Treatment of transformers and voltage regulators in branch current state estimation for distribution networks

The branch current state estimators available in the existing literature consider the distribution networks as composed of lines and cables. In this paper, a general technique is demonstrated in order to handle other key distribution network components such as transformers and voltage regulators. It is also demonstrated how to consider the tap positions of transformers and regulators as state variables in the estimation process given that they are rarely telemetered. The performance of iterative optimization algorithms depends strongly on the initial solution. In this paper, the load allocation algorithm is used in order to obtain an initial solution and associate loads with pseudo-measurements. The latter step is necessary in order to assure observability of the network. The load allocation algorithm used in this study is a straightforward tool based on ladder iterative algorithm.