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| A Neutral DC Current Blocking Device for Grounding Transformer Based on Inverse Parallel Thyristors Protection |
| Wang Sheng1, 2, Lu Jiming1, Mao Chengxiong1, Wang Dan1, Mei Guihua3 |
| 1. Huazhong University of Science and Technology Wuhan 430074 China2. Chongqing Electric Power Company Chongqing 400080 China3. Guangdong Electric Power Research Institute Guangzhou 510600 China |
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Abstract When HVDC power system operates in ground return mode, the AC grounding transformers around the electrodes always suffer from DC biases due to the DC currents through their neutral points. In this paper, a novel transformer neutral DC current blocking device (NCBD) based on inverse parallel thyristors protection is proposed and developed to solve such problem. Based on the analysis of the topology and operating principles of NCBD, the main circuit is simplified by removing the front-end rectifier circuit and the turn-off circuit of thyristor. Thus, the cost of the device can be cut down a lot. Moreover, the reliability and intelligence of NCBD are improved by its dual redundant structure, which is made up of a set of hardware integrated circuit and a set of microcomputer measure-controlling system. Simulation results, high current tests and field operation results confirm that the NCBD can resolve the demand of DC bias restraint effectively, and provide a practical based engineering solution.
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Received: 01 April 2009
Published: 04 March 2014
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2010, Vol. 25 
