Welcome to the 7th report this year of the data acquired with the PQopen measurement network.
News of PQopen Network
New Locations in the Netherlands
I got many requests for additional measurements in the Netherlands because of the observation of the country-wide oscillation phenomenon. Three new installations are active, one near Venlo (including PV power analysis) and a second in Middelburg, at the very western part of the country and a third in Groningen in the north.
3rd party measurement data from Baltic
Thanks to Beckhoff Automation, PQopen gets temporary data from Lithuania: Kaunas. Due to some difficulties with GNSS synchronisation in this area (because of jamming) the data source was only active for some weeks. We hope, this will be resolved soon or fixed with an alternative system.
Summary
In the summary, the 1s-mean value of the mains frequency is evaluated.
| Statistics | Value and occurance |
|---|---|
| MIN | 49.8743 Hz (2026-07-12 00:00:54 CET) |
| 1% Percentile | 49.9488 Hz |
| MEAN | 50.0000 Hz |
| 99% Percentile | 50.0481 Hz |
| MAX | 50.1126 Hz in AT/Graz (2026-07-24 18:03:28 CET) |
Daily Mean
The daily mean can give you an overview of the „accuracy“ of the grid control and their effect on grid synchronized clocks. July was much smoother than the month before.
Rate of Change of Frequency (ROCOF)
The ROCOF is an indicator for potential events and the steadiness of the frequency. The higher the value, the more disturbances are at work (oscillations, transients…).
Frequency Spread
I introduced the metric „Frequency Spread“ in the posting, where I analysed the dynamic of the frequency the past 15 years. From now on, I want to use this metric in this report.
Inter-Area oscillations
The inter-area oscillations is a long-known phenomenon resulting from the wide area of interconnected countries. In Spain, two modes can be detected, the east-center-west and the east-west mode.
Oscillations in the Netherlands
Other Abnormalities
Less deviations of frequency below 49.9 Hz and over 50.1 Hz, a fall of >80% can be noticed compared to previous month:
| ENTSO-E Central Europe | < 49.9 Hz | > 50.1 Hz |
|---|---|---|
| Count of threshold crossings | 5 (-18) | 17 (-4) |
| Number of seconds below/above | 50 (-399) | 115 (-59) |
Events
Below, there are several graphs, each representing a detailed time series plot of cycle-by-cycle frequency as well as 10-cycle moving average, phase angle difference and voltage magnitude.
Some readers had the idea of automatically analyzing these traces and doing some sort of „triangulation“ for estimating the area of event root. I had no time in february to give it a try, but it is on my list. If someone of you is interested of trying this, please use the archived data or the API for more recent events.
List of all detected events
| Timestamp (UTC) | Timestamp (CET) | Text | Category |
|---|---|---|---|
| 2026-07-30 01:52:30 | 2026-07-30 03:52:30 | AT/Graz (low impact) | Frequency Swing |
| 2026-07-29 15:26:16 | 2026-07-29 17:26:16 | Northern Germany | Generation Outage |
| 2026-07-25 11:50:56 | 2026-07-25 13:50:56 | Southern-East Europe IV | Frequency Swing |
| 2026-07-25 11:50:53 | 2026-07-25 13:50:53 | Southern-East Europe III | Frequency Swing |
| 2026-07-25 11:35:19 | 2026-07-25 13:35:19 | Southern-East Europe II | Frequency Swing |
| 2026-07-25 08:31:59 | 2026-07-25 10:31:59 | Southern-East Europe | Frequency Swing |
| 2026-07-25 01:41:11 | 2026-07-25 03:41:11 | Short Event in Nordic System | Frequency Swing |
| 2026-07-22 05:42:24 | 2026-07-22 07:42:24 | Spain | Generation Outage |
| 2026-07-22 04:13:22 | 2026-07-22 06:13:22 | Northern Germany | Voltage Dip |
| 2026-07-22 04:13:22 | 2026-07-22 06:13:22 | Northern Germany | Frequency Swing |
| 2026-07-21 20:37:48 | 2026-07-21 22:37:48 | Incident in Southern-East Europe | Frequency Swing |
| 2026-07-20 11:36:39 | 2026-07-20 13:36:39 | Short peak after voltage drop | Oscillation |
| 2026-07-19 09:56:30 | 2026-07-19 11:56:30 | Nordlink: Switch from Bipolar- to Unipolar Mode (loss of 685MW) due to failure | Transmission Outage |
| 2026-07-15 08:33:57 | 2026-07-15 10:33:57 | DE/Berlin | Voltage Dip |
| 2026-07-14 13:57:02 | 2026-07-14 15:57:02 | CH/Solothurn | Voltage Dip |
| 2026-07-13 13:06:28 | 2026-07-13 15:06:28 | France: Nuclear Power Plant PALUEL 4 (1330 MW) | Generation Outage |
| 2026-07-12 19:00:00 | 2026-07-12 21:00:00 | Trip of Forsmark 1? (1100 MW) | Generation Outage |
| 2026-07-12 07:59:19 | 2026-07-12 09:59:19 | Event between FI and EST | Frequency Swing |
| 2026-07-11 22:25:08 | 2026-07-12 00:25:08 | NORDIC: Trip of Generation Unit after Short Circuit | Generation Outage |
| 2026-07-11 14:01:56 | 2026-07-11 16:01:56 | Spain: Nuclear Power Plant VANDELLOS (1050MW) | Generation Outage |
| 2026-07-10 23:41:12 | 2026-07-11 01:41:12 | Unknown Outage Sweden | Generation Outage |
| 2026-07-08 08:06:17 | 2026-07-08 10:06:17 | Northern-East Germany | Generation Outage |
| 2026-07-08 00:45:54 | 2026-07-08 02:45:54 | Finnland (NORDIC Grid) | Voltage Dip |
| 2026-07-07 13:50:39 | 2026-07-07 15:50:39 | SE/Malmoe | Voltage Dip |
| 2026-07-06 17:43:24 | 2026-07-06 19:43:24 | Northern Germany | Frequency Swing |
| 2026-07-02 17:48:32 | 2026-07-02 19:48:32 | Northern Germany | Frequency Swing |
| 2026-07-02 16:41:20 | 2026-07-02 18:41:20 | Start of 15 Minutes Oscillation of 2.9 Hz in northern Germany | Oscillation |
| 2026-07-02 15:14:23 | 2026-07-02 17:14:23 | Netherlands | Frequency Swing |
| 2026-07-01 14:48:42 | 2026-07-01 16:48:42 | Start of series of Events in Spain | Frequency Swing |
| 2026-07-01 12:07:02 | 2026-07-01 14:07:02 | Temporary separation of Turkey from ENTSOE-CE grid | Frequency Swing |
Central Europe Area
Nordic Area
CE & Nordic Area
Yours,
Michael