Over Head Line Insulators : Presentation Topic in Electrical Engineering Seminar

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1. OVER HEAD LINE INSULATORS SUBMITTED BY- SANDIP KUMAR SAHOO GUIDED BY- Asst. Prof Arindam Bhattacharjee

2. Insulators The insulators for over head line provides insulation to the power conductors from ground. The insulators are connected to the cross arm of the tower and the power conductor passes through the clamp of the insulator.

3. properties of insulators High mechanical strength High dielectric strength High insulation resistance Insulation Material should be non porous Free from impurities. Withstand the flashover phenomenon

4. Insulator materials The materials most commonly used for insulators of an over head transmission line are - Porcelain Glass Steatite Synthetic Resin

5. 1. Porcelain High mechanical strength Low leakage current Dielectric strength is 60 kv /cm Dust deposit and temperature change do not affect its surface. High Cost

6. 2. glass Easy fault detection Can withstand high stress and low thermal expansion Electric strength is 140 KV/cm Cheaper than Porcelain Moisture condenses on the surface increases the leakage current Limited range up to 33 KV

7. 3. steatite It is a magnesium silicate i.e the combination of magnesium oxide( MgO ) and Silica( SiO 2 ) in various proportions. High tensile strength. Used to manufacture strain type insulators

8. 4. Synthetic resin Synthetic resin insulators are manufactured from the compounds of Silicon, Rubber, resin etc. The insulators have high electric strength and lower weight. They are comparatively cheaper. Leakage current is higher.

9. Types of insulator Pin type insulator Suspension type insulator Strain type insulator Shackle type insulator

10. 1. Pin type insulator It is designed to be mounting on a pin which is installed on the cross arm of the pole The grove of the insulator holds the conductor Used up to 33 KV For high voltage it is bulky and costly Pin type insulators have Rain shades

11. 2. Suspension type insulator It is used at voltage above 33KV. These insulators have number of porcelain disc units connected in series to form a chain The top most disc of the chain is connected to the cross arm and the lower one holds the conductor. Each disc is designed to handle 11KV and depending upon the operating voltage the no of disc can be connected in series.

12. ADVANTAGES & DISADVANTAGES ADVANTAGES Easy maintenance Low mechanical stress Safe from lightening Can satisfy future load demand DISADVANTAGES High cost Requires more height of supporting structure More space between conductors

13. 3. Strain insulator It is same as suspension type insulator but the disc are arranged in a horizontal manner Used at sharp corner and dead end High mechanical strength and high insulating properties

14. 4. Shackle insulator Are used in low voltage distribution lines These are single, round porcelain parts mounted either horizontally or vertically In early days these insulators were used as strain insulators These are directly fixed to the pole with a bolt or to the cross arm

15. Thank you