Ques. What are the objections to this type of switch?
Ans. The considerable space required for the horns and arcs, and the line surges caused by the arc.
Horn switches were used extensively for high pressure alternating current circuits before the introduction of oil switches.
Fig. 2,221.—Sectional view of Pacific weatherproof oil switch for use in places exposed to the weather. All moving and contact parts are supported from the cast iron top and are readily removable for inspection or repair.
Oil Switches.—The extensive use of high pressure currents and alternating current motors and other devices introducing inductance make it necessary to use switches radically different from the ordinary air break types.
Fig. 2,222.—General Electric central station triple pole single throw oil switch; view of switch in tank. This type is for pressures up to 110,000 volts, being adapted for stations employing open wiring, since the connections are made at the top of the switch and its construction obviates the need for isolating it in a cell. One tank with two breaks in series are used for each phase.
The opening of circuits of considerable current value with inductive loads is not possible with old style switches which were quite adequate for the service for which they were designed. These circuits are controlled with ease and certainty by the oil switch.