Voltage and power characteristics in German low voltage grids: Field experience in presence of high photovoltaic installations and voltage-regulated distribution transformers (VRDT)

Decentral generators in distribution grids lead to new challenges regarding voltage quality. Voltage control utilizing innovative equipment, such as voltage-regulated distribution transformers (VRDT), is being discussed as a method to avoid cost intensive grid expansion. In this paper, a method using measurement data in the low voltage level is developed to evaluate voltage and power quality and to provide an evaluation basis for the control quality of VRDT. This method is then applied to three field trial grids of the “Smart Area Aachen” project. In comparison, it was found that the voltage quality of the grid areas differs significantly with regard to the investigated criteria. Similarly, the frequency and impact of VRDT switching is highly individual for the different grids.