How Electricity is Generated

How Electricity is Generated

How to generate electricity? How is electricity created? This article explains the different methods of producing electricity- from the economically feasible methods using fossil fuels to the other unconventional energy sources like wave energy, wind turbine, and geothermal, which are greener.

First Law of Thermodynamics

How to generate electricity? What are the different methods of generating electricity? The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created nor destroyed, but can be transformed from one form to another. The generation of electricity is the conversion of energy like chemical, thermal, and potential (or kinetic) into the mechanical work of rotating a shaft. This mechanical rotation then gets converted to electricity in a generator. So basically it is not the generation of power, but the conversion of one form of energy into an electrical form of energy.

Different Methods to Produce Electricity

There are a number of methods to produce electricity. Some are economically viable but polluting, and others are more green but expensive. The different methods by which electricity can be generated are as follows:

1.       Thermal Power Plants: Here petroleum and petroleum products can be used for producing steam to run steam turbines generating electricity. In thermal power plants coal, petroleum products like furnace oil and natural gas can be used.

2.       Nuclear Power Plants: They use the heat of nuclear reactions like fission to heat water and again pass the steam to expand in the steam turbines to generate electricity.

3.       Hydro-electric Power Plants: They utilize the flow of water to generate electricity. In rivers dams are created to hold a reserve of water and this water is led through tunnels to water turbines situated below. The potential energy of the water is converted to the kinetic energy of the turbine and it is coupled to a generator generating electricity.

4.       Gas turbines using petroleum products and natural gas are also used for generation of electricity.

5.       Power plants running on petroleum products having an internal combustion diesel engine also are used for the generation of electricity.

6.       Geo-thermal power plants utilize the hot water and steam from natural hot water sources.

7.       Solar power is also used for generating electricity. Solar energy can be utilized directly in solar cells to generate electricity. The solar energy can also be used in solar thermal power plants where solar energy is used to heat water and then convert it into steam to drive steam turbines. Solar ponds are also used for generating electricity.

8.       Wind power can drive windmills and turbines to generate electricity. Wave energy of the oceans can be used to generate electricity using special machines using float chambers.

9.       Biomass can be used to replace coal and petroleum products in a thermal power plant.

10.    The other forms of electricity generation like osmotic gradient, static electricity, chemical reactions, and fuel cells are also used but not on very large scale. Though we use batteries a lot, we are discussing production for domestic uses like home lighting and industrial power supplies.

Principle of Generation

All the methods described above primarily produce mechanical power and cause turning of the shaft. They are called “prime movers." At the end of the shaft, a generator is coupled which generates electricity The principle of generation of electricity is based on Faraday's law of electromagnetic induction, which simply states that when a conductor is rotated or moved through a magnetic field, electrical potential is generated between the two ends of the conductor. When the two ends are connected to an external load, then electricity will flow through the load.

Faraday's Law of Electromagnetic Induction

 

 

 

Electric Fuses – Devices to Prevent Circuit Damage and Fire

Electric Fuses – Devices to Prevent Circuit Damage and Fire

 

There are a lot of different types of fuses found in electrical equipment today. But do you really know how they work?

Fuse – An Overview

Fuses, also called “fusible links", are small electrical devices, which provide protection for an electrical circuit whenever an uncontrollable amount of current flows. The basic components of most fuses are metal alloys that are designed to easily melt, breaking the circuit when an excessive amount of electric current flows through it.

The Mechanism: How It Works

To make the discussion much simpler, let us concentrate on fuses that are used in most households. There are many types of fuses used in many different types of applications from protecting your computer's power supply to protecting heavy industrial equipment. Although varied in purposes, the same principles are employed.

The basic mechanism of the fuse is very easy to understand. When a device in your house develops a "short circuit" (meaning the current it normally uses to power it is now being diverted, because of a failure, to ground) it will conduct an excessive amount of current. The fuse that is protecting this outlet will pass that current but in doing so will get very hot and the metal element inside will melt, breaking the path of the current flow. Until this fuse is replaced with a new one, that outlet will not work.

Usually, fusible links are encased in an enclosure called the “fuse box" where the mains wiring comes in and is distributed to your house's outlets. The main fuse links your house to the power coming from the power company and then smaller individual fuses protect the wiring going to the networks of electric outlets in your home. Many applications today, such as household protection, are being replaced with electromechanical circuit breakers. These devices perform the same function as fuses but use a different mechanism to detect the excessive current flow and interrupt the circuit. They have the feature that once they trip and protect the circuit, they can be reset and used again, so you don't need keep a supply on hand as you do with fuses.

Are Fuses Always Reliable?

Fuses are very reliable devices to protect your equipment, provided that they are properly specified for the application. A fuse that is under-rated will fail when normal currents are flowing, while a fuse that is over-rated will allow more current to flow than the circuit may be designed for, creating a hazardous condition. The time it takes a fuse to interrupt a circuit depends on the current being applied, the fuse construction and the temperature of the fuse. All these factors have to be considered when designing the fuse into a system.

Some Terms Used with Fuses

Rated current - The amount of current the fuse can pass with out interrupting the circuit. This should be selected depending on how much current the device uses under all normal conditions.

Voltage rating – This rating should be greater than or equal to the amount of voltage being applied to a circuit. This has implications in how much energy the fuse will be able to block.

Voltage Drop – How much voltage will the fuse develop across it at nominal current flow. This has implications on low voltage circuits.

Breaking Capacity – The maximum amount of current the fuse can safely interrupt. This is chosen depending on how much energy is available from the source providing the current.

 

Electrical Transmission Efficiency Explained

Electrical Transmission Efficiency Explained

 

Do you know what is meant by efficiency of electricity transmission? If not, just find out from this article

Introduction

We know that transmitting electrical power over long distances does involve some amount of losses. This gives rise to the concept of efficiency in transmission and like any other situation; the efficiency just gives an idea about the amount of useful energy which reaches the other side compared to the amount of energy which was fed at one end. So let us see how electrical transmission efficiency is defined and calculated.

Transmission Efficiency

The general formula for efficiency applies to this case also and

Efficiency of transmission = Po/Pi * 100

Po is the amount of power reaching the receiving end

Pi is the amount of power fed at the sending end

So say for example that 1000 watts of power were fed to a feeder and 900 watts is received at the other end then the efficiency of transmission is 90%. This description will become clearer if you see the derivation of this formula and the diagram given alongside it.

As you can see in the picture it shows 2 feeder wires where the end x, y is the sending side while the end u, v is the receiving side. The voltage and current of the power being sent are 220V and 5A respectively.

Let us assume the resistance of each feeder wire to be 1 ohm for simplicity

This means that the drop in potential over one feeder wire would be I * R = 5 Volts. Hence the total drop including both feeders will be 10 Volts.

This obviously means that the voltage obtained at the other end would not be 220 but 210 volts only.

Power associated with 220V and 5A = V * I = 1100 watts

Power associated with 210V and 5A = 1050 watts

So efficiency of transmission = 1050/1100 * 100 = 95.4%

Another method of expressing this efficiency is the equation

E = 100 – (IR/Vi * 100)

Where Vi is the input voltage and E is efficiency.

Hence you can see that for efficiency to be maximum the right hand side figure has to be minimum. This in turn means that Vi should be as high as possible hence the need to step up voltage while transmitting.

Another corollary from this equation is that when voltage is high, current is low. This means that the diameter of the conductor required is lesser and this results in material cost savings for the conductor as thinner cables can be used.

Feeder Vs Distributor

We saw the difference between feeder and distributor in our previous article. You will remember that a feeder does not have any tapping of power midway but only at its end while a distributor is tapped at various places because of its function. Hence the above equation only applies to a feeder setup and not a distributor.

 

 

Power Loss Calculations In Electric Supply

Power Loss Calculations In Electric Supply

 

Learn how the losses during transportation of electricity are calculated by engineers

Introduction

We know that transmitting electrical power over long distances does involve some amount of losses. This gives rise to the concept of efficiency in transmission and like any other situation; the efficiency just gives an idea about the amount of useful energy which reaches the other side compared to the amount of energy which was fed at one end. So let us see how electric power transmission losses are calculated and how electrical transmission efficiency is defined. This discussion applies to both HVDC transmission as well as HVAC and whatever mode of transport is used.

Power Transmission Losses

The general formula for efficiency applies to this case also and

Efficiency of transmission = Po/Pi * 100

Po is the amount of power reaching the receiving end

Pi is the amount of power fed at the sending end

So say for example that 1000 watts of power were fed to a feeder and 900 watts is received at the other end then the efficiency of transmission is 90%. This description will become clearer if you see the derivation of this formula and the diagram given alongside it.

As you can see in the picture it shows 2 feeder wires where the end x, y is the sending side while the end u, v is the receiving side. The voltage and current of the power being sent are 220V and 5A respectively.

Let us assume the resistance of each feeder wire to be 1 ohm for simplicity

This means that the drop in potential over one feeder wire would be I * R = 5 Volts. Hence the total drop including both feeders will be 10 Volts.

This obviously means that the voltage obtained at the other end would not be 220 but 210 volts only.

Power associated with 220V and 5A = V * I = 1100 watts

Power associated with 210V and 5A = 1050 watts

So efficiency of transmission = 1050/1100 * 100 = 95.4%

Another method of expressing this efficiency is the equation

E = 100 – (IR/Vi * 100)

Where Vi is the input voltage and E is efficiency.

Hence you can see that for efficiency to be maximum the right hand side figure has to be minimum. This in turn means that Vi should be as high as possible hence the need to step up voltage while transmitting.

Another corollary from this equation is that when voltage is high, current is low. This means that the diameter of the conductor required is lesser and this results in material cost savings for the conductor as thinner cables can be used.

Feeder Vs Distributor

We saw the difference between feeder and distributor in our previous article. You will remember that a feeder does not have any tapping of power midway but only at its end while a distributor is tapped at various places because of its function. Hence the above equation only applies to a feeder setup and not a distributor.

 

 

Transporting D.C. Power Over Long Distances

Transporting D.C. Power Over Long Distances

 

Do not be surprised to hear that even DC power can be hauled effectively over huge distances, and might be more efficient than AC transmission. Just find out for yourself

Introduction

We learnt about the basics of power transmission in our previous article. Now we will take a look at the hvdc transmission basics and transmission of DC power over long distances. If you are thinking that you have mainly heard about AC being transmitted over long distances, you are quite right in this regard. Mostly AC power is transmitted but then there are advantages of both types of power transmission which we shall see below.

DC Power Transmission

It is true that initially the transmission of AC power was the only effective mode of power transmission due to high losses associated with the DC transmission. But this has certainly changed over the years with the development of new techniques and technologies and the use of DC transmission is certainly on the rise.

Some of the main advantages of using DC over AC are as follows.

A DC power line only requires two lines of conductors to be transported as compared to AC power which required an additional line as well. This may not seem a big deal but just imagine the saving of material and cost when such a transmission has to be carried across hundreds and thousands of kilometers. A good example of this is the power transmission lines that carry DC power from Nelson River to Winnipeg over a distance of 1000 kilometers. Mathematically speaking, using 2 lines instead of 3 means that two-thirds cost savings are achieved in conductor cost. Of course there can be 3 wires in a DC system as well but that is for another purpose as we shall see later.

Since AC power flows in sinusoidal mode, the peak voltage is much higher than the effective voltage while they are same in DC power. This means that for a given effective voltage, the interference from AC power cables will be much higher than that of DC power cables.

Of course this does not mean to say that DC power has not disadvantages. The main disadvantage of DC power is that transformers only work on AC power. That means that stepping up/down of voltages is only feasible with AC power only. Normally transmission is associated with high voltages (and low currents) to minimize losses. This is so because transmission losses are proportional to the square of the current. Of course there are limitations of increasing voltage because of the cost of the transformers, which could rise prohibitively as the voltages get higher. We will take up this issue in detail in later articles.

AC to DC Conversion

Because of the above mentioned limitations of voltage stepping, a practical method is to

○         Generate AC power

○         Increase its voltage using transformer

○         Transmit it in DC form

○         Convert back to AC at substation

○         Step it down and distribute as usual

AC to DC conversion can be carried out using either

○         Mercury Arc rectifiers

○         Rotary converters

○         Motor-generator sets

We will study all the above concepts and equipment in future articles

Overhead and Underground Transmission

The power plants are normally located at remote areas and the consumers are located literally everywhere. Hence when long distances are involved in power transmission, there are various types of terrains which might fall in the way. There could be mountains, rivers and even parts of the ocean. You can see the picture which shows what types of terrains might need to be covered for power transmission.

Depending on the terrain, either overhead or underground cabling can be used and each of them has their own advantages. Overhead transmission is relatively cheaper and moreover it could be easier to repair in case of any damage simply because of its physical visibility.

Underground cabling could mean more cost of installation but could result in substantial space savings as well as it is more aesthetically appealing then the array of wires and poles covering the space.

 

 

The Basic Force behind Electricity – Potential Difference

The Basic Force behind Electricity – Potential Difference

 

Behind every successful man is a woman (and vice versa), and it obviously means that there is lot of understanding between the duo. But do you know that not only understanding it but differences can also be the force behind some phenomenon.

Introduction

I cannot say of human beings, but for electricity to flow there needs to be differences of potential between two points, and it is this difference of potential that is known as the potential difference - simple, isn't it?

Well if you are bit confused by my comparisons just remember that the phenomenon that take place in the intangible realms of matter need to be explained to the mind's eye through such comparisons only. Nobody can see current with the naked eye (just ping me if you can see it) flowing through a wire hence such analogies are necessary to explain such unviewable events.

A Simple Voltaic Cell

We will not talk about huge electricity generation plants in these initial stages but only about a humble yet equally powerful source of electrical energy namely the voltaic cell. Just imagine two plates made out of copper and zinc and immersed in sulphuric acid. I will go into the details of the chemical reaction that takes place but just remember that electrons get removed from the copper plate and get deposited on the zinc plate during the process thus leaving them positively and negatively charged respectively. The positively charged plate or electrode is known as anode while the other is known as cathode.

You might think that the electrons tend to go to the anode which is absolutely right; but cannot do so through the cell electrolyte. Electrons can only travel if there is an external wire connecting the two plates or electrodes thus completing a closed circuit. As the electrons go towards the anode, the cathode gets depleted but is amply compensated by the ongoing chemical reaction within the cell.

The Units of P.D.

The unit of potential difference is known as volt (doesn't the word seem very familiar) and yes these are the same volts which you refer every time you purchase some electronic equipment. However in the strict technical sense of the word, a volt is the electrical force required to make a current of one ampere flow through a conductor of one ohm resistance and is symbolized by the letter V (as in victory of electricity over darkness).

The potential difference that we discussed above is not of much practical use except that it makes the current flow. This electricity is then harnessed in different ways to move different types of equipment, machinery etc for the requisite purpose. The same electricity which runs a toy train is also powerful enough to run a full sized train and it is surprising to note that how powerful the tiny atomic particles can be. On the bigger scale electricity is produced in power plants and power houses.

One interesting fact is that though the current involves flow of charged particles there are two directions for which it is defined. The flow of current is taken to be opposite to the direction in which electrons are flowing, hence a reader should always keep this in mind to avoid ambiguity and confusion.

 

What are the Common Insulating Materials Used in Electrical Engineering?

What are the Common Insulating Materials Used in Electrical Engineering?

 

The main aim of an insulating material is to separate electrical conductors without passing current from one to the other and to safeguard individuals from electrically energized wires and parts. A complete knowledge of insulating materials and standards for safe working practices is required.

A material that responds with very high resistance to the flow of electrical current or totally resists electric current is called an insulating material. In insulating materials, the valence electrons are tightly bonded to their atoms.

In the electrical field, the purpose of any insulating material is to separate electrical conductors without passing current through it. Material like PVC, glass, asbestos, rigid laminate, varnish, resin, paper, Teflon, and rubber are very good electrical insulators. Insulating material is used as a protective coating on electrical wire and cables.

The most significant insulating material is air. Beside that solid, liquid, and gaseous type of insulators are also used in electrical systems.

Why electrical insulation is required

Electrical shock caused by the flow of current through the human body can result in physiological effects ranging from fatal injuries resulted by involuntary moments to death from ventricular fibrillation (the rhythmic pumping action of the heart ceases) or muscular contraction.

DC voltage up to 40 volts and AC voltage up to 60 volts are considered safe limits, in the best circumstances, for the human body, but beyond this is considered a hazard, and to prevent it electrical insulation is required. Resistance to the electrical current is measured in ohms. Metals react with very little resistance to the flow of electrical current and are called conductors. As previously mentioned, materials like asbestos, porcelain, PVC, dry wood react with a high resistance to flow of electrical current and are called insulators.

Dry wood contains a high resistance, but when wet with water, its resistance drops and it may allow electricity. The same thing is applicable for human skin. When skin is dry, it has a high resistance to electric current, but when it is moist, there is a drop in resistance. Therefore any electrician should take precautions when water is present in the environment or on the skin and necessary insulating materials should be used. The best remedy to safeguard individuals from electrically energized wires and parts is through insulation.

Application of insulating materials

Cables and transmission lines:

Insulating material is generally used as a protective coating on electrical conductor and cables. Cable cores which touch each other should be separated and insulated by means of insulation coating on each core, e.g. polyethylene, cross linked polyethylene-XLPE, polyvinyl chloride-PVC, Teflon, silicone etc. Hanging disk insulators (bushings) are used in high voltage transmission bare cables where they are supported by electrical poles. Bushings are made from glass, porcelain, or composite polymer materials.

Electronics systems:

All electronic appliances and instruments widely contain PCB (printed circuit boards) having different electronics components on them. PCBs are manufactured of epoxy plastic and fiberglass. All electronics components are fixed on the insulated PCB board. In SCR (semiconductor rectifiers), transistors and integrated circuits, the silicon material is used as a conductive material and can be converted into insulators using a heat and oxygen process.

Power systems:

Transformer oil is widely used as an insulator to prevent arcing in transformers, stabilizers, circuit breakers, etc. The insulating oil can withstand insulating properties up to a specified electrical breakdown voltage. Vacuum, gas (sulfur hexafluoride), and ceramic or glass wire are other methods of insulation in high voltage systems. Small transformers, power generators, and electrical motors contain insulation on the wire coils by the means of polymer varnish. Fiberglass insulating tape is also used as a winding coil separator.

Domestic portable appliances:

All hand held electrical appliances are insulated to prevent their user from electrical shock hazard.

○      Class 1 insulation contains only basic insulation on the wire and the metal body is earthed at the main grounding system. The third pin on the power plug shall be for the grounding connection.

○      Class 2 insulation denotes a device with "double insulation." All internal electrical components shall be totally enclosed within an insulated body which will prevent any shorting with conductive parts.

Electrical cable insulating tape:

PVC tapes are widely used to insulate electrical wires and other live conductive parts. It is made of vinyl as it stretches well and provides effective and long-lasting insulation. Electrical tape for class H insulation is made of fiberglass cloth.

Personal protective equipment:

PPE protects humans from the hazards of shock with electrical circuits. PPE such as insulating head protection, eye and face protection, and insulating gloves are necessary for protection against all common electrical hazards. Insulated tools and protective shields are must for an electrician's safe working. Dielectric shoes (non-metallic safety footwear) or electrical hazard footwear is made with non-conductive, electrical shock-resistant soles and heels.

Electrical rubber mats:

Insulating mats for electrical purposes have a wide application in various substations, power plants, etc. The mats are used for floor covering below control panels to provide for the safety of workman due to any possible leakage of current.

List of some common insulating materials

○      A.B.S.

○      ACETATE

○      ACRYLIC

○      BERYLLIUM OXIDE

○      CERAMIC

○      DELRIN

○      EPOXY/FIBERGLASS

○      GLASS

○      KAPTON

○      KYNAR

○      LEXAN

○      MERLON

○      MELAMINE

○      MICA

○      NEOPRENE

○      NOMEX

○      NYLON

○      P.E.T. (Polyethylene terephthalate)

○      PHENOLICS

○      POLYESTER (MYLAR)

○      POLYOLEFINS

○      POLYSTYRENE

○      POLYURETHANE

○      PVC (Polyvinylchloride)

○      SILICONE/FIBERGLASS

○      SILICONE RUBBER

○      TFE (TEFLON)

○      THERMOPLASTICS

○      ELECTRICAL INSULATING PAPERS, TAPES, and FOAMS

○      NEOPRENE

○      POLYSTYRENE

○      POLYURETHANE

○      SILICONE

○      VINYL

○      LAMINATES

Electrical Insulating Material Standards

ASTM's insulating material standards are instrumental in specifying, evaluating, and testing the electrical and physical properties of materials used primarily as electrical insulation in devices and related equipment. These properties include dielectric breakdown voltage, dielectric strength, AC loss, permittivity (dielectric constant), DC resistance and conductance, dissipation factor, ion exchange capacity, ionic resistivity, and other physical properties. These electrical insulating material standards allow manufacturers, particularly those in the semiconductor industry, to examine and assess such materials and equipment to ensure their qualification for safe use.

Conclusion:

The control of electrical hazards is an important part of every safety and health program. A complete knowledge of insulating materials and standards for safe working practice is required for an electrician. Everyone has the right to work in a safe environment.

 

 

 

 

 

What is Electrical Drive?

What is Electrical Drive?

Whenever the term electric motor or electrical generator is used, we tend to think that the speed of rotation of these machines is totally controlled only by the applied voltage and frequency of the source current. But the speed of rotation of an electrical machine can be controlled precisely also by implementing the concept of drive. The main advantage of this concept is, the motion control is easily optimized with the help of drive. In very simple words, the systems which control the motion of the electrical machines, are known as electrical drives. A typical drive system is assembled with a electric motor (may be several) and a sophisticated control system that controls the rotation of the motor shaft. Now days, this control can be done easily with the help of software. So, the controlling becomes more and more accurate and this concept of drive also provides the ease of use. This drive system is widely used in large number of industrial and domestic applications like  factories, transportation systems, textile mills, fans, pumps, motors, robots etc. Drives are employed as prime movers for diesel or petrol engines, gas or steam turbines, hydraulic motors and electric motors.

Now coming to the history of electrical drives, this was first designed in Russia in the year 1838 by B.S.Iakobi, when he tested a DC electric motor supplied from a storage  battery  and propelled a boat. Even though the industrial adaptation occurred after many years as around 1870. Today almost everywhere the application of electric drives is seen. The very basic block diagram an electric drives is shown below. The load in the figure represents various types of equipments which consists of electric motor, like fans, pumps, washing machines etc. 

 

Digital Electronics

Digital Electronics

 

We know there are two types of signals, one is analog or continuous signal and the second one is Digital or discrete signal. So the science or field of research in the area of engineering is termed as Analog and Digital Electronicsrespectively. Now coming to the area of Digital Electronics, it is essential to understand wide range of applications from industrial electronics to the fields of communication, from micro embedded systems to military equipment. The main and perhaps the most revolutionary advantage of digital electronics is the decrease in size and the improvement in technology. We have chosen to discuss various topics of Digital Electronics from the very fundamentals of this subject such as Number systems, logic circuits going deep into those topics, like discussing various types of number systems, which we should use and how, inter relation among those number systems to the somewhat tougher concepts of Digital Electronics like TTL, PMOS-NMOS logic, Flip Flops etc. to get an idea about the whole subject.

All the topics of the related articles have been amply presented by diagrams, designs, tables and examples to make every topic understandable as much as possible. The topics are written in such a manner that if one go through them he will grasp the very basic idea at first attempt and further reading will enhance the technical knowledge. 
Now let us inform you what we have included in the topics of Digital Electronics, as we have already discussed we have started from the very basic topics of Digital Electronics like Number system. Then we have discussed the extension of number system like various types of number system, interrelation among different types of number systems making oneself absolutely comfortable with the fundamentals of Number system. Then we have enlightened the very important field of Digital Electronics i.e. Binary Arithmetic and Boolean algebra. And we have discussed about them in elaborated manner. From binary addition, binary subtraction, binary multiplication and binary division to the basics of Boolean algebra.
After that we have written topics about various types of codes such as ASCII code, Gray Code, Hamming code which have made the input output format very easy. Then various types of logic gates (AND gate, OR gate, NOT gate, NAND gate, NOR gate, EX-OR gate) have been discussed in an elaborated manner with diagrams, explanations and truth tables to make each one of them very easy to understand.

These may be classified as the fundamentals of Digital Electronics without which the subject cannot be understood at all. So after discussing about them we have gone deep into the subject. Topics like TTL, Logic Families, various MOS gates, Flip Flops (J-K, D, T etc.) have been discussed.
The sole purpose of introducing this subject in our Electrical Engineering website is because now days all the engineering streams are interrelated and the knowledge of Digital Electronics is very much essential for an electrical Engineer and we have tried our best to make oneself familiar with the subject technically as much as possible.

 

 

 

Electrical Switchgear Protection

Electrical Switchgear Protection

 

Definition of Switchgear

A switchgear or electrical switchgear is a generic term which includes all the switching devices associated with mainly power system protection. It also includes all devices associated with control, metering and regulating ofelectrical power system. Assembly of such devices in a logical manner forms a switchgear. This is very basic definition of switchgear.

Switchgear and Protection

We all familiar with low voltage switches and re-wirable fuses in our home. The switch is used to manually open and close the electrical circuit in our home and electrical fuse is used to protect our household electrical circuit from overcurrent and short circuit faults.

In same way every electrical circuit including high voltage electrical power system needs switching and protective devices. But in high voltage and extra high voltage system, these switching and protective scheme becomes complicated one for high fault current interruption in safe and secure way. In addition to that from commercial point of view every electrical power system needs measuring, control and regulating arrangement. Collectively the whole system is called switchgear and protection of power system. The electrical switchgear have been developing in various forms.

Switchgear protection plays a vital role in modern power system network, right from generation through transmission to distribution end. The current interruption device or switching device is called circuit breaker in switchgear protection system. The circuit breaker can be operated manually as when required and it is also operated during over current and short circuit or any other faults in the system by sensing the abnormality of system. The circuit breaker senses the faulty condition of system through protection relay and this relay is again actuated by faulty signal normally comes from current transformer or voltage transformer.
A switchgear has to perform the function of carrying, making and breaking the normal load current  like a switch and it has to perform the function of clearing the fault  in addition to that it also has provision of metering and regulating the various parameters of electrical power system. Thus the switchgear includes circuit breaker, current transformer, voltage transformer, protection relay, measuring instrument, electrical switch,electrical fuse, miniature circuit breaker, lightening arrestor or surge arrestor, electrical isolator and other associated equipment.

Electric switchgear is necessary at every switching point in the electrical power system. There are various voltage levels and hence various fault levels between the generating stations and load centers. Therefore various types of switchgear assembly are required depending upon different voltage levels of the system. Besides the power system network, electrical switchgear is  also required in industrial works, industrial projects, domestic and commercial buildings.