Deepakkumar Yadav
Q. Important Definitions 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 (α) It is number … Read more
Practical Considerations in using Gases for Insulation Purpose Air has great advantage of being low in cost, therefore it found some application at increased pressure in condensers, cables and other insulation constructions. But it does not satisfy the second requirement, since ionization of air is accompanied by emission of ozone, nitrous and nitric oxides causing … Read more
Gases as Insulating Medium Gases used as insulation must satisfy the following basic requirements Gas must be chemically inert and should not react with dielectrics, in combination with which it is used, and with other materials used in the construction of the apparatus. During the ionization of the gas, which to a certain degree is … Read more
Control of Over Voltages due to Switching and Power Frequency (a) Energization of TL in or more steps by inserting resistances and withdrawing them afterwards It is normal practice to have a series resistance with the circuit breaker contacts during switching ON and then but short circuiting this resistance after a few cycles. (b) Eliminating … Read more
Distribution of Switching Surges (EHV and UHV Systems) Switching surges originate when there is sudden release of internal energy stored in the electrostatic form (in the capacitance) or in the electromagnetic form (in the inductance). This can happen in following situations : (i) Current chopping phenomenon : Interruption of magnetizing currents (transformers/reactors re switched … Read more
Working Principle of Timer The on-delay relay timer provides a change to the state of the contacts that are controlled by the energizing of the timer. The on-delay relay timer can be set or programmed to a predetermined time and this is called the preset time. Preset time can be as low as milliseconds to … Read more
Methods of Calculation of Electric Field There are different graphical, experimental and numerical field calculation methods. Special methods like method of images, conformal mapping, co-ordinate transformation are applied to simple geometrical configuration. The experimental measurement of field strength in small air gaps stressed by high voltages is a very difficult process and not quite accurate. … Read more
Fields in Multidielectric, Isotropic Materials Many insulating materials used in high voltage insulation system are formed with different layers of various insulating materials. Different materials have different permittivities. e.g. Bakelite sheets or mica sheets or materials used in transformers. The necessity of using such a material is Different layers are used to control electric stresses. … Read more
Working Principle of DC Generator An electrical generator is a machine which converts mechanical energy (or power) into electrical energy (or power). The energy conversion is based on the principle of the production of dynamically (or motionally) induced e.m.f. As seen from Figure, whenever a conductor cuts magnetic flux, dynamically induced e.m.f. is produced in … Read more
Motor Principle An Electric motor is a machine which converts electric energy into mechanical energy. Its action is based on the principle that when a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force whose direction is given by Fleming’s Left-hand Rule and whose magnitude is given by F = BIl Newton. … Read more