ENTSO-EThe Polish transmission system operator, PSE, and the German 50Hertz, announce today they started operation of four phase shifter transformers, PST, in the Polish substation of Mikułowa. PSTs are potentiometers whose effect is analogous to a valve for regulation of the waterflow in a waterpipeline.
This is part of a two stage process to improve use of interconnection between the two countries notably for trading purposes. High unscheduled flows on the German-Polish border have prevented both TSOs from offering trading capacities in direction to Poland so far.
The second stage depends on the building of a transmission line in Germany, the Uckermark line, which is now put on hold due to permitting issues. PSE and 50Hertz have worked out an alternative until the permitting issue can be resolved and two out of the four planned additional PSTs will start operation in the German substation of Vierraden.
If the permittiing issue is resolved, the final mode of operation with all four PST in Vierraden and a connection to the Uckermark line is expected for 2020.
**Substation of Mikulowa, Poland** [](/map/Pages/default.aspx) **Substation of Vierraden, Germany** [](/map/Pages/default.aspx)