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German grid operator 50Hertz is installing phase shifters to raise electrical resistance that stops excess renewable power supply from spilling over into Poland’s PSE grid zone – causing diplomatic spats. Electrical current normally takes the path of least resistance, but if Germany’s north-south routes are congested e.g. by ample wind power supply – this excess supply sometime takes a detour through neighbouring countries.
Toning down tensions between the two uneasy neighbours, 50Hertz and PSE already in March 2014 struck a contract to initiate virtual Phase Shifting Transformer (vPST) on the German-Polish border. Loop flows however need to be physically controlled, the two TSOs concluded, after a vPST Pilot Project based on redispatching showed that “these measures were insufficient.”
Poland forges ahead with pPST
According to the PST agreement, the Polish grid operator swiftly installed physical Phase Shifting Transformers (pPST) in the Mikułowa substation. Since the start of this year, it controls power flows on the cross-border line Mikułowa-Hagenwerder (see map).
50Hertz is now installing physical Phase Shifting Transformers (pPST) in Vierraden substation that controls the power flows on the cross-border line Vierraden-Krajnik. Start of these devices is scheduled for October 2017.
Poland has been adamant that negative effects of unplanned cross-border electricity flows into Central Eastern Europe need to be limited, as it seeks to strengthen its internal energy market – before buying into the idea of a pan-European power grid.
Spill-over effects on cross-border trading
Stormy weather can create a huge and sudden supply of green power from wind farms in north Germany. At the same time, the abundance of electricity pushes prices down in the common German-Austrian trading zone which propels up demand from industries and international traders. Hence, substantial volumes of electricity need to be transported from northern to southern Germany and on via Austria.
At times, the amount of power being traded between Germany and Austria is twice what the connections between their two grids can handle, meaning half of the volume overflows into the Czech and Polish grid systems, and even to neighbouring countries further east.
Such unforeseen excess power supply causes congestion on interconnectors, preventing electricity being traded internationally. The Agency for the Cooperation of Energy Regulators (ACER) has estimated that loop flows from Germany cost the Polish and Czech economies €25 million a year in lost revenues from power trading.
Split-up of market zones?
As a possible solution, ACER called for caps on volume of electricity trade between Germany and Austria. However, critics said would effectively end the common power market between the two neighbours. Regulators of both countries are evaluating the matter and cautioned that the common price zone could be split at the earliest before the winter of 2018/19.
Splitting the German grid, would be an alternative solution which would take the strain of the severely restricted capacity of north-south grid connections. Yet this would also mean higher power prices in Bavaria and Baden-Württemberg, Germany's two highly industrialised southern states, and is therefore politically unlikely.
