Application of the criterion of small current grounding direction of the energy method
DOI:DOI: 10.19783/j.cnki.pspc.211519
Key Words:small current grounding system  energy method  distributed capacitance  resonance frequency
Author NameAffiliation
YANG Tao 1. Hangzhou Yineng Electric Power Technology Co., Ltd., Hangzhou 310007, China
2. State Grid Zhejiang Electric Power Co., Ltd. Electric Power Research Institute, Hangzhou 310007, China
3. Nanjing Zhihui Power Technology Co., Ltd., Nanjing 211100, China
4. College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China 
JIN Huafeng 1. Hangzhou Yineng Electric Power Technology Co., Ltd., Hangzhou 310007, China
2. State Grid Zhejiang Electric Power Co., Ltd. Electric Power Research Institute, Hangzhou 310007, China
3. Nanjing Zhihui Power Technology Co., Ltd., Nanjing 211100, China
4. College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China 
ZENG Bingyuan 1. Hangzhou Yineng Electric Power Technology Co., Ltd., Hangzhou 310007, China
2. State Grid Zhejiang Electric Power Co., Ltd. Electric Power Research Institute, Hangzhou 310007, China
3. Nanjing Zhihui Power Technology Co., Ltd., Nanjing 211100, China
4. College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China 
LIANG Haidong 1. Hangzhou Yineng Electric Power Technology Co., Ltd., Hangzhou 310007, China
2. State Grid Zhejiang Electric Power Co., Ltd. Electric Power Research Institute, Hangzhou 310007, China
3. Nanjing Zhihui Power Technology Co., Ltd., Nanjing 211100, China
4. College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China 
ZHAO Fang 1. Hangzhou Yineng Electric Power Technology Co., Ltd., Hangzhou 310007, China
2. State Grid Zhejiang Electric Power Co., Ltd. Electric Power Research Institute, Hangzhou 310007, China
3. Nanjing Zhihui Power Technology Co., Ltd., Nanjing 211100, China
4. College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China 
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Abstract:It is difficult to accurately determine the ground fault direction using a single-point electrical quantity in a small current grounding system. Thus an improved energy method-based grounding direction criterion is proposed. From the superposition principle, a single-phase ground fault transient equivalent circuit is analyzed, and the zero-sequence energy at the measurement point is composed of the capacitor charging energy at the initial moment of the fault and the steady-state oscillation energy to maintain the LC oscillation. The characteristics of the zero-sequence energy in different grounding modes and resistances are analyzed. To simplify the setting principle, the zero-sequence energy function is discretized and quadratic integration and a practical quadratic integral criterion is proposed. Simulation tests for a metallic fault and a 3000  resistance grounding fault are conducted on the neutral point ungrounded or the neutral point fully compensated ground via the arc suppression coil. Results show that the criterion can distinguish the fault direction in the above fault conditions. This work is supported by the National Key Research and Development Program of China (No. 2017YFB0903100).
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