基于非周期分量衰减速率的变压器励磁涌流鉴别方法

提出一种基于非周期分量与基波分量比值(简称k0)衰减速率的励磁涌流鉴别方法。首先利用变压器仅一侧有电流还是多侧都有电流的特点,实现变压器空充与非空充状态的初步划分。判出空充状态后,利用三相差流中k0衰减速率的差异进一步判别励磁涌流与故障电流。基于k0衰减速率的励磁涌流鉴别方法原理简单可靠、计算量小,易于工程实现,对传统的二次谐波判据是个有益的补充。Matlab仿真和现场误动数据表明该方法不仅能够在变压器剩磁较大时确保空载合闸的成功率,当变压器空充到轻微匝间故障时亦能大大缩短保护的闭锁时限。

A novel identification criterion for transformer inrush current based on decay rate of aperiodic component

A novel identification criterion for transformer inrush current based on the decay rate of the ratio of aperiodic component and fundamental component (referred to as k0) is proposed. Under the no-load closing status of a transformer, the current only exists on the power source side, while under other operating conditions, the current exists on all sides. Therefore it is possible to make use of this difference to identify the no-load closing status first. In case of no-load closing status, the decay rate of k0 is then adopted to distinguish between inrush current and internal fault current. The simplicity of the proposed criterion in principle and computation enables its implementation in real-time applications. Simulation results by Matlab and the malfunction data on the field indicate that the proposed method can not only reliably block the protection when the transformer is in the ultra-saturation condition, but also provide a faster operation speed under slight internal faults, which is a beneficial complementary to the conventional second-harmonic criterion. This work is supported by National Natural Science Foundation of China (No. 51777071).