Central European clocks run slow under persistent frequency deviation

UPDATE: On 8 March Entso-e reported that the deviations had ceased, but added: “This is a first step in the resolution of the issue. The second step is now to develop a plan for returning the missing energy to the system and putting the situation back to normal.”

European electricity system operators are struggling to trace and resolve a persistent deviation that has been depressing the system frequency since mid January.

European organisation Entso-e said, “This average frequency deviation, that has never happened in any similar way in the CE Power system, must cease”.

The deviation is small – the system is averaging 49.996Hz instead of 50Hz and it can operate down to 46.7Hz. But Ensoe-e points out that it has real effects. For one thing it means clocks that take their time from the grid frequency have lost around six minutes since the issue began. But it also means the system has delivered less energy than it should, by around 113GWh. That raises a financial issue over who will provide compensation.

It is not clear exactly how the deviation has arisen. The CE Power system covers a huge swathe of Europe, including 25 countries from the Netherlands to Poland and Spain to Turkey. It is a single ‘synchronous’ system which means all the system users can affect the voltage and frequency and all the system operators can act to maintain it within limits. (This is unlike the UK’s interconnections with Europe, which allow for frequency and voltage at each end of the connection to be managed independently.)

Ensto-e says the deviation is originating from Kosovo and Serbia and it hopes to have a technical solution this week. But it says there is also a political dimension, because “political disagreements [between the] Serbian and Kosovan authorities have led to the observed electricity impact”. It urged European and national governments and policy makers to take swift action to resolve the political dispute so the technical issue would not re-emerge.

It is not clear when that issue, or the issue of compensation for the missing energy, will be settled.