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After analyzing the faulty or accidental transformer, we found that the deformation of the transformer winding has become one of the main causes of other faults and accidents. During the operation of the power transformer, its windings are seriously deformed and continue to operate, which will cause power outages and even cause the entire transformer to burn out. Analysis of the main reasons, winding winding process, mechanical structure strength and other design and manufacturing reasons lead to its ability to withstand the impact of current and resistance to external mechanical interference is poor, so the transformer windings are subject to internal electric power and external mechanical force After the influence is easily deformed, especially the short-circuit impulse current and the electric force formed by the short circuit at the outlet of the transformer will cause the winding to be distorted and deformed instantaneously or even be damaged.
Electric power is the main cause of winding deformation. In the winding structure, the high voltage winding is in the outer layer. The axial tensile stress and the radial expansion stress will loosen the compression screw at the end of the winding, causing the pull plate and various fasteners to bend and deform, and the windings to relax; in the inner column or in the middle The middle and low voltage windings are often affected by the axial and radial compressive forces, which results in loosening of the press nails at the end of the winding, displacement of the spacers, tilting of the stays, distortion of the strands, or occurrence of a large area of ​​indentations and upturns. The ampacity of the winding tapping zone and the rectifying zone is unbalanced, and it is easy to produce a transverse leakage magnetic field. When the short circuit occurs, the line pie is easily deformed or damaged under the action of the electromotive force.
The mechanical force is also a major factor influencing the winding deformation. A strong mechanical external force will cause the overall deformation of the transformer winding.
Remedial measures and technical improvement of short circuit faults in power transformers
Based on the above, in order to prevent the winding deformation caused by short-circuit faults and other issues, to reduce the transformer short-circuit accident rate, the academic community to the power transformer short-circuit fault remedial measures were discussed, but also put forward some technical improvements.
To reduce the occurrence of power transformer short-circuit accidents, we must first make a good selection of transformers, select transformers that meet the requirements of short-circuit tests, and reasonably determine the capacity and short-circuit impedance of the transformers; second is to optimize the operating conditions of the transformers, mainly to improve the power lines. Insulation level, to reduce the impact and hazards of the near area; the third is to optimize the operation of the transformer, to determine the mode of operation based on the precise calculation of the short-circuit current, while taking certain protective measures to limit the hazard of short-circuit current; To improve the level of operation and management, to avoid short circuit caused by misuse, to strengthen the transformer inspection and maintenance.
November 06, 2021