Winding Deformation Tester (Transformer Winding Deformation Tester), also commonly known as Transformer Winding Deformation Analyzer, is a professional instrument used to detect the mechanical condition of power transformer windings. It mainly determines whether the winding has undergone displacement, distortion, bulging, or inter-turn short circuits by analyzing the frequency response characteristics or short-circuit impedance changes of the winding. The following is the core information about this instrument: 1. Working Principle Currently, there are two mainstream testing methods, and many modern instruments have both functions: Frequency Response Analysis (FRA): Principle: Inject sinusoidal wave signals of different frequencies (usually from tens of Hz to several MHz) into the transformer winding, measure and record the amplitude ratio and phase difference between the input and output signals, forming a "frequency response curve." Judgment: Compare the currently measured curve with the original curve (fingerprint data) from the factory or with the curve of the undamaged phase in the same type of three-phase transformer. If the curve shows significant deviation in a specific frequency band (such as resonance point shift, amplitude change), it indicates mechanical deformation of the winding. Advantages: High sensitivity, can detect minor deformations, and is currently the most effective method internationally recognized. Low Voltage Impedance (LVI) Method: Principle: Apply low voltage on the low-voltage side and measure the short-circuit impedance value of the winding. Judgment: Compare the measured impedance value with the factory value or historical data. If the impedance change exceeds a certain standard (usually ±2% or ±3%, depending on the standard), the winding is considered possibly deformed. Advantages: Simple operation, intuitive results, often used as an auxiliary verification method for FRA. 2. Main Application Scenarios After suffering short-circuit impact: When a short-circuit fault occurs at or near the transformer outlet, the huge electromagnetic force may cause winding deformation, requiring immediate testing. After transportation and installation: Large transformers may experience severe vibration or collision during long-distance transportation or hoisting. Regular preventive tests: As part of condition-based maintenance, establish a health record for the winding. Before and after major repairs: Evaluate the repair effect or determine whether a cover lifting inspection is needed. 3. Test Result Criteria The test itself does not directly give a "pass/fail" conclusion but relies on professional analysis of the spectrum. Common analysis dimensions include: Low frequency band (1kHz - 100kHz): Mainly reflects deformation of the overall winding structure (such as axial displacement). Medium frequency band (100kHz - 600kHz): Mainly reflects internal distortion or local deformation of the winding. High frequency band (600kHz - 1MHz+): Mainly reflects changes in inter-turn capacitance, corresponding to inter-turn short circuits or minor deformations. The commonly used correlation coefficient method (R value) quantifies curve similarity. Typically, R > 0.95 is considered normal, and R < 0.90 may indicate problems (specific thresholds refer to standards such as DL/T 911). 4. Applicable Standards In China, the following standards are mainly followed: DL/T 911-2016 "Frequency Response Analysis Method for Power Transformer Winding Deformation" GB 1094.5 "Power Transformers - Part 5: Ability to Withstand Short Circuit" 5. Purchasing and Usage Precautions Anti-interference capability: The electromagnetic environment on site is complex, so the instrument must have good anti-interference filtering function. Wiring method: Usually end-to-end or end-to-ground wiring is used, and the instrument manual must be strictly followed to ensure good grounding. Data analysis software: Good supporting software should have functions such as automatic comparison, correlation coefficient calculation, and report generation. If you need parameter comparisons for specific models (such as brands like Wuhan Huatian, Baoding Tianwei, OMICRON, etc.) or need to know specific test wiring diagrams, please let me know, and I can provide more detailed information.
