调压变不同分接头下特高压变压器直流偏磁特性分析

Analysis of DC Magnetic Bias Characteristic of UHV Transformer Under Different Taps

特高压变压器采用中性点调压方式,主体变通过调压绕组和补偿励磁绕组的并联支路与地相连,当中性点流入(或流出)直流电流时,不同分接头下特高压变压器直流偏磁特性存在差异:①不同分接头对应接入的调压绕组匝数和电阻不同,导致调压绕组和补偿励磁绕组分得的直流电流值不同,铁心饱和程度不同;②调压变正调压与负调压状态对应接入的调压电压相位不同,受直流偏磁影响导致的铁心半波饱和位置不同。文中通过对特高压变压器的主体变、调压变和补偿变联合仿真,利用场路耦合法求解各变压器绕组的实时电压电流,分析了不同调压情况下3台变压器直流偏磁特性及其相互影响关系。

UHV transformer adopts the neutral point voltage regulation mode and the main body of the transformer is connected to the ground through the parallel branch of the voltage regulating winding and the compensation excitation winding.When the DC current flows in(or flows out)the neutral point,the DC magnetic bias characteristic of UHV transformer under different taps has difference:①The different number of turns and resistance with corresponding connection at different taps lead to different DC current of the voltage-regulating winding and the compensation excitation winding as well as different saturation level of the cores.②The different phase of voltage regulation with corresponding connection at positive and negative adjustment condition of voltage regulation transformer leads to different half wave saturation position of core due to the influence of DC magnetic bias.In this paper,field-circuit coupling method is used to solve the real time voltage and current of each transformer winding,the DC magnetic bias characteristic and their interaction relation of 3 sets transformers at different taps are analyzed by way of joint simulation of the main transformer,voltage regulation and compensation of UHV transformers.