When faced with a transformer that requires winding deformation assessment, design and selection personnel often ask: between the frequency response method and the impedance method, which should be the primary approach? How much does the degree of operational automation of the tester affect on-site efficiency? The following outlines several key points from an engineering selection perspective.
1. Clarify the division of labor between the frequency response method and the impedance method. The frequency response method determines structural changes by scanning the winding frequency response characteristic curve, and is suitable for detecting defects such as winding deformation and displacement; the impedance method assists in determining changes in winding geometric dimensions by measuring changes in short-circuit impedance. During selection, it should be confirmed whether the equipment supports both test modes simultaneously, so as to allow cross-verification under different working conditions. Scanning frequency accuracy is the foundation for the comparability of frequency response method data, and a frequency accuracy of no greater than 0.01% for the sinusoidal signal output by the signal source is the basic threshold.
2. Pay attention to frequency synthesis and sampling accuracy. Equipment using DDS digital frequency synthesis technology and high-speed A/D sampling can achieve frequency accuracy of up to 0.001%, which helps improve the repeatability of frequency response curves. For occasions requiring multiple repeated measurements for comparison, frequency accuracy is directly related to curve overlap, and this parameter should be checked as a mandatory indicator during selection.
3. Automation capability affects on-site efficiency. Transformer winding testing involves climbing and wiring; after parameter settings are completed, completing all measurements with one key press can reduce the number of times of climbing the transformer and wiring, and shorten testing time. During selection, it should be examined whether the equipment supports three-phase automatic testing, single-key startup after parameter setting, and continuity of the measurement process.
4. Wiring and switching methods for three-phase automatic testing. Three-phase automatic testing can reduce phase-to-phase wire changing operations and lower the probability of wiring errors. During selection, it is necessary to confirm whether the equipment has a three-phase automatic switching function and whether the switching process affects measurement stability.
5. Environmental adaptability and data management. On-site testing needs to consider the equipment's anti-interference capability in the electromagnetic environment of substations, as well as the convenience of data storage, export, and comparative analysis. During selection, it is advisable to combine the actual testing process to evaluate the degree of software support for historical data management and curve comparison functions.
