a piece of copper wire moves past a magnetic pole, the electrons in the wire tend to move. The amazing fact is that this principle is still responsible for the generation of the bulk of the electric power being generated today. • In power stations, other forms of energy, such as that in fossil fuel, nuclear fuel, hydraulic head or wind, are first converted into mechanical energy and then into three-phase electrical energy when the magnetic field of the rotor “cuts” the copper phase conductors.
- 7. • The main advantage of electrical power is the ease whereby it can be transmitted over long distances to remote parts of a country. • Thomas Alva Edison (1847 – 1931) patented, after extensive research, the first incandescent light bulb and initiated the construction of the first power station in Pearl Street, New York, including a network that supplied 110 volts DC to 59 clients.
- 8. • During a span of a few years similar power networks were established in the major cities of America, Britain, Europe and even in remote parts of the world, such as Kimberley in South Africa where electric street lights were switched on at the diamond mines on 1 September 1882 – three days before the commissioning of the Pearl Street Power Station in New York.
- 9. • It was soon realised that a low voltage power lines such as those run by Edison are limited in their length due to voltage drop constraints. • Nikola Tesla (1856 – 1943) conceived the concept of alternating current in 1886, together with the concept of using transformers to step up the voltage, causing a proportional reduction in current. • The use of higher voltages therefore permitted the construction of longer lines to supply power to remote areas. The use of the higher voltages, however, uncovered the problems associated with high voltage insulation.
- 10. • An impolite campaign raged in the late 1880’s between Tesla and Edison, the so-called “War of the Currents”. Edison, a protagonist of direct current, initiated a business-driven smear campaign against Tesla. Edison stated that alternating current was only useful for the electric chair and he went so far as to attend various executions1. • Recent research indicates that Edison might have had a point as 50 or 60 Hz alternating current apparently more readily induces ventricular fibrillation than direct current. Direct current is however also dangerous and the advantages of alternating current ensured Tesla’s victory.
- 11. • Ironically, with the advent of high voltage power electronics devices, direct current has made a comeback. Long high voltage direct current (HVDC) lines are used, even for inter- continental power transmission. • The continued efforts of electrical power engineers during the past century in various countries of the world resulted in the development of sophisticated and surprisingly reliable power grids, considering the size of the networks and the severity of the environmental conditions.
- 12. Need for Generating High Voltages in Laboratory 1. High ac voltage of one million volts or even more are required for testing power apparatus rated for extra high transmission voltages (400KV system and above). 2. High impulse voltages are required testing purposes to simulate over voltages that occur in power systems due to lighting or switching surges. 3. Main concern of high voltages is for the insulation testing of various components in power system for different types of voltages namely power frequency, ac high frequency, switching or lightning impulses.
- 13. Applications of High Voltages 1. High voltages are applied in laboratories in nuclear research, in particle accelerators and Van de Graff generators. 2. Voltages up to 100KV are used in electrostatic precipitators. 3. X-Ray equipment for medical and industrial application also uses high voltages.
- 14. Electric Field Stresses Dated : 25-10-2017
- 15. Electric Field • It is essential for high voltage engineers to have a knowledge of the field intensities in various media under electric stresses. • It also helps in choosing proper electrode configurations and economical dimensioning of the insulation, such that highly stressed regions are not formed and reliable operation of the equipment results in its anticipated life.
- 16. Electric Field • The field intensity E at any location in an electrostatic field is the ratio of the force on an infinitely small charge at that location to the charge itself as the charge decreases to zero.
- 17. Electric Field • The force F on any charge q at that point in the field is given by F = q E • The electric flux density D associated with the field intensity E is D = 𝜀 E • where 𝜀 is the permittivity of the medium in which the electric field exists.
- 18. Electric Field • The work done on a charge when moved in an electric field is defined as the potential. The potential 𝜑 is equal to 𝜑 = − 𝐸 𝑑𝑙 𝑙 • where l is the path through which the charge is moved.
- 19. ELECTRIC FIELD STRESSES • Like in mechanical designs where the criterion for design depends on the mechanical strength of the materials and the stresses that are generated during their operation, in high voltage applications, the dielectric strength of insulating materials and the electric field stresses developed in them when subjected to high voltages are the important factors in high voltage systems.
- 20. ELECTRIC FIELD STRESSES • In a high voltage apparatus, the important materials used are conductors and insulators. While the conductors carry the current, the insulators prevent the flow of currents in undesired paths. • As already mentioned, the most important material used in a high voltage apparatus is the insulation. The dielectric strength of an insulating material can be defined as the maximum dielectric stress which the material can withstand.
- 21. ELECTRIC FIELD STRESSES • The electric breakdown strength of insulating materials depends on a variety of parameters, such as pressure, temperature, humidity, field configurations, nature of applied voltage, imperfections in dielectric materials, material of electrodes, and surface conditions of electrodes.
- 22. ELECTRIC FIELD STRESSES • An understanding of the failure of the insulation will be possible by the study of the possible mechanisms by which the failure can occur. • The most common cause of insulation failure is the presence of discharges either within the voids in the insulation or over the surface of the insulation. • The probability of failure will be greatly reduced if such discharges could be eliminated at the normal working voltage. Then, failure can occur as a result of thermal or electrochemical deterioration of the insulation.
- 23. Uniform and Non Uniform Electric Fields Dated : 21-11-2017
- 24. • In general, electric field between any two electrodes can be either uniform and uniform. • In a uniform field gap, the average field E is the same throughout the field region, whereas in a non uniform field gap, E is different at different points of the field region. • Uniform or approximately uniform field distributions exist between two infinite parallel plates or two spheres of equal diameter when the gap distance is less than the diameter of the sphere.
- 25. • Spherical electrodes are frequently used for high voltage measurements for triggering in impulse voltage generation circuits. • Sometimes, parallel plates of finite size are used to simulate uniform electric fields, when gap separation is much smaller than plate size. • Most of the practical high voltage components used in electric power systems normally have non uniform field distribution.
- 26. NUMERICAL METHODS FOR ELECTRIC FIELD COPUTATION Dated : 21-11-2017
- 27. • In recent years, several numerical methods for solving partial differential equations which include Laplace's and Poisson’s equations have become available. • There are inherent difficulties in solving these equations for two or three dimensional fields with complex boundary conditions, or for insulating materials with different permittivity and or conductivities. • Proper design of any high voltage apparatus requires a complete knowledge of the electric fields distribution.
- 28. • For a simple physical system with some symmetry, it is possible to find an analytical solution. However, in many cases, the physical systems are very complex and therefore in such cases, numerical methods are employed for the calculation of electric fields. • Essentially three types of numerical methods are commonly employed in high voltage engineering applications. They are: • Finite Element Method (FEM) • Charge Simulation Method (CSM) • Surface charge Simulation Method (SCSM)
- 29. FINITE ELEMENT ANALYSIS SOFTWARE COMSOL MULTIPHYSICS Dated : 21-11-2017
- 30. Figure 2: Zinc-Oxide surge arrester structure.Figure 1:Paper-resin capacitor bushing structure
- 31. Figure 3: 2D Surge Arrester model.
- 32. Figure 4: 2D axial-symmetric surge arrester bushing (a) model geometry and (b) with meshing.
- 33. Figure 5: Surge arrester bushing model geometry with boundaries for calculation of (a) electric field distribution and (b) temperature distribution
- 34. Figure 6: Simulation of electric field distribution in surge arrester bushing model (a) with metallic interfaces and using the FEA software.
- 35. Figure 7: Simulation of electric field distribution in surge arrester bushing model (b) without metallic interfaces and using the FEA software.
- 36. Thank You… Dated : 21-10-2017