SWITCHING EQUIPMENT 



571 



enough play to permit it to clear the top stud. Subsequently 

 the remaining parts of the support can be easily removed for 

 repair or inspection. The individual laminations of the bus are 

 separated by fillers, and the 

 number of laminations can be 

 varied at will by using pillars 

 of the proper length. 



The bus supports should 

 be located near openings in 

 the compartments so as to be 

 accessible for cleaning and 

 inspection (Fig. 363). This 

 also refers to all the clamped 

 joints between the buses and 

 the connections. 



For very high voltages the 

 buses generally consist of 

 round copper rods or tubing, 

 the sizes given in Table LVI, 

 page 638, being quite com- 

 mon. These buses are gener- 

 ally supported from the roof 

 trusses by suspension insula- 

 tors and the connections on 

 post-type insulators mounted 

 on the walls (Fig. 364). 



For long buses, provision 

 must also be made for expan- 

 sion and contraction due to 

 temperature changes. The 

 diagram in Fig. 365 gives the 

 linear expansion of copper 

 buses, the values being based 

 on an installation tempera- 

 ture of 25 C. = 75 F. The actual expansion over any tem- 

 perature range on the chart is the algebraic sum of the expansion 

 values shown for the temperature limiting range. The chart 

 has been corrected for variations in the coefficient, and the actual 

 temperatures should, therefore, be used. 



The problem of bringing a high-tension wire out of a building 



FIG. 362. Bus-bar Support for Large 

 Capacities in Compartments. 



