基于S变换与RF算法的高压发电机定子单相接地保护

为了解决现有并列运行的多台高压发电机定子单相接地保护无选择性的问题，文中提出了一种基于S变换与随机森林(RF)算法的高压发电机定子单相接地保护方案。该方案利用S变换构造高压发电机定子单相接地故障下暂态零序电流幅-时-频矩阵，提取S变换幅-时-频矩阵相关系数、S变换暂态能量特征和暂态零序有功功率特征作为特征向量，将特征向量输入到RF保护判别模型中得到判别结果，从而辨识出发生故障的高压发电机。仿真结果表明在不同的故障条件下该保护方案的故障判别准确率较高，有望改善高压发电机定子单相接地保护的性能，弥补了单一故障特征量判别法的不足，且无须设置整定值，有效减少了系统运行方式对保护的影响。

Stator Single-phase-to-ground Fault Protection for Powerformers Based on S-transform and Random Forest Algorithm

At present, the single-phase-to-ground fault protection has no selectivity when it is used for multiple Powerformers in parallel. To solve this problem, a new stator single-phase-to-ground fault protection scheme based on S-transform and random forest(RF)algorithm is proposed. The scheme uses S-transform to construct the amplitude-time-frequency matrix of transient zero-sequence current in single-phase-to-ground fault of multiple Powerformers. The correlation coefficient of S-transform amplitude-time-frequency matrix, S-transform transient energy characteristic and zero-sequence active power characteristic are extracted as feature vectors which are input into the discriminant model of RF protection model to obtain the discriminant results, and then the fault Powerformer is identified. The simulation results show that the protection scheme has a high accuracy rate of fault identification under different fault conditions, which is expected to improve the performance of single-phase-to-ground protection of multiple Powerformers and make up for the deficiency about the discrimination method of the single fault characteristic quantity. In addition, the protection scheme does not need to set the setting value, which effectively reduces the impact of the system operation mode on the protection.