Abstract: Thyristor controlled reactors（TCR） are critical components of static var compensators（SVCs） to ensure the safe and stable operation of SVCs.Comprehensive analysis of fault states of a TCR is given in detail.This includes line to line fault,phase to ground fault and turn to turn fault.TCRs are modeled based on the quasi-steady-state model used in HVDC and extended arbitrarily periodical current to three-phase system.The study shows that the line current of a TCR doesn’t contain the third harmonics in the normal condition;however,it does contain positive and negative components of the third harmonics in the fault state.Non-characteristic third harmonic current is introduced and studied qualitatively as well as quantitatively.Numerical simulations using PSCAD validate correctness of the proposed method.