Last Updated on October 22, 2023 by Kevin Chen
Image of switchgear source: study electricals
The term ‘switch’ is commonly used in the field of electronics to refer to a controlling device. A switchgear is a device used for controlling, switching and even protecting electrical circuits. The switchgear determines where the currents should flow to, when it should be on/off and generally how it should operate.
Switchgear does not refer to any specific electronic device. Instead, it encompasses an array of devices such as the switch, load isolators, fuses GFCIs, contactors among many others.
Some of these devices can work independently while others are used in combination with other electronic devices.
If you are in the field of electricity and electronics, we have essentials that you should know about switchgear.
Read on as we break down the details.
History and evolution of switchgear
Where did the switchgear come from and how have they evolved to be of so much important in the modern electric world?
We can trace the history of switchgear back to the 20th century when there was a steady increase in the demand of electricity.
During that era, switchgears were mainly used for the industrial applications whereby they controlled and protected electric circuits in the industrial machineries.
The early versions of switchgears comprised of very basic elements or electronic components. These include circuit breakers, fuses and in some cases the disconnect switches.
The first switchgear was introduced between 1920s and 1930s and was basically metal-enclosed. Later on in the 1950s, air circuit breakers were introduced to be part of the key components that make up a switchgear. They served as a replacement for the oil-filled circuit breakers.
Starting from the 1950 to the 1970s, solid-state relay components such as control systems were integrated into the switchgears with the goal being to improve the accuracy and operability of these devices. Later on, we witnessed the introduction of digital technology into the switchgears.
As the demand for electricity soared, then there was need to integrate more components into a switchgear. Engineers started coming up with complex designs and newer systems that are more functional and effective.
Today, most switchgears feature advanced components. They are characterized by sophisticated technologies such as intelligent electronic devices, monitoring systems, gas-insulation among many others. They are also more accurate and reliable.
When buying a switchgear today, it will be intelligent to inquire about the detailed features that it has. This way, you will know whether it is suitable for your application area or not. Also, you cannot ignore the convenience that comes with using a smart and sophisticated switchgear.
Functions of a switchgear
Let’s discuss the main functions of a typical switchgear
Control
This is the primary function of a switchgear. From the very first switchgear that was invented to the lates model, they are used for controlling various aspects of electric circuits.
How does the control mechanism take place?
Well, it happens when the switchgear opens and controls the circuit when necessary. It is able to achieve this using component such as fuses, circuit breakers switches and contactors.
Protection role
Switchgear also play the protection role. They are capable of protecting both the circuit and the devices attached to the circuit from hazards associated with electric current such as overload and short circuit.
When it comes to the protection, most switchgears will break the contact with the power source to cut the supply of the electric current. Devices such as fuses and relays form part of the protective switchgear components.
Monitoring
This is another vital function of modern switchgears. They are design to monitor various activities in an electric system and circuit.
Electric devices such as relays and meters are part of the switchgear family and they play critical role when it comes to monitoring the state of aa circuit.
Even the most advanced devices such as intelligent electronic devices (IEDs) are also part of the switchgear family.
They record parameters such as volts, frequency, current, power factor among others.
The parameter to be measured will always depend on the application of the circuit.
Isolation
In the field of electrics and electronics, isolation usually refers to the act of protecting some electronic components from an environment or the behavior of other electronics.
For example, a capacitor may be isolated from the magnetic field.
A switchgear can be installed on a circuit to isolate components from the negative effects of various events. For example, when a particular section of an electric system is damaged, a switchgear will disconnect that section from the rest of the circuit.
Power factor correction
Power factor refers to the ratio of the active power to the real power supplied. A switchgear can improve this ratio hence improving the energy efficiency of a device.
The better the power factor also means that there will be minimal power loss from the device.
Fault detection
Switchgears are also used to detect faults in an electric circuit. After the detection appropriate measures will be taken to prevent a particular fault from causing any serious damage to the circuit or even the device.
The role of fault detection is performed by components such as protective relays.
Load shedding
What happens when an electric circuit is connected to more loads than what is recommended? There will be an overload of current and this may end up blowing up some devices.
Some switchgear devices are designed to play the role of load shedding. They do this by intelligently analyzing the circuit and switching of those devices that are not critical at that particular moment.
The good news is switchgears can easily achieve this without interrupting the normal functioning of the circuit.
In short, switchgears play vital roles in the operation of electric circuits and devices. They guarantee efficiency and safety of the devices.
Components of a switchgear
Now that you know the roles and functions of a switchgear, let’s look in details the key components that make up a switchgear. We will look at the roles that they play in the overall functioning of a switchgear.
Circuit breakers
Any functional switchgear should have a circuit breaker. The primary function of the breaker in a switchgear is to protect the circuit from various electrical hazards such as current overload, short circuit , ground faults among others.
The a circuit breaker achieves this role by opening or breaking the circuit in case it senses any of these hazards. And once the hazard has been corrected, you will switch or adjust the breaker back to its initial position.
Although there are different types of circuit breakers, all of them share a common goal and that is to protect the circuit.
Contactors
Most switchgears, especially those on the motor systems have contactors. These are components that control the behavior of the motors in response to the supply current. A contactor can start the motor, stop, change the direction and even determine the overall speed of the motor.
The different types of contactors used in switchgears include vacuum contactors, break contactors and magnetic contactors. The choice of the contactor in a switchgear will depend on the application area.
Isolators
In switchgear, isolators are used to isolate various components from different forces. For example, an isolator can provide isolation against an electric fault. Isolators can be single-pole, double-pole or triple-pole.
Most isolators operate in line with the circuit breakers. For example, once the breaker cuts off the power supply, an isolator will isolate that particular segment of the circuit.
Protective relays
When used in a switchgear, a relay performs two roles: detect a fault and isolate it. The relay operates by monitoring and detecting any faults in an electric system. From there, it will isolate that problem then initiate the switchgear to cut off the current from the faulty source.
Protective relays will note the key electrical parameters such as voltage, current and frequency to determine how a switchgear should react. Each relay is designed for a specific purpose. This is why we have overcurrent relay and power relay.
Meters
In a switchgear, a meter serves as a monitoring tool. It takes note of key electrical parameters such as current and voltage of the circuit. This data is then relayed to other components of switchgear which will react accordingly. For example, a protective relay will cut of the power supply.
Fuses
This is a device that melts to cut off the power supply in case of a current overload. It is usually used in most electronic devices and appliances where it is strategically positioned near the power sources.
This fuses have a rated current capacity and will melt in case the current trips beyond the rated value.
Current transformers
Depending on the type of switchgear used, a transformer can either be a step up or step down. Their role is to transform the electrical power from one level to another. It can transform to a higher power or a lower power depending on the intended purpose of the gear or application area.
Busbars
Busbars majorly perform the role of electric distribution. They ensure that the electric current in a switchgear is equally distributed to other key components.
Surge arrestor
This is another key component of a switchgear though is mainly found on the high voltage (HV) switchgears.
The main function of surge arrestors is to protect devices from current overloads, lightning impulses, voltage overload and even switching impulses.
Equipped with all these key components, you should expect your switchgear to operate smoothly and effectively.
Classification of switchgear
Switchgears are divided into three major classes; low voltage (LV), medium voltage (MV) and high voltage (HV) switchgears. As you can see, the classification is mainly based on their power capacity.
Low voltage switchgear
This class encompasses of switchgears rated below 1500V. As the name suggests, they are mainly used on low-voltage applications. These switchgears are made of low-power devices such as air circuit breakers (ACBs), miniature circuit breakers, and the molded circuit breakers.
You are likely to find this type of switchgear on a low voltage distribution board.
Medium voltage switchgear
This type is used on applications rated between 3kv going up to 33kV. From these figures, it is clear that the switchgear is ideal for the relatively small electrical networks, such as those found in substations.
The main function of a medium voltage switchgear is to interrupt electric current to a network in case of a fault. It can still perform other expected functions of a switchgear which include; switching inductive currents, switching capacitive currents and performing the normal ON/OFF switching functions.
High voltage switchgear
You will need this class of switchgear for any electrical application that is rated above 36kV. It is mainly used in major applications such as those for the transmission lines. SF6 and vacuum circuit breakers belong to this class of switchgears.
The level of power that passes through this switchgear means that extra caution should taken when handling them. They also come with advanced safety features since the damage due to high voltage is likely to be major.
Must-have features of a switchgear
The key features that any switchgear should have include the following:
Fast response
Switchgears are designed to operate swiftly. They should be able to respond fast to any changes in the circuit. This essential to prevent the possibility of damage in the circuit or even device.
Fast respond also ensures that the systems continue running normally, without interruption.
High reliability
When put in place, a switchgear should be super reliable. This means that it should be trusted to function perfectly no matter what. Given the critical roles that they play, there should be minimal chances of failure by the switchgear.
Provision for the manual operation
Sometimes the automated feature in modern switchgears can fail. To take care of this, most switchgear have the provision for the manual control
Absolute differentiation
A switchgear should be able to differentiate normal and fault situations. This differentiation should be extended to the key components of the switchgear; it should identify the normal and faulty components.
Now you have all the essential information about switchgears. You can appreciate their roles and importance in electric circuits. In case you would like to buy switchgears in China, ensure that you get from the right sources.
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