How Britain Narrowly Escaped A Grid Blackout In June 2026

October 30, 2026 by Maya Posch 13 Comments

Amidst one of the worst heatwaves in European history, Britain’s national grid saw itself faced with a quiet crisis this summer. On June 23rd, the grid frequency dropped to 49.657 Hz, down from the nominal 50 Hz — getting very close to the lower bound before safeties would start disconnecting parts of the grid. In a video by [The Electric Brit] this event is investigated, including its causes and how France’s spare capacity managed to save the day.

Under normal operating conditions the UK grid is kept above 49.8 Hz, with the statutory lower limit being 49.5. Meaning that another drop of 0.157 Hz would have set in motion a series of quite extreme grid protection mechanisms including the possibility of local blackouts.

Fortunately the cessation of energy exports and the importing of French power from hydro and nuclear power stations managed to nip this issue in the bud before it could get any worse. Although an example of correct grid management, it also shows how poorly planned maintenance and events like a heatwave can line up quite a few holes in the cheese slices that invite disaster.

The problems here began weeks prior to the event, with 21.2 GW of generating capacity offline. Of this, 12.6 GW was planned maintenance, another 8.6 GW was unexpectedly offline, while another 2.6 GW of gas generation was mostly unavailable due to the heatwave curtailing production. A couple of interconnections with Ireland and other nations were also down for maintenance, leaving the grid control room with precious few options.

Although the UK’s transmission system operator (TSO) NESO had its predicted capacities for variable renewable sources (VRE) like solar, it could not see local demand and production from e.g. rooftop solar in the control room. This became rather exciting when the evening neared and rooftop solar output dropped. Here NESO turned out to be lucky, but such hidden factors form a major risk factor when such consumers return to grid power.

As VRE sources fell quiet across Europe that evening, this put the onus on remaining generating sources and brought the slowly developing crisis to its apex. Fortunately importing energy from France saved the day here, but there are many lessons to be learned here, many grounded in how complex AC grid management is once you consider all aspects that affect not just generators but also transmission lines.

This event is different from the frequency oscillations that triggered the blackout on the Iberian peninsula in 2025. In that case a problem existed with reactive power management, with oscillations amplified by grid-following converters from solar farms and insufficient capacity on the grid to absorb this surge in reactive power, ultimately leading to the cascading blackout.

Amidst these lessons on grid-management the discussions on whether baseload power generating is truly dead among other tropes, as well as the calls by European TSOs to make grid-forming converters mandatory on VRE generators will no doubt intensify.

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How The Grid’s Harmonic Filters Keep The Power Clean

August 21, 2026 by Maya Posch 15 Comments

A fun way to think about a national electrical grid is as a massively upscaled electrical circuit, one in which you have multiple power supplies injecting AC power, with various bits and bobs involving resistors, inductors and capacitors in between working to synchronize and clean-up this power before it gets to the end users. Recently [Jordan Taylor], also known as [The Electric Brit] took a look at the grid’s harmonic filters that do a lot of this sinewave scrubbing after the HVDC to AC conversion.

Using a UK-based line-commutated converter (LCC) HVDC converter station as a physical example [Jordan] takes us through the elements of this harmonic filter, what it is, what it does and why it’s a necessity. The design considerations with components at this immense scale are also covered, along with the types of filters possible.

The Cliff’s Notes version is that following the conversion step from said HVDC there are harmonics introduced in the AC, not unlike in a much lower-voltage converter. This results in a noisy sinewave that can potentially cause harm to AC-powered devices, not to mention cause heating and other losses along the way. The answer is naturally to add an LC-filter, just on a slightly larger scale than for consumer electronics.

Also noted by [Jordan] is the nice synergy of these harmonic filters when it comes to absorbing and generating reactive power on the AC grid, due to their massive capacitors and inductors. This helps to dampen oscillations on the grid and thus further contributing to its stability.

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Line Power With No Transformer

February 24, 2025 by Al Williams 43 Comments

Normally, when you want a low DC voltage from the AC line, you think about using a transformer of some kind. [RCD66] noticed that an AC monitor meter must have some sort of power supply but had no transformers in sight. That led to an exploration of how those work and how you can use them, too. You can watch the work in the video below.

Sensibly, there is a transformer in the test setup — an isolation transformer to make it safe to probe the circuit. But there’s no transformer providing voltage changes. Isolation is important even if you are taking apart something commercial that might be trasformerless.

The circuit is simple enough: it uses a capacitor, a resistor, and a pair of diodes (one of them a zener diode). He uses this basic circuit to drive simple regulators with input and output filter capacitors. We’ve seen many variations on this design over the years.

You can’t draw a lot of power through this arrangement. But sometimes it is all you need. However, this is pretty dangerous, as we’ve discussed before. Be sure you understand exactly what the risks are before you decide to build something like this.

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Moving Power Grids In A Weekend, The Baltic States Make The Switch

February 9, 2025 by Jenny List 35 Comments

A significant event in the world of high-power electrical engineering is under way this weekend, as the three Baltic states, Lithuania, Latvia, and Estonia, disconnect their common power grid from the Russian system, and hook it up to the European one. It’s a move replete with geopolitical significance, but it’s fascinating from our point of view as it gives a rare insight into high voltage grid technology.

There are a few news videos in the air showing contactors breaking the circuit, and even a cable-cutting moment, but in practice this is not as simple a procedure as unplugging an appliance from a wall socket. The huge level of planning that has gone into this move is evident in the countrywide precautions in case of power loss, and the heightened security surrounding the work. As we understand it at the moment the three countries exist as a temporary small grid of their own, also isolating the Russian exclave of Kaliningrad which now forms its own grid. The process of aligning the phase between Baltic and European grids has been under way overnight, and an online monitor shows significant frequency adjustments during that time. At some point on Sunday a new connection will be made to the European grid via Poland, and the process will be completed. We imagine that there will be a very relieved group of electrical engineers who will have completed their own version of a Moon landing when that has happened.

If you happen to live in either region, there’s still some time to watch the process in action, by monitoring the supply frequency for yourself. It’s not the first time that geopolitics have affected the European grid, as the continent lost six minutes a few years ago, and should you Americans think you are safe from such problems, think again.

Cascade Failures, Computer Problems, And Ohms Law: Understanding The Northeast Blackout Of 2003

February 25, 2022 by Ryan Flowers 16 Comments

We’ve all experienced power outages of some kind, be it a breaker tripping at an inconvenient time to a storm causing a lack of separation between a tree and a power line. The impact is generally localized and rarely is there a loss of life, though it can happen. But in the video below the break, [Grady] of Practical Engineering breaks down the Northeast Blackout of 2003, the largest power failure ever experienced in North America. Power was out for days in some cases, and almost 100 deaths were attributed to the loss of electricity.

[Grady] goes into a good amount of detail regarding the monitoring systems, software simulation, and contingency planning that goes into operating a large scale power grid. The video explains how inductive loads cause reactance and how the effect exacerbated an already complex problem. Don’t know what inductive loads and reactance are? That’s okay, the video explains it quite well, and it gives an excellent basis for understanding AC electronics and even RF electronic theories surrounding inductance, capacitance, and reactance.

So, what caused the actual outage? The complex cascade failure is explained step by step, and the video is certainly worth the watch, even if you’re already familiar with the event.

It would be irresponsible to bring up the 2003 outage without talking about the Texas ERCOT outages just one year ago– an article whose comments section nearly caused a blackout at the Hackaday Data Center!

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Simple AC Current Detector Built On A 9 Volt

January 4, 2021 by Zoe Skyforest 58 Comments

When working around mains voltages, it can be useful to know whether a given circuit is live or not. While this can be done by direct connection with a multimeter, non-contact methods are available too. A great example is this simple wireless AC current detector from [NEW PEW].

The circuit is a simple one, and a classic. The spring from a ballpoint pen is soldered to the base of a BC547 transistor, and when held close enough to a conductor carrying AC power, a current is induced in the spring which is sufficient to turn the transistor on. The transistor then switches on a second BC547, which lights an LED. The whole circuit is built on top of a battery clip so it can be run straight from the top of a standard 9 volt battery.

It’s a circuit you’ll find all over the place, even built into many modern multimeters. It can be particularly useful to help avoid drilling through mains wires embedded in the walls of your home. Of course, if you’d like even more information about what’s lurking within your walls, consider this capacitive imaging hack. Video after the break.

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Power Measurement Oscilloscope Style

April 24, 2019 by Al Williams 7 Comments

If you want to measure voltage you reach for a voltmeter. Current? An ammeter. Resistance? An ohmmeter. But what about measuring AC power? A watt meter? Usually. But if you know what to do, you could also reach for your oscilloscope. If you don’t know what to do, [Jim Pytel] has the video answers for you. Truth is, an oscilloscope can measure almost anything if you know how. [Jim] shows how to measure the voltage and current in a circuit and then it is simply a matter of doing a little math, something modern scopes can do very easily.

We like that [Jim] shows a circuit and how the math works before he verifies the math with the scope. Of course, theory doesn’t always match practice. The method uses a small current-sensing resistor that throws readings off a bit. The scope and signal generator are not perfect, either. However, the results match up pretty nicely with the computed results.

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