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Page 167

| heights to allow for expansion under normal and abnormal conditions. Any gauges should be checked to make sure that they indicate actual oil levels properly. |

| Oil valves should be checked for leaks as well as for their ability to open and close readily without sticking. |

| Bushings |

| The external surfaces of bushings should be cleaned to remove any accumulation of dirt or other deposits (cement, dust, metallic particles, salt, and so forth), and the bushings should be checked for cracks and breaks. The dielectric strength of the bushings may be determined by a power-factor test or by a megohmmeter (Megger). |

| Bushing supports should be inspected to ascertain that vibrations from the breaker operations have not caused the bushings to move, resulting in misaligned contacts. |

| Mechanisms.. |

| The mechanisms should be operated several times to make sure that they (and the breakers) are working smoothly and freely without binding. If the breakers are normally operated electrically or pneumatically, they should first be operated manually to determine the absence or presence of binding. Toggles, buffers, stop clearances, dashpots, and other auxiliary devices should be cleaned of dirt and grime. The length of the breaker stroke (lift rod) and its opening and closing speed should be measured and adjusted according to the manufacturer's specifications. Opening and closing times should be rechecked after the breaker has been properly filled with oil and is ready to be restored to service. |

| Electrical Operation |

| Operating voltage at the mechanism terminals with full operating current should be checked to determine its adequacy. Closing relays, indicating lamps, trip coils, tripping control switches, and the like, should be checked to make sure that they are operating properly, especially that the (usually red) indicating lamp is actually in the trip coil circuit. |

| Pneumatic Operation |

| Air pressure should be checked to ascertain its adequacy for correct operation and to make sure that it is restored after each breaker operation. Air connections should be checked for leaks. Air valves should be operated to make sure that they open and close the breaker properly. Opening and closing |

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