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Page vi

| 3 Installation |

| 43 |

| Distribution Transformers: Overhead |

| 43 |

| Distribution Transformers: Pad-Mounted |

| 47 |

| Distribution Transformers: Underground |

| 47 |

| Substation Power Transformers |

| 49 |

| Protection |

| 51 |

| Self-Protected Distribution Transformers |

| 51 |

| Customer Installations |

| 53 |

| Autotransformers |

| 53 |

| Review |

| 54 |

| 4 Operation and Maintenance |

| 56 |

| Heat Indicators |

| 56 |

| Ammeters |

| 57 |

| Transformer Load Monitoring |

| 57 |

| Ambients |

| 57 |

| Larger Installations |

| 58 |

| External Inspection |

| 58 |

| Internal Inspection |

| 59 |

| Maintenance |

| 60 |

| Oil |

| 60 |

| Askarels |

| 62 |

| Gaskets |

| 62 |

| Winding Insulation |

| 62 |

| Drying Out Transformers |

| 64 |

| Radiators |

| 65 |

| Electrical Grounds |

| 65 |

| Cautions |

| 65 |

| Review |

| 67 |

| 5 Principal Transformer Connections |

| 70 |

| Polarity |

| 70 |

| Test for Polarity |

| 72 |

| Importance of Impedance |

| 72 |

| Single-Phase Transformer Connection |

| 72 |

| Polyphase Systems |

| 73 |

| Two-Phase Transformer Connections |

| 75 |

| Three-Phase Transformer Connections |

| 75 |

| Delta-Delta Connection |

| 75 |

| Open-Delta Connection |

| 77 |

| Delta-Wye Connection |

| 77 |

| Wye-Delta Connection |

| 78 |

| Open Wye-Open Delta Connection |

| 79 |

| Wye-Wye Connection |

| 80 |

| Single-Bushing Transformer |

| 81 |

| Harmonics: Third Winding |

| 81 |

| Polarity of Three-Phase Transformers |

| 82 |

| Other Connections |

| 83 |

| Parallel Connection: Single-Phase |

| 83 |

| Phase Transformation: Three-Phase/Two-Phase |

| 84 |

| Scott Connection |

| 84 |

| Wye To Two-Phase Connection |

| 85 |

| Boost or Buck Connection |

| 86 |

| Review |

| 86 |

| 6 Other Transformer Types |

| 89 |

| Autotransformers |

| 89 |

| Autotransformer Connections |

| 91 |

| Voltage Regulators |

| 91 |

| Instrument Transformers |

| 95 |

| Street Lighting Transformers |

| 97 |

| Constant-Current Transformer |

| 98 |

| IL and SL Transformers |

| 99 |

| Other Customer-Type Transformers |

| 100 |

| Sign Lighting |

| 100 |

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