Tables > Live Parts > Clearance > Minimum clearance

	Nominal Voltage Rating KV Impulse Withstand B.I.L. KV *Minimum Clearance Of Live Parts, Inches Phase-To-Phase Phase-To-Ground Indoor Outdoor Indoors Outdoors Indoors Outdoors 2.4 - 4.16 60 95 4.5 7 3.0 6 7.2 75 95 5.5 7 4.0 6 13.8 95 110 7.5 12 5.0 7 14.4 110 110 9.0 12 6.5 7 23 125 150 10.5 15 7.5 10 34.5 150 150 12.5 15 9.5 10   200 200 18.0 18 13.0 13 46   200   18   13     250   21   17 69   250   21   17     350   31   25 115   550   53   42 138   550   53   42     650   63   50 161   650   63   50     750   72   58 230   750   72   58     900   89   71     1050   105   83
For SI units: one inch = 25.4 millimeters *The values given are the minimum clearance for rigid parts and bare conductors under favorable service conditions. They shall be increased for conductor movement or under unfavorable service conditions, or wherever space limitations permit. The selection of the associated impulse withstand voltage for a particular system voltage is determined by the characteristics of the surge protective equipment. Reprinted with permission from NFPA 70-1999, the National Electrical Code®, Copyright 1998, National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the referenced subject which is represented only by the Standard in its entirety.
See also Tables Minimum size equipment grounding conductors for grounding raceway and equipment