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Page 179

| Figure 10-1 Switches: (A) Typical circuit, (B) air switch, and (C) oil switches. |

| Switches are almost always used in series with a circuit breaker or fuses (to be discussed later), both of which can safely interrupt short-circuit currents. |

| The two basic types of switches are oil switches and air switches. As their names imply, oil switches are those whose contacts are opened in oil, and air switches are those whose contacts are opened in air (Fig. 10-1). |

| Oil Switches. |

| Oil switches suitable for switching load currents but not for interrupting short-circuit currents are widely used in high-voltage circuits (such as utility primary circuits). They are also used where low-voltage currents may be rather sizable, that is, where the arc that may form, though not as great or persistent as that from a short circuit, may not be successfully handled by other devices (Fig. 10-2). |

| Oil switches are one of the more dependable and convenient discon- |

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