Enhanced method for voltage range controlled OLTC-equipped distribution transformers

Increasing load and the growing proportion of injected power from distributed energy generation lead to higher loading of distribution grids. Without suitable improvements like e. g. additional cables or substations, violations of voltage constraints in low voltage distribution grids have to be expected. A further alternative is represented by on-load tap-changers (OLTC) which are combined with distribution transformers. This paper presents an enhanced method for controlling them using a voltage range as input parameter. The voltage drop or rise between the substation and the first nodes of the strings is taken into account as it can be determined with little effort. This enables the consideration of similar loading in the strings of a distribution grid. The results of the simulations prove the advantages compared to the underlying approach. The improved method features less switching operations which leads to less wear and accordingly to lower maintenance effort.