Internal fault probability-based time domain differential protection applied to transmission lines connecting battery energy storage stations

Battery energy storage station (BESS) presents disparate fault current characteristics in charge and discharge states. Classic and recently proposed differential protection algorithms, including phasor-based and time-domain algorithms, are heavily influenced by operating state of BESS. Problems such as low sensitivity and ineffectiveness may arise, especially in charge state. In response to this issue, this paper applies Bayes' Theorem to calculate the probability of internal fault occurrence, named as internal fault probability. In this article, fault current characteristics of BESS under different operating states are described, and then the causes of performance problems of classic and recently proposed differential protection algorithms are analyzed. Subsequently, virtual operating current vector is developed, and the difference of virtual operating current vector in time-domain waveform under various conditions is described. On this basis, internal fault probability-based differential protection (IFP-DP) is presented. Besides, its operating performances under internal and external faults are analyzed. The advantageous performance of IFP-DP is fully validated by changing fault location, type, resistance, operating state and considering outliers, current transformer (CT) saturation, and loss of data. Proposed IFP-DP exhibits gratifying performance in operating time, sensitivity and security in the presence of BESS. •The difference of fault current characteristics of BESS in charge and discharge states is illustrated.•Probability of internal fault occurrence is derived by applying Bayes’ Theorem.•Based on time-domain waveform characteristics of virtual operating current vector, IFP-DP is presented.•Proposed IFP-DP shows advantageous performance in operating speed, sensitivity and security in the presence of BESS.