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.