Development of high frequency circuit model for oil-immersed power transformers and its application for lightning surge analysis
Development of high frequency circuit model for oil-immersed power transformers and its application for lightning surge analysis
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DOI：
10.1109/tdei.2011.5739460
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发表时间：
2011-03
影响因子：
3.1
通讯作者：
S. Okabe;M. Koto;G. Ueta;T. Saida;S. Yamada
中科院分区：
文献类型：
--
作者：
S. Okabe;M. Koto;G. Ueta;T. Saida;S. Yamada
油浸式电力变压器的耐雷击电压由变压器端子处产生的雷击过电压的大小决定。这个过电压值通常是通过使用电磁瞬变程序（EMTP）进行雷电浪涌分析获得的，其中变压器通常由单个集总电容模拟。然而，由于在实际系统中会产生从几kHz到几MHz的高频浪涌过电压，因此必须开发能够模拟该高频范围的变压器电路模型，以便进行进一步的准确分析。本文建立了油浸式变压器高频电路模型，并与实际生产的模型绕组的测量结果进行了对比，验证了模型的有效性。因此，三个串联LC并联电路的高频模型可以充分模拟绕组在几MHz高频范围内的阻抗特性。在使用该高频模型对500kv变电站进行雷电浪涌分析后，即使锋面上升更陡峭，波形的峰值也被评估为低于传统集总电容模拟的峰值。这种现象可以用变压器内部电容电路的充电过程来解释。将各模型分析的波形转换为等效的标准雷击波形，并对其峰值进行比较。因此，在本分析条件下，集总电容模拟得到的峰值相对较高。
The lightning impulse withstand voltage for an oil-immersed power transformer is determined by the value of the lightning surge overvoltage generated at the transformer terminal. This overvoltage value has been conventionally obtained through lightning surge analysis using the electromagnetic transients program (EMTP), where the transformer is often simulated by a single lumped capacitance. However, since high frequency surge overvoltages ranging from several kHz to several MHz are generated in an actual system, a transformer circuit model capable of simulating the range up to this high frequency must be developed for further accurate analysis. In this paper, a high frequency circuit model for an oil-immersed transformer was developed and its validity was verified through comparison with the measurement results on the model winding actually produced. Consequently, it emerged that a high frequency model with three serially connected LC parallel circuits could adequately simulate the impedance characteristics of the winding up to a high frequency range of several MHz. Following lightning surge analysis for a 500 kV substation using this high frequency model, the peak value of the waveform was evaluated as lower than that simulated by conventional lumped capacitance even though the front rising was steeper. This phenomenon can be explained by the charging process of the capacitance circuit inside the transformer. Furthermore, the waveform analyzed by each model was converted into an equivalent standard lightning impulse waveform and the respective peak values were compared. As a result, the peak value obtained by the lumped capacitance simulation was evaluated as relatively higher under the present analysis conditions.