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| A Novel Method to Rapidly Identify Inrush Current and Internal Fault Current Based on Variation Characteristic of Fundamental Current Amplitude |
| Ma Jing1, Wang Zengping1, Wu Jie2 |
| 1. Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Under Ministry of Education North China Electric Power University Beijing 102206 China 2. Zhejiang Electric Power Design Institute Hangzhou 310014 China |
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Abstract A new transformer protection principle based on two-instantaneous-value-product algorithm to extract the feature of fundamental current amplitude is put forward in this paper. First, the algorithm of two-instantaneous-value-product is developed, and variation trends of fundamental current amplitudes are analyzed in the case of inrush currents and internal fault currents. Whether the fundamental current amplitude reveals the descending feature or not can be used to distinguish the inrush current and the internal fault. The computational simplicity of the proposed scheme enables its implementation in real-time applications with low-cost microprocessors. Dynamic testing results indicate that this method is able to clear internal fault even light fault less than a cycle and can not be affected by the current transformer saturation. Moreover, compared with the second harmonic restraint principle and the waveform comparison principle, the proposed algorithm has better performance.
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Received: 15 November 2007
Published: 14 February 2014
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2009, Vol. 24 
