Study on Over-Voltage of 220 kV Transformer＇s Neutrals and Protection Strategy  

作　　者：H.P. Yu S.M. Chen P.C. Yang H. Yin G.L. Wu 

机构地区：[1]State Key Lab of Control and Simulation of Power Systems and Generation Equipments, Department of Electrical Engineering, Tsinghua University, Beoing 100084, China [2]Chongqing Electric Power Research Institute, Chongqing 401123, China

出　　处：《Journal of Energy and Power Engineering》2011年第11期1102-1108,共7页能源与动力工程（美国大卫英文）

摘　　要：In order to limit short-circuit current and satisfy the need of relay setting, only part of the 220 kV power transformer is grounded, so on the neutrals of ungrounded transformers will appear the over-voltage. Currently the value of over-voltage on transformer neutral point and the corresponding protection strategy is based on theoretical formula. This article uses the PSCAD/EMTDC software to calculate the over-voltage on the neutral point of 4 ungrounded power transformers in Chongqing 220 kV power grid. The result shows that the power frequency transient over-voltage on the neutrals may reach 178 kV. If the single-phase grounding fault occurs in ungrounded power system, the power frequency over-voltage on the neutrals will be more serious and rise to 138.6 kV. Non-full phase operation may cause serious ferro-resonance over-voltage on the neutrals of no-load transformer, which may last for seconds and may rise to 723.7 kV, causing serious threat to the transformer neutrals and line-side equipment. The article also studies the gap parameter which should be taken on the neutrals of 220 kV transformers at the end.

关 键 词：Neutral point power transformer ARRESTER GAP power frequency over-voltage lightning over-voltage. 

分 类 号：TM41[电气工程—电器] TM7