Correct option is C
Safety factor:
· The ratio of puncture strength to flashover voltage is known as the safety factor.
· Safety Factor = puncture strength / Flash over voltage
· For pin-type insulators, the value of the safety factor is about 10.
Advantages of Pin Type Insulator
· The mechanical strength of this insulator is high.
· It is not expensive.
· It has a good creepage distance.
· It is applicable to a high voltage transmission line.
· The designing of this insulator is simple.
· Easy maintenance.
· It is used vertically & horizontally.
Disadvantages of Pin Type Insulator
· It is applicable for only transmission lines.
· It must be used by the spindle.
· The voltage rating is up to 36kV.
· The insulator pin can damage the thread of an insulator.
· For above 50KV, these insulators will become uneconomical and bulky.
