变压器铁芯饱和统一模型建立及其判别方法

建立了变压器铁芯饱和的统一模型,推导出磁链最大值与电压突变时刻、突变前后电压相角差及突变后电压幅值的关系式,铁芯是否饱和与这些参数密切相关。发现电压降低(如系统发生故障或者非同期合闸操作)情况下也会产生铁芯饱和,因而以电压幅值降低作为变压器不会产生励磁涌流的依据并不可靠。进而提出一种基于电压量积分的铁芯饱和判别方法,该方法对空载合闸、故障切除、和应涌流、系统故障或操作等电压突变引起变压器铁芯饱和而产生励磁涌流,都能在半个周期左右的时间完成判别,为差动保护不经涌流闭锁提供了一种有效、快速的实现方法,可显著提高运行变压器发生内部故障时差动保护的动作速度。

Unified Model Development and Identification Method of Transformer Core Saturation

A unified model for transformer core saturation is developed. The flux saturation resulting from the changes in voltage, including amplitude change and angle change, is the fundamental cause of inrush current. And the flux saturation is correlated with the moment of voltage leap, the angle difference and the amplitude. Voltage angle changes may also lead to inrush current while the voltage amplitude decreases, hence the reducing of voltage amplitude cannot be used to assert that there''s no inrush current. Proceeding from the root causes of inrush current, a kind of iron core saturation criterion based on voltage integration is put forward. The proposed method can produce excitation inrush current because of transformer core saturation, which is caused by no-load closing, fault clearance, sympathetic inrush current, system fault or operation, and other abrupt changes in voltage. This criterion provides an effective and fast method for differential protection without inrush current atresia and will greatly accelerate the operation of differential protection of transformer when internal fault occurs.