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In electric power, a bushing is a hollow electrical insulator that allows an electrical conductor to pass safely through a conducting barrier such as the case of a transformer or circuit breaker without making electrical contact with it. Bushings are typically made from porcelain, though other insulating materials are also used.
Transformer in-service interruptions and failures usually result from dielectric breakdown, winding distortion caused by short circuits, hots spots caused by localized deviations in winding and electromagnetic fields, deterioration of insulation, effects of lightning and other electrical disturbances, inadequate maintenance, loose connections ...
This is because the line might become inadvertently charged (e.g. through a back-charged transformer, possibly as a result of an improperly connected, inadequately isolated emergency generator at a customer facility), or inductively coupled from an adjacent in-service line. To prevent this, the line is first grounded via a clamp known as a bond ...
Transformers designed for below-grade installation can be designed for periodic submersion in water. [14] Distribution transformers may include an off-load tap changer, which slightly adjusts the ratio between primary and secondary voltage to bring the customer's voltage within the desired range on long or heavily loaded lines. [citation needed]
Some CT configurations slip around the bushing of a high-voltage transformer or circuit breaker, which automatically centers the conductor inside the CT window. Current transformers can be mounted on the low voltage or high voltage leads of a power transformer. Sometimes a section of a bus bar can be removed to replace a current transformer.
Preventive maintenance or preventative [16] maintenance (PM) has the following meanings: The care and servicing by personnel for the purpose of maintaining equipment in satisfactory operating condition by providing for systematic inspection, detection , and correction of incipient failures either before they occur or before they develop into ...
Single- and three-phase pad-mounted transformers are used in underground industrial and residential power distribution systems, where there is a need for safe, reliable, and aesthetically appealing transformer design. Their enclosed construction allows the installation of pad-mount transformers in public areas without protective fencing.
An oil sample tube is used to draw, retain and transport the sample of transformer oil in the same condition as it is inside a transformer with all fault gases dissolved in it. It is a gas tight borosilicate glass tube of capacity 150 ml or 250 ml, having two airtight Teflon valves on both the ends.