STATION WIRING 



627 



bus-bars. They are seldom insulated because the addition of insu- 

 lation on a group of bars greatly reduces their carrying capacity 

 by stopping the air circulation between the laminations. 



Where the voltage exceeds 13,200 bare conductors consisting 

 of solid wire, copper tubing or iron pipe are generally employed. 

 The use of tubing or pipe makes it possible to reduce the number 

 of expensive insulators for supporting it. To insulate such high- 

 voltage conductors is expensive and quite unnecessary because 

 when properly installed they are widely spaced and kept well 

 away from the floor. 



Table LI I gives dimensions for the spacing of rigid conductors. 

 These values are based on striking distances between points, and 

 are for guidance in determining proper distances between con- 

 ductors and for general construction work. 



TABLE LH 

 SPACING OF RIGID CONDUCTORS 



CORRECTION FOR ALTITUDE 

 Sea level to 1000 feet Use table. 



1000 to 3000 feet Add 10 per cent to spacing in table. 

 3001 to 5000 feet Add 20 per cent to spacing in table. 

 5001 to 7000 feet Add 30 per cent to spacing in table. 

 7001 to 9000 feet Add 40 per cent to spacing in table. 



