In this paper, a state estimation based method is proposed to determine harmonic current contributions of plants supplied from a point of common coupling (PCC). This work mainly aims to reduce gross error of capacitive voltage transformer (CVT) measurements at harmonic frequencies using robust weighted least absolute value (WLAV) state estimation method, which provides the optimum state estimates for harmonic voltages in the presence of a redundant enough measurement set. Estimated harmonic voltages are then used to solve the harmonic current contribution problem based on superposition theorem. It has been shown that the proposed method can provide optimum harmonic estimates when CVTs are used. The use of the proposed method with proper measurement placement makes resistive-capacitive voltage transformers (RCVTs) redundant. Results of the proposed method are comparable with measurements of RCVTs, which have the disadvantages of having high costs and being cumbersome to install.