Hello again, fellow hackers! This is an article that belongs to the "extras" category of my series on Electricity/Electronics, meaning that the knowledge I share here WON'T be required to build the circuits we will see in this series, but might still be of interest. Today, we are going to talk about how electricity is distributed. The reason to this is because after writing part 2 of my series, I noticed a lot of my readers were interested in how electricity works today. So I decided to write an article about how it is generated and distributed.
Besides that it is just interesting to know, because our world runs on electricity, it is also useful to hackers. As OTW stated a few times here on Null Byte, It is very likely that the next big war will be fought with electronic warfare. Knowing how electricity is distributed might help you fight an enemy nation, by exploiting their electricity grid. In this modern time, the chances of a nation surviving without electricity is pretty much nil.
Now that we know more about why it can be useful for us to know how electricity is distributed, Let's get to it:
First the reason why the world runs on AC electricity. "Almost all devices use DC (Direct Current). Why the hell do we distribute electricity as AC?!" you may be asking yourself right now. And that is a good question. AC comes with a lot of advantages over it's DC competitor. The first and foremost reason is that AC voltage is easy to manipulate, because of a device called the transformer (we will talk more about transformers in part 4 of the basics). We want to transport electricity at a high voltage because then the current is reduced, while we can still provide the same power. This is the law of electric power, which means: electric power (P) equals voltage (U) multiplied by current (I).
Let's say we want to transport 500 Mega Watt (MW), which is 500000000 Watt. At a voltage of 230V, we would have this amount of current:
I = 500000000/230 = 2173913 Ampere. You can see that this is A LOT of current!
Now, let's see how much current we would need to provide 500000000 Watt at a voltage of 380000V, the average voltage of the transmission net.
I = 500000000/380000 = 1315 Ampere. You can see that the current is still really high, but is reduced a lot, because the voltage is higher.
A large amount of current requires thicker wires, but a large amount of voltage doesn't. So when they keep the current low, they can use thinner wires, making things cheaper, but still being able to transmit the same amount of power. However, putting 380kV at your outlet is simply way too dangerous! This is why the voltage is "stepped down" before it enters your house. Transformers only work with AC electricity. This is why we use AC electricity: because it is very easy to manipulate.
Another fun fact: have you ever wondered why there are always 3 wires on high-voltage transmission lines (like the one in the cover image of this article)? That is because pretty much the entire world uses the "3-phase AC system" for transportation of electricity. The 3 wires on the high voltage poles each represent a phase. The thing coming out of your outlet is a single-phase system. The 3-phase system is also used a lot in industrial appliances. We will cover both systems in Part 3 of the basics.
The electricity grid is very country-specific, but it usually contains 4 parts:
- The generator. 25kV.
- The transmission net. 111-500kV. depends per country.
- The distribution net. 11-75kV. depends per country.
- The consumer. 230V-400V. Depends on the consumer's needs.
Let's take a look at them one by one.
This is the first part of the electricity net. Power plants generate a relatively low voltage, about 25kV (25000 Volt), depending on the size of the unit. Some power plants generate more, others generate less.
There are a lot of ways electricity can be generated: the sun, wind, coal, nuclear energy, and so on... My country, Belgium, gets most of it's electricity from nuclear power plants (39.54% at the time of writing this article). The second biggest source of our energy comes from natural gas (33.96% at the time of writing this article). I don't know about other countries, but you can easily google the statistics.
At the power plant, a step-up transformer raises the voltage to the needed voltage on the transmission net, which in my country is 380kV.
The inside of a nuclear reactor
The transmission net is responsible for the transportation of electricity from the power plant to sub-stations and to heavy industrial consumers.
The average voltage of the transmission net is 111kV-500kV. The reason this voltage is so high, is because the transmission net takes the biggest load. A lot of distribution nets are connected to a single transmission net, thus combining all the loads of these distribution nets to the transmission net. Not even mentioning the heavy industry that also puts a lot of load on the transmission nets!
Parts of the transmission net can be easily recognized by the iconic high metal pillars that carry the wires. Like the one in the cover image of this article or the image below:
Now a question you may be asking yourself: why are the wires so high from the ground and so far away from each other? The answer to that is because they are under a high voltage. The higher the voltage, the more likely the electricity will "jump" to another wire, resulting in a short circuit, or jump straight to the ground, which results in a loss. To prevent this from happening, we try to make the distance from the ground and other wires as large as possible, and thus decreasing the risk of "jumping electricity". For those who don't know what "jumping electricity" looks like:
This video was recorded at a substation that takes electricity from the transmission net and transforms it to put it on the distribution net. These sub stations have circuit breakers, just like in your house. Except these are quite a lot larger. What you see here is one of those circuit breakers. Apparently, something was wrong with this circuit breaker, so they decided to test it. The result: an 8.5 second long arc of electricity.
Besides transporting electricity to the sub-stations, the transmission net is also responsible for supplying heavy industrial consumers, like international harbors. These heavy industrial consumers require a lot of voltage to run heavy machinery. However, they don't use 380kV! They usually use 33kV for their equipment. These heavy industrial users usually have their own sub-station at the facility that transforms the 380kV from the transmission net to the 33kV they need. The reason why heavy industrial consumers are connected directly to the transmission net is because they would draw too much current if they were connected to the distribution net, so there would be no electricity left for us.
As the name suggests, the distribution net is responsible for bringing the electricity to us. The distribution net starts with a sub-station that transforms the 380kV from the distribution net to a more stable 75kV. From there, electricity is distributed to cities in the region, where it enters the final stage of transformation to 230/400V (see: Step 4: The Consumer). It also distributes electricity to medium and light industry. In some cases, these consumers also have another sub-station at the facility.
In most cases, the distribution net is under ground, and thus it is not visible. But sometimes it is distributed via poles. They are smaller than the towers of the transmission net, but larger than the poles on your street. These poles look like this:
You can clearly see that the wires are shorter to the ground and to each other now, because the voltage is reduced compared to the transmission net. Thus decreasing the risk of "jumping electricity".
This is the final step in electricity delivery. At this stage, electricity from the distribution net enters your street and goes to a so called "pole transformer", where it is transformed into 230V. From there, wires go over your street and enter your house. Now the circuit is complete! But there is more to the story.
There are commonly 2 types of pole transformers: the ones that change 75kV to 230V, and the ones that change 75kV to 400V. The first type, the 230V transformer, is used to provide electricity to houses, local shops, offices, etc... But places like a local bakery or a local garage require 400V to run the furnaces/machinery.
A pole transformer looks like this:
This is it again for another article, guys and gals! This is not knowledge we will use in our designs or circuits, but it is still useful to know. Not only because it is fun to know how things work, but also because it might help you one day if you are ever employed in electronic warfare!
So next time you plug something in the outlet, turn on a light, or start your computer, think back to this article. Now you know how much effort there is put into the transportation of electricity from the power plant to your house. The electricity that is powering your computer right now goes a LONG way! Not to mention the industrial electricians who maintain the transmission and distribution net and work under voltages of 75kV/500kV everyday. Yes, when they do repairs to the net, they work under voltage. You can't just simply call a power plant to stop generating electricity.