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How to deal with oil-immersed distribution transformers after short-circuit faults?

Although the transformers are now designed to be maintenance-free, some manufacturers have cut corners during manufacturing, causing short-circuits in oil-immersed distribution transformers. After the distribution transformer short-circuit fault, should it be handled?
1. The performance of the insulation should be guaranteed when replacing the insulation.
The replaced insulation shall be tested for performance and shall be used in accordance with the requirements. In particular, the insulation of the lead frame wood block should be taken seriously. The wooden block should be immersed in the thermal transformer oil of about 80 °C for a period of time before installation to ensure the insulation of the wooden block.
2. The transformer insulation test shall be carried out 24 hours after the transformer is oiled.
Since some moisture-insulated parts are immersed in the thermal transformer oil for a long time, water molecules will diffuse to the surface of the insulating paper, and if the test is done after oiling, the insulation defects are often not detected. For example, a low-voltage side of a 1500KVA/35kv power transformer is replaced with a piece of wood supporting the copper row. After the transformer is filled, the test is normal. The 10kV low-voltage side reduces the insulation resistance of the core, the clamp and the ground to about 1mΩ. After inspection by the hood, it was found that the insulation of the 10kv copper platoon was very low. Therefore, the insulation test should be carried out more reliably after the transformer is oiled for 24 hours.
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3, iron core reload should pay attention to its sharp corners.
When reloading the iron yoke, pay attention to the sharp angle of the oil-immersed power transformer core chip, and measure the insulation between the oil passages in time, especially pay attention to the sharp corner of the chip at the oil passage, to prevent the chip from overlapping and causing the core Multi-point grounding. For example, a 650kva 20kv transformer, when replacing the winding iron yoke on the low-voltage side, because there is no attention to the chip angle when reloading, and the oil-to-tank insulation is not measured in time, the insulation between the oil channels is measured after installation. Finally, it took a long time to find out because the core of the core chip shorted the oil passage.

ZTELEC specializes in manufacturing oil-immersed distribution transformers that are safe, energy efficient and maintenance free.

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