HVE-UNIT-I T2.pptx unit 2 high voltage age

ppt

1. Version: MAMCET_VP-1.1 M.A.M. COLLEGE OF ENGINEERING AND TECHNOLOGY Siruganur, Tiruchirappalli – 621 105. 21-06-2024 Year & Sem. : IV Year (EEE) – VII Semester Faculty : Mr. J.Nagendran Regulation : R2017 Course Code : EE8701 UNIT : I COURSE NAME EE8701-High Voltage Engineering J.Nagendran , AP/EEE, Department of Electrical and Electronics Engineering, M.A.M. College of Engineering and Technology, Siruganur , Tiruchirappalli – 621 105.

2. GENERAL OBJECTIVE To learn about Mechanism of lightning 21-06-2024 J.Nagendran AP/EEE, Department of Electrical and Electronics Engineering, M.A.M. College of Engineering and Technology, Siruganur , Tiruchirappalli – 621 105.

3. SPECIFIC OBJECTVES Students will be able to Discuss the various theories of charge formation in clouds Explain the mechanism of lightning 21-06-2024 J.Nagendran AP/EEE, Department of Electrical and Electronics Engineering, M.A.M. College of Engineering and Technology, Siruganur , Tiruchirappalli – 621 105.

4. Charge formation in the clouds: During thunderstorms, positive and negative charges become separated by the heavy air currents with ice crystals in the upper part and rain in the lower part of the cloud. this charge separation depends on the height of the clouds which range from 0.2 to 10 k.m with their charge centers probably at a distance of about 0.35 to 2 K.m as shown in fig 21-06-2024 J.Nagendran AP/EEE, Department of Electrical and Electronics Engineering, M.A.M. College of Engineering and Technology, Siruganur , Tiruchirappalli – 621 105.

5. Charge Distribution Theory: J.Nagendran -AP/EEE,M.A.M College of Engineering and Technology Willson’s theory: Willson‘s theory based on the following assumption   Large Number of ions present in the atmosphere. Many of the these ions attach themselves to small dust particles and water particles Electric field exists in the earth atmosphere during fair weather which is directed downwards towards the earth.

6. J.Nagendran -AP/EEE,M.A.M College of Engineering and Technology Simpson’s Theory: Below Region A:   Air current travels above 800Cm/Sec and no rain drops fall through. In Region A: Air velocity is high enough to break the falling rain drops causing a positive charge sprays in the cloud and negative charge in the air. The spray is blown upwards but as the velocity of air decreases, the positively charged water drops recombine with the large drops and fall again. In Region B:   It becomes negatively charged by the air current. In Region C: The temperature is low (below freezing point) and only ice crystals exist. the impact of air on these crystals makes them negatively charged.

7. M echanism of lightning Strokes J.Nagendran -AP/EEE,M.A.M College of Engineering and Technology

8. M echanism of lightning Strokes J.Nagendran -AP/EEE,M.A.M College of Engineering and Technology Type of lightning streamer:   Pilot streamer Stepped Leader Return Stroke Second Charge center Dart leader Heavy return Streamer