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Short circuit vacuum drying of current transformer

2017-08-02 12:03:16   COMMENT:0 HITS:
      The current transformer usually uses oil free drying, but some manufacturers believe that the product should be energized under the condition of full oil, so as to observe the temperature rise of the product. This is especially important for 220kV and above the current transformer insulation, because these products are relatively thick, without oil, the conduction effect is poor, even if it appears from the outside temperature is low, while the internal insulation may overheat and aging even by Tan jiao. Therefore, it is better to heat the product under the condition of oil, and then release the oil inside the product without any oil drying until the temperature rises and tends to be stable. In the absence of oil vacuum, the current passing through the primary winding shall not exceed 70% of the rated current.
Operation points are as follows:
(1) dismantle the metal expander and install a temporary cover plate with a vacuum, oil filling and measuring joint or valve
(2) the primary winding is connected in series, and the copper wire is used for reliable short connection.
(3) I open the two junction box, dismantle the external wiring, measure the DC resistance of the secondary winding with the double arm bridge, record the corresponding temperature, and use this data as the reference value to calculate the average temperature of the two winding in the drying process.
(4>) the insulation resistance of the one or two winding to the ground is measured by the insulation resistance meter, and the corresponding temperature is recorded
(5) measurement of volt ampere characteristic under the condition of primary winding short circuit. At this point, all the parallel windings of the protective windings are applied AC voltage to measure the current of the two winding < or primary winding) to achieve the rated current of the transformer. The applied AC voltage is recorded.
(6) thermocouples are set on the exposed part of the primary winding, the short circuit and the connecting line, and the thermometer is set on the outer surface of the porcelain sleeve, the middle, the lower and the top cover, so as to measure and control the drying temperature.
(7) connect the heating circuit and the vacuum pipeline.

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