A reliability model for overcurrent relays considering harmonic-related malfunctions

•A 32-state Markov model for overcurrent relays considering harmonic impacts.•Calculation procedure of Markov model’s steady-state probabilities.•Appropriate procedures for estimation of the model’s transition rates.•A four-state classified model to facilitate the application of the detailed model.•Identifying the main factors affecting the reliability of OC relays.•Comparative analyses between the proposed model and the existing ones.