[Electric engineering.] . e and the ground. Example.—A ground occurred on a conductor of a cable 10,000 feetlong composed of three No. 10 wires. One good wire was used to com-plete the loop. On testing with one end of the battery grounded as inFig. 38, the bridge was balanced with the following resistances:in — 10 ohms, n = 1,000 ohms,^ = 1,642 ohms. Where was the ground,the resistance per 1,000 feet of the conductor being .9972 ohm ? Solution.—The length of the loop formed by joining the two wiresof the cable at the distant end will be 20,000 feet; hence,and R = 20 X .9972 = , 1,000 X 1
[Electric engineering.] . e and the ground. Example.—A ground occurred on a conductor of a cable 10,000 feetlong composed of three No. 10 wires. One good wire was used to com-plete the loop. On testing with one end of the battery grounded as inFig. 38, the bridge was balanced with the following resistances:in — 10 ohms, n = 1,000 ohms,^ = 1,642 ohms. Where was the ground,the resistance per 1,000 feet of the conductor being .9972 ohm ? Solution.—The length of the loop formed by joining the two wiresof the cable at the distant end will be 20,000 feet; hence,and R = 20 X .9972 = , 1,000 X - 10 X 1,6421,000 + 10 = Hence the distance of the fault from the testing station must .9972 X 1,000 = 3, ft. Ans. 42. Locating a Partial Ground Without an Avail-able Good Wire.—The following method for locating apartial ground or escape is rather unreliable in practice,because the resistance of the partial ground may changebetween the two measurements, and so give a more or less HB>. incorrect result. However, it is about the only way wherethere is no available good wire and when the tests must bemade from one end only. The normal resistance of theline must be known from some previous measurement,unless it can be calculated from the length and size of the 15 ELECTRIC TRANSMISSION. 37 wire. Let this resistance be a; then measure the resistanceof the line B B, with the distant end B grounded as shownin Fig. 39, and call this c. Also measure the resistance
Size: 2402px × 1040px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookidelectricengi, bookyear1902
