A. Pin Type
B. Disc Type
C. Shackle type
D. Pin and Shackle Type
Answer: B. Disc Type
Explanation:
Disc type insulators:
Pin Insulator:
- The pin insulator is used in power distribution for the voltage up to 33kV
- It is placed on the cross arm of the supporting tower
- The pin insulator has grooves on the upper end for keeping the conductor
- The conductor is tied to the insulator on the top groove on straight line positions and the side groove in angle positions by annealed binding wire of the same material as that of the conductor
- A lead thimble is cemented into the insulator body to receive the pin
Suspension type insulator:
- It consists of a number of porcelain discs connected in series by metal links in the form of a string.
- These are the string of insulators in vertical position.
- The conductor is suspended at the bottom end of this string while the other end of the string is secured to the cross-arm of the tower.
- Used above 132 kV
Strain insulators:
- When there is a dead end of the line or there is corner or sharp curve, the line is subjected to greater tension.
- These are the string of insulators in horizontal position.
- In order to relieve the line of excessive tension, strain insulators are used.
Shackle insulators:
- They are frequently used for low voltage distribution lines.
- Such insulators can be used either in a horizontal position or in a vertical position.
- Used at low voltage.