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Page 52

| Figure 3-10 Self-protected transformer. |

| size transformers, for industrial or similar installations are essentially substations and are treated as such. |

| For transformers installed underground, lightning arresters are usually not necessary. However, if the primary supply is from a nearby overhead line which is subject to lightning (Fig. 3-11), the arresters are installed at the transformer, or at the pole, or at both locations. Submersible type oil filled fused cut-outs are used. Leads connecting the several pieces of apparatus are waterproof lead or plastic sheathed wires. Where self-protected transformers are used, no external connections or protective devices are used. |

| In all installations, special care should be taken with the installation of neutral or ground wires. These must not only be continous with special attention paid to splices and connectors, but they should also be of ample size to allow for abnormal fault currents, or for the flow of a sum of the neutral or ground currents from several units. |

| In this regard, it should be noted that waterpipe grounds should be supplemented by driven grounds as the use of nonconducting pipe in water supply systems no longer provides a good trustworthy ground source. |

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