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Page 171

| Figure 9-11 Connection for power-factor test. |

| leak through it, and the power factor will become increasingly greater, approaching 100 percent. |

| Power-factor readings are taken periodically as part of maintenance programs. These readings are compared, not with readings of other bushings, but with previous readings on the same bushing. To what extent power factor increases may be acceptable is a matter of judgment. High values may depend on the importance of the installation and other factors. Values will vary with temperatures, and excessive readings should be compensated for by any differences in temperatures at the times the tests were made. |

| Breaker Travel Indicator.. |

| This instrument records in graphic form (a chart wrapped around a turning cylinder) the time and smoothness of the lift rodthat is, its acceleration and any hindrance to its motion when opening and closing the contacts in the breaker. The travel indicator is a mechanical device attached to an extension of the lift rod through a fitting provided for checking the rod. The shape and timing shown by the curve produced on the chart will determine the need for maintenance (Fig. 9-12). |

| Vacuum and Sulphur Hexafluoride Breakers |

| Although the practices previously described apply specifically to air and oil circuit breakers, most of the details also apply to vacuum and sulphur hexafluoride breakers. In the latter, the contacts and operating rods operate in a |

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