Generally, the power supply bureau sends electricity for 5 times or 3 times. Before sending electricity, check whether the bolts are tightened and whether there are metal foreign bodies on the iron core; Whether the insulation distance meets the power transmission standard; Whether the functions of electrical appliances are operating normally; Whether the connection is correct; Shake whether the insulation of each component meets the power transmission standard; Check whether there is frost on the detector body; Check the shell for leaks that allow small animals to enter (especially in the cable entry area); Whether there is discharge sound during power transmission; Every time the power transmission sounds from big to small, if the sound is very loud (only in the case of vibration sound), several possibilities are not excluded:

(1) Noise caused by loose bolts of the shell (pay special attention to the low net);

(2) The output voltage is too large (about 420V), which can be solved by adjusting the tap position. If it is 428V, adjust the high-voltage tap position upwards and put it in the 10500V gear (10 2× 2.5%/0.4 as an example), that is, the 2-3 tap position (one end of copper wire is grounded before tap adjustment, and the other end is placed in the exposed copper part of the high-voltage connection cable for discharge).

(3) There are foreign objects (bolts, nails, etc.) in the fan.