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Page 208

| Figure 11-9 Oil fuse. |

| The heavy magnetic field produced by the current being interrupted induces electric currents in the tank, which, in turn, produce magnetic fields that tend to snuff out any arc that forms. Moreover, the confined chamber in which the fuse operates also acts as an explosion chamber to help extinguish the arc. The inside of the tank is lined with insulating material to prevent arcing to the tank, which is usually grounded. Gases that form are allowed to expand into sealed expansion chambers at the top of the cut-out, while the contacts and the remnants of the fuse link remain under cool oil at all times. The carrier assembly can only be inserted in the open position, providing a safety feature that prevents premature blowing of the fuse before the assembly is locked closed should a fault persist in the circuit. |

| Because of their relatively high cost, oil fuses are ordinarily limited in use to transformer vaults and underground lines where voltages do not exceed 15,000 V. As a rule, they are constructed as single-pole units. |

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