i f Selecting Weights or Different Type Measurements n WLS State Estimation

Power system state estimation provides accurate and complete data for several online advanced application software in energy management systems. Its main consideration is how to acquire accurate data. State estimation are usually solved by weighted least squares estimation, and selecting a reasonable weight for every measurement is the most important means to achieve a good estimation. Traditionally variance of measurement is selected as its weight. But measurements of different type have different effect on the accuracy of state estimation even if they have same error. Selection of weights must take the measurement type into account, so a method of selecting weights for measurements of different type is presented. Firstly accuracy index of state estimation is defined as the sum of the squares of errors of every measurement; then accuracy index of state estimation for every measurement is calculated by perturbation method; finally mean accuracy index of state estimation of measurements of each type is calculated and used to design a coordination factor to adjust weights for measurements of different type. IEEE30 network is analyzed by the proposed method, and the results prove the effectiveness of the proposed method.