The Mystery of the 60-Second Oscillations in Global Power Grids Has Been Solved
For years, power grid operators around the world observed something strange and inexplicable: the grid frequency would drop briefly every minute, with near-metronomic precision. The phenomenon, present across European, North American, Australian, and even Malaysian systems, did not pose an immediate threat to grid stability, but its disturbing regularity kept specialists on alert. Now, a team of researchers led by Dirk Witthaut at Germany's Forschungszentrum Jülich has finally uncovered what was causing this artificial heartbeat in the global energy infrastructure.
The answer came not from electrical engineers, but from a puzzle brought years ago by Tennet Germany — the country's largest transmission system operator. According to a study published in the journal Nature Energy on October 30, the cause is large-scale battery storage systems that check their state of charge precisely at the start of every minute, when all clock-synchronized devices execute this routine simultaneously. The individual effect is negligible, but when thousands of devices act in unison, the sum propagates through the grid and becomes measurable.
The clue that pointed to a clock
The periodicity was the key. Frequency fluctuations are normal in any power grid — supply and demand are constantly balancing — but no natural oscillation repeats with the exact precision of a 60-second cycle. "We quickly realized the cause had to be something controlled by a clock," Witthaut explained. There was no other explanation for such a regular pattern.
The group investigated various possibilities, including hydropower turbines, which seemed the most obvious suspect. Computational models of the Scandinavian grid's control system showed that it was possible to generate a resonance peaking once per minute, but they could not explain why the phenomenon persisted minute after minute without ceasing. Natural mechanical resonances tend to come and go, not repeat indefinitely.
The breakthrough came when the team focused on software-controlled digital devices. The modern power grid is increasingly populated by photovoltaic inverters, battery systems in uninterruptible power supplies (UPS), and smart chargers — all operated by code that, in many cases, synchronizes its internal clock via NTP (Network Time Protocol) over the internet. When thousands of these devices execute a diagnostic routine at the same millisecond, the result is a coherent spike in power demand.
Confirmation at the Living Lab Energy Campus
Proof came from Jülich's own Living Lab Energy Campus, where researchers installed more than 80 power quality meters (Class A, per IEC 61000-4-30 standard) at various points across the local infrastructure. Measurements taken every three seconds revealed the pattern: at the transformer connected to the battery energy storage system, narrow current peaks repeated every minute. The manufacturer itself confirmed these were periodic state-of-charge checks executed by the battery's energy management system (EMS).
Data collected by grid operator TenneT across multiple countries — from Mallorca to Malaysia, Greece and Ireland — showed that the amplitude of the one-minute signal had grown significantly over recent years. In Ireland, where data centers with large battery storage account for about one fifth of the country's electricity demand, the signal's amplitude quadrupled between 2016 and 2021. In Germany, the share is smaller, around 3%.
Why this matters
The phenomenon did not cause blackouts, but it contributes to wear on hydroelectric turbines — each demand spike forces abrupt adjustments in generators that, over years, reduce equipment lifespan. Even more important, the study reveals a systemic vulnerability in the energy transition: as inverter-based generation displaces traditional synchronous generators, system inertia declines, making the grid more sensitive to coherent power imbalances.
The solution is technically straightforward but semantically complicated. As Witthaut explained, simply distributing the check times randomly rather than scheduling them for the start of each minute would resolve the issue at the source. Software changes in energy management systems would fix the problem. The obstacle is that there are no binding standards for these diagnostic routines, and standardization would require global coordination among manufacturers from different countries — something harder to achieve than modifying a single script.
The study also points to a broader trend: the growing digitization of energy infrastructure creates a new class of systemic risks that exist neither in circuit physics nor in classical control theory. They are emergent effects of cyber-physical systems, where the collective behavior of thousands of autonomous devices produces outcomes that no individual operator intended.
Sources: TechCrunch, Forschungszentrum Jülich, techXplore, heise online
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