What is porcelain Pin insulator?
 
Porcelain pin insulators as one main type of porcelain insulators which is popularly used in transmission line and distribution line up to 33kV. It is usually used to isolate wires from the physical support just like pole or tower. Porcelain pin insulators are including a porcelain insulated body and assembly with the cast iron spindle long or short.

Insulators are required to withstand both mechanical and electrical stresses. The electrical breakdown of the insulator can occur either flash-over or puncture. In flash over, an arc occurs between the line conductor and insulator pin and the discharge jumps across the air gaps.

In the case of puncture , the discharge occurs from conductor to pin through the body of the insulator. When such breakdown is involved, the insulator is permanently destroyed due to excessive heat. In practice, sufficient thickness of porcelain is provided in the insulator to avoid puncture strength to flash-over voltage is known as the safety factor.The value of safety factor is high so that flashover takes place before the insulator gets punctured. For pin type insulator, the value of safety factor is about 10.
 
Porcelain Pin Insulator Picture:
ANSI 55 Series Porcelain Pin Insulator types:

Type No. ANSI 55-1 ANSI 55-2 ANSI 55-3 ANSI 55-4 ANSI 55-5
Creepage distance - mm 102 127 127 229 305
Dry arcing distance - mm 57 86 114 127 159
Cantilever failing load - kN 13 11 11 13 13
Dry flashover voltage - kV 35 45 55 65 80
Wet flashover voltage - kV 20 25 30 35 45
Impulse flashover Pos. - kV 50 70 90 105 130
Impulse flashover Neg. - kV 70 85 110 130 150
Low frequency puncture voltage - kV 50 70 90 95 115
Test voltage to ground - kV 5 5 10 10 15
Max RIV at 1000kHz - µV 50 50 50 50 100

ANSI 56 Series Porcelain Pin Insulator types:

Type No. ANSI 56-1 ANSI 56-2 ANSI 56-3 ANSI 56-4 ANSI 56-5
Creepage distance - mm 330 432 533 686 865
Dry arcing distance - mm 178 203 229 279 356
Cantilever failing load - kN 11 13 13 13 13
Dry flashover voltage - kV 95 110 125 140 175
Wet flashover voltage - kV 60 70 80 95 125
Impulse flashover Pos. - kV 150 175 200 225 270
Impulse flashover Neg. - kV 190 225 265 310 340
Low frequency puncture voltage - kV 130 145 165 185 225
Test voltage to ground - kV 15 55 30 30 44
Max RIV at 1000kHz - µV 100 100 200 200 200

BS Series Porcelain Pin Insulator types:

Type No. P-11-Y P-15-Y P-22-Y P-33-Y PW-11-Y PW-22-Y PW-33-Y
Creepage distance - mm 155 298 432 630 432 673 900
Cantilever failing load - kN 11 11 11 13 11 11 11
Dry flashover voltage - kV 75 80 110 130 100 125 140
Wet flashover voltage - kV 50 55 70 95 65 95 110
Dry withstand voltage - kV 65 70 100 125 90 110 125
Wet withstand voltage - kV 45 50 65 90 60 90 100
Impulse flashover Pos. - kV 115 130 175 215 150 190 210
Impulse flashover Neg. - kV 150 175 225 290 / / /
Low frequency puncture voltage - kV 135 150 160 210 140 180 200
Test voltage to ground - kV 15 15 22 30 22 60 44
Max RIV at 1000kHz - µV 100 100 100 200 100 200 200