An Adaptive Algorithm for the Differential Protection of the UHV Voltage-Regulating Transformer with On-Load Tap Changer
Zheng Tao1, Lu Geye1, Huang Ting1, Zhao Yanjie2, Liu Lianguang1
1. State Key Laboratory of New Energy Power System North China Electric Power University Beijing 102206 China; 2. Nanjing Power Supply Company Jiangsu Electric Power Company Nanjing 210019 China
Abstract：On-load voltage regulation technology has been successfully applied in the ultra-high voltage (UHV) transmission system, leading to a higher requirement for operating reliability of the UHV transformer. During on-load voltage regulating process, it is impossible to adjust the balance coefficient since the actual tap position of the voltage-regulating transformer (VRT) is unavailable for the protection relay. Thus, a fixed ratio is chosen to calculate the differential current, which may probably exist great errors. In practical engineering, the insensitive differential protection is added to avoid the unbalanced current caused by voltage regulation, which increases the complexity of the field operation and decreases the sensitivity of the relay action. Thus, this paper proposes a new method to identify the online tap position adaptively based on the structure of the UHV transformer. The differential current is modified by calculating the online ratio of the VRT to obtain the accurate value during online voltage-regulating process. Digital simulations have demonstrated that the percentage of short-circuit turns and the online tap position have little effect on the operating characteristic of the adaptive differential protection. The sensitivity deficiency of the existing protection strategy is effectively solved during the turn-to-turn faults.
郑涛, 陆格野, 黄婷, 赵彦杰, 刘连光. 特高压有载调压变压器差动保护自适应算法[J]. 电工技术学报, 2017, 32(20): 271-280.
Zheng Tao, Lu Geye, Huang Ting, Zhao Yanjie, Liu Lianguang. An Adaptive Algorithm for the Differential Protection of the UHV Voltage-Regulating Transformer with On-Load Tap Changer. Transactions of China Electrotechnical Society, 2017, 32(20): 271-280.
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2017, Vol. 32 
