Switchgear & Switchboard (Complete Guide)

Switchgear &  Switchboard (Complete Guide)

Switchgear and switchboard are important components in electrical systems. The difference between them may be tricky.

In my work, 11KV and 3.3KV switchgears are used to control and protect the generation turbines. This is the main difference between switchgear and switchboard.

This means, switchgear is more complicated than switchboard. Let’s discuss this topic in details.

Are switchboard and switchgear the same?

No, Switchgear and switchboard are not the same,

  • Switchgear is for medium and high voltages and is much complicated, to provide a higher level of protection.
  • Switchboard is for low voltage, typically up to 600V, and is used to just distribute electrical power to loads.

What is Switchboard?

A switchboard, is an electrical equipment that distribute electrical power from source to loads. It divides the circuit into branch circuits and provides protection using fuses or circuit breakers for each circuit.

A switchboard consists of an assembly of electrical equipment in an enclosure like fuses and circuit breaker.

Switchboard can handle power directly to loads or to another switchboard that in turns feeds other loads.

What is Switchgear?

 Switchgear is an electrical device used for the protection, isolation and control of electrical equipment with a variety of controls.

It contains circuit breakers, fuses, switches, protection relays and other power conductors. 

These components protects against faults and short circuits without affecting the other electrical devices in the circuit or the other consistent of circuit.

Why switchgear is called switchgear?

The word gear, in the term switchgear, means an Integrated system of devices to do one major job.

In our case “switching” is the major job of this combination, with all devices that help in doing this job, starting from sensing devices, protection devices and relays that takes the action and ends with circuit breakers.

Switchgear devices include:

  • Potential transformers.
  • Current transformers.
  • Advanced protection relays.
  • Monitoring devices.
  • Circuit breakers.
  • Emergency shutting down devices.

Electrical switchboard vs panel board

Switchboard and panel board provide the same purpose. Yet they have some differences. Below are some of them:

  • Panelboards are limited up to 1200 A. Switchboard can have overcurrent devices up to 5000A
  • Switchboard are free standing mounting units. While panelboard are surface/flush mounted. 
  • Switchboard and panelboard are both in default front access. However if required, switchboard can be designed with front and rear access.

Differences between Switchgear & Switchboard

Size

When we look at their location on which they are installed, there seems no big difference between them.

Both are best in their work and location. However switchboard takes a slightly less room. It is because they only need the front access for work.

Switchgear takes slightly more space because, their working system is slightly different as compared to the other device. They need both rear and front access of the current which make them to take more space.

Price

Switchgear is more expensive than the switchboard.

In addition to this it will also be seen that the individually installed switchgears are costlier as compared to the switchboards installed in groups.

Circuit Breakers difference

This is the one of the major difference between these two electrical instruments due to which one can distinguish them as the two different devices.

In case of the switchgears the low-voltage circuit breakers are used.

On the other hand in case of the switchboards molded case circuit breaker and insulated case circuit breaker are used.

Read Also my articles about circuit breakers,

  1. Vacuum Circuit breaker
  2. SF6 Circuit Breaker
  3. Air circuit breaker and its application

Switchboard vs Switchgear in Testing

When these electrical instruments are tested at 2200V, they show great difference in testing process.

  • Switchboard is short circuited tested at 20% power factor for 3 cycle duration.
  • On the other hand switchgears are tasted at 15% for duration of 30 cycles.

Switchboard vs Switchgear Applications

When we talk about the switchboard vs switchgear applications by taking into account all above mentioned factors both have better uses than each other.

Which of them should be used is based on the information available and the present conditions and application.

For example, if you want to compare switchboard vs switchgear to be used such as in a round-the-clock operation in an air port or a medical organization like hospitals, you may go to the switchboard because it’s lower in cost.

But if it used to protect the high power outage and only 10 minutes would be enough to make the big losses of wealth and property then, you will move toward the costly but secured instrument i.e. switchgear setup.

Switchgears are used where the high or medium voltages are required, such as in switching on the transformers, motors, generators.

They can also be used where the low voltage current is required to get the more safety and protection.

Voltage levels

Switchgear system is designed for medium and high voltages. Its voltage capacity is up to 350KV.

While the switchboard is designed for low voltages. Its capacity lies below 600 volts only.

Safety Features

In case of safety features switchgears are best choice. Switchgears have both abilities of automatic as well as manual control.

In the case of emergency they can be operated manually otherwise they work automatically.

Switchgears are enclosed in the metallic cabinets and can be placed either indoor or outdoor.

Switchboards are also made of the metallic or wooden cases with a meter to display the amount of currents.

Switchgear components, And how does it work?

All types of electrical control and protection devices (such as MCB‘s, contactors, MCCB’s) can be used as required in switchgears.

But the main devices are circuit breakers and protection relays.

Relays open the faulty circuit branch and isolate it from the healthy ones. This power isolation ensures power continuity to other loads.

The faulty branch remains isolated until repair or replacement.

Classification of switchgear

Several different classifications can be made

By voltage class

  1. Low voltage (< 1 kV AC)
  2. Medium voltage types(1 kV AC  to approximately 75 kV AC)
  3. High voltage (75 kV to approximately 230 kV AC)
  4. Extra high voltage, ultra high voltage (> 230 kV)

By insulating medium

  1. Oil
  2. Gas
  3. SF6
  4. Air
  5. Vacuum

By type of current

  1. Alternating
  2. Direct

By construction type

  1. Indoor
  2. Outdoor

Housing

  • Lower voltages types may be entirely enclosed within a building
  • Higher voltages types is mounted outdoors and insulated by air
  • Switches may have motor drives to allow remote control or manually operated

Switchgear Manufacturers

Many Manufacturers are in this large industry. I will list some of the leading manufacturers:

  • ABB international electrical company.
  • Schneider Electric
  • Toshiba Corporation
  • Mitsubishi Electric
  • Siemens
  • Eaton Corporation Inc
  • General Electric (GE)
  • Hyundai Heavy Industries
  • Fuji Electric, a Japanese electrical equipment firm.

Switchgear Main Purpose

Switch gear is a multipurpose system. One of the basic functions of switchgear is to provide suitable protection for electrical loads against short-circuit and overload fault currents.

Switchgear also provides isolation of circuits from power supplies. This electrical isolation is important in case of maintenance of an equipment.

It is also used to enhance system availability by allowing more than one source to feed loads as needed.

In this case the switchgear has two or more power sources, If the main source is down, then the spare or the emergency source will feed the loads.

It also is used to control, protect, operate and isolate electrical equipment in industrial buildings.

Switchgear Maintenance

In my work, we have low and medium voltage switchgear. Both need maintenance to make sure power continuity for all loads. Let’s discuss switchgear maintenance types.

When a fault occurs in an electrical system, a high amount of current or voltage passes through the circuit, Which causes damage to the electrical system.

So, to protect the electrical system from damages we should make proper maintenance for the switchgear to ensure it will do what it should do, i.e protection.

Importance of Switchgear maintenance

Switchgears are one of the important parts of the system protection devices. If switchgear is working well and properly maintained, the chance of a system being wiped by high voltage electrical surges or faults will be less.

That is the reason switchgear importance is the prime concern. It protects the whole system from unexpected shutting down or damage.

Hence, switchgear maintenance strategies will help to save time, cost, and the whole system from damages and power loss.

Switchgear Maintenance Strategies

There are four common strategies involved in switchgear maintenance. We are discussing each strategy in detail.

Reactive Strategy

In this strategy, we wait till the device stop working due to faults. Once the device stops working, we inspect the machine and replace the nonfunctional device with a working one. In short, we wait for a breakdown operation (Run to fail).

  • The basic advantage of this strategy is that we get a complete value of our device. Similarly, it requires less maintenance time and effort.
  • One of the main disadvantages is that there will be unscheduled downtime when a failure occurs. Similarly, the repair may be expensive.

Preventative Maintenance Strategy

In this strategy, an inspection is carried out to find any issue in the switchgear. It’s one of the best strategies to avoid inconvenience or system shutdown.

Depending on the type of system and device used, we decide the number of inspections and the frequency of each.

Manufacturer recommendation is the best way to set a good maintenance program.

The benefit of this strategy is to avoid any hassle. However, this strategy has the drawback of involving more risk and waste of time.

Read my article about preventive maintenance here.

Condition-based Maintenance

This type of maintenance strategy depends upon the working condition of the switchgear.

The condition may be based on the temperature, sparking, or any other variable factors. This strategy is applied when certain parameters are not working and the machine gives us a signal or warning.

  • One of the advantages of condition-based maintenance is reducing maintenance costs and minimizing the occurrence of serious faults.
  • On the other hand, it will increase operational costs like you will need a professional person to constantly monitor the overall situation. Also, you will need different sensors and devices to install on the machine to monitor the real-time situation.

Predictive maintenance strategy

This maintenance strategy is almost similar to the Condition-based maintenance strategy. However, it involves data analysis to make accurate predictions for upcoming failures.

Using this maintenance strategy, we become aware of any incoming failure but involves a high amount of cost.

A good team regular training is a must to get them ready to perform this maintenance program.

For more information about Electrical Maintenance read my article here.

Now, Let’s have a closer look at low voltage switchgear maintenance

What is Low Voltage Switchgear?

Low voltage electrical switchgear refers to a centralized collection of protection devices, which are used to protect, control and isolate electrical equipment at low voltage levels i.e less than or equal to 1000 V.

Low Voltage Switchgear Preventive Maintenance

Low voltage swich gear should be inspected using thermal image
Low voltage swich gear should be inspected using thermal image

To make sure good performance of switchgear it should be periodically inspected, and a scheduled preventive maintenance plan should be applied.

The following are some important items of PM plane of the company that I work for “Leading oil and gas company”

  • Its often to inspect medium and low voltage switchgear using thermal imaging to prevent any failure before it occurs. This test discovers any loosen connection of the connection joints.
bad circuit braker due to loosen connection
bad circuit braker due to loosen connection

Loosen connection increases resistance of the joint and cause overheating. This fault is common with circuit breakers, contactors, overloads and power cables connecting joints.

  • Partial discharge test using either fixed or portable testers is another way of testing medium and low voltage switchgear.

 This test is to determine any cracks in the insulation. Also any treeing on the power cables insulation could be detected by this way.

  • Check voltage and current of all devices, and compare them with the rated values.
  • Check all contactors for any noise, If there is noise repair the contactor or replace it.
  • If the panels have dust, switch off power and use vacuum cleaner for cleaning. Accumulated dust causes contactors failure and can cause short circuit.
  • Check for any physical damages, cracks or breaks.
  • Check grounding cables connection, and measure its resistance. Make sure that its value is not greater than 5 Ohm.
  • All indication lamps should be working. If any lamp is not working, replace it.
  • If the building has air condition, make sure it works perfectly to compensate the temperature.
  • Make sure that the emergency exit doors have clear path and easy to open.
  • Make sure that Emergency lighting is working.
  • All voltage and current readings should be recorded in a datasheet. This datasheet is a strong reference for the equipment.

Why does switchgear need batteries?

Batteries play essential role in switchgear they provide power to:

  • Station control systems.
  • Station emergency systems and lights.
  • Switchgear digital relays.
  • Circuit breakers close and trip circuits.

This is important to have a stable power supply independent of substation or generation plant output power.

The batteries are connected to an automatic charging system to assure they are always charged to be ready for any fault or emergency situation.

You may ask, why switchgear control system is DC?

Switchgear control system is DC because, if a black out occur and we need to restore the station, AC will not be available and DC batteries will take its important role.

So, you will find a special room for the batteries. These batteries should have regular preventive maintenance to keep them ready all the time.

Why does switchgear has heaters?

Heaters inside switchgear panels and enclosures are used to  maintain temperature and minimize moisture.

Moisture causes electrical equipment oxidation and leads to short circuit and internal failure.

Space heaters or anti condensation devices are widely used inside switchgear, switchboards, electric motors and generators for the very same purpose.

I have written a detailed article about motor space heater, you can find it here.

Switchgear and protection devices

protection relay in a switchgear
protection relay in a switchgear

Switchgear is mainly used to control, protect and isolate electrical equipment, also switchgear is used to de-energize equipment to allow maintenance work to be done and to clear faults.

In other words switchgear has to perform the functions of carrying, making and breaking the normal load current like a switch

Switchgear and protection devices has to perform clearing fault currents for which sensing devices like current transformers, potential transformers and various types of relays are employed.

What type of protection devices are used in switchgear?

All kinds of protection devices may be used as required, such as:

  • fuses
  • circuit isolators
  • circuit breakers
  • advanced protection relays and CT’s  

At faults conditions, the switchgear and protection devices must operate quickly so that no more damage is done to the power plant major parts like generators, transformers and other equipment by the short-circuit high currents.

Switchgear and protection devices must be able to discriminate between the healthy section and the faulty section

To ensure continuity of power supply it should isolate the faulty section from the system without affecting the healthy section of the power system, we can achieve that by a combination of protection devices and smart controllers to take the right action in the correct time.

A good designed switchgear protection system can handle any fault with minimizing the damages and the unnecessary power losses to healthy circuits and branches.

Is switchgear the same as circuit breaker?

No, switchgear is so different from circuit breaker, they are totally different. Switchgear is a combination of many protection and monitoring devices and it has circuit breakers as well.

While circuit breaker is the well known device that is used for overcurrent and short circuit protection.

How can you learn switchgear designing?

Designing switchgear is a team effort. You will need to learn electrical engineering first. Then, you should have a strong electrical protection knowledge.

You will need some soft ware to use in selecting and choosing the protection devices ratings. Some good examples of software programs are:

  • Eplan, promis and AUTOCAD (ELECTRICAL). For drawings.
  • Matlab and Etab for simulation and calculations.

You better learn these from the free versions of each one and build some basic circuits. You can find many free tutorial videos on YouTube.

It will be good to start with them. After having the basics, you can join a good paid course.

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