The Electrical Grid Demystified

Our society needs energy, and lots of it. If you’re reading this then the odds are astronomically good that you’re on a computer somewhere using energy, with the power cord plugged into the mysterious “black box” that is the electrical grid. The same is true if you’re reading this on a laptop or phone, which was charged from said black box even though it may not be connected at this moment. No matter where you are, you’re connected to some sort of energy source almost all the time. For almost every one of us, we have power lines leading up to our homes, which presumably connect to a power plant somewhere. This network of power lines, substations, even more power lines, and power plants is colloquially known as the electrical grid which we will be exploring in a series of articles.

While the electrical grid is a little over a century old, humanity has been using various energy sources since the agricultural revolution at least. While it started with animal fat for candles, wind for milling grain, and forests for building civilizations, it moved on to coal and steam during the industrial revolution and has ended up in a huge interconnected network of power lines connected to nuclear, natural gas, coal, solar, and wind sites around the world. Regardless of the energy source, though, there’s one reason that we settled on using electricity as the medium for transporting energy: it’s the easiest way we’ve found to move it from place to place.

Origins of the Commercial Grid

Although the potential to use electricity as an energy delivery method was recognized fairly early it wasn’t until Thomas Edison came along that the first practical and commercial electrical grid was implemented. His first grid supplied power to a handful of electric lights in New York using a direct current (DC) generator. Using DC has its drawbacks, though. This was an era before switch-mode power supplies, let alone the transistor itself, was invented, so it was virtually impossible to transform DC voltages. To avoid safety and cost issues the voltage of the generator was kept to a modest 100 volts. And, since resistive losses in wires are greater if the voltage is lower, this meant that essentially every block would need its own separate generator and electrical grid to be economically feasible on a larger scale.

As much as Edison hoped his project would be commercially successful, the inventor of the modern electric grid was one of his direct competitors: Nikola Tesla. Tesla used an alternating current (AC) system, which meant that he could generate large amounts of power at a remote location, use a transformer to step the voltage up in order to deliver the power at minimal resistive losses even over huge distances, and then use another transformer to step the voltage back down to a safe level for consumption. Through the eye of history it’s obvious that this method would be the clear winner over Edison’s DC system, but not before a vicious battle between the two called the War of Currents took place.

Picking a Phase and a Frequency

Once Tesla’s system was proven the most effective it was constant improvement on his original system that led us to the system we have now. At first commercialization was slow because there were so many different standards. Some power plants used a two-phase system (two wires carrying useful energy together with a neutral wire) while others used three or more phases. While it’s easy to run resistive loads (such as incandescent light bulbs or heaters) on any phase of AC electricity, industrial-sized motors generally need to have the same number of phases that the generator powering them has. Eventually we settled on a three-phase system because it delivers the most cost-effective amount of energy per wire.

While the phasing issue was easy to sort out, as commercialization meant that new power companies were financially incentivized to use a three-phase system, there was another quality of the power system that didn’t have a straightforward solution: the system frequency. In North America a 60 Hz frequency is used for electrical grids but in Europe and much of the rest of the world a 50 Hz system is used. While it is true that a higher system frequency can mean the ability to use less iron in transformers, a 10 Hz difference doesn’t make for a notable cost savings to explain why the two systems came to coexist. (Where it does make a difference is in systems where weight is a huge concern, like on board airplanes where a system frequency in the 400 Hz range is often used.) A possibly apocryphal story for the 60 Hz/50 Hz split is that Tesla calculated that 60 Hz was the most efficient frequency, then in true Tesla fashion didn’t share his math with anyone. The US adopted it on faith, but when AC technology made its way to Europe the engineers there found that a 50 Hz system frequency made their math slightly easier even if there was a slight efficiency decrease. The real reason is possibly that 60 Hz is easier in conjunction with keeping time, and 50 Hz is easier to do math on.

Generally the two system frequencies are isolated to their own independent power grids by large oceans, but there’s one place in particular where the two have mixed. Japan has a 50 Hz grid in the north half of the island, including Hokkaido and Tokyo, and a 60 Hz grid in the southern half which includes Osaka. Early in the electrification of Japan, the northern half bought generators from a European 50 Hz source while the southern half bought generators from an American 60 Hz source. At the time the two areas were far enough apart that interconnecting the two grids wasn’t considered, but now the two are tied together using huge DC converter stations which is the only possible way to connect two incompatible system frequencies.

While Japan has two grids separated by frequency by way of a historic quirk, the grid in North America is even more complicated. There are actually three separate grids even though they all operate on 60 Hz, since even if the system frequency is the same the waves themselves have to be synchronized to each other. The two largest ones split the continent in half by east and west. The third is Texas. They are a separate grid essentially as a way for that state to get around federal regulations for energy that is transported across state lines which (in a roundabout way) is related to how much oil Texas produces. The system arose in the 1930s and has continued on to today. Like the grids of Japan, however, the Texas grid is connected to the others by means of several large DC converter stations, so they aren’t exactly an island. While the separation helps them avoid federal regulations, it also grants them some isolation and immunity from blackouts that may occur on other grids, while still being able to import and export power to other companies in other states.

Whatever the reason, this is the system we have now. There are many electrical grids across the world, and even within countries and states themselves. Even if you are reading this from a laptop powered by a solar cell and a battery, you’re on one of the smaller electrical grids around. Indeed some grids are very large, some are small, some have different frequencies, but they all serve one purpose: to deliver energy as efficiently as possible.