Outdoor Air Switches

Interrupting Attachments

Arcing Horn The Arcing Horn is the simplest form of interrupting attachment. It consists of a stationary horn attached to the jaw of the switch and a movable horn attached to the blade. The purpose of the arcing horn is to avoid arcing at the main contacts of the switch during current interruption. Arc extinction is achieved by stretching out the arc. Arcing horns are used to make or break: x Magnetizing current of small transformers x Charging current of substation busses or short Transmission lines The arcing horn has been designed to require only minimum contact pressure in order to maintain minimum operating effort. Arc reach, which is the perpendicular distance between the peak of an arc and a straight line drawn between the two parting contacts (Fig. 2), should be considered for phase spacing and clearance to ground. It may be necessary to keep the arc to a minimum of 2 feet, depending upon location of equipment and recognizing environment and personnel considerations. In order to reduce the possibility of phase-to-phase faults, horn-gap switches are mounted on wider phase spacing than used for disconnect switches. For phase spacing of horn-gap switches and arc reach for various currents and voltages see Table 7.

Note: 1. Use Disc. Switch Dimension (Table 4) if greater.

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