Gaining experience with a regulated distribution transformer in a smart grid environment

The regulated distribution transformer can be a powerful tool against voltage range problems in low voltage grids with a high amount of distributed power generation. To gain experience with this new technology the German DSO EnBW Regional AG has equipped one of its MV/LV-substations with a regulated 400-kVA-transformer developed by Siemens AG. This paper outlines the general benefits of using regulated distribution transformers and EnBW's steps to implement and test the aforementioned prototype. The technology of this transformer with its on-load voltage regulation is described in detail as well as the process of finding and optimizing a suitable voltage control algorithm. After several months of successful operation it can be stated, that the regulated distribution transformer has proved its potential for a permanent use the realization of a new “smarter” distribution grid.