. American hydroelectric practice; a compilation of useful data and information on the design, construction and operation of hydroelectric systems, from the penstocks to distribution lines . n be set for the conditions of that line, in every case being set lowenough so that the arrester will discharge in case of any disturbance, butwill not be subject to continuous discharges in regular operation. Ground Gaps and Line-to-Line Gaps.—Any telephone line paralleling ahigh voltage power line will have a voltage induced between the telephoneline and ground. The ground gaps should therefore be adjust
. American hydroelectric practice; a compilation of useful data and information on the design, construction and operation of hydroelectric systems, from the penstocks to distribution lines . n be set for the conditions of that line, in every case being set lowenough so that the arrester will discharge in case of any disturbance, butwill not be subject to continuous discharges in regular operation. Ground Gaps and Line-to-Line Gaps.—Any telephone line paralleling ahigh voltage power line will have a voltage induced between the telephoneline and ground. The ground gaps should therefore be adjusted in pro-portion to this voltage. The probable setting of these ground gaps shouldbe between 1/64 and 1/16 in. The protection to the telephone instrumentis provided by a vacuum gap connected from line to line. This vacuumgap is paralleled by a very small air gap which comes into play only incase the vacuum gap has been destroyed by a small but continuous dis-charge. If it is found at any time that the compound has melted from thebottom of the vacuum gap, this unit must be replaced, as the vacuum is Auxiliary Gaps,54 Setting; notnecessary for22000 Volts orlower TelephoneTransformer. Telephone Construction and Connections for Peck Arresterfor Use Near 35,000 Volt Power Lines SPECIAL PLANT AND LINE PROBLEMS 321 destroyed when the compound is melted, and the discharge voltage of thegap changes from approximately 350 to several hundred volts higher. Thedesigner has found that vacuum gaps are damaged very seldom, but it wasthought advisable to provide the auxiliary gaps as an added protection, asthe vacuum gaps will sometimes go down. The air gap from Hne to line isset in. and should not be changed. In the P-B arrester all of the protective gaps are themselves protected by12-in, expulsion fuses connected between these gaps and the line. Thesefuses should have a capacity of between 5 and 7 amp. The fuses and gapsare mounted on a hinged base so that the working parts of the ar
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