基于多状态模型的变压器绕组早期故障保护方法研究

Research on Early Fault Protection Method of Transformer Winding Based on Multi-state Model

针对变压器传统差动保护在绕组发生变形或轻微匝间短路等早期故障的情况下无法动作的问题,提出一种基于变压器多运行状态模型的变压器早期故障保护新策略。首先建立三相三柱式变压器正常运行、各种区外故障以及空载合闸工况下的状态空间方程,并利用离散迭代法对状态方程进行精确求解;把模型预测电流波形和和实测电流波形转换为灰度图像,分别计算图片前景和背景最优分割值,求取差值并和保护门槛值比较,形成变压器早期绕组故障保护的新方案。该方案仅采集变压器端口的电压和电流,不用安装额外的传感器,可灵敏检测出变压器绕组变形和轻微匝间故障。最后,通过仿真和动模实验验证了方案的有效性。

Aiming at the problem that traditional differential protection of transformers cannot operate in the case of early faults such as winding deformation and slight inter-turn short circuit, this paper proposed a novel early fault protection strategy for transformers based on the transformer multi-operating state model. Firstly, the state space equation of three-phase three-column transformer was established under normal operation, various out-of-area faults, and the no-loaded closing conditions, and the discrete iteration method was used to solve the state equations. The predicted current waveform of the model and the measured current waveform were converted to a grayscale image. The optimal segmentation value of foreground and background of the picture was calculated. The difference was obtained and compared with the protection threshold. A new solution for early winding fault protection of transformers was formed. In this scheme, only the voltage and current of the transformer port can be collected to detect the transformer winding deformation and minor inter-turn faults sensitively, without adding additional sensors. Finally, the effectiveness of the scheme was verified by simulation and dynamic model experiments.