Protection of electrical transmission lines

A review of some of the principal headings with an occasional comment will give a rapid survey of the scope of this paper. The conditions of single grounds occupy most of the treatment, although incidentally the subject of short circuits and high frequency oscillations are brought in briefly where they are particularly pertinent. The general principles of the arcing ground suppressor are described. Its mechanical features, consisting of an oil switch, electrostatic or electromagnetic selective relay, and safety auxiliary devices, are treated in detail. Then follows a discussion of the security with a metallic ground and the practical tests of the arcing ground suppressor. The electrostatic capacities of the line wires are so changed by the accidental grounds, that considerable space is given to this subject under the three heads of analogy, physical theory, and mathematical solutions. This subject has a strong bearing on the design of the suppressor but has only a convincing and theoretical connection with the use of it. In connection with the arcs on lines, tests are given of arc length, voltage, and currents. These are illustrated by simultaneous photographs of arcs on horns and oscillograms with curves of subsequently calculated lengths, voltages, and currents.