Detection of Transformer Circular Flow Effects

To calculate partial power flows of transformers, until now only phase-shifting transformers (PST) can be considered. In this work, the algorithm for the calculation of partial power flows is extended to all transformers. First of all, the PST, which are modeled so far by the help of phase-shifting distribution factors (PSDF), play a significant role for power flow controlling assets. In addition to these, however, any other transformer with longitudinal or longitudinal and angle regulation can also be considered as a driver of circular flows. In contrast to previously used methods such as PSDF or heuristic methods for placing PST, the principle shown here uses the current equation to calculate the influence of all transformers on other equipment. Every transformer is represented by a pair of current sources, which stand for the current driven by the regulation-driven voltage difference inside each transformer. The presented method is validated on a test grid with two voltage levels and five transformers.