77MAVvU/x.s7o.\ ni-i'D\Vl-:i; HY ALTERNATING CURRENT 379 



into the city underground, or occasionally overhead, at 13,200 



Figure 342 shows a typical system. No attempt is made to 

 show switches, circuit -breakers, etc. Power is generated at 

 6,600 volts and is delivered directly to the 6,600-volt bus-bars. 

 It is then stepped up to 110,000 volts, the transmission voltage, 

 by delta- V transformer banks whose secondaries are connected 

 to the 110,000-volt bus-bars. 

 The power then passes out 

 over the duplicate trans- 

 missinn lines to a sub-station 

 (I in the outskirts of the 

 district where the power is to 

 be utilized. It is then stepped 

 down to 13,200 volts by 

 Y-Y-transformer banks and 

 delivered to the 13,200-volt 

 bus-bars at this sub-station. 

 The power then leaves these 

 13,200-volt bus-bars for the 

 various distributing sub- 

 stations in the district. One 

 distributing sub-station is 

 shown. Here the voltage is 

 stepped down to a three-phase, 

 four- wire system. This sys- 

 tem has 4,000 volts between 

 conductors, or 2,310 volts to neutral, for distribution to the con- 

 sumers. 



Usually the lighting and the power loads are connected to 

 separate feeders, in order to avoid the anno\ -ing flickering of the 

 lamps when motors are thrown on or off the line. The lighting 

 loads are usually supplied by 10:1 transformers located on the 

 poles, from whose secondaries 230-1 15-vol t . three-wire s\ 

 are obtained. Fig. 343. Tin- two mming from tl 



crossarm to the crossarm next beneath and going through the 

 fuse cut-outs to the transformer are the 2,300-voh lines. The 

 i l.Vvolt secondary \\ -. tin front side of the trans- 



former and feed three vert icall v-.-m-angcd conductors of t he thiee- 



ioal 2300-230/1 16-ToU 



linhtiiiK lr:ui>foinu-r :mcl >>rotidary 3- 

 uiic mains. 



