Standard		ANSI
Class		55-1	55-2	55-3	55-4	55-5
Main Dimensions (mm)	Max. Unit Spacing(H)	89	83	95	111	124
	Nominal Diameter(D)	83	95	121	140	178
Creepage Distance (mm)		102	127	178	229	305
Dry Arcing Distance (mm)		57	86	114	127	159
Cantilever Strength (KN)		13	11	11	13	13
Low Frequency Flashover Volatge (KV)	Dry	35	50/45	65/55	70/65	85/80
	Wet	20	25	35/30	40/35	45
Critical Impulse Flashover Voltage (KV)	Positive	50	75/70	100/90	110/105	140/130
	Negative	70	95/85	130/110	140/130	170/150
Power Frequency Puncture Voltage (KV)		50	70	90	95	115
Radio Interference Voltage	Test volatge to ground (KV)	5	5	10	10	15
	Max. RIV at 1 MHz (μV)	50	50	50	50	100