Researchers Solve Mystery of Worldwide Coordinated Power Grid Disturbances

Image: TechCrunch · Source

A German research team uncovered that synchronized state-of-charge checks by internet-connected UPS and battery systems cause coordinated frequency drops every 60 seconds on power grids globally.

For years, grid managers around the world have been puzzled by minuscule, coordinated frequency drops occurring on power grids every 60 seconds. These subtle sags appeared simultaneously across continents, from Europe to Australia, the U.S., and Malaysia, baffling experts and raising concerns about grid stability.

Dirk Witthaut and his team at the Forschungszentrum Jülich in Germany undertook an extensive investigation after receiving the puzzle from Germany’s largest transmission system operator, Tennet Germany. Recognizing that grid frequency must remain within precise limits to prevent blackouts or equipment damage, the researchers initially suspected hydropower plants, historically linked to ultra-low frequency oscillations due to turbine resonance.

Using modeling on the Scandinavian grid, they found conditions under which hydropower systems could cause a resonance once every minute. However, such mechanical resonances typically fluctuate rather than persist with the exactness observed. The persistent minute-interval nature suggested a source governed by an accurate clock.

To explore this, the team installed over 80 smart power quality meters at their local campus, equipped with various energy systems including battery energy storage with uninterruptible power supplies (UPS). Data revealed that disturbances peaked exactly each minute, matching patterns on larger grids.

The decisive breakthrough was identifying that many stationary batteries and data center UPS units globally perform synchronized state-of-charge checks every 60 seconds. Because these devices connect to the internet, their clocks are nearly perfectly synchronized, causing simultaneous minor power disturbances that collectively become detectable on wide-area power grids.

Focusing on Ireland, where data centers consume about 18% of the grid’s load, they analyzed grid data from 2016 to 2021. They found that the amplitude of these minute-by-minute frequency drops quadrupled from 3 to 12 milli-Hertz (mHz), with recent drops exceeding 20 mHz. Though Ireland’s 50 Hz grid can tolerate swings up to 200 mHz, the cumulative effect of many such synchronized disturbances risks pushing the system toward instability.

The researchers propose a straightforward solution: manufacturers should introduce randomization into the timing of state-of-charge checks in UPS and grid-scale battery systems to avoid synchronized impacts. While UPS units currently are the main drivers, similar effects could arise from IoT devices frequently performing synchronized operations. However, IoT devices often remain unpatched, with less than 3% running the latest firmware.

This phenomenon’s global nature implies regulatory responses will require international coordination. Although the cause is now understood, mitigating these subtle but widespread disturbances will be essential to maintaining future grid resilience.

Source: TechCrunch, November 2026.