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Page 136

| Sulphur Hexafluoride (SF6) Breaker.. |

| This type of breaker (Fig. 8-6) is similar to the vacuum type of breaker except that the vacuum is replaced by an inert, nontoxic, odorless gassulphur hexafluoride (SF6). This gas, under pressures that may vary from 45 to 240 lb/sq in, extinguishes the arc so rapidly as almost to prevent its formation. It also has excellent heat-dissipating characteristics, and its dielectric strength is very much greater than that of oil. |

| The breakers are constructed in modules capable of operation at voltages from 34.5 kV at gas pressures of 45 psi to 362 kV at 240 psi. (Fig. 8-7). By |

| Figure 8-6 Sulphur hexafluoride circuit breaker, 34.5 to 69 kV. (Courtesy, Westinghouse Electric Co.) |

| Figure 8-7 Features of sulphur hexafluoride interrupting module. (Courtesy, Westinghouse Electric Co.) |

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