News Details

    Power frequency partial discharge-free test transformers produce no noise during normal operation, which is a normal phenomenon. However, sometimes excessive noise may occur, indicating that faults can be diagnosed by listening to the sounds. In fact, the sounds of a transformer can also indicate whether there is damage. If the transformer exhibits certain sound issues, it means that a fault has occurred and maintenance is required. Common dry-type transformers that produce these sound problems during operation indicate that your transformer is already damaged. Let's take a closer look below:

 

    The power frequency partial discharge-free test transformer has abnormal noise. If the transformer's sound is louder than normal and accompanied by noise, but the current and voltage are normal, it may be caused by loose clamps or screws pressing the iron core, leading to vibration of the silicon steel sheets.

 

    Power frequency partial discharge-free test transformers produce discharge sounds. If partial discharge occurs in the transformer or on its surface, the sound will be mixed with "crackling" discharge sounds. When this happens, if it is at night or in rainy weather, blue corona or sparks can be seen near the transformer bushing, indicating severe contamination of the porcelain parts or poor contact of the equipment clamps. If the discharge is inside the transformer, it may be static discharge from ungrounded components or discharge from the tap changer contacts. In such cases, the transformer should be further tested or taken out of service.

 

    The transformer produces a water boiling sound. If the transformer's sound is mixed with a water boiling sound, accompanied by temperature changes and oil level rise, it should be judged as a short-circuit fault in the transformer winding, or severe overheating caused by poor contact of the tap changer. In this case, the transformer should be taken out of service for inspection.

 

    The transformer produces a cracking sound. If the transformer's sound is mixed with uneven cracking sounds, it indicates insulation breakdown in the transformer or on its surface. In this case, the transformer should be taken out of service for inspection.

 

    Wiring method for the power frequency partial discharge-free test transformer:

 

    1. Short-circuit the "input" and "output" terminals of the transformer and use a megohmmeter to test the insulation resistance to the ground wire. When measured with a 1000V megohmmeter, the resistance should be greater than 2 megohms.

 

    2. The cross-section of the input and output power lines should be selected according to the current value requirements; it is recommended to configure according to a current density of 2-2.5 A/mm2.

 

    3. The input and output three-phase power lines should be connected to phases A, B, and C according to the busbar colors yellow, green, and red on the transformer terminal board. The neutral line should be connected to the transformer's neutral point, and the ground wire, power frequency partial discharge-free test transformer housing, and the transformer's phase should be connected. Usually, the ground wire and neutral wire we refer to are both led out from the transformer's neutral point. (For example, the transformer box should be connected correspondingly to the box's ground wire mark.) Check the input and output lines to ensure they are correct.

 

    4. First, conduct a no-load power-on test to observe whether the input and output voltages meet the requirements. At the same time, observe whether the machine has abnormal sounds, sparks, odors, or other abnormal phenomena. If any abnormality is found, disconnect the input power.

 

    5. Only after the no-load test is completed and normal can the load be connected.