Defect Identification Method for Energy Storage Springs in On-Load Tap Changers Based on High-Frequency Current Characteristics
Liu Haoyu1, Gao Shuguo1, Fang Tiancheng2, Zhang Fan2, Guo Meng3, Ji Shengchang2
1. State Grid Hebei Electric Power Research Institute Shijiazhuang 050021 China; 2. State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong University Xi’an 710049 China;; 3. State Grid Hebei Electric Power Co. Ltd Shijiazhuang 050021 China
Abstract:The on-load tap changer (OLTC) is the only component inside a transformer that requires frequent operation. Its energy storage spring is prone to loosening and degradation after repeated switching, which results in insufficient release restoring force and may cause severe mechanical failures such as switching malfunctions. To address this issue, this paper proposes a defect identification method for OLTC energy storage springs based on high-frequency current characteristics. First, a simulated test platform under rated OLTC operating conditions was constructed using the resonance method. Experimental observations showed that during the switching process, the critical make-and-break actions of the moving and stationary contacts induced high-frequency current spikes coupled onto the grounding wire, and a correspondence between the occurrence timings of these current spikes and the switching sequence was established. Subsequently, based on an original spring with a restoring force of 600 N, three types of defective energy storage springs were fabricated with restoring forces of 545 N, 470 N, and 400 N, respectively. The experimental results indicated that the reduction of restoring force led to prolonged bridging time, an extended interval before the first high-frequency current spike, and a significant increase in the total number of spikes. In addition, spring defects caused a decrease in the rotational kinetic energy of the main shaft and slower movement of the contacts, which resulted in multiple pulse-like high-frequency current waveforms with intervals of approximately 10 ms and a notable increase in the number of arc reignitions between contacts. On this basis, a peak screening algorithm combining time interval and amplitude saliency was proposed. The algorithm includes three steps: noise filtering, extraction of significant high-frequency current timings, and elimination of asynchronous switching peaks. Four time-domain features were introduced for current characterization, namely the coefficient of variation of peak values, the number of peaks, the maximum inter-peak interval, and the peak range. In practical OLTC switching tests, the heating of transition resistors prevented continuous switching operations and resulted in low testing efficiency. To address the problem of long test cycles, a data augmentation method based on an improved conditional generative adversarial network (CGAN) was developed. The traditional CGAN was optimized by incorporating label embedding (LE) and mini-batch discrimination (MBD), which enhanced both stability and generalization ability of the model. An adaptive boosting algorithm (AdaboostM2) was then employed for defect classification using the augmented dataset. Experimental results demonstrated that the minimum distinction error between generated and original data was only 1.13%. After data augmentation, the balanced accuracy of defect identification reached 96.67%, representing a 19.60% improvement compared with the original dataset. Moreover, the CGAN+LE+MBD approach significantly reduced the interference of noisy data with large variance during the augmentation process. When different levels of additive noise were applied, the proposed model still maintained strong robustness under a signal-to-noise ratio of 20 dB. This work provides an effective framework for capturing the degradation signatures of OLTC springs and offers significant technical value for accurate defect identification and early warning of potential failures.
刘浩宇, 高树国, 方天承, 张凡, 郭猛, 汲胜昌. 基于高频电流特征的有载分接开关储能弹簧缺陷识别方法[J]. 电工技术学报, 2026, 41(13): 4584-4597.
Liu Haoyu, Gao Shuguo, Fang Tiancheng, Zhang Fan, Guo Meng, Ji Shengchang. Defect Identification Method for Energy Storage Springs in On-Load Tap Changers Based on High-Frequency Current Characteristics. Transactions of China Electrotechnical Society, 2026, 41(13): 4584-4597.
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