Switching Transient Characteristics Analysis and Transition Resistance Selection Method for On-Load Tap-Changer of Converter Transformer
Chai Jianlong1, Li Xuan2, Yang Ming1, Sima Wenxia1, Liu Hui3, Li Gang4
1. State Key Laboratory of Power Transmission Equipment Technology Chongqing University Chongqing 400044 China; 2. State Grid Corporation of China Beijing 100031 China; 3. State Grid Lishui Power Supply Company Lishui 323000 China; 4. China Electric Power Research Institute Beijing 100192 China
Abstract：The vacuum on-load tap-changer (OLTC) enables continuous voltage regulation in converter transformers. In HVDC systems with a high proportion of power electronic devices, the interaction of multiple factors—such as trigger angle, commutation angle, and power-factor angle—generates substantial harmonics, leading to complex transient behavior during vacuum OLTC operation. This results in high rates of change of breaking current and recovery voltage, complicating the switching process. Existing research lacks a systematic analysis of the transient characteristics during vacuum OLTC switching. Moreover, the appropriate selection of transition resistance is essential for reliable OLTC operation. The selection methods for transition resistance in converter transformer OLTCs follow traditional AC approaches, neglecting the influence of resistance on high switching electrical stress. In this work, the coupling relationship among trigger angle, commutation angle, and power factor angle was investigated, and their collective impact on the transient characteristics of vacuum OLTC switching was revealed. First, based on an analysis method for electrical stresses during the switching process of vacuum on-load tap-changer in converter transformer, the load current of the converter transformer was accurately characterized. A vacuum OLTC with isolated contacts and a “three vacuum tubes, double resistance” configuration was used as the research object, and analytical expressions for breaking characteristic parameters—such as breaking current, recovery voltage, and their rates of change—were derived. Second, a transition resistance selection method tailored for converter transformer vacuum OLTCs was proposed, which specifically considered the influence of the transition resistance on the high rates of change of breaking current and recovery voltage. Based on these analytical expressions, a recommended range for transition resistance was determined, taking the rated step power and short-term emergency load current limit of the converter transformer considered as primary constraints. The transition resistance that minimized the total switching capacity was identified by calculating the switching capacity of main and transition contacts. Under the principle of balanced contact erosion loss, matching resistance values were obtained for different contact materials, allowing flexible selection according to engineering requirements. Finally, the selected resistance was validated using an electrical stress rate-of-change verification method. Taking an actual ±800 kV UHVDC transmission project as an example, the variation patterns of OLTC breaking characteristics are quantitatively analyzed with trigger angle, commutation angle, and power-factor angle as variables. The coupling effects among these parameters on switching transients are further examined. Results indicate that the trigger angle α and commutation angle μ influence the transient characteristics through both harmonic content in the load current and the power-factor angle. The transition resistance is selected and verified accordingly. To ensure OLTC reliability, the recommended transition resistance range is 2.063 Ω<R<5.835 Ω. When minimizing total switching capacity, R=3.369 Ω is suitable; for E-Cu and Cu-W contact materials, the matching values are 2.895 Ω and 2.917 Ω, respectively. The proposed method offers broad applicability. By solving analytical expressions for OLTC breaking characteristic parameters and selecting the corresponding parameters according to different HVDC systems, quantitative analysis of switching transients and transition resistance selection can be performed for any topology.
[1] Xiahou D, Zhao T, Yi X Q, et al.Electromagnetic transient simulation analysis on electrical fault of vacuum type on-load tap changer in converter transformer[J]. IET Conference Proceedings, 2022, 2021(15): 1314-1319. [2] 张德明. 变压器真空有载分接开关[M]. 北京: 中国电力出版社, 2015. [3] Samadi A, Eriksson R, Soder L, et al.Coordinated active power-dependent voltage regulation in distribution grids with PV systems[J]. IEEE Transactions on Power Delivery, 2014, 29(3): 1454-1464. [4] 李想, 杨骁, 刘伟, 等. 非对称星型混合式有载分接开关切换时序分析及其优化[J]. 电工电能新技术, 2025, 44(1): 10-22. Li Xiang, Yang Xiao, Liu Wei, et al.Switching timing analysis and optimization of hybrid on load tap changer with asymmetric-star topology[J]. Advanced Technology of Electrical Engineering and Energy, 2025, 44(1): 10-22. [5] 张德明. 真空分接开关技术的论述(1)[J]. 变压器, 2011, 48(8): 54-56. [6] 高煜, 赵学童, 李刚, 等. 换流变压器用有载分接开关过渡电阻温升的动态仿真[J]. 电工技术学报, 2025, 40(7): 2226-2235. Gao Yu, Zhao Xuetong, Li Gang, et al.Simulation on dynamic temperature rise of transition resistance in on-load tap-changer used in converter transformer[J]. Transactions of China Electrotechnical Society, 2025, 40(7): 2226-2235. [7] Qian Guochao, Dai Weiju, Hong Zhihu, et al.Electrical stress analysis for vacuum on-load tap-changer transition circuits under the influence of harmonic currents[C]//2023 IEEE International Conference on Power Science and Technology (ICPST), Kunming, China, 2023: 370-375. [8] 吕玮, 陈羽, 孙超, 等. 分体分步式换流变有载分接开关研制[J]. 高压电器, 2024, 60(1): 154-162. Lü Wei, Chen Yu, Sun Chao, et al.Development of split-step on-load tap-changer for converter transformer[J]. High Voltage Apparatus, 2024, 60(1): 154-162. [9] 王绍武, 李鹏, 李金忠, 等. 变压器真空有载分接开关研究综述[J]. 中国电机工程学报, 2022, 42(18): 6893-6908. Wang Shaowu, Li Peng, Li Jinzhong, et al.Overview of transformer vacuum-type on-load tap changers[J]. Proceedings of the CSEE, 2022, 42(18): 6893-6908. [10] 薛振华, 孙继星, 闫胜春, 等. 直流条件下真空断路器开断过程重击穿特性[J]. 电气工程学报, 2025, 20(3): 300-308. Xue Zhenhua, Sun Jixing, Yan Shengchun, et al.Restrike characteristic of vacuum breaker in its open process under DC voltage[J]. Journal of Electrical Engineering, 2025, 20(3): 300-308. [11] 王季梅. 真空开关的现状及发展趋势[J]. 电力设备, 2005(2): 1-5. Wang Jimei.Present situation and development tendency of vacuum switch[J]. Electrical Equipment, 2005(2): 1-5. [12] 程显, 白青林, 葛国伟, 等. 真空与气体一体化串联机械开关及其直流快速转移应用[J]. 电工技术学报, 2024, 39(5): 1464-1473. Cheng Xian, Bai Qinglin, Ge Guowei, et al.High speed switch with series-connected vacuum and gas interrupters and its DC fast transfer application[J]. Transactions of China Electrotechnical Society, 2024, 39(5): 1464-1473. [13] 王海涛, 王彦岭, 李书舸, 等. 不同电流下Ce掺杂AgCuO触头材料转移行为研究[J]. 电工技术学报, 2025, 40(2): 574-586. Wang Haitao, Wang Yanling, Li Shuge, et al.Study of materials transfer behavior of Ce-doped AgCuO contact materials at different current levels[J]. Transactions of China Electrotechnical Society, 2025, 40(2): 574-586. [14] 夏承东, 田保红, 刘平, 等. CuCr合金触头材料的研究现状[J]. 铸造技术, 2007, 28(1): 139-141. Xia Chengdong, Tian Baohong, Liu Ping, et al.Current research status on CuCr alloy for contact material[J]. Foundry Technology, 2007, 28(1): 139-141. [15] Li Wangpei, Thomas R L, Smith R K.Effects of Cr content on the interruption ability of CuCr contact materials[J]. IEEE Transactions on Plasma Science, 2001, 29(5): 744-748. [16] 陈艺煌, 邵振国, 林俊杰, 等. 融合多源量测数据的区间型抗差谐波状态估计[J]. 电工技术学报, 2024, 39(23): 7394-7405. Chen Yihuang, Shao Zhenguo, Lin Junjie, et al.Interval harmonic robust state estimation method based on multi-source measurement data fusion[J]. Transactions of China Electrotechnical Society, 2024, 39(23): 7394-7405. [17] Kim C K, Sood V K, Jang G S, et al.HVDC Transmission: Power Conversion Applications in Power Systems[M]. New York: Wiley-IEEE Press, 2009. [18] 沈大中, Axel Kraemer, Dieter Dohnal.真空有载分接开关在高压直流换流变压器中的运用[J]. 南方电网技术, 2011, 5(1): 25-28. Shen Dazhong, Kraemer A, Dohnal D.Application of vacuum on-load tap-changers in HVDC converter transformers[J]. Southern Power System Technology, 2011, 5(1): 25-28. [19] Shen Dazhong, Kraemer A, Dohnal D.Vacuum switching technology improves the switching capacity of on-load tap-changers in HVDC applications[C]//2006 International Conference on Power System Technology, Chongqing, China, 2006: 1-6. [20] 朱英浩, 沈大中. 有载分接开关电气机理[M]. 北京: 中国电力出版社, 2012. [21] 张长虹, 范广伟, 邓军, 等. 换流变真空有载分接开关谐波电流切换试验技术的研究与分析[J]. 高压电器, 2025, 61(2): 26-34. Zhang Changhong, Fan Guangwei, Deng Jun, et al.Research and analysis on harmonic current switching test technology of vacuum type on-load tap-changer for converter transformer[J]. High Voltage Apparatus, 2025, 61(2): 26-34. [22] 杨鸣, 赵小涵, 司马文霞, 等. 单相变压器内部短路多尺度故障分析模型构建方法[J]. 电工技术学报, 2025, 40(13): 4085-4099. Yang Ming, Zhao Xiaohan, Sima Wenxia, et al.Construction method of multi-scale fault analysis model for single-phase transformer with internal short circuit[J]. Transactions of China Electrotechnical Society, 2025, 40(13): 4085-4099. [23] 杨鸣, 黄琳榆, 孙金昊, 等. 变压器类装备电磁暂态模型构建技术综述[J]. 高电压技术, 2025, 51(1): 1-20. Yang Ming, Huang Linyu, Sun Jinhao, et al.Review of transformer modeling technologies for electromagnetic transient analysis[J]. High Voltage Engineering, 2025, 51(1): 1-20. [24] 闫晨光, 张芃, 徐雅, 等. 换流变压器有载分接开关级间短路故障差动保护动作特性[J]. 电工技术学报, 2023, 38(21): 5878-5888, 5912. Yan Chenguang, Zhang Peng, Xu Ya, et al.Differential protection performance for converter transformer intertap short-circuit faults in on-load tap changers[J]. Transactions of China Electrotechnical Society, 2023, 38(21): 5878-5888, 5912. [25] 司马文霞, 刘蕙, 厉璇, 等. 换流变压器真空有载分接开关切换过程电气应力解析方法[J]. 中国电机工程学报, 2022, 42(18): 6908-6919. Sima Wenxia, Liu Hui, Li Xuan, et al.Analysis method of electrical stresses during switching process of vacuum on-load tap-changer in converter transformers[J]. Proceedings of the CSEE, 2022, 42(18): 6908-6919. [26] 吉锋. 变压器的有载分接开关(上)[J]. 变压器, 1986, 23(4): 2-17. [27] 张德明. 提高ZY1A型有载分接开关可靠性(上)[J]. 变压器, 1990, 27(11): 4-9. [28] 刘雪丽, 李金忠, 高飞, 等. ±800kV换流变压器用真空式有载分接开关关键技术研究[J]. 中国电机工程学报, 2016, 36(19): 5350-5356, 5417. Liu Xueli, Li Jinzhong, Gao Fei, et al.Key technology research for vacuum type on-load tap-changer of ±800kV direct current convertor transformers[J]. Proceedings of the CSEE, 2016, 36(19): 5350-5356, 5417. [29] 沈大中, Axel Kraemer, Dieter Dohnal.真空有载分接开关在高压直流换流变压器中的运用[J]. 电气制造, 2011(3): 52-56. [30] 张德明. 分接开关过渡电阻匹配的探讨与计算[J]. 上海电器技术, 2006(1): 17-26. Zhang Deming.Discuss and calculate for transition resistance of tap changer[J]. Shanghai Electric Appliance Technology, 2006(1): 17-26. [31] 国家能源局. 换流变压器有载分接开关使用导则: DL/T 2003—2019[S]. 北京: 中国电力出版社, 2020. [32] 张德明. 浅论真空有载分接开关研发技术的要素(上)[J]. 变压器, 2014, 51(7): 35-40. Zhang Deming.Brief discussion on key factors of development technology of vaccum on-load tap- changer[J]. Transformer, 2014, 51(7): 35-40. [33] 李鹏, 李金忠, 汪可, 等. 一种带隔离触头的真空有载分接开关过渡电路及调压方法: CN111986902A [P].2020-11-24. [34] 朱英浩, 沈大中. 换流变压器用有载分接开关[M]. 北京: 中国电力出版社, 2016. [35] 王兆安, 刘进军, 王跃, 等. 谐波抑制和无功功率补偿[M]. 3版. 北京: 机械工业出版社, 2016. [36] (奥)George J. Wakileh. 电力系统谐波: 基本原理、分析方法和滤波器设计[M]. 徐政, 译. 北京: 机械工业出版社, 2011. [37] 国家电网公司. 特高压直流输电技术研究成果专辑(2012年)[M]. 北京: 中国电力出版社, 2015. [38] 韩民晓, 文俊, 徐永海. 高压直流输电原理与运行[M]. 3版. 北京: 机械工业出版社, 2020. [39] (德)科雷默尔. 有载分接开关原理和应用[M]. 沈祖俊, 译. 沈阳: 辽宁科学技术出版社, 2006. [40] 国家质量监督检验检疫总局, 中国国家标准化管理委员会. 电力变压器第7部分:油浸式电力变压器负载导则: GB/T 1094.7—2008[S]. 北京: 中国标准出版社, 2009.
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