A massive power outage in South America last month left most of Argentina, Uruguay, and Paraguay in the dark and may also have impacted small portions of Chile and Brazil. It’s estimated that 48 million people were affected and as of this writing there has still been no official explanation of how a blackout of this magnitude occurred.
While blackouts of some form or another are virtually guaranteed on any power grid, whether it’s from weather events, accidental damage to power lines and equipment, lightning, or equipment malfunctioning, every grid will eventually see small outages from time to time. The scope of this one, however, was much larger than it should have been, but isn’t completely out of the realm of possibility for systems that are this complex.
Initial reports on June 17th cite vague, nondescript possible causes but seem to focus on transmission lines connecting population centers with the hydroelectric power plant at Yacyretá Dam on the border of Argentina and Paraguay, as well as some ongoing issues with the power grid itself. Problems with the transmission line system caused this power generation facility to become separated from the rest of the grid, which seems to have cascaded to a massive power failure. One positive note was that the power was restored in less than a day, suggesting at least that the cause of the blackout was not physical damage to the grid. (Presumably major physical damage would take longer to repair.) Officials also downplayed the possibility of cyber attack, which is in line with the short length of time that the blackout lasted as well, although not completely out of the realm of possibility.
This incident is exceptionally interesting from a technical point-of-view as well. Once we rule out physical damage and cyber attack, what remains is a complete failure of the grid’s largely automatic protective system. This automation can be a force for good, where grid outages can be restored quickly in most cases, but it can also be a weakness when the automation is poorly understood, implemented, or maintained. A closer look at some protective devices and strategies is warranted, and will give us greater insight into this problem and grid issues in general. Join me after the break for a look at some of the grid equipment that is involved in this system.
The power grid is a complicated beast, regardless of where you live. Power plants have to send energy to all of their clients at a constant frequency and voltage (regardless of the demand at any one time), and to do that they need a wide array of equipment. From transformers and voltage regulators to line reactors and capacitors, breakers and fuses, and solid-state and specialized mechanical relays, almost every branch of engineering can be found in the power grid. Of course, we shouldn’t leave out the most obvious part of the grid: the wires that actually form the grid itself.
You might be reading this six minutes early. Assuming that the Hackaday editors have done their job, this article should have appeared in your feed right on the half-hour. We have a set schedule to keep you supplied with the tastiest of hardware hacks and news. For some of you though perhaps there has been a treat, you’ve seen it and all the other stories six minutes early.
Think for a minute of a modern car on a hot day. When you turn on the air conditioning you will hear a slight dip in the engine revs as it accommodates the extra load. So it is with an alternating current power grid; a simple example is a power station supplying a city. In periods such as cold nights when the demands of the city go up, the result would be that the power station needs to work harder to satisfy it, and until that happens there would be a slight dip in its line frequency. Power grids compensate for this by increasing and decreasing the available generating capacity in real time, maintaining a mean frequency such that the “grid time” of a clock controlled by it matches an atomic clock as closely as possible over time.
It is at this point we leave the realm of electrical engineering and enter that of international politics, normally something far removed from Hackaday’s remit. It is fair to say that the history between Serbia and Kosovo is extremely delicate, and to understand some of the context of this story you should read about the war at the end of the 1990s. After the conflict the Serbian-majority region of what is now Kosovo refused to pay the Kosovan utility for its electricity, eventually leading to the Kosovans refusing to pay for that region’s share of the power received by Kosovo from Serbia. The resulting imbalance between demand and supply was enough to drag the supply frequency down across the whole continent, and though a short-term agreement has been reached the problem still remains on the grid.
Clocks and Mains Frequency
So if you are a continental European and you find yourself six minutes behind your British or American friends, don’t worry. We know that among our readers are people with significant experience in the power generation world, perhaps some of you would like to use your six minutes to give us a bit of insight in the comments. Meanwhile here at Hackaday we maintain an interest in the mechanics of power distribution even if some might say that it is Not A Hack. We’ve taken a look at utility poles, and examined how power grids are synchronised.
As for those slow clocks, the use of mains frequency to keep accurate time is quite brilliant and has been used reliably for decades. Tightly regulating grid frequency means that any clock plugged into an outlet can have the same dead-on accuracy for the cost of a few diodes. These clocks count the zero crossing of the alternating current. There may be moment to moment drifts but the power utility injects or removes cycles over the long term so the sum of crossings is dead on over the course of the day. It’s an interesting phenomenon to experiment with and that’s why we see it in microcontroller projects from time to time.
The electrical grid transmits power over wires to our houses, and our Bryan Cockfield has covered it very well in his Electrical Grid Demystified series, but what part does the earth ground play? It’s commonly known to be used for safety, but did you know that in some cases it’s also used for power transmission?
Typical House Grounding System
A pretty typical diagram for the grounding system for a house is shown here, along with a few of the current carrying conductors commonly called live and neutral. On the far left is the transformer outside the house and on the far right is an appliance that’s plugged in. In between them is a breaker panel and a wall socket of the style found in North America. The green dashed line shows the normal path for current to flow.
Notice the grounding electrodes for making an electrical connection with the earth ground. To use the US National Electrical Code (NEC) as an example, article 250.52 lists eight types of grounding electrodes. One very good type is an electrode encased in concrete since concrete continues to draw moisture from the ground and makes good physical contact due to its weight. Another is a grounding rod or pipe at least eight feet long and inserted deep enough into the ground. By deep enough, we mean to include factors such as the fact that the frost line doesn’t count as a good ground since it has a high resistance. You have to be careful of using metal water pipes that seemingly go into the ground, as sections of these are often replaced with non-metallic pipes during regular maintenance.
Notice also in the diagram that there are places where the various metal cases are connected to the grounding system. This is called bonding.
Now, how does all this system grounding help us? Let’s start with handling a fault.
I found myself staring up at the sky on the night of March 13, 1989, with my girlfriend and her parents in the backyard of their house. The sky was on fire, almost literally. Red and pink sheets of plasma streamed out in a circle from directly overhead, with blue-white streaks like xenon flashes occasionally strobing across the sky. We could actually hear a sizzling, crackling sound around us. The four of us stood there, awestruck by the aurora borealis we were lucky enough to witness.
At the same time, lights were winking out a couple of hundred miles north in Québec province. The same solar storm that was mesmerizing me was causing fits for Hydro-Québec, the provincial power authority, tripping circuit breakers and wreaking havoc. This certainly wasn’t the first time the Sun threw a fit and broke systems on Earth, but it was pretty dramatic, and there are some lessons to be learned from it and other solar outbursts.
January, for many of us in the Northern Hemisphere, can be a depressing month. It’s cold or wet depending where you live, the days are still a bit short, and the summer still seems an awfully long way away. You console yourself by booking a ticket to a hacker camp, but the seven months or so you’ll have to wait seems interminable.
If you want an interesting project to look forward to, take a look at [Benadski]’s idea for a decentralised low voltage local DC power grid for the upcoming SHA 2017 hacker camp in the Netherlands. The idea is to create a network that is both safe and open for hacking, allowing those with an interest in personal power generation to both have an available low-voltage power source and share their surplus power with other attendees.
The voltage is quoted as being 42V DC +/- 15%, which keeps it safely under the 50V limit set by the European Low Voltage Directive. Individuals can request a single 4A connection to the system, and villages can have a pair of 16A connections, which should supply enough for most needs. Users will need to provide their own inverters to connect their 5V or 12V appliances, fortunately a market served by numerous modules from your favourite Far Eastern sales portal.
This project will never be the solution to all power distribution needs, but to be fair that is probably not the intention. It does however provide a platform for experimentation, collaboration, and data gathering for those interested in the field, and since it is intended to make an appearance at future hacker camps there should be the opportunity for all that built up expertise to make it better over time.