直流偏磁对变压器电流影响及其抑制研究
高歌，徐建源，曹辰
（沈阳工业大学 电气工程学院，辽宁 沈阳 110870）
摘 要：以SZ11-100000/220 变压器为研究对象，应用PSCAD/EMTDC搭建变压器模型进行时域仿真，分析不同直流偏置量下变压器励磁电流及谐波特性的影响规律。基于阻容隔直法抑制措施进行优化分析，提出一种具有故障保护作用的阻容隔直法抑制措施。通过设计电路主要参数，搭建变压器模型，仿真分析直流偏磁抑制措施使用前后的变压器直流偏磁情况。仿真结果表明，变压器励磁电流畸变程度与流入中性点的直流量呈正相关。当直流分量为5 A时，励磁电流正半周为6.23 A，负半周为-0.30 A，并出现偶次谐波。当采取所提出的抑制措施后，中性点的直流量控制在了可允许范围内，极大地减弱了直流偏磁程度，若系统故障，装置中旁路立即接地，保护了电容器安全运行。
关键词：变压器；直流偏磁；阻容隔直法；励磁电流；谐波特性；抑制措施
中图分类号：TM401+.1 文献标识码：A 文章编号：1007-3175(2020)04-0011-05
Research on the Influence of Transformer Current and Its Suppression Under DC Bias
GAO Ge, XU Jian-yuan, CAO Chen
（School of Electrical Engineering, Shenyang University of Technology, Shenyang 11 0870, China）
Abstract: Taking SZ11 -100000/220 transformers as the research object, PSCAD/EMTDC was used to build the transformer model for time domain simulation. The influences of transformer excitation current and harmonic characteristics under different DC offsets are analyzed. Based on the optimization analysis of resistive-capacitor DC-blocking method, a resistive-capacitor DC-blocking method with fault protection is proposed. By devising the main parameters of the circuit, a transformer model is built, and the DC bias of the transformer before and after the DC bias suppression measures are simulated and analyzed. The simulation results show that the degree of distortion of the transformer's excitation current is positively related to the direct current flowing into the neutral point.When the DC component is 5 A, the positive half cycle of the excitation current is 6.23 A, the negative half cycle is -0.30 A, and even harmonics appear.When the proposed suppression measures are taken, the DC value of the neutral point is controlled within the allowable range, which greatly reduces the degree of DC bias.If the system fails, the bypass in the device is immediately grounded to protect the capacitor's safe operation.
Key words: transformer; DC bias; resistive-capacitor DC-blocking method; excitation current; harmonic characteristics; suppression measures
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