630 



ELECTRICAL EQUIPMENT 



TABLE LIII 



CONDUIT SIZES FOR DIFFERENT SIZE WIRES 



the alternating main conductors depends on the size, length of 

 run and whether they are lead covered or not. When lead cov- 

 ering on cables is required, multiple-conductor cables are always 

 preferable, since the eddy currents in the lead sheaths of the single- 

 conductor cables increase the energy loss. In fact, single-con- 

 ductor, lead-covered cables should not be used in large sizes on 

 alternating-current circuits without careful consideration. 



With high-voltage, single-conductor, lead-covered cables, static 

 discharges may take place through the insulation to the lead, 

 which rapidly injures the insulation and a breakdown soon fol- 

 lows. If the cable is not lead-covered a static discharge may take 

 place to the duct, this also having a tendency to break down the 



