Blackout risk from bureaucracy: why grid frequency drops at the same time on many evenings

Maurice Forgeng, Epoch Times

In brief:

• On the evening of Friday 23 October, the grid frequency dropped sharply at around 10 pm.
• At this time of day, the frequency often drops sharply when there is a lot of wind power.
• The cause is a statutory noise protection regulation that applies, among other things, to wind turbines.

Evening, 10 pm in Germany: time and again, a look at the grid frequency shows that at precisely this time of day it makes a more or less pronounced jump downwards.

This happened most recently on Friday 23 October. Within 29 seconds, around 2,800 megawatts (MW) of capacity were lost in the German and European interconnected grid respectively. This led to a grid frequency jump of 167 millihertz (mHz) to 49.88 hertz (Hz).

Netzfrequenzsprung Level 4, ∆f↓ = -165mHz in 30s ==> Netzlastdifferenz ≈ -2700MW https://t.co/GvpADACqa5 #Netzfrequenzinfodienst #Netzfrequenzsprung #RJ2ET https://t.co/0eK1g7QkXE
— RJ2-Netzfrequenzinfodienst (@_RG_CE) [October 23, 2026])

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The grid frequency should always be 50 Hz. This is the case when power plants generate exactly as much electricity every second as consumers are drawing at that moment. In normal operation, deviations of up to 0.150 Hz are possible. Grid operators compensate for these with what is known as primary control reserve, which amounts to around 3,450 MW. In this particular case, the deviation was within this range, so the grid frequency could be stabilised within about five minutes.

However, if the frequency threatens to move above 50.2 or below 49.8 Hz, as has happened several times in the past, grid operators have to take more far-reaching measures. On the one hand, this involves disconnecting areas with excessive consumption from the grid, also known as a brownout. On the other hand, flexible power plants have to be ramped up immediately. Both are intended to prevent a widespread power outage. If this fails, technical installations automatically disconnect from the grid to protect themselves, and a national or even international power outage can occur, as happened on the Iberian Peninsula.

Wind power and bureaucracy

Such a frequency jump occurs more often above all in the winter months, when there is more wind power on the grid. The regularity of this 10 pm jump was confirmed at the end of last winter by the grid frequency information service RJ2. “In recent months, anomalies in the form of grid frequency trigger and frequency jump reports have increasingly been observed at 22:00 (CET/CEST) each time,” the website stated in March of this year.

According to RJ2’s experts, the reason for the regular evening frequency jumps lies in the field of wind power – or, more precisely, in a bureaucratic regulation. At this time, many operators of wind turbines located near residential areas have to throttle down or shut off their turbines.

The rule comes from the Technical Instructions for the Protection against Noise, or TA Lärm for short. Accordingly, lower noise limits generally apply to outdoor technical installations during the night hours from 10 pm to 6 am than during the day. In residential areas, the permitted immission guide values are 35 to 45 decibels (dB), depending on the type of area.

Residents might perceive the noise as disturbing, and it might impair their sleep. Since the noise level of a wind turbine is often above the permitted guide value, the operator must observe a night-time quiet period for the affected turbines. Some wind turbines have noise levels of more than 100 dB directly at the turbine.

Only from 6 am does the mandatory night-time quiet period end, and the turbines may turn again and feed electricity into the grid.

Different levels

If several turbines that are currently producing a lot of electricity and feeding it into the grid drop out at the same time, a grid frequency jump occurs. “A grid frequency jump occurs immediately after a major interconnected grid disturbance or in the event of unusually strong load changes,” writes RJ2.

The grid frequency service has introduced five levels to illustrate the intensity of a frequency jump. A level 1 jump is in the range of 1,400 to 1,800 MW. Friday evening’s frequency jump was in the range of level 4, the second-highest level.

Such jumps occur more and more often as the number of wind turbines increases. Each level rises in steps of 400 MW. Higher levels occur less often. The last time level 5 was reached was on 24 March 2026. In 62 seconds, the grid frequency fell by almost 0.2 Hz, or the output by 3,200 MW.

How dangerous are the frequency jumps?

The frequency jumps caused by switching off wind turbines are usually particularly large when there is a lot of wind, that is, when the turbines are feeding in a lot of electricity.

Such strong frequency jumps put the stability of the grids to the test. The control reserve – often from flexible gas-fired power plants – must be able to step in quickly enough to compensate for the loss of wind power.

“If something goes wrong during the change in power plant dispatch, things can get tight,” energy expert Herbert Saurugg remarked recently. Regions with many wind turbines are particularly at risk. In an emergency, regional power cuts can occur there if grid operators cannot stabilise the frequency quickly enough.

Before a widespread power outage – a blackout – actually occurs, utilities prefer regional controlled shutdowns, so-called brownouts.

A possible solution

But there is an obvious solution: a legal adjustment to stagger the switch-off and switch-on times of wind turbines. The frequency jumps arise mainly because all turbines switch off at exactly 10 pm. The electronic inverters stop feeding in instantly. The mechanical control power plants, however, are not that fast. They need a few seconds to minutes to ramp up their output.

If some turbines were to switch off as early as 9:45 pm or at least 9:55 pm, and others only at 10:05 pm or even 10:15 pm, the period would be stretched from around one minute to ten or 30 minutes. This would give grid operators considerably more leeway to ramp up the control reserve. The grid players could cope better with the drop in output. Similarly, in the morning, if the wind is still blowing, the turbines could be switched back on in a staggered fashion.

How many partial shutdowns would make sense and which turbines should go offline first and last is unclear at present and must be clarified and regulated by the legislator.

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This article first appeared in German on Epoch Times – with kind permission of Maurice Forgeng.
Cover image: muenzi1958 / Pixabay