17-12-2012, 12:07 PM
A SUMMER TRAINING PRESENTATION ON INSULATORS FROM BHEL JAGDISHPUR(SULTANPUR)
1A SUMMER TRAINING.pptx (Size: 186.05 KB / Downloads: 81)
INSULATOR
A perfect insulator is a material that does not respond to electric field and resist the flow of electric charge through it.
Perfect insulator do not exist.
Dielectric material with high dielectric constant are considered as insulator.
DIELECTRIC STRENGTH
The dielectric strength of an insulating material is defined as maximum dielectric stress which the material can withstand without any conduction.
The electric stress to which an insulating material is subjected is numerically equal to voltage gradient and which is equal to electric field intensity.
Voltage at which current starts flowing through the dielectric is known as breakdown voltage.
GAS INSULATOR
Air at atmospheric pressure is the most common gaseous insulation.
Breakdown strength of air is 3okv/cm.
other gases such as nitrogen (N2), carbon dioxide (CO2), Freon (CCl2F2) and sulphur hexafluoride (SF6) are also .
Breakdown strength can be increased by operating gases at higher pressure.
LIQUID INSULATOR
Liquids are usually 103 times denser than gases.
So, they possess much higher dielectric strength of the order of 107 V/cm.
Petroleum oils are the commonest insulating liquids
Fluorocarbons ,silicones, esters are also used as insulating oil.
SOLID INSULATOR
Solid dielectrics have higher breakdown strength compared to liquids and gases.
Many inorganic and organic materials are used as insulator.
Inorganic insulators used are ceramic and glasses
Organic insulator commonly used are PVC, polythene,cross linked polythene etc.
Dielectric strength can be up to 10MV/cm
CONCLUSION
Engineers need to develop knowledge and skills necessary to evaluate and compare suppliers and products from many different countries
An understanding of the basics of insulator manufacturing, design and application is more essential than ever before