Townsend’s Criterion for Breakdown Equation I = I0 ead / I – γ (ead – 1) gives the total average current in a gap before the occurrence of breakdown. As distance between electrodes d is increased, the denominator of the equation tends to zero, and at some critical distance d = ds 1 – γ (exp (αd) – 1) = … Read more

Various Factors Influencing the Breakdown In Gases Q. Discuss the various factors which affects the breakdown of gases. Distance between electrode Shape of electrode Size of electrode Material of electrode Material in the gap  Temperature Pressure Applied voltage Polarity of the small electrode Humidity Dust Irradiation Nearby earthed objects Miscellaneous 1. Distance between Electrodes If … Read more

Townsend’s Current Growth Equation  At any distance x, let number of electrons be nx. Since current is the rate of flow of electrons, so we will start with the electron equation. dnx = nx.α. dx/ where, α = Townsends first ionization coefficient which represents the number of electrons liberated by a free electron due to its … Read more

Important Definitions about Ionization Q. Define Townsend’s first and second Ionization constant. How the condition for breakdown is obtained in a Townsend’s discharge ? Primary Ionization It is the process of liberation of free electrons from gas molecules with simultaneous production of positive ions due to collision with free electrons. Townsend’s Primary Ionization coefficient It … Read more

Types of Ionization Q. Explain the terms Ionization  and hence explain different ionization processes with reference to breakdown in gases ? Ionization by collision Photo ionization Secondary Ionization process Electron decay and attachment process 1. Ionization by Collision : The process of liberating an electron from a gas molecule with the simultaneous production of a … Read more

Numerical Methods of Calculation of Electric field There are numerous to solve partial differential equation having Laplace and Poisson equation but there are many difficulties in solving these equations for 2D and 3D fields with complex boundary conditions or for insulating material with different permittivities and conductivities. There are 3 types of numerical methods commonly … Read more

Power Frequency Over Voltages in Power Systems Following are some of the reasons for power frequency over voltages : Disconnection of inductive loads or connection of capacitive loads Ferranti effect Sudden loss of loads Saturation in transformers Unsymmetrical faults etc.

Estimation of Electric Field in Some Geometric Boundaries In a uniform field gap, the average field E is the same throughout the field region whereas in non-uniform field gap, E is different at different points of field region. Uniform field distribution is present between 2 spheres of equal diameter when the gap distance is less … Read more

Charge Simulation Method of calculation of Electric Field Q. Describe in brief the charge simulation method for estimation of Electric Field Intensity. It describes the surface charge present at the boundary of an electrode by fictitious , discrete charges in the interior of the electrode. Point, line or ring type charges are possible depending upon … Read more