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Page 196

| should be resilvered, if indicated. Arcing horns of air-break switches, should be cleaned and cleared of pittings, or replaced if necessary. They should be adjusted so that they barely touch the movable switch member when opened and closed. All bolts, nuts, clamps, guide plates, and other similar items should be tightened and adjusted. Insulators should be cleaned and inspected for cracks and signs of flashover or fatigue (when the insulator and blade assembly move as a unit). |

| For oil switches, in addition to checking and adjusting contacts, the oil should be changed, filtered, tested, and replaced. The inside of the tank and the mechanism parts should be cleaned, and the tank refilled to proper oil levels. Bearings and bushings should be checked and replaced if necessary. Loose bolts, nuts, linkages, and the like, should be tightened. Gaskets should be replaced and the tank painted if necessary. |

| For all switches, the operating mechanisms should be checked to see that they operate freely and with positive action, especially the opening and closing of switch contacts. If switches are motor operated, the motors and electric supply and controls should be checked. Locking arrangements, including the locks themselves, should be checked to make sure that they are reasonably safe from being tampered with by unauthorized people. Electrical grounds should be checked for continuity and tightness, and ground sources should be checked to be sure that their resistance is sufficiently low. |

| Since some of these switches may not be used over long stretches of time, it is good practice to open and close them periodically (while de-energized, of course) to make sure that they are in good mechanical operating condition. The ideal frequency of such testing depends in great part on the geographical location of the switches and their exposure to cold, rain, ice, salt, polluted atmosphere, and other local adverse conditions. |

| Table 10-1 provides a detailed breakdown of troubleshooting procedures for disconnecting devices. |

| Review |

| 1. Less expensive equipment, of lesser circuit breaking capability, can be used to accomplish many of the circuit breaking operations. These are generally referred to as switches, and provide for physical separation in the electric circuit and the restoration of its continuity. |

| 2. Switches may be used to: de-energize equipment or portions of circuits upon which work is to be performed; isolate faulted equipment or faulted portions of circuits; provide electric supply from alternate circuits; distribute loads throughout an electric circuit to avoid or eliminate overloading or portions of the circuit; ground circuits; serve temporarily in place of circuit breakers; and to serve and meet particular situations. |

| 3. Switches range from small snap switches to large air or oil switches |

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