Researchers at Germany's Forschungszentrum Jülich have solved a years-long mystery that has puzzled grid managers worldwide: the minute-by-minute frequency dips appearing simultaneously on power grids across continents are caused by the synchronised state-of-charge checks of uninterruptible power supplies (UPS) and other battery storage systems.
The investigation began when Dirk Witthaut and his team at Jülich took up the puzzle brought by Tennet Germany, the country's largest transmission system operator. Using data from more than 80 smart power quality meters installed around their own campus, the researchers detected the same 60-second pattern on a transformer connected to a battery energy storage system. They found that many stationary batteries, from data-centre UPSes to grid-scale batteries, check their charge status every minute. Because these devices are internet-connected, their clocks are in near-perfect synchronicity. When they all check their charge together, the disruption becomes apparent.
Such frequency drops aren’t unheard of, but they are troubling, and their regularity can make the phenomenon feel more ominous. If oscillations get too large, or if grid operators don’t know the cause and respond improperly, they can lead to blackouts. Even if the sags don’t cause blackouts, they can damage equipment in power plants if they go unchecked.
Evidence came from Ireland, where data centres represented 18% of the load on the country's grid by 2022. Between 2016 and 2021, the minute-by-minute frequency drop on the Irish grid quadrupled from 3 milli-Hertz (mHz) to 12 mHz, with some drops recently exceeding 20 mHz. Ireland's 50 Hz grid is built to withstand swings of plus or minus 200 mHz. If other loads also cause the frequency to sag, the extra bump from UPS checks could push the grid toward blackout conditions.
The researchers also detected similar periodic fluctuations in IoT devices including a smart oven and Raspberry Pi clusters, suggesting the problem could persist even if UPS behaviour is addressed.
Witthaut and his team say the problem is entirely preventable. They recommend that UPS and grid-scale battery manufacturers add randomness to the charge-check schedule. For IoT devices, the fix is a simple software patch, but many go unpatched: a recent study found that fewer than 3% are running the latest firmware. Regulators may need to step in, but given the global nature of the issue, international coordination would be required.
Analysis
Why This Matters
- The phenomenon adds to the cumulative load on power grids, potentially pushing them toward blackout conditions when combined with other disturbances.
- A solution requires software updates across millions of devices, many of which are rarely patched, especially among IoT products.
- The global synchronisation means no single regulator can fully resolve the issue; international coordination is needed.
Background
For years, grid operators worldwide observed mysterious frequency dips occurring every 60 seconds at the same time across different continents. The regularity ruled out mechanical causes like hydropower turbine resonance, which had been the initial suspect. The mystery was solved by a team at Forschungszentrum Jülich in Germany, who discovered that the universal synchronization of internet-connected clocks in UPS systems was the cause.
What to Watch
- Whether battery manufacturers and data-centre operators voluntarily implement randomised charge-check schedules.
- The speed at which regulators in different countries act to mandate changes.
- Whether the growing number of IoT devices with similar periodic behaviours amplifies the problem before fixes are deployed.
Checked
12 claims in this story checked against 1 source: 12 supported.
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- SupportedCoordinated UPS battery checks caused frequency drops on grids worldwide.TechCrunch: “Every 60 seconds, the frequency on the grid would drop a tiny bit. Even weirder: The sags happened at the exact same time on power grids across countries and continents.”
- SupportedThe minute-by-minute disturbances were traced to synchronized state-of-charge checks in data centres and other settings.TechCrunch: “It turns out that many stationary batteries, from data center UPSes to large grid-scale batteries , check their state-of-charge every minute. Since these devices are internet-connected, their clocks are in near perfect synchronicity.”
- SupportedResearchers at Forschungszentrum Jülich solved a mystery that had puzzled grid managers for years.TechCrunch: “For years, mysterious electrical anomalies have been flummoxing grid managers around the world.”
- SupportedThe frequency dips appeared simultaneously on power grids across continents.TechCrunch: “The sags happened at the exact same time on power grids across countries and continents.”
- SupportedTennet Germany brought the puzzle to Dirk Witthaut, and it is Germany’s largest transmission system operator.TechCrunch: “Germany’s largest transmission system operator, Tennet Germany, brought the puzzle to Witthaut”
- SupportedThe researchers installed more than 80 smart power quality meters around the Jülich campus.TechCrunch: “the researchers started close to home, installing more than 80 smart power quality meters around the Jülich campus.”
- SupportedTheir measurements found a minute-by-minute pattern on a transformer connected to a battery energy storage system.TechCrunch: “The measurements recorded on the transformer attached to the battery energy storage system peaked every minute, just like on the bigger power grids.”
- SupportedBy 2022, data centres represented 18% of Ireland’s grid load.TechCrunch: “By 2022, data centers represented 18% of the load on Ireland’s grid”
- SupportedBetween 2016 and 2021, the minute-by-minute frequency drop on Ireland’s grid quadrupled, from 3 mHz to 12 mHz.TechCrunch: “between 2016 and 2021, the minute-by-minute frequency drop on the Irish grid quadrupled from 3 milli-Hertz (mHz) in 2016 to 12 mHz in 2021.”
- SupportedSome recent drops on the Irish grid exceeded 20 mHz.TechCrunch: “More recently, some drops have exceeded 20 mHz.”
- SupportedIreland’s 50 Hz grid is built to withstand swings of plus or minus 200 mHz.TechCrunch: “Ireland’s 50 Hz grid is built to withstand swings of plus or minus 200 mHz”
- SupportedThe researchers detected periodic power fluctuations in IoT devices, including a smart oven and Raspberry Pi clusters.TechCrunch: “In devices as diverse as a smart oven and Raspberry Pi clusters, they were able to detect periodic power fluctuations.”
