. Development and electrical distribution of water power . Ground Fig. 68. type. This is made of ordinary copper wire size No. 000, bentin the form shown in Fig. 68. Two of these bent pieces supportedon insulators form an arrester; one horn is connected to a line wire,while the other is connected to the ground through a fuse. The dimensions given in the figure are those for a 5o;ooo-volt LIGHTNING PROTECTION J39 system. For smaller potentials the air gap between the horns iscorrespondingly diminished. A simple and effective form of arrester used in Europe com-prises a plate of copper attached
. Development and electrical distribution of water power . Ground Fig. 68. type. This is made of ordinary copper wire size No. 000, bentin the form shown in Fig. 68. Two of these bent pieces supportedon insulators form an arrester; one horn is connected to a line wire,while the other is connected to the ground through a fuse. The dimensions given in the figure are those for a 5o;ooo-volt LIGHTNING PROTECTION J39 system. For smaller potentials the air gap between the horns iscorrespondingly diminished. A simple and effective form of arrester used in Europe com-prises a plate of copper attached to each of the line wires againstwhich a small stream of water is thrown from a nozzle. The re- , Arrestersi. To Transformer,Choking- Coils Tig. 69. sistance of the water is too high to allow any appreciable leakageof current, but forms a good path for lightning or static discharges. To thoroughly protect a line there should be installed twochoke coils in series with each wire, and two different forms oflightning arresters attached to the line next to the outer choke coil,and two more arresters of different types installed between the chokecoils; and this arrangement should be duplicated at both ends of theline. Fig. 69 indicates this method of protection, using standardcylinder arresters and horn arresters, a single wire only of the cir-cuit being shown. In long lines standard or horn arresters should be placed everytwo or three miles along the line, the distance apart depending onthe frequency and violence of thunder-storms and other atmos-pheric electrical disturbances. In regions where such phenomena are frequent, it is advisableto use the overhead barbed wire, before described, in additi
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