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Why does the DC resistance tester make a noise?

time:2020/11/10   source:华天电力  reading:223 time

The DC resistance tester will produce a continuous "hum" sound when it is running. If the sound produced by the instrument is uneven or has other special noises, it should be regarded as abnormal economic operation of the transformer. It can also find out system faults according to different situations, analyze and deal with them in a timely and effective manner, mainly in the following aspects:


Transformer DC Winding Resistance Tester.png


1. Overvoltage occurs in the power grid. When single-phase grounding or electromagnetic resonance occurs in the power grid, the sound of the transformer is sharper than usual. When this happens, a comprehensive judgment can be made in conjunction with the instructions of the voltmeter.


2. Due to the overload operation of the transformer, the load changes greatly, and the DC resistance test instrument has intermittent "wow" or "creak" sound, and the pointer of the monitoring and measuring instrument swings, the pitch is high, and the volume is loud.


3. Whether the transformer clamps or screws are loose, the sound is louder than usual and there are obvious noises. But when there is no obvious abnormality in the current and voltage, it may be that the internal clamps or the screws that press and fix the iron core are loose, which may increase the vibration between the traditional silicon steel sheets.


4. The transformer performs partial discharge. If the drop-out fuse or tap switch of the transformer can contact bad society, there will be a "creaking" discharge sound. If the transformer bushing of the transformer is dirty, the enamel on the surface falls 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 "creak" 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.


5. Short circuit of transformer winding. The sound is mixed with the sound of water boiling, and the temperature changes sharply, and the oil level rises. It should be judged that a short-circuit fault has occurred between the transformer windings. If it is severely affected, there will be a huge roar, and then we may cause a fire. At this time, The transformer should be stopped immediately for analysis and inspection.


6. Flash discharge of transformer shell. This sound will appear when the high-voltage environment of the transformer windings causes the outgoing wires to flashover and discharge to each other or to the shell. At this time, different transformers can be deactivated for inspection.


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