. The Street railway journal . e of A feeder (.437—.15)leaves .287 ohms, beyond the end of A feeder to theground. If we know that the length of the trolley from Ato B is (say) 2400 ft. and of uniform cross section, we maydivide the resistance of this length by its length, or .3 ohmsby 2400 ft., which is equivalent to .000125 per ft. If this re-sistance per foot is divided into the found resistance fromB to ground, or .0125 ohms, we have 102 ft. from B. Thesame calculation on the A circuit would give 2296 ft.,which is the distance from A. Any other leak on the sys-tem can be located by removing
. The Street railway journal . e of A feeder (.437—.15)leaves .287 ohms, beyond the end of A feeder to theground. If we know that the length of the trolley from Ato B is (say) 2400 ft. and of uniform cross section, we maydivide the resistance of this length by its length, or .3 ohmsby 2400 ft., which is equivalent to .000125 per ft. If this re-sistance per foot is divided into the found resistance fromB to ground, or .0125 ohms, we have 102 ft. from B. Thesame calculation on the A circuit would give 2296 ft.,which is the distance from A. Any other leak on the sys-tem can be located by removing the ground connectionfrom the ground bus, and applying it to any other feederterminal with all the feeder switches open. A connectionto each independent section will then show if there is aleak. The practical test for line insulation resistance is tomake the test after the line is erected, by the method shownin Fig. 5. Open the station circuit breaker and across theterminals of the open breaker place the leads to a 500 volt. FIGS. 6-10.—METHODS OF SETTING POLES meter. Of course all circuit breakers feeding in this sec-tion must be opened, and all lamp circuits on this sectiondisconnected, otherwise the voltmeter continues to readbus voltage. The voltmeter will show when all circuitsare open (this also makes a good method of determiningin an unknown system of wiring, which feeders are con-nected together). When a steady deflection of the volt-meter is obtained on connecting across the open breakerthe resistance of the line can be found by multiplying thevoltmeter resistance by the bus-bar voltage at the time ofmaking the observation, dividing this product by the voltsshown by the voltmeter when connected across the opencircuit breaker, and subtracting from this result the volt-meter resistance. It must be remembered that the leakageis that of the total connected system, and not that of thefeeder connected. These tests can be made to determine the differences inresistance du
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
