UPFC串联变压器匝间故障特性分析

串联变压器是统一潮流控制器(UPFC)的核心器件之一，其工作电压通常小于其额定电压。由于串联变压器特殊的运行特性，串联变压器的匝间故障纵差保护灵敏度大为降低。文中分析了UPFC串联型变压器匝间短路时影响差流的相关因素，找到了造成差动保护灵敏度降低的原因。并由此引入电压调整系数，调整差动计算中的变压器二次额定电流计算值。分析了引入电压调整系数后对差动保护的影响；给出了电压调整系数取值时需要注意的问题。最后以实际工程为例建立仿真模型，从保护灵敏度和防误动特性两方面，对所提方法进行了验证。

Analysis of Inter-turn Fault Characteristics of UPFC Series Transformer

Series transformer is one of the core components of unified power flow controller(UPFC), whose working voltage is usually less than its rated voltage. The sensitivity of longitudinal differential protection of series transformer with inter-turn fault is greatly reduced. In this paper, the relevant factors affecting differential current of UPFC series transformer during inter-turn short circuit are analyzed, and the reasons causing the sensitivity reduction of differential protection are found. The voltage adjustment coefficient is introduced to adjust the calculation value of the secondary rated current of transformer in differential calculation. The effect of voltage adjustment coefficient on differential protection is analyzed. At the same time, attention points are given to determine the value of voltage adjustment coefficient. Finally, a simulation model is built for a practical project, and the proposed method is validated from two aspects of protection sensitivity and anti-malfunction characteristics.