SWITCHING EQUIPMENT 



577 



switches, and the water piping, if water-cooled transformers are 

 provided, should be so arranged that connections can be made or 

 broken for any unit without disturbing the operation of the other. 



Figs. 368 to 370 illustrate typical outdoor arrangements, 

 and Fig. 371 shows how the low-tension leads can be brought from 

 the building through tunnels to the outdoor structure. The 

 bads shown in the illustration come from the low-tension terminals 

 of a transformer located above. 



Disconnecting Switches. In all high-tension circuits it is 

 customary to install knife-type disconnecting switches for iso- 

 lating oil circuit breakers, feeders, etc., and for making various 



FIG. 369. 66,000-volt Outdoor-Substation. 



connections that do not have to be opened under load. For 

 voltages of 2500 or less, these disconnecting switches are mounted 

 directly on a base of marble or similar material, while for higher 

 voltages post insulators of various kinds mounted on pipe work 

 or steel bases are used to support the switch jaws. Up to 33,000 

 volts, these disconnecting switches are made for either front 

 connection or rear connection or both. For higher voltages they 

 are invariably made for front connection only, and in order to 

 insure rigidity and prevent oscillations where the blade becomes 

 very long, as for switches of the higher voltages, the blades may 

 be of a truss design (Fig. 372). 



