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Diagnosis of heating fault of power transformer core

2019-04-02 09:14:59

Gas chromatography analysis is an important method for diagnosing the heating failure of power transformer core. Practice shows that in the case of local overheating, the transformer oil contains a large amount of CH4 and C2H4. When the fault involves solid insulation, the oil contains a large amount of CO and CO2. Based on this characteristic, the gas image method and the three-ratio method can be used to judge the nature of the core thermal fault. In the diagnosis, the three-ratio method is combined with the four-ratio method to distinguish whether the core thermal fault occurs in the magnetic circuit or in the electrical circuit. In addition, measuring DC resistance can make further judgments on the thermal fault of the conductive loop.

    Different reasons for the heating failure of the power transformer core require different treatment methods.
    1. The transformer low-voltage winding is overheated due to the winding structure and other reasons, and the low-voltage winding of the transformer can be changed to a double-helical structure.
    2. For the overheating failure of the iron core caused by blockage of the cooler tube, it should be treated regularly with compressed air or water to clean the cooling tube set.
    3. If the iron core is faulty caused by the tap changer, connect the lead wire and the tap changer correctly, and tighten the nut to avoid loose heating.
    4. In order to avoid overheating of the iron core after the lead wire and the copper tube of the casing are connected, the following measures can be taken:
    The current lead wire insulation method is not changed, and the length of the lead cable is accurately cut only when each product is tested, so that the lead length and the sleeve are accurately assembled;
    Change the insulation wrapping method of the lead cable, keep the insulation of the lead cable intact, and do not allow the insulation to loosen the copper.
    5. In order to prevent overheating failure of the iron core caused by magnetic leakage, magnetic shielding can be added to the inner wall of the transformer tank and the steel plate of the winding.
    When dealing with the thermal failure of the power transformer core, only to find the corresponding processing method, it can effectively handle the thermal failure of the transformer core and improve the reliability of the safe operation of the transformer.