How Do Substations Work?


When you plug in an electric device, it’s
easy not to even consider where the electricity actually comes from. The simple answer is a power generating station,
also known as a power plant, usually someplace far away. But the reality is much more complicated than
that. Generation is only the first of many steps
our power takes on its nearly instantaneous journey from production to consumption. The behaviour of electricity doesn’t always
follow our intuitions, which means the challenges associated with constructing, operating, and
maintaining the power grid are often complicated and sometimes unexpected. Many of those challenges are overcome at facility
which, at first glance, often looks like a chaotic and dangerous mess of wires and equipment,
but which actually serves a number of essential roles in our electrical grid, the substation. I’m Grady and this is Public Works, my video
series on infrastructure and the humanmade world around us. This video is sponsored by NordVPN. Visit NordVPN.com/practicalengineering to
get 75% off a 3-year plan. More on that later. As simple as it is to imagine, the power grid
isn’t just an interconnected series of wires to which all power producers and users collectively
connect. In reality, the electricity normally makes
its way through a series of discrete steps on the grid normally divided into three parts:
generation, or production of electricity; transmission, or moving that electricity from
centralized plants to populated areas; and distribution, or delivering the electricity
to every individual customer. If you consider the power grid a gigantic
machine (and many do), substations are the linkages that connect the various components
together. One of the cool parts about our electrical
infrastructure is that most of it is out in the open so anyone can have a look. I’m somewhat of an infrastructure tourist,
a regular beholder of the constructed environment, and my goal is for you too to be able to mentally
untangle this maze of modern electrical engineering so that the next time you feast your eyes
on a substation, you’ll be able to appreciate it as much as I do. Originally named for smaller power plants
that were converted for other purposes, “substation” is now a general term for a facility that
can serve a wide variety of critical roles on the power grid. Those roles depend on which parts of the electrical
grid are being connected together and the types, number, and reliability requirements
of the eventual customers downstream. And the first and often simplest of these
roles is switching. The general layout of a substation consists
of some number of electric lines (called conductors if you want to fit in with the electrical
engineers) coming into the facility. These high voltage conductors connect to a
series of some or many pieces of equipment before heading out to their next step in the
power grid. As a junction point in the grid, a substation
often serves as the termination of many individual power lines. This creates redundancy, making sure that
the substation stays energized even if one transmission lines goes down. But, it also creates complexity. The connections to these various devices are
called buses, often rigid, overhead conductors that run along the entire substation. The arrangement of the bus is a critical part
of the design of any substation because it can have a major impact on the overall reliability. Like all equipment, substations occasionally
have malfunctions or things that simply require regular maintenance. To avoid shutting down the entire substation,
we need switches that can isolate equipment, transfer load, and control the flow of electricity
along the bus. This may seem obvious, but turning on and
off high voltage lines isn’t as simple as flipping a light switch. At high voltages, even air can act like a
conductor, which means even if you create a break in a line, electricity can continue
flowing in a phenomenon known as an arc. Not only does arcing defeat the purpose of
a switch, it is incredibly dangerous and damaging to equipment. So, switching in a substation is a carefully-controlled
procedure with specially-designed equipment to handle high voltages. Disconnect switches are often just called
switchgear in addition to the equipment that serves another important role in a substation:
protection. I mentioned earlier that much of our electrical
infrastructure is exposed and out in the open. That’s nice for people like me who enjoy
having a look, but it also means being vulnerable to an endless number of things that can go
wrong. From lightning strikes to rogue tree limbs,
windstorms to squirrels, grid operators contend with so many threats to their infrastructure
on a day by day basis. When something causes a short circuit on the
power grid, also called a fault, it can severely damage power lines and other equipment. Not only that, because of the overwhelming
complexity of the power grid, faults can and do cascade in unexpected and sometimes uncontrollable
ways, leaving huge populations without power for hours or days. Many of the ways we protect equipment from
faults are handled at a substation. One of the most common types of electrical
fault is a short circuit to ground. This type of fault creates a low-resistance
path for current to flow and leads to an overload of power lines and equipment. The simplest way to protect against this type
of fault is with a fuse, a device that physically burns out at a certain current threshold. Fuses are dead simple and don’t require
much maintenance, but they have some disadvantage too. They’re one-time use and can’t be used
to interrupt current for other types of faults. On the other hand, circuit breakers are a
class of devices that serve similar roles as fuses, but provide more sophistication
for dealing with a wide variety of faults. Like disconnect switches, circuit breakers
need to be carefully designed to interrupt huge voltages and currents without damage. As soon as contacts within a circuit breaker
are moved apart from one another, an electrical arc forms. This arc needs to be extinguished as quickly
as possible to prevent damage to the breaker or unsafe conditions for workers. Extinguishing the arc is accomplished by a
material called a dielectric that doesn’t conduct electricity. For lower voltages, the circuit breakers can
be located in a sealed container under vacuum to avoid electricity conducting in the air
between the contacts. For higher voltage, breakers are often submerged
in tanks filled with non-conductive oil or dense dielectric gas. These breakers give grid operators more control
about how and when current gets interrupted. Not every fault is the same and sometimes
operators even know about a disturbance ahead of time and can trigger breakers early to
prevent cascading failures. Many faults are temporary like lightning strikes
or swaying tree branches. A special kind of circuit breaker called a
recloser can interrupt current for a short period of time and re-energize the line to
test if the fault has cleared. Re-closers usually trip and reclose a few
times, depending on their programming, before deciding that a fault is permanent and locking
out. If electricity demand on the grid gets so
high that it can’t be met by the utility, substations may also be used to shed load. Rolling blackouts are used to lower the total
electrical demand to avoid bigger failures on the grid. One of the most important parts of the power
grid is that different segments flow at different voltages. Voltage is a measure of electrical potential,
somewhat equivalent to the pressure of a fluid in a pipe. At large power plants, electricity is produced
at a somewhat low voltage of around 10-30 kilovolts or kV. From there, the voltage is increased much
higher using transformers so that it can travel along transmission lines. Using a higher voltage reduces the losses
along the way, making them more efficient but also much more dangerous. This is why overhead transmission lines are
so tall – to keep them out of the way of trees and human activities. But, when transmission lines reach the populated
areas which they serve, it’s not feasible to keep them so high in the air. So, prior to distribution, the voltage of
the grid needs to be brought back down, again using transformers located within a substation. A transformer is an extremely simple device
that relies on the alternating current of the grid to function. It consists of two adjacent coils of wire. As the voltage in one coil changes, it creates
a magnetic field. This field couples with the other coil, inducing
a voltage. The incredible part of a transformer has to
do with the number of loops in each coil. The induced voltage will be proportional to
the ratio of loops. For example, if the transmission side of a
transformer has 1000 loops while the distribution side has 100, the voltage on the distribution
side will be 10 times less. This simple but incredible fact makes it possible
for us to step up or down voltage as necessary to balance the safety and efficiency along
each part of the power grid. The simplicity of transformers is great in
a lot of ways, but it also means that it can be difficult to make fine adjustments to the
power leaving the substation. Because of this, many many substations include
equipment for monitoring and controlling the power on the grid. Instrument transformers are small transformers
used to measure the voltage or current on the grid or provide power to system monitoring
devices. Depending on varying transmission and distribution
losses, the voltage on the grid can swing outside an acceptable range. Regulators are devices with multiple taps
that can make small adjustments – up or down – to the distribution voltage on feeder lines
leaving the substation toward customers. If you look closely you can sometimes see
the regulator dial indicating the tap position. All that different equipment requires lots
of maintenance. The final and most important role of a substation
is that it be safe for electricians and linemen to inspect, repair, and replace equipment. Substations are usually the only locations
where extra-high voltage power lines get close to the ground, so safety is absolutely critical. The buswork running along the substation is
protected from short-circuit by large insulators to avoid arcs to ground. Even the connections into each piece of equipment
are done through a device called a bushing which maintains a safe distance between energized
lines and the grounded metal housings. Some substations have large concrete walls
to serve as fire barriers between equipment. All substations are built with a grid of grounding
rods and conductors buried below the surface. In the event of a fault, the substation needs
to be able to sink lots of current into the ground to trip the breakers as quickly as
possible. This grounding grid also makes sure that the
entire substation and all its equipment are kept at the same voltage level, called an
equipotential, so that touching any piece of equipment doesn’t create a flow of electricity
through a person. Finally, substations are surrounded by large
fences and warning signs to make absolutely sure that any wayward citizens know to stay
out. In many ways, the grid is a one-size-fits-all
system – a gigantic machine to which we all connect spinning in perfect synchrony across,
in some cases, an entire continent. On the other hand, our electricity needs,
including when we need it, how much we need, and how reliably it should be delivered vary
widely. Power requirements are vastly different between
a sensitive research facility and a suburban residential neighborhood, between a military
base and country club golf course, and between a steel mill and a bowling alley. Likewise, every electrical substation is customized
to meet the needs of the infrastructure it links together. As the grid gets smarter, as demand patterns
change, and as we (hopefully!) continue to replace fossil fuel generation with sources
of renewable energy to curb global warming, managing our electrical infrastructure will
only get more challenging. So, substations will continue to play a critical
role in controlling and protecting the power grid. Just like electricity on the grid, internet
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100 thoughts on “How Do Substations Work?

  1. yeah that's a good point, a switch is going to be a little less useful if the electricity just continues to flow through the air

  2. Oh my God.

    I thought it was called a substation because our utility company where I live is SUB (Springfield Utility Board), so "SUB-Station." I didn't know that was the name for ALL of these facilities. =[

    Well, learn something new every day.

  3. Trained and working in electricity and electronics for many years, I was amazed at the clarity and simplicity (and accuracy!) of your presentation. I've never seen anything else as good; congratulations!

  4. I appreciate your videos, but could you lay off the global warming propaganda. Getting political has nothing to do with the educational value of your videos in my opinion, and actually takes away from it.

  5. Please forgive my ignorance of this subject matter, but is it possible to over generate power vs. demand? I know that if they don't generate enough power black outs can happen. What happens of they generate more power than is being used (if this is even a thing)? Thanks for your great videos. I am learning a lot.

  6. Great video…up until the propaganda piece at 11minutes in. But I shouldn't be surprised. Not many people look at the pros and cons of things they talk about.

    If it wasn't for fossil fuels, billions of people wouldn't be alive today.

  7. There's other reasons why power lines are kept so high. For one, there is more space under the lines which means that trees don't have to be pruned as often as they would if the lines were lower down. Also, in my area, it is particularly notable that the higher the voltage of the power lines, the higher up they are.

  8. Need one on natural gas. Come visit WV and I'll shown you around from well head to burner tip and everything in between.

  9. The timing of this new series is really weird and convenient.n I'm a Civil Engineer and started my career four years ago in bridges (lots of coordination with hydraulics/soils) and now I moved over to working for an electric utility. Thanks for the quality content! 🙂

  10. Curious as to where you are at 1:54 . From the flora and landscape it looks very much like land with an underlying chalk geology but it sounds like you're based in the US rather than the south of England (for example).

  11. Could you do a technical analysis of the 2003 blackout – why was it so widespread and why did it last several days?

  12. Growing up, I saw substations all over the place. But all the ones I remember seeing have been taken down or eliminated. They are no longer where they once were. Why would the eliminate them and where would they have moved?

  13. I love your videos. Short, to the point, and easy to understand. It is easy to tell that you actually understand the topics you are presenting on, thank you!

    Topic suggestion: The types of renewable energy generation and the challenges of converting to them.

  14. A substation in a maintained grassy field seems reckless. You got to pay someone to maintain the lawn in a dangerous high voltage environment.

  15. Your a "infrastructure tourist". I love it. I was in the High Voltage electrical field for 36 years, and i agree. wherever i go i am a 'infrastructure tourist" too! subscribed!

  16. Air is a dielectric too, hence the clip of contact arcing at the substation. The good thing though is that air has a relatively high dielectric constant.

  17. Can you do a video on information infrastructure, as a utility maintenance contractor I have to work around it all the time and would like to know what I am really avoiding.
    Thank you for your great videos.

  18. Great video, a few minor comments (yea, I'm going to be that guy)
    1. The purpose of the Switch at the substation is often not for breaking load and faults. Most switches in the US are used simply as a "visible break". A worker can look at a switch and visually tell that downstream conductors and equipment won't be energized. This is important because often you can't tell if a breaker is open at a glance because the breaking mechanism is internal. The breaker's job is to stop the power flow. The switch's job (most of the time) is to visually show that the line is dead. Open breaker first, then the switch.
    2. Instrument transformers often don't energize the monitoring equipment anymore. Microprocessor relays are powered by a giant substation battery bank. All intelligence and monitoring in modern substations are powered by the substations batteries. The batteries are powered by the distribution side of the substation via a service transformer.
    3. "Recloser" is mostly a distribution term and a distribution equipment. Substation breakers can be set to reclose but are not often referred to as a recloser.
    4. Substations are already "smart". "Smart Grid" (a terrible term) often refers to adding intelligence and flexibility to the distribution system.

  19. I'm wondering why power lines run overhead? If there were underground would they be more dependable out of the weather where trees & lightening would not affect them. In California PG&E had power lines start a fire burned down thousands of homes costing milligan's. Would this pay the extra cost to go underground?

  20. Simple animations, good quality photos, and clear explanations. Your videos are the best of their kind! Thank you for your work!

  21. You conclude with a comment on global warming. The last ice age NYC was under 2000 feet of ice, isn't that a more significant problem than warming? Hard to grow food in ice. Source NY Times how ice age shaped NY . 2018.

  22. How is frequency adjusted? Here in the US its 60hz but not everything runs on 60hz, how do they adjust the frequency?

  23. Couldn’t explain it better myself. I worked in substations and power systems for over forty years. There are two other type of stations that look very similar to substations. They are called switching stations and capacitor stations.

  24. I’m a substation engineer and this is the most succinct, “common man” explanation of what a substation does that I’ve ever heard. From now on, I’m showing people this video before I even try to explain my job.

  25. Hey practical engineering, you should do a video on the natural gas industry/ infrastructure. Im a GIS analyst( design pipe networks and update the network maps) and would be happy to answer any questions you may have. Been in the field for only about 4 months but would provide what i could!

  26. The video did a good job explaining the source of power going in and what happens at a substation but only a mention of what happens to the power going out and certainly no in-depth explanation.

  27. I just had this exact thought like 3 hours ago, and now its in my recommendations? Google you're going too far.

  28. Grady, I love your videos! However, I'd like to reach out to you to address a few things to help make this video much better. I work in substations daily for over 3 years, and I want to help clear up a few things, please. Thank you in advance!

  29. Loved this video! I used to work with a rural electric cooperative on the software/networking side and have visited substations to help troubleshoot wireless networking issues, even so, I learned a-lot in this video!

    Also, I have an off-topic comment about the ad spot: I appreciated the nuance in your NordVPN ad message, usually they make it seem like all web traffic is insecure, I like that you mention that some of it is already secure, and provided a valid reason for using NordVPN regardless (so you don't have to keep track what is/isn't secure). I hope to see more NordVPN and other VPN messaging becoming more nuanced instead of fear mongering and inaccurate as I've seen before.

  30. Clarification: disconnectors are not designed to interupt large currents. They should only be operated when the breaker for that circuit has been opened and no load remains on the line.

  31. induction, hvdc, amps, watts, current, resistance, capacitance, phase, frequency, smart meters, emp, ac vs dc. challenges of underground infrastructure, filtering, induction, data theft over power (air gapped spying), surge suppression, fuses, breakers, grounding, isolation, production, global electric circuit… and go. Great show. Oh and Induction (it's that important)

  32. Awesome video Grady! I will be passing this along to future interns in the Substation Engineering department I work in.

  33. Great video until you regurgitated the renewables myth. Renewables do not have the energy density to replace fossil fuels at any useful scale, and also have no grid inertia which is a essential for transmission and a stable grid. 4th gen nuclear or ideally thorium reactors are the only solution if you think increasing atmospheric CO2 from 0.03% to 0.04% is a problem. Which it isn't. watch https://youtu.be/UFHX526NPbE or https://youtu.be/UWahKIG4BE4

  34. The grid can’t store electricity. So, what do they do; make not enough electricity ? What happens if they make too much?

  35. As a latch key child, I’d go out back and throw the main breaker and wait for my older sister to evacuate the premises, then I’d turn the power back on and I’d have the place to myself.

  36. My local substation: http://randomer.net/stuff/elk-substation-01.jpg Imaged with a 600mm lens from my roof. The camera also has a 1.6 crop factor so the setup is effectively 960mm. 🙂

  37. Great video! Sounds like many opportunities for losses. In general, what is the loss between power station and users?

  38. A reasonable and elementary description of the basic infrastucture. The last nonsense comment about the "golbal warming' hoax was inappropriate and fosters a continuing and dangerous lie, which gains no credibility by repeating it. Stick to the engineering and leave the actual science to those of us who actually study it.

  39. if i ever get the infinity gauntlet, i am making RF a real thing

    (modded minecraft power, it stands for Redstone Flux)

  40. If everyone were to shut off all their electricity at the same moment, what would be the impact on the power generating plant, if any?

  41. As a substation commissioning engineer, I gotta say Grady, you did a great job making this seem understandable to the average person. Might have to make my mom watch this so she’ll stop calling me an electrician lol.

  42. I love the video, but I don't like the comment at 8:12 "the voltage on the distribution side will be ten times less". If the input is 500V, what is ten times less than 500? Is it 500-(500*10) = -4500? I think what you mean is "its reduced by a factor of ten" meaning 500V goes to 500/10 = 50V.

  43. @Practical Engineering – Thanks for the informative video. BTW… Nord VPN's offer of 75% discount ends in a few hours… However I'm getting pretty sick of their kind of convoluted advertising with over-inflated subscription fees, that are then ceremoniously reduced to more realistic prices, promoted through (generous) in-site discounts. I mean who (in their right mind) would pay £329.61p for a VPN connection? CyberGhost subs as one example offer considerably cheaper subs and accept PayPal payments, unlike NORD. It pays to shop around!

    This is my opinion I could be wrong.

  44. You forgot to explain how the waveforms are synchronised in complex networks with several alternative routes for the current.

  45. @06:38 that’s the resign you do not mess with a broken prowerline on the ground … it can be in the check loop or be energized again when YOU holding/moving it to the “side” ! This also is valid for (broken) overhead power lines of electric trains/trams!

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