SWITCHING EQUIPMENT 



499 



cells, depending on the ampere capacity or the voltage. It may 

 be operated by hand from the switchboard by means of operating 

 rods through a system of bell _^^ 



FIG. 306. Small and Moderate-capac- 

 ity Oil Circuit Breaker. Remote 

 Controlled and Mounted on Pipe 

 Frame Work. 



cranks, or electrically by 

 means of a solenoid con- 

 trolled from the main switch 

 board. 



The stationary contacts 

 consist of copper fingers 

 flared at the tips, one ex- 

 tending so as to act as an 

 arcing tip. The movable 

 contact blades are wedge- 

 shaped, confining the arc of 

 the blade, protecting the 

 actual contact surfaces from 

 the damaging effect of the 

 arc. 



The oil vessel is of heavy 

 sheet metal lined with treat- 

 ed laminated wood. Multi- 

 pole switches of smaller 



capacity have all poles in one tank with treated wooden barriers 

 between each pole, while for larger capacities one tank is pro- 

 vided for each pole. 



In the more important large capacity stations where it is of the 

 utmost importance to prevent trouble in any one circuit or phase 

 being communicated to other par.ts of a station or system, the oil 

 circuit breakers are located in separate compartments, and in some 

 cases barriers isolate each phase, and even each oil tank is separated 

 if additional safety factors are desired. 



The oil circuit breaker with the highest rupturing capacity 

 which has so far been put into service is of the general type shown 

 in Fig. 307 and its ultimate development with maximum isolation 

 in Fig. 308. 



These switches are generally known as type H, and are made 

 for carrying very high currents (up to 4000 amperes), and are most 

 generally used for the ordinary generator voltages up to 13,200, 

 although they can be obtained for voltages up to 70,000. 



Each pole is made up in part, of two separate seamless steel 



