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Detection Technology

Abnormal sound from the DC resistance tester

time:2021/5/2   source:华天电力  reading:308 time

When the transformer DC resistance tester is in normal operation, it will emit a continuous and uniform "humming" sound. If the sound produced is uneven or there are other special noises, it should be regarded as abnormal operation of the transformer, and the fault can be found out according to the different sound and processed in time. The main faults are as follows:

The power grid has overvoltage. When single-phase grounding or electromagnetic resonance occurs in the power grid, the sound of the transformer is sharper than usual. When this happens, you can make a comprehensive judgment based on the instructions of the voltmeter.

Transformer overload operation. The load changes greatly, and because of the effect of harmonics, a "wow" or "gluck" intermittent sound occurs in the transformer DC resistance tester, and the pointer of the monitoring and measuring instrument swings, and the pitch is high and the volume is loud.

Transformer DC Winding Resistance Tester.png

The transformer clamps or screws are loose. When the sound is louder than usual and there is obvious noise, but there is no obvious abnormality in the current and voltage, it may be that the internal clamp or the screw that presses the iron core is loose, causing the silicon steel sheet to vibrate.

Partial discharge of transformer. If the transformer's drop-out fuse or tap switch is in poor contact, there will be a "creaking" discharge sound; if the transformer's transformer bushing is dirty, the surface enamel is peeling off or there are cracks, a "hissing" sound can be heard ; If there is a partial discharge or poor electrical connection inside the transformer, a "squeak" or "crack" sound will be emitted, and this sound will vary with the distance from the fault. At this time, the transformer should be deactivated immediately.

The transformer winding is short-circuited. The sound is mixed with the sound of boiling water, and the temperature changes sharply, and the oil level rises. It should be judged that the transformer winding has a short-circuit fault. In severe cases, there will be a huge roar, and a fire may follow. At this time, the transformer should be stopped immediately for inspection.

The transformer shell flashover discharge. This sound will appear when the high voltage of the transformer winding causes the outgoing wires to flashover and discharge to each other or to the shell. At this time, the transformer should be deactivated for inspection.

Odor, abnormal color

The rupture of the explosion-proof membrane of the explosion-proof tube: the rupture of the explosion-proof membrane of the explosion-proof tube will cause water and moisture to enter the transformer, resulting in the emulsification of the insulating oil and the reduction of the insulation strength of the transformer.

Bushing flashover discharge, bushing flashover discharge will cause heat generation, aging, insulation damage and even explosion.

Overheating of the lead (terminal) and line card causes abnormality; the fastening part of the sleeve terminal is loose or the nose of the lead is slippery, etc., the contact surface is seriously oxidized, which makes the contact overheated, the color darkens and the surface coating is also Destroyed.

Sleeve fouling causes abnormality; fouling of the sleeve produces corona, flashover will produce ozone smell, and the burning of cooling fan and oil pump will give off a burnt smell.

In addition, excessive moisture absorption, damaged gaskets, and too much water entering the oil chamber can cause discoloration of the moisture absorbent.

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