. Electric railway journal . d by the General Electric Company foroperating this type of equipment, and as the control hasbeen fully described in previous issues of the ELECTRICRailway Journal no further description of the con-trol equipment and the operation of same will be givenat this time. On a system equipped with automatically controlledsubstations when an overload or short circuit occurs onone of the trolley sections the feeder or feeders fromone or more substations supplying current to this sec-,tion are not disconnected from the direct-current busat the substation by the tripping of a
. Electric railway journal . d by the General Electric Company foroperating this type of equipment, and as the control hasbeen fully described in previous issues of the ELECTRICRailway Journal no further description of the con-trol equipment and the operation of same will be givenat this time. On a system equipped with automatically controlledsubstations when an overload or short circuit occurs onone of the trolley sections the feeder or feeders fromone or more substations supplying current to this sec-,tion are not disconnected from the direct-current busat the substation by the tripping of an automatic circuitbreaker, but instead a resistance of sufficient value tolimit the current to a pre-determined value is insertedin series with these feeders by the opening of the linecontactors. These under normal conditions form ashort circuit around the resistance. Under certain conditions, such for instance as quitean extensive break in the trolley system in congesteddistricts or due to conflagration of a serious nature. FIG. 6. INTERIOR OF SINGLE-UNIT AUTOMATIC SUBSTA-TION AT DES MOINES, SHOWING 500-KW. CONVERTERAND M0T0R-0PF;RATED CONTROLLrER cycle current at a potential of 4,500 volts, these linesentering the stations through roof bushings. One sta-tion is located in the underground district and thelines for this station are carried in a conduit line con-structed of 3-in. fiber duct. The station which islocated on the Flint Valley Division of the Inter-Urbansystem is supplied with current from the three-phase,25-cycle, 22,500-volt transmission lines, which also sup- FIG. 7. SINGLE-UNIT AUTOMATIC SUBSTATION, SHOWING MOTOR-OPERATED DRUM CONTROLLER, CONTROL PANELS AND RESISTANCE adjacent to the trolley lines, it is desirable to have somemeans for shutting off the current entirely from thesesections without interrupting the supply of power tothe other sections. Of course this could be accomplishedby calling out the trouble car and having the discon-necting switches in the f
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