A tale of two transformers: An algorithm for estimating distribution secondary electric parameters using smart meter data

One of the main objectives for the Smart Metering and Infrastructure (SMI) System currently being installed at BC Hydro, is to improve the company´s ability to detect and locate electricity theft [1]. Some of the methods used to detect theft depend on accurate topology data for distribution transformer secondary networks and accurate estimates of the voltage at the transformer. The topology data from the Geographic Information System (GIS) is sometimes inaccurate. This paper describes a methodology to confirm the accuracy of the topology and to estimate the transformer secondary voltage, based only on the topology structure and hourly load and voltage data from each smart meter connected to the transformer. The method uses Linear Programming (LP) optimization and simultaneously provides estimates of the impedances of each segment of the secondary line. The degree of convergence indicates the accuracy of the given topology, and in many cases the locations of topology errors can be identified.