This paper proposes a state estimator for distribution management systems in Korea and summarizes the field test results. The purpose of the proposed state estimator is to ensure the accurate identification of the distribution system state using the existing measurement infrastructure of the Korean distribution network. For this, this study focused on the following points; Firstly, in order to ensure redundancy in the measurement data, pseudo-injections were generated through the estimation of section loads while considering the accuracy of the measurement devices and modified the weights based on measurement accuracy. Secondly, the number of state variables was reduced by performing a system reduction to focus on the nodes with measurement data in order to ensure redundancy. Thirdly, a voltage-based least squares state estimation method and a modified normalized residual test for bad data detection were proposed in the developed state estimator. The effectiveness of the proposed method in this paper is verified through a test conducted on the field test network in Shinan, Korea.