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| currents are relatively small. Their advantages are simplicity of construction, low cost, and relatively low maintenance requirements. |

| As a means of extending the short-circuit duty of this type of breaker, a blast of air trained on the arc from a reservoir of compressed air enables a heavier arc to be extinguished. |

| Oil Circuit Breaker. |

| Oil circuit breakers have their contacts immersed in insulating oil. They are used to open and close high-voltage circuits carrying relatively large currents in situations where air circuit breakers would be impractical because of the danger of the exposed arcs that might be formed (Fig. 8-4). |

| When the contacts are drawn apart, the oil covering them tends to quench the arc by its cooling effect and by the gases thereby generated, which tend to blow out the arc. At the instant the contacts part, the arc formed at |

| Figure 8-4 Oil circuit breaker. |

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