626 ELECTRICAL EQUIPMENT 



moisture resisting to be largely used in braided form in relatively 

 dry places. In lead-covered form, there is little likelihood of an 

 appreciable amount of moisture being absorbed at the ends of the 

 cable while open for the purpose of jointing or terminating. This 

 type of cable is likewise mechanically stronger and less likely to 

 have the insulation injured during installation. 



Of two cables the one insulated with paper and the other 

 insulated with varnished cloth each properly proportioned to 

 stand the working pressure and the same factory tests, if each 

 is installed by the same installation gang and under the same con- 

 ditions, that insulated with varnished cloth will have the greater 

 factor of safety after installations for the reason just mentioned, 

 that it is less likely to be injured by bending and less likely to 

 absorb moisture while the ends are open. It, therefore, does not 

 require so much skill ir handling and jointing. Varnished cloth 

 insulation likewise has the characteristic of being better able 

 safely to withstand, temporarily, higher voltage surges without 

 injury than either rubber or paper insulation. , 



When cables are run exposed the insulation should be pro- 

 tected by a good fireproof covering of asbestos so that in case of a 

 short-circuit the trouble will not be communicated to adjacent cir- 

 cuits. When run in conduit or ducts this type of covering absorbs 

 moisture and the weatherproof covering should be substituted; 

 as a fact, a lead covering is usually required for damp places. 



All lead-covered cables should be provided with endbells for 

 preventing moisture from entering the cable at the ends. These 

 endbells and terminals may be designed for either horizontal 

 or inverted positions and for convenient connections to the 

 machine terminals or busbars. 



Open Wiring. If the number of cables in close proximity 

 does not make the run too congested or hazardous, it may be per- 

 missible to use wires or cables insulated for full potential, rigidly 

 supported on insulators also good for full-working potential. 

 This arrangement gives double protection, since either the insu- 

 lation or the insulators afford sufficient protection in case one 

 should fail. On the other hand, the runs, being exposed, are under 

 constant observation. Where the conductor does not exceed No. 

 0000 B. & S. size, it should be solid and not stranded, the former, 

 of course, being more rigid. Where the amount of current to be 

 carried is large copper bars are used. This is usually the case for 



