Accurately Track Your Mains Frequency

February 15, 2022 by Jenny List 27 Comments

Depending upon where in the world you live, AC mains frequency is either 50Hz or 60Hz, and that frequency is maintained accurately enough over time that it can be used as a time reference for a clock. Oddly it’s rarely exactly that figure though, instead it varies slightly with load on the network and the operators will adjust it to keep a constant frequency over a longer period. These small variations in frequency can easily be measured, and [jp3141] has created a circuit that does exactly that.

It’s a surprisingly straightforward device, in which a Teensy takes its power supply from a very conventional if now a little old-school mains transformer, rectifier, and regulator. A sample of the AC from the transformer passes through a low-pass filer and a clamp, and thence to the Teensy where it is fed into one of the on-board comparators from which its period is measured using one of the timers. Even then the on-board crystal isn’t considered accurate enough, so it is in turn disciplined by a 1 pulse per second (PPS) signal from a GPS receiver.

The Teensy then reports its readings over a serial line every five seconds to a Raspberry Pi, which collates and graphs the data. In case you are wondering what the effect of mains frequency variations might be, we once covered the story of how an entire continent lost six minutes.

Emulating A Power Grid

June 26, 2021 by Bryan Cockfield 23 Comments

The electric power grid, as it exists today, was designed about a century ago to accommodate large, dispersed power plants owned and controlled by the utilities themselves. At the time this seemed like a great idea, but as technology and society have progressed the power grid remains stubbornly rooted in this past. Efforts to modify it to accommodate solar and wind farms, electric cars, and other modern technology need to take great effort to work with the ancient grid setup, often requiring intricate modeling like this visual power grid emulator.

The model is known as LEGOS, the Lite Emulator of Grid Operations, and comes from researchers at RWTH Aachen University. Its goal is to simulate a modern power grid with various generation sources and loads such as homes, offices, or hospitals. It uses a DC circuit to simulate power flow, which is visualized with LEDs. The entire model is modular, so components can be added or subtracted easily to quickly show how the power flow changes as a result of modifications to the grid. There is also a robust automation layer to the entire project, allowing real-time data acquisition of the model to be gathered and analyzed using an open source cloud service called FIWARE.

In order to modernize the grid, simulations like these are needed to make sure there are no knock-on effects of adding or changing such a complex system in ways it was never intended to be changed. Researchers in Europe like the ones developing LEGOS are ahead of the curve, as smart grid technology continues to filter in to all areas of the modern electrical infrastructure. It could also find uses for modeling power grids in areas where changes to the grid can happen rapidly as a result of natural disasters.

The Regulatory Side Of Rolling Your Own Moderate Solar Farm

June 17, 2021 by Donald Papp 25 Comments

[Russell Graves] lives in Idaho and recently connected his solar installation to the grid, which meant adhering to regulatory requirements for both the National Electric Code (NEC) as well as complying with the local power company’s own regulations. His blog post is an interesting look at the whole regulatory process and experience, and is of interest to anyone curious about running their own solar farm, whether they have plans to connect it to the grid or not.

A circuit breaker that met NEC code, but not the power company’s requirements.

The power company has a very different set of priorities from the NEC, and part of [Russell]’s experience was in having to meet requirements that weren’t documented in the expected places, so study of the materials didn’t cut it. In particular, the power company needed the system to have disconnects with conductors that visually move out of position when disconnected. [Russell] was using NEC-compliant circuit breakers that met NEC code, but they didn’t meet the power company requirement for conductors that can be visually confirmed as being physically disconnected. Facing a deadline, [Russell] managed to finesse a compliant system that was approved, and everything got signed off just as winter hit.

How well does his solar farm work out? Sometimes the panels produce a lot of power, sometimes nearly nothing, but it has been up and running for all of winter and into spring. Over the winter, [Russell] pulled a total of 3.1 MWh from the grid, mainly because his home is heated with electric power. But once spring hit, he started pushing considerably more into the grid than he was pulling; on some days his setup produces around 95 kWh, of which about 70 kWh gets exported.

[Russell] didn’t go straight to setting up his own modest solar farm; we saw how he began by making his own ideal of a perfect off-grid office shed that ran on solar power, but it has certainly evolved since then and we’re delighted to see that he’s been documenting every bit of the journey.

What’s The Deal With Rolling Blackouts In California’s Power Grid?

August 31, 2020 by Bryan Cockfield 148 Comments

A heat wave spreading across a large portion of the west coast of the United States is not surprising for this time of year, but the frequency and severity of these heat waves have been getting worse in recent years as the side effects from climate change become more obvious. In response to this, the grid operators in California have instituted limited rolling blackouts as electricity demand ramps up.

This isn’t California’s first run-in with elective blackouts, either. The electrical grid in California is particularly prone to issues like this, both from engineering issues and from other less obvious problems as well.

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Ask Hackaday: Is Our Power Grid Smart Enough To Know When There’s No Power?

June 23, 2020 by Jenny List 63 Comments

Just to intensify the feeling of impending zombie apocalypse of the COVID-19 lockdown in the British countryside where I live, we had a power cut. It’s not an uncommon occurrence here at the end of a long rural power distribution network, and being prepared for a power outage is something I wrote about a few years ago. But this one was a bit larger than normal and took out much more than just our village. I feel very sorry for whichever farmer in another village managed to collide with an 11kV distribution pole.

What pops to mind for today’s article is the topic of outage monitoring. When plunged into darkness we all wonder if the power company knows about it. The most common reaction must be: “of course the power company knows the power is out, they’re the ones making it!”. But this can’t be the case as for decades, public service announcements have urge us to report power cuts right away.

In our very modern age, will the grid become smart enough to know when, and perhaps more importantly where, there are power cuts? Let’s check some background before throwing the question to you in the comments below.

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The Hornsdale Power Reserve And What It Means For Grid Battery Storage

December 16, 2019 by Lewin Day 130 Comments

Renewable energy has long been touted as a major requirement in the fight to stave off the world’s growing climate emergency. Governments have been slow to act, but prices continue to come down and the case for renewables grows stronger by the day.

However, renewables have always struggled around the issue of availability. Solar power only works when the sun is shining, and wind generators only when the wind is blowing. The obvious solution is to create some kind of large, grid-connected battery to store excess energy in off-peak periods, and use it to prop up the grid when renewable outputs are low. These days, that’s actually a viable idea, as South Australia proved in 2017.

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Anatomy Of A Power Outage: Explaining The August Outage Affecting 5% Of Britain

September 7, 2019 by Jenny List 18 Comments

Without warning on an early August evening a significant proportion of the electricity grid in the UK went dark. It was still daylight so the disruption caused was not as large as it might have been, but it does highlight how we take a stable power grid for granted.

The story is a fascinating one of a 76-second chain of unexpected shutdown events in which individual systems reacted according to their programming, resulted in a partial grid load shedding — what we might refer to as a shutdown. [Mitch O’Neill] has provided an analysis of the official report which translates the timeline into easily accessible text.

It started with a lightning strike on a segment of the high-voltage National Grid, which triggered a transient surge and a consequent disconnect of about 500MW of small-scale generation such as solar farms. This in turn led to a large offshore wind farm deloading itself, and then a steam turbine at Little Barford power station. The grid responded by bringing emergency capacity online, presumably including the Dinorwig pumped-storage plant we visited back in 2017.

Perhaps the most interesting part followed is that the steam turbine was part of a combined cycle plant, processing the heat from a pair of gas turbine generators. As it came offline it caused the two gas turbines feeding it to experience high steam pressure, meaning that they too had to come offline. The grid had no further spare capacity at this point, and as its frequency dropped below a trigger point of 48.8 Hz an automatic deloading began, in effect a controlled shutdown of part of the grid to reduce load.

This is a hidden world that few outside the high-power generation and transmission industries will ever see, so it’s very much worth a read. It’s something we’ve touched on before with the South American grid shutdown back in June, and for entirely different reasons in 2018 when an international disagreement caused the entire European grid to slow down.

Header image: Little Barford combined-cycle power station against the sunset. Tony Foster, (CC BY-SA 2.0).