Measurement of Characteristic Parameters of Internal Windings in Transformers - Yangzhou Darui
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The transformer winding deformation frequency response tester, based on the measurement of characteristic parameters of internal windings in transformers, adopts the internal fault frequency response analysis (FRA) method currently being developed and perfected in developed countries, and can accurately judge internal faults in transformers.
After the transformer design and manufacturing are completed, its coils and internal structure are determined. Therefore, for a multi-winding transformer coil, if the voltage levels are the same and the winding methods are the same, the corresponding parameters (Ci, Li) of each coil should be determined. Thus, the frequency domain characteristic response of each coil is also determined, and the frequency spectrum among the corresponding three-phase coils has a certain comparability.
If a short circuit occurs between turns or phases during the test, or if the transformer is impacted during transportation, causing relative displacement of the coils, or if the coils deform due to electromagnetic pulling forces under short circuit and fault conditions during operation, the distributed parameters of the transformer windings will change. This in turn affects and changes the original frequency domain characteristics of the transformer, such as amplitude changes in the frequency response and shifts in resonance frequency points. The HX021 transformer winding frequency response tester, developed based on the response analysis method, is such a novel non-destructive testing device for internal faults in transformers. It is suitable for detecting internal structural faults in power transformers from 63kV to 500kV.
The transformer winding deformation frequency response tester quantifies the response changes of internal winding parameters in different frequency domains. Based on the magnitude of the change, the amplitude, region, and trend of the frequency response change, it determines the degree of change in the internal windings of the transformer, and then can judge whether the transformer has been severely damaged and whether major repair is needed.
For transformers in operation, regardless of whether frequency domain characteristic diagrams have been previously saved, the degree of fault can also be judged by comparing the differences in characteristic spectra between the coils of the faulty transformer. Of course, if a set of original winding characteristic diagrams of the transformer is preserved, it will be easier to provide a more powerful basis for the operating status, post-accident analysis, and maintenance of the transformer.
The transformer winding deformation frequency response tester is composed of a laptop computer and a microcontroller to form a high-precision measurement system. It is compact in structure, simple to operate, has relatively complete testing and analysis functions, and can be operated by following the instruction manual or after short-term training.
2. Main technical features:
The acquisition control uses a high-speed, highly integrated microprocessor.
Communication between the laptop and the instrument uses a USB interface.
The hardware core uses DDS digital high-speed frequency sweeping technology (from the United States). Through testing, it can accurately diagnose faults such as winding distortion, bulging, displacement, tilting, inter-turn short circuit deformation, and phase-to-phase contact short circuits.
High-resolution dB value measurement, dual-channel 16-bit A/D (changing the tap changer during field tests results in obvious output changes).
The signal output amplitude can be adjusted by software, with a maximum peak value of ±10V.
The computer generates electronic documents (Word) from the test results.
Precision, high-stability components are selected. For repeated tests on the same phase, the measurement repeatability rate is above 99.5%.
The finished circuit board has special surface treatment, resistant to water and harmful gas pollution.
The laptop and measuring instrument are powered by isolated power supplies to eliminate external interference.
The instrument has a dual measurement system function of linear frequency sweep measurement and segmented frequency sweep measurement, compatible with the two current domestic technical schools of measurement modes.
The amplitude-frequency characteristics comply with the national technical indicators for amplitude-frequency characteristic testers. The horizontal coordinate (frequency) has both linear and logarithmic scales, so the printed curves can be either linear or logarithmic, and users can choose according to actual needs.
Fully meets the technical conditions of the power standard DL/T911-2004 "Frequency Response Analysis Method for Deformation of Power Transformer Windings".
Note: The above information and technical parameters are compiled and released by Yangzhou Darui Electric Co., Ltd.
