Electrostatic motors are now common in MEMS applications, but researchers at the University of Wisconsin and spinoff C-Motive Technologies have brought macroscale electrostatic motors back. [via MSN/WSJ]

While the first real application of an electric motor was Ben Franklin’s electrostatically-driven turkey rotisserie, electromagnetic type motors largely supplanted the technology due to the types of materials available to engineers of the time. Newer dielectric fluids and power electronics now allow electrostatic motors to be better at some applications than their electromagnetic peers.

The main advantage of electrostatic motors is their reduced critical materials use. In particular, electrostatic motors don’t require copper windings or any rare earth magnets which are getting more expensive as demand grows for electrically-powered machines. C-Motive is initially targeting direct drive industrial applications, and the “voltage driven nature of an electrostatic machine” means they require less cooling than an electromagnetic motor. They also don’t use much if any power when stalled.

Would you like a refresher on how to make static electricity or a deeper dive on how these motors work?

Drive along nearly any major road in the United States and it won’t be long before you see evidence of the electrical grid. Whether it’s wooden poles strung along the right of way or a line of transmission towers marching across the countryside in the distance, signs of the grid are never far from view but often go ignored, blending into the infrastructure background and becoming one with the noise of our built environment.

But there’s one part of the electrical grid that, despite being more widely distributed and often relegated to locations off the beaten path, is hard to ignore. It’s the electrical substation, more than 55,000 of which dot the landscape of the US alone. They’re part of a continent-spanning machine that operates as one to move electricity from where it’s produced to where it’s consumed, all within the same instant of time. These monuments of galvanized steel are filled with strange, humming equipment of inscrutable purpose, seemingly operating without direct human intervention. But if you look carefully, there’s a lot of fascinating engineering going on behind those chain-link fences with the forbidding signage, and the arrangement of equipment within them tells an interesting story about how the electrical grid works, and what the consequences are when it doesn’t.

From The Ground Up

The most basic function of a substation is to transform voltages, either stepping up the voltage from the point of production for efficient transmission over long distances, or stepping voltages down from transmission systems to feed regional or local distribution systems. That makes substations conceptually simple, but as is always the case in engineering, the details are where things get interesting.

While the equipment mounted above the ground is the easiest part of a substation to observe, what you don’t see is arguably far more important, at least in terms of safety. A note to frame the discussion: we’ll be concentrating on open-air substations, rather than substations that are inside a structure, which are an important and interesting part of the grid, but harder to observe casually.

Substations must have an extensive grounding system, both for worker safety and to provide the needed neutral reference. Most substations use a grid of thick copper conductors buried just below the surface, tied together at regular intervals to ground rods extending 25 feet (7 meters) or more into the soil below. Horizontal and vertical conductors are tied together with exothermically welded connections or cold-forged fittings to form low-impedance electrical connections between every element of the grid. The grounding grid spreads out under the entire area of the substation, and everything is bonded into the ground system by heavy, low-impedance braided straps.

Over the grounding grid is a layer of crushed rock about 6 inches (15 cm) thick. The gravel serves several functions, including aiding water drainage and inhibiting weed growth. But the main function is worker safety in the event of a ground fault, which could cause a lethal voltage difference between the above-ground equipment and the earth. The high resistivity of the gravel (3,000 to 5,000 ohm-meters) compared to the soil makes it less likely that a worker will conduct these voltages through their body. Also, gravel reduces the possibility of lethal voltages between one foot and the other while walking, or step voltages.

Every substation also has a fence or physical barrier of some sort. Most are imposing structures of heavy-duty chain-link topped with razor wire, but in some residential areas, a more decorative option might be used to appease the neighbors. Some substations also have sound barriers, to reduce the incessant 60 Hz hum of the equipment within that could annoy nearby residents. The characteristic hum has also been known to attract bears, who apparently think they’ve found the world’s largest beehive. A sturdy barrier is critical to avoiding unpleasant consequences for the bear, or for those with a greedy eye on the multiple tons of copper most substations contain.

Rule of Threes

Of the above-ground equipment in the substation, the most visually striking structures are those that support and terminate the wires coming into and leaving the yard. These are loosely referred to as “high side” and “low side” lines based on the voltages they carry. A substation might have a 345 kV high side to receive power from a transmission line and several 25 kV lines on the low side feeding different local distribution lines. Some substations will also have multiple high-side feeds from different transmission lines, or may have multiple low-side inputs from wind or solar plants that the substation will combine into one or more high-side transmission lines.

Something that stands out about most substations is that there seem to be three copies of each piece of equipment. Each set of high-side lines comes into the substation in a set of three, there are often three transformers (or one transformer with three input bushings and three output bushings), and all of the gear between the input and the output seems to be in triplicate. This is thanks to the three-phase electrical system in North America. Electrical transmission and distribution systems are all three-phase power, and while residential customers rarely enjoy such service to the home, commercial and industrial installations almost universally have it.

While the high-side and low-side lines entering and leaving the substation are generally — but not always — overhead wires, inside the substation, most of the components are connected by a series of overhead busbars. Busbars are simply pieces of metal pipe, often galvanized steel or aluminum and usually in groups of three, which are attached to equipment bushings either directly or via jumper wires. Busbars have the advantage of not sagging or swaying in the wind, but do have a few disadvantages, too. When busbars get hot they expand, and since they’re rigid and supported firmly on each end they’ll either buckle or break their supports. That means busbars have to be provided with expansion joints.

Another potential failure mode for busbars is ice damage, which I witnessed back in the 1980s. During a late winter thaw, meltwater had accumulated in a busbar at a substation near my home. When the temperature dropped precipitously that night, the freezing water exerted enough pressure to burst the busbar, which caused a fault on one of the phases bad enough to trip the entire substation. This knocked out power to the entire town and resulted in the local utility asking for help from my volunteer fire company.

The substation techs used the enormous generator on our truck to power a welder so they could make an impromptu repair to the busbar and restore power. It was a long, bitterly cold night, but I got to walk around inside a substation and check things out. It was pretty cool.

Plenty of Protection

That brings up the topic of control and protection. The vast majority of the equipment inside a substation is devoted to circuit protection, in the form of circuit breakers, fuses, reactors, and capacitors, followed by the equipment needed to control and monitor the circuits. Lightning protection is also vital, since a nearby strike can induce currents that can permanently damage equipment. Protection starts at the top with static lines on the highest part of transmission towers that are designed to catch discharges and run them directly to ground. Static lines are now often hybrid cables called OPGW, or optical ground wire, which has one or more optical fiber pairs at its core. These fibers are used for control and communications between substations; some utilities even lease the extra pairs out to communications providers.

Circuit breakers play a last-ditch role in substation protection, and are capable of disconnecting the entire substation in a catastrophic fault. They’re pretty easy to spot thanks to their angled bushings, usually two per breaker with one breaker per phase, although some breakers have three bushings each. The breakers are just super-sized versions of those in your home panel and work in a similar way, albeit tripping at a much higher current — often 5,000 amps or more. They also have to switch very rapidly, a tough job when there’s enough voltage to keep an arc going between the contacts even when they’re fully separated. So circuit breakers are often filled with a dielectric gas such as sulfur hexafluoride (SF₆), a liquid dielectric like mineral oil, or even evacuated completely. Air blast breakers which literally blow the arc out are also used.

Another interesting bit of control equipment in the yard is the voltage regulators, which are essentially autotransformers that can adjust the voltage on a phase within a small percentage range. These are easily recognizable as a set of three tall cylinders, each bearing a large dial on the top. The dial shows how much voltage is being boosted or bucked, and is usually angled downward for easier reading from the ground. Substation switchyards also often contain banks of high-voltage capacitors, which adjust the power factor and compensate for noise on the line. Capacitor banks are usually located on the distribution side of a substation along with neutral grounding reactors, which are large, cylindrical inductors that are connected in series between the neutral of a transformer and ground and limit current if there’s a phase-to-ground fault.

Sprinkled liberally around the substation are instrumentation transformers whose entire job is to monitor the flow of current into and out of almost every piece of equipment. Current transformers, or CTs, are just permanently installed, beefed-up versions of the clamp meter you might use for measuring current in an electrical panel and work pretty much the same way, with current in the conductor under measurement inducing a proportional current in a toroidal coil. Voltages are measured with voltage transformers (VTs), the most common of which is the capacitive voltage transformer, or CVT. These use high-voltage capacitors as a voltage divider and a transformer to isolate and further step down the voltage to a reasonable instrumentation range. The outputs of instrumentation transformers are generally piped into a supervisory control and data acquisition (SCADA) system that remotely monitors and controls everything in the substation, right down to alarm contacts on the fence gates.

The Diva Treatment

Since the primary job of the substation is changing one voltage to another, the main power transformers are the centerpiece of the switchyard. In a lot of ways, transformers are the divas of the substation — they’re expensive to procure, require a lot of maintenance, and the show won’t go on until they’re happy. The transformers are easy to spot, since they’re generally the largest pieces of equipment in the yard. In keeping with the rule of threes, there are usually three identical units, one for each phase, although some transformers have windings for all three phases in a single massive enclosure.

Almost all substation transformers are filled with mineral oil, which acts as a liquid dielectric and helps cool the transformer thanks to giant radiators and fans for forced-air cooling. A large transformer can hold thousands of gallons of oil, an environmental disaster waiting to happen if there should be a leak, which given some recent rural substation attacks is not unthinkable. That makes secondary containment a necessity, with deep pits dug around the transformer foundation pads. The pits are lined with thick plastic sheets and backfilled with gravel. They’re designed to contain the entire volume of oil if necessary, and sump pumps with oil separators keep rainwater from accumulating in the pit.

In keeping with the diva treatment, transformers require constant monitoring to ensure they operate at their peak. Aside from the instrumentation used to measure their electrical status, transformers need to have their oil checked regularly for chemical changes that could indicate internal problems like arcing and overheating. This can either be performed by a technician visiting the substation and taking samples of the oil, or through online dissolved gas analysis (DGA), which uses a compact gas chromatograph to automatically sample the oil and measure the amount of acetylene, ethylene, and methane dissolved within it. Continuous measurements are collected via SCADA and provide a much more accurate picture of transformer health than monthly or quarterly sampling.

And finally, to push the diva metaphor even further, transformers are often provided with pressure-relief devices to protect the system in the event of an explosion within the transformer enclosure. PRDs can be as simple as a burst disc that shatters under increased pressure, but are more commonly sensors that detect and characterize the pressure wave from an internal explosion as it propagates through the oil. If the pressure wave looks like a catastrophic internal failure has occurred, the SCADA system will disconnect the transformer, in an attempt to save it from irreparable damage.

While high-voltage transmission lines are probably the most visible components of the electrical grid, they’re certainly among the least appreciated. They go largely unnoticed by the general public — quick, name the power line closest to you right now — at least until a new one is proposed, causing the NIMBYs and BANANAs to come out in force. To add insult to injury, those who do notice the megastructures that make modern life possible rarely take a moment to appreciate the engineering that goes into stringing up hundreds of miles of cable and making sure it stays up.

Not so the Bonneville Power Administration, the New Deal-era federal agency formed to exploit the hydroelectric abundance of the Pacific Northwest of the United States, which produced this 1950 gem detailing the stringing and sagging of power lines. Unsurprisingly, the many projects needed to wire together the often remote dams to the widely distributed population centers in an area that was only just starting to see growth began in the BPA’s offices, where teams of engineers hunched over desks worked out the best routes. Paper, pencil, and slide rules were the tools of the trade, along with an interesting gadget called a conductor sag template, a hardware implementation of the catenary equation that allowed the “sagger” to determine the height of each tower. The conductors, either steel-cored aluminum or pure copper, were also meticulously selected based on tensile strength, expected wind and ice loading, and the electrical load the line was expected to carry.

Once the engineers had their say, the hard work of physically stringing the wires began out in the field. One suspects that the work today is much the same as it was almost eighty years ago, save for much more stringent health and safety regulations. The prowess needed to transfer the wires from lifting sheaves to the insulators is something to behold, and the courage required to work from ladders hanging from wires at certain death heights is something to behold. But to our mind, the real heroes were the logistics fellows, who determined how much wire was needed for each span and exactly where to stage the reels. It’s worth sparing a moment’s thought for the daring photographer who captured all this action, likely with little more than a leather belt and hemp rope for safety.

Older consumer electronic devices follow a desirability curve in which after they fall from favour they can’t be given away. But as they become rarer, they reach a point at which everyone wants them. Then, they can’t be had for love nor money. CRT TVs are now in the first stage, they’re bulky and lower-definition than modern sets, and thus thrift stores and dumpsters still have them in reasonable numbers. To retrogamers and other enthusiasts, this can be a bonanza, and when he saw a high-end late-model JVC on the sidewalk [Chris Person] wasted no time in snapping it up. It worked, but there were a few picture issues, so he set about fixing it.

The write-up is largely a tale of capacitor-swapping, as you might expect from any older electronics, and it results in a fine picture and a working TV. But perhaps there’s another story to consider there, in that not so many of us here in 2024 are used to working with CRTs. We all know that they conceal some scary voltages, and indeed, he goes to significant lengths to discharge his CRT. It’s worth remembering though, that there’s not always a need to discharge the CRT if no attempt will be made to disconnect it, after all the connector and cable to the flyback transformer are secured by hefty insulation for a good reason. It’s a subject we’ve looked at here at Hackaday in the past. You could argue that, in some ways, newer TVs are harder to get into than these old CRTs.

When you think about additive manufacturing, thoughts naturally turn to that hot-glue squirting CNC machine sitting on your bench and squeezing whatever plastic doodad you need. But 3D printing isn’t the only way to build polymer structures, as [Riley] shows us with this fascinating attempt to create electrospun heart valves.

Now, you may never have heard of electrospinning, but we’ll venture a guess that as soon as you see what it entails, you’ll have a “Why didn’t I think of that?” moment. As [Riley] explains, electrospinning uses an electric field to build structures from fine threads of liquid polymer solution — he uses polycaprolactone (PCL), a biodegradable polyester we’ve seen used in other medical applications, which he dissolves in acetone. He loads it into a syringe, attaches the positive terminal of a high-voltage power supply to the hypodermic needle, and the negative terminal to a sheet of aluminum foil. The charge turns the PCL droplets into fine threads that accumulate on the foil; once the solvent flashes off, what’s left is a gossamer layer of non-woven plastic fabric.

To explore the uses of this material, [Riley] chose to make an artificial heart valve. This required a 3D-printed framework with three prongs, painted with conductive paint. He tried a few variations on the design before settling on a two-piece armature affixed to a rotating shaft. The PCL accumulates on the form, creating a one-piece structure that can be gingerly slipped off thanks to a little silicon grease used as a release agent.

The results are pretty impressive. The structure bears a strong resemblance to an artificial tricuspid heart valve, with three delicate leaves suspended between the upright prongs. It’s just a proof of concept, of course, but it’s a great demonstration of the potential of electrospinning, as well as an eye-opening look at what else additive manufacturing has to offer.

It used to be that nearly every home had at least one decent high-voltage power supply. Of course, it was dedicated to accelerating electrons and slamming them into phosphors so we could bathe ourselves in X-rays (not really) while watching Howdy Doody. These days the trusty tube has been replaced with LEDs and liquid crystals, which is a shame because there’s so much fun to be had with tens of thousands of volts at your disposal.

That’s the impetus behind this inexpensive high-voltage power supply by [Sebastian] over at Baltic Labs. The heavy lifting for this build is done by a commercially available power supply for a 50-watt CO₂ laser tube, manufactured — or at least branded — by VEVOR, a company that seems intent on becoming the “Harbor Freight of everything.” It’s a bold choice given the brand’s somewhat questionable reputation for quality, but the build quality on the supply seems decent, at least from the outside. [Sebastian] mounted the supply inside a rack-mount case, as one does, and provided some basic controls, including the obligatory scary-looking toggle switch with safety cover. A pair of ammeters show current and voltage, the latter with the help of a high-voltage resistor rated at 1 gigaohm (!). The high-voltage feedthrough on the front panel is a little dodgy — a simple rubber grommet — but along with the insulation on the high-voltage output lead, it seems to be enough.

The power supply’s 30 kV output is plenty for [Sebastian]’s current needs, which from the video below appear to mainly include spark gap experiments. He does mention that 50 kV commercial supplies are available too, but it would be tough to do that for the $150 or so he spent on this one. There are other ways to go, of course — [Niklas] over at Advanced Tinkering recently shared his design for a more scratch-built high-voltage supply that’s pretty cool too. Whatever you do, though, be careful; we’ve been bitten by a 50 kV flyback supply before and it’s no joke.

When you have a bunch of 230 kV transmission lines running over your property, why not use them for some scientific experiments? This is where the [Double M Innovations] YouTube channel comes into play, including a recent video where the idea of harvesting electricity from HV transmission lines using regular fences is put to an initial test.

As for the results, they were rather concerning and flashy, with the 1000 VAC-rated multimeter going out of range on the AC side of the bridge rectifier, and the capacitor slowly charging up to 1000 V before the experiment was stopped.

Based on the capacity of the capacitor and the final measured voltage of 907 VDC, roughly 36.2 Joule would have been collected, giving some idea of the power one could collect from a few kilometers of fencing wire underneath such HV lines, and why you probably want to ground them if energy collecting is not your focus.

As for whether storing the power inductively coupled on fence wire can be legally used is probably something best discussed with your local energy company.

Thanks to [Keith Olson] for the tip.