Deepakkumar Yadav
Factors on Which Breakdown Voltage (BDV) Depends The Breakdown voltage depends on the : Field Gap separation Cathode work function Temperature of cathode Liquid viscosity The liquid temperature The density and Molecular structure of the liquid Typical breakdown system of some liquids are : Hexane 1.1 – 1.3 (MV/cm) Benzene 1.1 (MV/cm) Transformer oil 1.0 … Read more
Conduction and Breakdown in Pure Liquids : When the fields are high (> 100 kV cm ) the current not only increase rapidly. but also undergo violent fluctuations which will die down after some time. Figure A. This is the condition nearer to breakdown. However if this figure is redrawn starting from very small currents, … Read more
Breakdown in Pure and Commercial Liquids Q. Explain the phenomenon of ‘ tracking in solid insulating materials under electrical stress. How it can be minimized. Pure Liquids Liquids which are chemically pure, structurally simple and do not contain any impurity even in traces of 1 in 109, are known as pure liquids. E.g. n-hexane (C4H14). … Read more
Vacuum Breakdown Theories Particle Exchange Mechanism Field Emission Mechanism Clump Theory 1. Particle Exchange Mechanism (PEM) Figure A Assumption : Under the action of the high electric field a charge particle would be emitted from one electrode, and when this charge particle impinge on the other electrode, it liberates oppositely charged particles due ionization of … Read more
Breakdown In Vacuum Q. What is Vacuum ? The vacuum system is used to create and maintain pressure much below the atmospheric pressure. In vacuum system the pressure is always measured in terms of mm of Hg where standards atmosphere is equal to 760 mm of Hg at temperature of 0o C. mm of Hg = … Read more
Comparison between Townsend’s Theory and Streamer’s Theory Sr. No. Townsend’s Theory Streamer’s Theory 1. Theory states, current growth occurs as a result of ionization processes only. Theory states, breakdown voltages were bound to depend on gas pressure and geometry of the gap. 2. This mechanism predicts a very diffused form of discharge. This mechanism predicts … Read more
Principle of Streamers Theory With positive polarity of the point Figure A (a) an electron formed in the gap, while moving towards the point, falls in the region of strong field, starts ionizing and forms an electron avalanche. If voltage between the electrodes increases slowly upto the time of formation of the corona (i.e. fulfilment … Read more
Streamer Theory or Kanal Theory Q. Explain the streamer theory of breakdown in air at atmospheric pressure. A narrow river of conducting particles. Stage when secondary avalanche (due to positive ions) has crossed. Streamer has crossed 1/2 the gap length. Gap has been bridged by a conducting channel i.e. Streamer. Figure A Figure B The … Read more
Comparison between Positive Corona and Negative Corona Sr. No. Positive Corona Negative Corona 1. Nature of discharge : With positive electrode corona discharge is in the form of uniform sheath all over the conductor surface. With negative electrode, corona discharge is spotty or filamentary all over the conductor surface. 2. It appears smaller than negative corona. It … Read more
Comparison Between Uniform Field and Non-uniform Field Sr. No. Point of comparison Uniform Field Non-uniform Field 1. Definition When electric field intensity is same everywhere in a gap and both electrode surfaces then it is known as uniform field. When electric field intensity is different everywhere in the gap and also on electrode surfaces it is known … Read more