page_66

< previous page | page_66 | next page >

Page 66

| Figure 4-8 Connections of the Megger ground tester showing the principle of operation. |

| from the transformer from the low side, and thus constitute a serious risk. |

| Transformers should never be moved or lifted by the bushings or other attachments. Lifting lugs are provided for this purpose. |

| When working on transformers, particularly the larger ones, care should be taken that nothing falls into the open tank. Objects, such as tools, may not only cause failure if lodged in critical places, but may be the source of puzzling and unexplainable noises emanating from the transformer when returned to service. |

| Cryogenic Transformers |

| Present-day transformer capacity ratings are based on holding the temperature of the hottest part of the insulation to about 100°C. The heat developed in the transformer stems from the 12R losses, the greatest part in the windings, and from eddy current and hysteresis losses. |

| Developing technology that calls for the use of high temperature super-conductors (HTS) in the windings and cooled by liquid nitrogen, has promises of meeting the needs for meeting the economic challenges of the future. |

| Major advantages of HTS transformers are: |

< previous page | page_66 | next page >