. Electrolysis and its mitigation. . great, particularly whenit is necessary to maintain the voltage drops in the track at verylow figures, such as is usually necessary for electrolysis protection, 102 Technologic Papers of the Bureau of Standards that only insulated negative feeders can be considered seriously,and they should always be installed in lieu of uninsulated feederswhen the conductance of the tracks is not in itself sufficient tocarry the current without excessive voltage drop. (c) Calculation of Insulated Negative Feeder System.—It is desir-able to state briefly here the methods of
. Electrolysis and its mitigation. . great, particularly whenit is necessary to maintain the voltage drops in the track at verylow figures, such as is usually necessary for electrolysis protection, 102 Technologic Papers of the Bureau of Standards that only insulated negative feeders can be considered seriously,and they should always be installed in lieu of uninsulated feederswhen the conductance of the tracks is not in itself sufficient tocarry the current without excessive voltage drop. (c) Calculation of Insulated Negative Feeder System.—It is desir-able to state briefly here the methods of procedure in laying outthe design of insulated negative feeder systems. A careful studyis first made of the load distribution over the entire territory sup-plied by the station under consideration, and from this study themost natural points for taking off the current are selected and thenumber of amperes that must be taken off at each point in orderthat the current in the rails shall not exceed a predeterminedvalue is NEGAT/VF BUS ^1G- 33-—Diagram illustrating calculations of insulated negative feeders A preliminary value of potential drop in the first feeder, whichis usually one of the largest and most important ones, is thenassumed, and from this drop and the current to be carried by thefeeder, together with its length, the cross section of the feeder iscalculated. When this is done, all of the other feeders must bedesigned consistently with this so as to avoid potential gradientsin the tracks greater than the value determined upon as the limitingallowable average gradient. Beginning thus with feeder No. i, Fig. 33, we find that the volt-age drop to be allowed on feeder No. 2 is the drop on No. 1 lessthe allowable drop on the tracks over the distance (a) betweenthe points at which the two feeders connect to the rails. Forinstance, if the assumed drop on feeder No. 1 is 15 volts and thedistance between the two taps is, say, 1200 feet and we are per-mitting a
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