Townsend Current Growth Equation: Referring to Fig. 2.1 shows the Townsend Current Growth Equation. let us assume that n0 electrons are emitted from the cathode. When one electron collides with a neutral particle, a positive ion and an electron are formed. This is called an ionizing collision. Let α be the average number of ionizing collisions made […]
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Ionization Processes: A gas in its normal state is almost a perfect insulator. However, when a high voltage is applied between the two electrodes immersed in a gaseous medium, the gas becomes a conductor and an electrical breakdown occurs.The processes that are primarily responsible for the breakdown of a gas are ionization by collision, photo-ionization,
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Collision Process in Gases: An electrical discharge is normally created from unionised gas by Collision Process in Gases. These processes are mainly gas processes which occur due to the collision between the charged particles and gas atoms or molecules. These are of the following two types. Elastic collisions: Elastic collisions are collisions which when occur,
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Surge Voltage and its Distribution and Control: The design of power apparatus particularly at high voltages is governed by their transient behavior. The transient high voltages or surge voltages originate in power systems due to lightning and switching operations. The effect of the surge voltage is severe in all power apparatuses. The response of a
Advantages and Disadvantages of Various Numerical Methods: For computing the electric fields, various methods have been used, viz. Finite Difference Method, Finite Element Method, Charge Simulation Method and Boundary Element Method. Each of these methods has its own advantages for solving a particular problem. With the FDM, the numerical evaluation of the difference equation is
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Boundary Element Method (BEM) in Electric Field: Though the charge simulation method is known for its accuracy and speed, it is not very efficient in case of multi-dielectric problems and very thin electrodes, which are often used to control and get the electric field strength in condenser bushings, transformers, etc. Such problems can be solved
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Charge Simulation Method for Electric Field: Charge Simulation Method (CSM) belongs to the family of integral methods for calculation of electric fields. There are two variations of this method: CSM with discrete charges and CSM with area charges. Charge Simulation Method with discrete charges is based on the principle that the real surface charges on
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Electric Field Equation: Electric Field Equation – 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 permittivities and/or conductivities. Proper
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Electric Stress Control: The Electric Stress Control distribution is usually governed by the Poisson’s equation: where φ is the potential at a given point, ρ is the space charge density in the region, and ε0 is the electric permittivity of free space (vacuum). However, in most of the high voltage apparatus, space charges are not normally
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Solid Dielectric Materials and Composites Materials: A good solid dielectric should have some of the properties mentioned earlier for gases and liquids and it should also possess good mechanical and bonding strengths. Many organic and inorganic materials are used for high voltage insulation purposes. Widely used inorganic materials are ceramics and glass. The most widely
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