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What is a Switchgear? – Definition, Functions, Classifications & More

Written by Edwin Jones / Fact checked by Andrew Wright

what is a switchgear

What is a switchgear? Think of a panelboard that distributes and controls power while protecting circuits at the same time. It’s a lot like panelboards in that it’s also composed of OCPDs (overcurrent protection devices), controllers, and switches housed in an enclosed, properly ventilated unit.

Switchgear is larger in more ways than one and is used mostly in high and medium voltage applications common in commercial and industrial settings. For example, medium voltage switchgears are rated for up to 35kV and 4,000A, compared to panelboards that max out at 600V and 1,200A. A high voltage switchgear pushes those limits further.

Read on for a more close-up take on what a switchgear panel is.

Switchgear Definition

In layman’s terms, the best switchgear meaning I can give is that it’s a heavier-duty version of panelboards, switchboards, and load centers. As such, they’re used to protect circuits against fault currents and control power distribution on a larger scale.

In fact, if we compare switchgear vs switchboard, which essentially stand next to each other in the overcurrent protection hierarchy, the former clearly handles more voltage than the latter. The difference is not even close, since a switchboard barely reaches 1kV in capacity.

A standard switchgear is usually made up of a line up of units, structures, or, individually, switchgear cell. Each metal enclosure contains switching devices, control panels, and overcurrent protection devices like fuses, disconnects, and circuit breakers.

Since they’re metal-clad and, thus, isolated, once a fault or overload occurs in a circuit, it won’t affect the other units even though they’re part of the switchgear line up or power network.

That answers “How does switchgear work when protecting circuits?” on a basic level, but it’s still worth knowing its different types, functions, features, evolution, and more to fully define switchgear, so do continue reading.

Switchgear Circuit Breakers and Compartments

Each electrical switchgear unit houses a switchgear circuit breaker whose type could vary (e.g. miniature circuit breakers, MCCBs, earth-leakage, etc.) depending on the requirement. Each one is attached to its respective bus bar and is served by its proper wire.

switchgear-electrical

Switchgears are meant to be maintained, which is why they tend to have a higher initial cost. Another standout quality of their breakers is that they can be removed (i.e. draw-out) and still be energized. Take note that not all are draw-out, as in the case of metal-enclosed interrupter switchgears (MEIS).

Metal-clad switchgears have dedicated compartments for breakers, in the same way that there are compartments for busbars, switches, and cables.

There’s even a separate low-voltage compartment in a medium voltage switchgear, which highlights the more complex nature of switchgears compared to other electrical panels.

What Are the Functions of a Switchgear?

Switchgear enjoys a robust application in power systems oriented toward commerce and industry due to the following functionalities:

switchgear-definition

  • It’s responsible for supplying power to a given area, normally one that spans a wide distance or has numerous separate structures like a university campus.
  • It protects against electrical issues like an overload and short circuit, much like a standard panelboard. It lends itself to better security, in short.
  • A conventional switchgear electrical assembly lets you handle higher voltage and currents while giving you the freedom to control the distribution of electricity in a facility. Its uses can be further subdivided based on the industry using the power switchgear.
  • For example, in water treatment plants, it’s often used to easily turn on and off large motors.
  • In power stations and nuclear plants, the main switchgear is all you need to decide which loads to turn on and off.
  • In construction, a switchgear engineer will plan out a switchgear diagram, mapping how he or she will be supplying and controlling power flow to the lights and tools in various areas based on their power demand.
  • In the switchgear building or substation, you can freely control and isolate electrical equipment and loads, thanks to the individual electrical disconnect switches found in each unit.

This level of control ensures you’ll be able to effectively do an emergency stoppage of power.

Overall, this leads to better organization of heavy-duty power supplies that would have been too complex to handle otherwise.

Fundamental Switchgear Components and Equipment

Much like your average load center, a switchgear is composed of different switches, circuit breakers, controller or transformer, and fuses. However, the broader scale of switchgears necessitates subcategorization for easier reference as follows:

main-switchgear

1. Power Conductors

Circuit breakers, surge arresters, switches, and fuses with their respective conductors fall under this category. These protect the circuit in various ways, mainly depending on how they’re designed.

  • Breakers and fuses are nothing short of necessary as they’re able to protect against a short circuit, unlike most protectors. A breaker will either trip automatically or manually, and usually the former is the case if there’s a fault detected.

A fuse, on the other hand, will blow and disconnect the circuit once it detects an abnormal amount of current passing through it. It needs to be replaced afterwards, unlike a breaker, which can be reset.

  • Found in both homes and substations, surge arresters have the ability to discharge or control surging currents (such as in the case of lightning strikes).
  • Switches could either be an air switch, oil switch, or disconnect switch. With their reliable switching operation, the first two allow you to open or close electrical circuits under normal load and when a short circuit occurs, highlighting their versatility.
  • Disconnect switches are off-load electrical isolators, which are used more during no-load (i.e. no current) conditions. You can just engage them if damaged electrical devices need to be isolated or the switchgear needs to be shut down for maintenance.

2. Control Systems

These are the switchgear’s monitoring and operating devices.

  • Switchgear devices such as the voltage transformer and current transformer let you optimally control the switchgear and can be used for metering as well. They’re both able to reduce current and voltage values so OCPDs can detect them. Switchgear and transformer may be put into one housing.
  • Protective relays are also grouped into control systems since they’re responsible for triggering the tripping mechanism of circuit breakers. More advanced options nowadays have a self-diagnosis capability that allows users to perform prompt remedial actions. Some even include voltage adjustment that actively keeps the voltage at a designated level.
  • Medium voltage switchgear comes with auto reclosures, which make it possible to speedily restore the power system to working condition after an electric fault.

Evolution of Switchgear

The electrical switchgear is older than you might think. After all, it’s an integral component of the first generator used by the earliest central power stations.

It’s so reliable that it underwent robust evolutions throughout the years since its inception. As companies innovated, how and where a switchgear is installed changed too, along with the electrical equipment, breakers, and insulation materials used.

They used to be mounted on walls. The first dielectric switchgear initially used air as insulation.

Inevitably, oil circuit breakers replaced air circuit breakers. Then, vacuum circuit breakers as well SF6, and air-blast alternatives sprung up in the 1970s and have since become the preferred choice, thanks to their ability to handle larger voltages and currents.

The modern metal-enclosed switchgear officially debuted at the start of the 20th century. Even now, fresh innovations are being introduced to handle ever-growing power needs.

Essential Features

These are usually asked in switchgear MCQ tests. If you happen to be studying electrical engineering, then you should familiarize yourself with these fundamental characteristics of a switchgear assembly:

1. Quick Operation

It should be able to address electrical issues with zero delays. Otherwise, short circuits, faults, and overloads will end up damaging vital electrical equipment and components of the power system (e.g. transformers, generators, etc.).

2. Complete Reliability

Companies should settle for no less than the most suitable switchgear that will be able to meet their power demands safely. Reliable operation features mean it should be able to fulfill all the functions said above with relative ease.

3. Manual Control Provision

You should be able to head to the switchgear room and perform an operation needed to address any electrical issue.

4. Absolutely Certain Discrimination

Switchgear is designed to ensure interruptions in the power supply system won’t take place even in the event of a fault or short circuit. It should be able to maintain that by being able to pinpoint and isolate the section affected by the issue.

Classifications of Switchgears

The three main types of switchgear in substation include:

1. Low Voltage Switchgear

Due to its inherently low voltage (limited to 1kV), a low voltage switchgear is usually paired with a power transformer, thus forming a basic substation.

Usually three-phase, this switchgear tops out at 6,000A, which is still way more than what an average home main panel can handle.

A low voltage switchgear often acts as a feeder to low voltage switchboards and other feeder circuits. It also lacks some of the components and compartments found in a medium voltage switchgear, as you’ll learn below.

2. Medium Voltage Switchgear

Arguably the most popular type of switchgear, medium-voltage models offered from companies like Eaton can manage up to 35kV with a 4,000A ceiling.

Medium voltage switchgears can be further subcategorized as metal-clad, metal-enclosed, vault, arc resistant, pad-mounted, and compact. Each has unique benefits.

  • For instance, arc-resistant switchgear is labeled as such because it can withstand a more powerful electrical fault or arc energy.
  • Metal-clad and metal-enclosed varieties are differentiated by the fact that the latter houses every necessary electrical device in single rather than separate compartments.
  • On the other hand, pad-mounted, vault, and compact medium voltage variations are named according to areas where they’re installed. Most industries choose compact if they have limited space, while vaults and pad-mounted options are optimal for subsurface installation.
  • High Voltage Switchgear

Given its name, expect this type of switchgear to handle peak voltage levels (i.e. anything above 36kV – up to 800kV and 80kA). The latter is particularly true for contemporary gas insulated switchgear.

Naturally, they require their own high voltage circuit breaker that can manage those lofty levels. High-voltage circuit breakers, particularly SF6 and air-blast varieties, suit high-load conditions of a substation switchgear best, with the former regarded as the least risky option.

Unsurprisingly, high-voltage switchgear voltage and amp ratings tend to increase over time as technology advances and demand grows. Most companies have either gas insulated switchgear or its air-insulated counterpart to choose from. 

Indoor and Outdoor Switchgear

Last but not least, switchgears can also be categorized as indoor or outdoor. A lot of companies opt for an indoor switchgear due to the better safety, reliability, space-saving, money-saving abilities, and durability it can guarantee.

FAQs

What is the importance of switchgear?

Almost any modern electric power system won’t be able to perform optimally and safely without it. There’s no better way to describe the switchgear than it being the control center of power distribution in any facility and acting as its electrical system’s protector at the same time.

It’s designed to be a centralized solution for such purposes, and it’s safe to say that it delivers every time, as most companies make reliability a priority.

Switchboard and switchgear: What is the difference?

Besides the amount of voltage that each one can handle, a switchboard’s manner of usage is evidently different from a switchgear.

A switchboard is mainly used to reroute power usually by dividing them into branch circuits, each of which is fed by a breaker or fuse. Meanwhile, switchgears focus more on protecting the electrical system and turning power on or off.

Moreover, switchgear breakers are made to ANSI standards while switchboard breakers are made to UL standards.

Is the circuit breaker a switchgear?

No, switchgear systems are composed of circuit breakers along with other relevant electrical circuit protection devices. At best, the circuit breaker housed in a switchgear enclosure is what makes it possible for a switchgear to perform its protective function.

Conclusion

I hope I’ve given you the most complete switchgear definition and a satisfactory answer to “What is a switchgear?” from the points I shared above.

To wrap up the function and importance of switchgear, it serves as the protective brain of a commercial or industrial facility’s power system. You can use it to control where you want to supply electricity while keeping your circuits protected at the same time.

The fact that it has had a rich history that’s full of innovation, despite its being a recent invention, speaks volumes about its sheer value to numerous major industries.

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