Harmonic state estimation (HSE) is the process of assigning a value to an unknown system state harmonic variable based on measurements from that system according to some criteria. Determining the best harmonic meters places in the system helps to increase the accuracy of the HSE. In this paper, a methodology is presented for optimal placement of power quality (PQ) meters in a power system. The PQ meters results are used to estimate the unknown harmonic variables. Mean square errors of estimated total harmonic distortions in normal condition is selected as the cost function, while single line and meter loss contingencies are also considered by formulating a multi-objective optimization exercise. To achieve this, seeker optimization algorithm (SOA) based on Pareto optimum method has been proposed here. Simulation are performed on an IEEE 14-bus test system. The simulation results demonstrate the effectiveness of the proposed methodology for harmonic state estimation and optimal meter placement.