Transmission and Distribution 10EE53 a resulting burst of noise. the limiting environmental design factor. State the various properties of an insulator. Give the list of important insulators and make the comparision of pin and suspension type insulators. Dec2015 Succinctly put, corona is a luminous partial discharge due to ionization of the air surrounding a conductor caused by electrical overstress. Many tests show that dry air at normal atmospheric pressure and temperature °C and 76 cm barometric (25 pressure) breaks down at 29.8 kV/cm (maximum, or peak, value) or 21.1 kV/cm (rms, or effective, value). There are always a few free electrons in the air due to ultraviolet radiation from the sun, cosmic rays from outer space, radioactivity of the earth, etc. As the conductor becomes energized on each half cycle of the ac voltage wave, the electrons in the air near its surface are accelerated toward the conductor on its positive half cycle and away from the conductor on its negative half cycle. The velocity attained by a free electron is dependent on the Intensity of the electric field. If the intensity of the electric field exceeds a certain critical value, any free electron in this field will acquire a sufficient velocity and energy to knock one of the outer orbit Page 30
Transmission and Distribution 10EE53 a resulting burst of noise. the limiting environmental design factor. State the various properties of an insulator. Give the list of important insulators and make the comparision of pin and suspension type insulators. Dec2015 Succinctly put, corona is a luminous partial discharge due to ionization of the air surrounding a conductor caused by electrical overstress. Many tests show that dry air at normal atmospheric pressure and temperature (25 °C and 76 cm barometric pressure) breaks down at 29.8 kV/cm (maximum, or peak, value) or 21.1 kV/cm (rms, or effective, value). There are always a few free electrons in the air due to ultraviolet radiation from the sun, cosmic rays from outer space, radioactivity of the earth, etc. As the conductor becomes energized on each half cycle of the ac voltage wave, the electrons in the air near its surface are accelerated toward the conductor on its positive half cycle and away from the conductor on its negative half cycle. The velocity attained by a free electron is dependent on the Intensity of the electric field. If the intensity of the electric field exceeds a certain critical value, any free electron in this field will acquire a sufficient velocity and energy to knock one of the outer orbit Page 30
T-D-QP-SOLUTION.docx