LIGHTNING PHENOMENA IN HIGH VOLTAGE ENGINEERING

An electric discharge between cloud and earth, between clouds or between the charge centers of the same cloud is known as lightning.

  • Lightning is a huge spark and takes place when clouds are charged to such a high potential (+ve or -ve) with respect to earth or a neighboring cloud that the dielectric strength of neighboring medium (air) is destroyed. 

  • There are several theories which exist to explain how the clouds acquire charge. The most accepted one is that during the up rush of warm moist air from earth, the friction between the air and the tiny particles of water causes the building up of charges.

  • When drops of water are formed, the larger drops become positively charged and the smaller drops become negatively charged. 

  • When the drops of water accumulate, they form clouds, and hence cloud may possess either a positive or a negative charge, depending upon the charge of drops of water they contain. 

  • The charge on a cloud may become so great that it may discharge to another cloud or to earth and we call this discharge as lightning. The thunder which accompanies lightning is due to the fact that lightning suddenly heats up the air, thereby causing it to expand. 


  • The surrounding air pushes the expanded air back and forth causing the wave motion of air which we recognize as thunder.

MECHANISM OF LIGHTNING DISCHARGE:
  • When a charged cloud passes over the earth, it induces equal and opposite charge on the earth below. Figure shows a negatively charged cloud inducing a positive charge on the earth below it. 
  • As the charge acquired by the cloud increases, the potential between cloud and earth increases and, therefore, gradient in the air increases. 
  • When the potential gradient is sufficient (5 kV/cm to 10 kv/cm) to break down the surrounding air, the lightning stroke starts. 
  • The stroke mechanism is as under:(i) As soon as the air near the cloud breaks down, a streamer called leader streamer or pilot streamer starts from the cloud towards the earth and carries charge with it as shown in Figure. 
  •  The leader streamer will continue its journey towards earth as long as the cloud, from which it originates, feeds enough charge to it to maintain gradient at the tip of leader streamer above the strength of air. 
  •  If this gradient is not maintained, the leader streamer stops and the charge is dissipated without the formation of a complete stroke. 



(ii) In many cases, the leader streamer continues its journey towards earth. As the leader streamer moves towards earth, it is accompanied by points of luminescence which travel in jumps giving rise to stepped leaders.
  • The velocity of stepped leader exceeds one-sixth of that of light and distance traveled in one step is about 50 m. It may be noted that stepped leaders have sufficient luminosity and give rise to first visual phenomenon of discharge.
(iii) The path of leader streamer is a path of ionization and, therefore, of complete breakdown of insulation. 

  • As the leader streamer reaches near the earth, a return streamer shoots up from the earth to the cloud, following the same path as the main channel of the downward leader. 
  • The action can be compared with the closing of a switch between the positive and negative terminals; the downward leader having negative charge and return streamer the positive charge. 
This phenomenon causes a sudden spark which we call lightning. With the resulting neutralization of much of the negative charge on the cloud, any further discharge from the cloud may have to originate from some other portion of it.

The following points may be noted about lightning discharge:

(a) A lightning discharge which usually appears to the eye as a single flash is in reality made up of a number of separate strokes that travel down the same path. The interval between them varies from 09005 to 05 second. Each separate stroke starts as a downward leader from the cloud.

(b) It has been found that 87% of all lightning strokes result from negatively charged clouds and only 13% originate from positively charged clouds.

(c) It has been estimated that throughout the world, there occur about 100 lightning strokes per second.

(d) Lightning discharge may have currents in the range of 10 kA to 90 kA.


Posted by at
Labels: , ,

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)

Labels

PROJECTS 8086 PIN CONFIGURATION 80X86 PROCESSORS TRANSDUCERS 8086 – ARCHITECTURE Hall-Effect Transducers INTEL 8085 OPTICAL MATERIALS BIPOLAR TRANSISTORS INTEL 8255 Optoelectronic Devices Thermistors thevenin's theorem MAXIMUM MODE CONFIGURATION OF 8086 SYSTEM ASSEMBLY LANGUAGE PROGRAMME OF 80X86 PROCESSORS POWER PLANT ENGINEERING PRIME MOVERS 8279 with 8085 MINIMUM MODE CONFIGURATION OF 8086 SYSTEM MISCELLANEOUS DEVICES MODERN ENGINEERING MATERIALS 8085 Processor- Q and A-1 BASIC CONCEPTS OF FLUID MECHANICS OSCILLATORS 8085 Processor- Q and A-2 Features of 8086 PUMPS AND TURBINES 8031/8051 MICROCONTROLLER Chemfet Transducers DIODES FIRST LAW OF THERMODYNAMICS METHOD OF STATEMENTS 8279 with 8086 HIGH VOLTAGE ENGINEERING OVERVOLATGES AND INSULATION COORDINATION Thermocouples 8251A to 8086 ARCHITECTURE OF 8031/8051 Angle-Beam Transducers DATA TRANSFER INSTRUCTIONS IN 8051/8031 INSTRUCTION SET FOR 8051/8031 INTEL 8279 KEYBOARD AND DISPLAY INTERFACES USING 8279 LOGICAL INSTRUCTIONS FOR 8051/8031 Photonic Transducers TECHNOLOGICAL TIPS THREE POINT STARTER 8257 with 8085 ARITHMETIC INSTRUCTIONS IN 8051/8031 LIGHTNING PHENOMENA Photoelectric Detectors Physical Strain Gage Transducers 8259 PROCESSOR APPLICATIONS OF HALL EFFECT BRANCHING INSTRUCTIONS FOR 8051/8031 CPU OF 8031/8051 Capacitive Transducers DECODER Electromagnetic Transducer Hall voltage INTEL 8051 MICROCONTROLLER INTEL 8251A Insulation Resistance Test PINS AND SIGNALS OF 8031/8051 Physical Transducers Resistive Transducer STARTERS Thermocouple Vacuum Gages USART-INTEL 8251A APPLICATIONs OF 8085 MICROPROCESSOR CAPACITANCE Data Transfer Instructions In 8086 Processors EARTH FAULT RELAY ELECTRIC MOTORS ELECTRICAL AND ELECTRONIC INSTRUMENTS ELECTRICAL BREAKDOWN IN GASES FIELD EFFECT TRANSISTOR (FET) INTEL 8257 IONIZATION AND DECAY PROCESSES Inductive Transducers Microprocessor and Microcontroller OVER CURRENT RELAY OVER CURRENT RELAY TESTING METHODS PhotoConductive Detectors PhotoVoltaic Detectors Registers Of 8051/8031 Microcontroller Testing Methods ADC INTERFACE AMPLIFIERS APPLICATIONS OF 8259 EARTH ELECTRODE RESISTANCE MEASUREMENT TESTING METHODS EARTH FAULT RELAY TESTING METHODS Electricity Ferrodynamic Wattmeter Fiber-Optic Transducers IC TESTER IC TESTER part-2 INTERRUPTS Intravascular imaging transducer LIGHTNING ARRESTERS MEASUREMENT SYSTEM Mechanical imaging transducers Mesh Current-2 Millman's Theorem NEGATIVE FEEDBACK Norton's Polarity Test Potentiometric transducers Ratio Test SERIAL DATA COMMUNICATION SFR OF 8051/8031 SOLIDS AND LIQUIDS Speed Control System 8085 Stepper Motor Control System Winding Resistance Test 20 MVA 6-digits 6-digits 7-segment LEDs 7-segment A-to-D A/D ADC ADVANTAGES OF CORONA ALTERNATOR BY POTIER & ASA METHOD ANALOG TO DIGITAL CONVERTER AUXILIARY TRANSFORMER AUXILIARY TRANSFORMER TESTING AUXILIARY TRANSFORMER TESTING METHODS Analog Devices A–D BERNOULLI’S PRINCIPLE BUS BAR BUS BAR TESTING Basic measuring circuits Bernoulli's Equation Bit Manipulation Instruction Buchholz relay test CORONA POWER LOSS CURRENT TRANSFORMER CURRENT TRANSFORMER TESTING Contact resistance test Current to voltage converter DAC INTERFACE DESCRIBE MULTIPLY-EXCITED Digital Storage Oscilloscope Display Driver Circuit E PROMER ELPLUS NT-111 EPROM AND STATIC RAM EXCITED MAGNETIC FIELD Electrical Machines II- Exp NO.1 Energy Meters FACTORS AFFECTING CORONA FLIP FLOPS Fluid Dynamics and Bernoulli's Equation Fluorescence Chemical Transducers Foil Strain Gages HALL EFFECT HIGH VOLTAGE ENGG HV test HYSTERESIS MOTOR Hall co-efficient Hall voltage and Hall Co-efficient High Voltage Insulator Coating Hot-wire anemometer How to Read a Capacitor? IC TESTER part-1 INSTRUMENT TRANSFORMERS Importance of Hall Effect Insulation resistance check Insulator Coating Knee point Test LEDs LEDs Display Driver LEDs Display Driver Circuit LM35 LOGIC CONTROLLER LPT LPT PORT LPT PORT EXPANDER LPT PORT LPT PORT EXTENDER Life Gone? MAGNETIC FIELD MAGNETIC FIELD SYSTEMS METHOD OF STATEMENT FOR TRANSFORMER STABILITY TEST METHODS OF REDUCING CORONA EFFECT MULTIPLY-EXCITED MULTIPLY-EXCITED MAGNETIC FIELD SYSTEMS Mesh Current Mesh Current-1 Moving Iron Instruments Multiplexing Network Theorems Node Voltage Method On-No Load And On Load Condition PLC PORT EXTENDER POTIER & ASA METHOD POWER TRANSFORMER POWER TRANSFORMER TESTING POWER TRANSFORMER TESTING METHODS PROGRAMMABLE LOGIC PROGRAMMABLE LOGIC CONTROLLER Parallel Port EXPANDER Paschen's law Piezoelectric Wave-Propagation Transducers Potential Transformer RADIO INTERFERENCE RECTIFIERS REGULATION OF ALTERNATOR REGULATION OF THREE PHASE ALTERNATOR Read a Capacitor SINGLY-EXCITED SOLIDS AND LIQUIDS Classical gas laws Secondary effects Semiconductor strain gages Speaker Driver Strain Gages Streamer theory Superposition Superposition theorem Swinburne’s Test TMOD TRANSFORMER TESTING METHODS Tape Recorder Three-Phase Wattmeter Transformer Tap Changer Transformer Testing Vector group test Virus Activity Voltage Insulator Coating Voltage To Frequency Converter Voltage to current converter What is analog-to-digital conversion Windows work for Nokia capacitor labels excitation current test magnetic balance voltage to frequency converter wiki electronic frequency converter testing voltage with a multimeter 50 hz voltages voltmeter

Search More Posts

Followers