Switchgear forms a vital part of electrical systems. Likewise, different types of switchgear fit different purposes. For example, some control and protect electrical equipment while others help to safely distribute power. In any case, all types of electrical switchgear serve an important purpose: ensuring the safe and reliable electrical systems. Learn the major categories of switchgear in this article.
First, here’s the switchgear meaning. Switchgear is used to refer to the combination of electrical disconnect switches, fuses, or circuit breakers and similar devices used to control and protect power systems. By doing so, the devices ensure the safety of operators and electrical circuits during maintenance or fault conditions.
Switchgear may come enclosed in a metal cabinet for indoor or underground installation, or it may be open equipment to be used outdoors or on power lines. Different types of switchgear may also use air, gas, oil, and other kinds of insulation. Some have cooling fans as well or they’re self-cooling.
Now that we have a general understanding of switchgear, let’s explore the three main types of electrical switchgear and where they’re used. This will provide you with a better understanding of the purpose and of this crucial equipment and its application in different situations.
Types of Switchgear
Switchgear is an important part of any substation, power plant, or other setting where electrical power needs to be distributed or managed effectively. There are three primary types of switchgear: low voltage (less than 1 kV), medium voltage (up to 36 kV), and high voltage (above 36kV). Let’s take a more in-depth look at each type.
Low Voltage Switchgear
Also called LV switchgear in short, low voltage switchgear is designed for systems that carry less than 1000 volts of electricity. Mostly built in the form of metal enclosed structures, this switchgear typically comprises these separate parts: breaker, bus, and cable compartments.
Individual breakers are housed in their own compartments, while solid barriers protect the bus compartment from the others. The cable compartment on the other hand, is accessed from the rear, although some also use front access.
Low voltage switchgear is designed with a broad range of capabilities including arc resistant and arc quenching capacities. Typically, this type of switchgear uses 30-cycle withstand current breakers. This means the breakers can tolerate 30 cycles of fault current without tripping or getting damaged.
LV Switchgear Application
As its name suggests, low voltage switchgear is meant for low voltage power systems- or electrical networks that carry less than 1 kV. As such, you‘ll find it extensively used in residential and commercial applications such as schools, hospitals, office buildings, and homes.
Low voltage switchgear is usually installed on the secondary side of transformers. Here, it ensures the safe distribution of power into residential buildings or industrial facilities. Other applications include coupling with MCCs to control motor systems, also called motor control center switchgear.
Medium Voltage Switchgear
Unlike low voltage switchgear, which is intended for use in lower voltage applications, medium voltage switchgear is rated for higher voltages of up to 36 kV. MV switchgear must withstand greater electrical distress, since it carries more voltage and current.
The switchgear is, therefore, available in a variety of insulation and designs including: mineral oil, sulfur hexafluoride (SF6), and other variations such as metal clad, metal enclosed, pad mount, vault, and submersible types.
Depending on the arc flash rating, this type of switchgear is further classified into type 1, 2, 2B, and type 2C switchgear. Type1 switchgear only has arc resistant devices in the front, while type2 has the entire assembly arc resistant. Type 2B switchgear must be arc resistant all around, type C switchgear between compartments as well as all around.
MV Switchgear Application
MV switchgear is often found on both the primary and secondary side of power. That means application in power generation plants as well as in electricity distribution systems. Most of the time, medium voltage switchgear is used in utility plants such as hydroelectric and solar.
Other MV switchgear applications include controlling power distribution in heavy industrial facilities such as oil and gas, mining, and the railway industry. In these situations, different classes of the switchgear, such as metal enclosed and metal clad medium voltage switchgear are used.
High Voltage Switchgear
Switchgear for 36 kV systems and above is known as high voltage or high tension switchgear. Because it handles higher levels of electricity, HV switchgear is prone to arc flashes and must use technologies to prevent or quench it.
High voltage switchgear is classified as 2 major types: air and gas insulated. Air insulated switchgear in the high voltage category is normally composed of large equipment and used outdoors. On the other hand, high voltage, gas insulated switchgear is typically an indoor equipment.
HV switchgear may use oil or oil-less breakers. Oil switchgear usually has mineral oil as an insulation medium. Oil-less breakers in these types of switchgear relies on other mediums for insulation, such as air, SF6, and even vacuum.
HV Switchgear Application
Generally, this type of equipment is employed in applications that involve power sources and power distribution networks. So you will mostly find HV switchgear in power plants, transmission lines, and other utility circuits where it’s used to monitor systems, isolate circuits in the event of faults and other functions.
Transmission lines convey electricity from generating plants to either to cities or neighboring countries. These require the use of high voltage switchgear consisting of switching and protection devices. The equipment includes isolators and reclosers that automatically break and re-establish connections when a fault is detected.
Electrical switchgear finds wide applications in residential, commercial, and industrial settings. As we have seen, the switchgear can be classified into low, medium and high voltage types. Each has its role in the management of electrical systems, and must be used accordingly. This ensures the proper and reliable operation of a power system, whether low or high voltage.