. Electric traction and transmission engineering . y point on the line from thestation,i = current at this point in amperes,e = voltage of track at this point above negative terminal of generator,r = resistance in ohms per foot of return, including rails and negative supplementary conductor,p = ohms per mil-foot of copper,Ai= copper cross section in circular mils equivalent in conductivity to the track rails,Ac= cross section of negative supplementary conduc-tor in circular mils. i = I li --) amperes, (3) Then e = firdl = T-^ (l - -4) volts. (5) Jo Ai + AA 2L/ ^^^ The curve coordinating voltag
. Electric traction and transmission engineering . y point on the line from thestation,i = current at this point in amperes,e = voltage of track at this point above negative terminal of generator,r = resistance in ohms per foot of return, including rails and negative supplementary conductor,p = ohms per mil-foot of copper,Ai= copper cross section in circular mils equivalent in conductivity to the track rails,Ac= cross section of negative supplementary conduc-tor in circular mils. i = I li --) amperes, (3) Then e = firdl = T-^ (l - -4) volts. (5) Jo Ai + AA 2L/ ^^^ The curve coordinating voltage to distance is therefore aparabola, and the area contained between it and the / axis,that is, the value of the integral in equation (2), is X i6o TRACTION AND TRANSMISSION. George I. Rhodes has compared various dispositions ofreturn copper and concludes that a maximum reductionof leakage current can be obtained by the use of severalinsulated negative feeders of such cross section that theaverage potentials at their feeding points are maintained. 12 3 4 NUMBER OF NEGATIVE FEEDERSFig. 69. equal, the negative bus bar being insulated from the groundat the station. If, in addition, use be made of negative boosters in thefeeders, the potentials at the feeding points can be main-tained uniform with that of the negative bus-bar even withwidely fluctuating loads. The amount to which the original leakage current isreduced by various numbers of such negative feeders andboosters as a percentage of what would exist in the caseof no feeders, is shown in Fig. 69. THE DISTRIBUTING SYSTEM. l6l If the contact-conductor sections be supplied by individ-ual feeders and the current of each be passed through thefield exciting coil of the booster which is connected to thetrack feeder for the corresponding section, as indicated inFig. 70, the potential of the track feeding points can bekept practically equal to that of the negative bus at thestation. It should be noted that the track rails are insu-l
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