April – VI Class
Electrical Safety
The major hazards associated with electricity are electrical shock and fire. Electrical shock occurs when the body becomes part of the electric circuit, either when an individual comes in contact with both wires of an electrical circuit, one wire of an energized circuit and the ground, or a metallic part that has become energized by contact with an electrical conductor.
The severity and effects of an electrical shock depend on a number of factors, such as the pathway through the body, the amount of current, the length of time of the exposure, and whether the skin is wet or dry. Water is a great conductor of electricity, allowing current to flow more easily in wet conditions and through wet skin. The effect of the shock may range from a slight tingle to severe burns to cardiac arrest. The chart below shows the general relationship between the degree of injury and amount of current for a 60-cycle hand-to-foot path of one second's duration of shock. While reading this chart, keep in mind that most electrical circuits can provide, under normal conditions, up to 20,000 milliamperes of current flow
Safety Precautions
There are various ways of protecting people from the hazards caused by electricity, including insulation, guarding, grounding, and electrical protective devices. Workers can significantly reduce electrical hazards by following some basic precautions:
1 | Inspect wiring of equipment before each use. Replace damaged or frayed electrical cords immediately. |
2 | Use safe work practices every time electrical equipment is used. |
3 | Know the location and how to operate shut-off switches and/or circuit breaker panels. Use these devices to shut off equipment in the event of a fire or electrocution. |
4 | Limit the use of extension cords. Use only for temporary operations. In all other cases, request installation of a new electrical outlet. |
5 | Use only multi-plug adapters equipped with circuit breakers or fuses. |
6 | Place exposed electrical conductors (such as those sometimes used with electrophoresis devices) behind Plexiglas shields. |
7 | Minimize the potential for water or chemical spills on or near electrical equipment. |
The following practices may reduce risk of injury or fire when working with electrical equipment:
8 | Avoid contact with energized electrical circuits. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
9 | Disconnect the power source before servicing or repairing electrical equipment. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
10 | When it is necessary to handle equipment that is plugged in, be sure hands are dry and, when possible, wear nonconductive gloves and shoes with insulated soles. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
11 | If it is not unsafe to do so, work with only one hand, keeping the other hand at your side or in your pocket, away from all conductive material. This precaution reduces the likelihood of accidents that result in current passing through the chest cavity. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
12 | Minimize the use of electrical equipment in cold rooms or other areas where condensation is likely. If equipment must be used in such areas, mount the equipment on a wall or vertical panel. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
13 | If water or a chemical is spilled onto equipment, shut off power at the main switch or circuit breaker and unplug the equipment. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
14 | If an individual comes in contact with a live electrical conductor, do not touch the equipment, cord or person. Disconnect the power source from the circuit breaker or pull out the plug using a leather belt. VII April- May Introduction of Alternating Current & Direct Current Electricity: Everything in the world is made up of atoms. Each atom has smaller parts in it. One of those parts is called electrons. Electrons can move from atom to atom. When an electron moves to a different atom, it causes another electron to have to move. When electrons move quickly from one atom to another is it called Electricity! Static and Dynamic electricity: Static electricity is usually caused when certain materials are rubbed against each other—like wool on plastic or the soles of your shoes on the carpet. It is also caused when materials are pressed against each other and pulled apart. The process causes electrons to be pulled from the surface of one material and relocated on the surface of the other material. It is called the triboelectric effect or triboelectric charging. Uses of static electricity Uses of static electricity include pollution control, Xerox machines, and painting. They use the property that opposite electrical charges attract. There are other uses involving the properties of repulsion and the creating of static electricity sparks. And also used in Furness to measure the high temperatures of the Furness. Dynamic electricity is a flow of electrical energy that occurs in a long period time there are three variables to make sure that the dynamic electricity to flow: Uses: energy provides us with electricity, heating and cooling, manufacturing, and transportation. Explore how our energy needs must be met in all four uses. Our lives would be much, much different without the products and opportunities energy provides. Source of AC and DC:Direct current (DC): is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, dynamo, and commutator-type electric machines of Sources of Alternating Current: AC electricity is created by an AC electricgenerator, which determines the frequency. What is special about AC electricity is that the voltage can be readily changed, thus making it more suitable for long-distance transmission than DC electricity. But also, AC can employ capacitors and inductors in electronic circuitry, allowing for a wide range of applications. Generating Stations Thermal Power Stations
Hydro Electric Power Stations Nuclear Power Station Renewable Energy
Thermal Power Plant In a thermal power plant, the energy stored in fuels such as coal, natural gas, and fuel oil is sequentially converted into electrical energy. A thermal power plant boiler triggers the first action towards the production of electricity and so is the most important part of a thermal power plant. A thermal power plant boiler has two functions namely the Combustion System the Water and Steam. Hydroelectric power We have used running water as an energy source for thousands of years, mainly to grind corn. A dam is built to trap water, usually in a valley where there is an existing lake. Water is allowed to flow through tunnels in the dam, to turn turbines and thus drive generators. Notice that the dam is much thicker at the bottom than at the top, because the pressure of the water increases with depth. Hydro-electric power stations can produce a great deal of power very cheaply. Nuclear Power Station Nuclear power is generated using Uranium, which is a metal mined in various parts of the world. The first large-scale nuclear power station opened at Calder Hall in Cumbria, England, in 1956. Some military ships and submarines have nuclear power plants for engines. Nuclear power produces round 11% of the world's energy needs, and produces huge amounts of energy from small amounts of fuel, without the pollution that you'd get from burning fossil fuels. Solar Power We've used the Sun for drying clothes and food for thousands of years, but only recently have we been able to use it for generating power. The Sun is 150 million kilometers away, and amazingly powerful. Just the tiny fraction of the Sun's energy that hits the Earth (around a hundredth of a millionth of a percent) is enough to meet all our power needs many times over. In fact, every minute, enough energy arrives at the Earth to meet our demands for a whole year - if only we could harness it properly. Currently in the UK there are grants available to help you install solar power in your home. April & & May Class VIII – safety rules Work near electricity · Learn how to recognize electrical wires. These may be overhead power lines, electrical wiring in a workplace, or cables buried under the ground. · Get an up-to-date map of the services in the area and use it.  ·Look for electrical wires, cables or equipment near where you are going to work and check for signs warning of dangers from electricity, or any other hazard. Remember to look up, down, and around you. · If you will be digging or disturbing the earth or cutting into surfaces, use a cable locator to find buried services and permanently mark the position of services you do find. · Work away from electrical wiring wherever possible. If you have to work near electrical wiring or equipment, ask for the electrical supply to be turned off. Make sure the power is off, and cannot be turned on again without you agreeing. · If the electrical supply cannot be turned off, consult a competent person who should be able to advise you on the best way to proceed. · Identify where it is safe to work. Put up danger notices where there are still live electrical circuits, and warn your co-workers where it is safe to work and where it is not safe. Remember to remove notices at the end of the work. Electrical wiringYou may not see electrical wires near where you plan to work but this doesn’t mean there aren’t any. Even if you do see wires, there may be others you cannot see. Electrical wiring may sometimes look like pipes, and may be a range of colours. Before you drill or start cutting into surfaces: · look for electrical wires and any other hazards such as asbestos. Remember to look on both sides of walls; · ask to see plans of the electrical installation, and use these to find electrical wiring; · If you are competent, use a suitable cable detector, or get a competent person to do it for you. Remember that some cable detectors won’t find a wire carrying a small current – consult the user guide. · look for nearby electrical equipment or installations and find where the wiring runs to these. · use equipment that will minimize the risks during the work. · wear suitable protective clothing. If you are in doubt STOP WORK and consult a competent person. Look for electrical wires and any other hazards such as asbestos. Cable colorsMany electrical cables are colored to show their purpose and the voltage they are carrying. However, there are many standards used around the world, and you should never assume that a cable of a particular color is at a particular voltage. . It is very important that you identify what voltages are present on an installation you are not familiar with. Making sure the power is offIf you are not competent to check if the power is off, ask a competent person to do it for you, and watch them doing it. If you have any doubts about the method they have used, ask someone you know is competent. When checking that power is off the competent person should be SURE that: 1. The device being used is suitable for the purpose of isolation. 2. The isolator being used to turn off the power is working correctly and reliably. 3. The switch being used is the only way that the circuit can be fed with electrical power. 4. The switch being used is locked in the off position and cannot easily be turned on again. 5. The equipment and method being used to check for voltage works and is reliable. 6. The isolation has been successful by confirming the circuit is no longer ‘live’. Some electrical systems and equipment must be earthed before it is safe to work near them. Check whether this is necessary, and if it is, ensure that this is done properly. Electric shock An electric shock occurs when a person comes into contact with an electrical energy source. Electrical energy flows through a portion of the body causing a shock. Exposure to electrical energy may result in no injury at all or may result in devastating damage or death. Burns are the most common injury from electric shock.
Steps to follow(First Aid)
April & May - IX Class Electrical Safety Devices A variety of electrical safety devices are available to protect against electric shock. When buying electrical fittings and appliances, always ask for products that have an enhanced level of safety, such as a built-in RCD or recessed sockets.  Fuse · Electric Fuse is a Safety device · It works on the principle of Joule’s law of heating · It consists of a fuse wire made of an alloy of tin and lead, which melts and breaks the circuit whenever current in the circuit exceeds safe limits due to overloading or short circuit TYPES OF FUSES contacts between which it is fixed and a body to support and isolate them. Many types of fuses also have some means for extinguishing t he arc which appears when the fuse element melts. In general, there are two categories of fuses viz. I) Low voltage fuses. II)High voltage fuses. Usually isolating switches are provided in series with fuses where it is necessary to permit fuses to be replaced or rewired with safety. In absence of such isolation means, the fuses must be so shielded as to protect the user against accidental contact with the live metal when the fuse is being inserted or removed. Low voltage fuses can be further divided into two classes namely I) Semi-enclosed or Re wireable type. II)Totally enclosed or Cartridge type. 1. REWIREABLE FUSES The most commonly used fuse in 'house wiring' and small current circuit is the semi-enclosed or rewireable fuse.(also sometime known as KIT-KAT type fuse). It consist of a porcelain base carrying the fixed contacts to which the incoming and out going live or phase wires are connected and a porcelain fuse carrier holding the fuse element, consisting of one or more strands of fuse wire, stretched between its terminals. The fuse carrier is a separate part and can be taken out or inserted in the base without risk, even without opening the main switch. If fuse holder or carrier gets damaged during use, it may be replaced without replacing the complete unit. The fuse wire may be of lead, tinned copper, aluminum or an alloy of tin-lead. The actual fusing current will be about twice the rated current. When two or more fuse wire are used, the wires should be kept apart and aerating factor of 0.7 to 0.8 should be employed to arrive at the total fuse rating. The specification for rewireable fuses are covered by IS: 2086-1963.Standard ratings are 6, 16, 32, 63, and 100A. A fuse wire of any rating not exceeding the rating of the fuse may be used in it that is a 80 A fuse wire can be used in a 100 A fuse, but not in the 63 A fuse. On occurrence of a fault, the fuse element blows off and the circuit is interrupted. The fuse carrier is pulled out, the blown out fuse element is replaced by new one and the supply can is resorted by re-inserting the fuse carrier in the base. Though such fuses have the advantage of easy removal or replacement without any danger of coming into the contact with a lie part and negligible replacement cost but suffers from following disadvantages: 1. Unreliable Operations. 2. Lack of Discrimination. 3. Small time lag. 4. Low rupturing capacity. 5. No current limiting feature. 6. Slow speed of operations. 2. TOTALLY ENCLOSED OR CARTIDGES TYPE FUSE. The fuse element is enclosed in a totally enclosed container and is provided with metal contacts on both sides. These fuses are father classified as  I) D-type. II) Link type. Link type cartridges are again of two types viz. Knife blade or bolted type.  It is a non interchangeable fuse comprising s fuse base, adapter ring ,cartridge and a fuse cap. The cartridge is pushed in the fuse cap and the cap is screwed on the fuse base. On complete screwing the cartridge tip touches the conductor and circuit between the two terminals is completed through the fuse link. The standard ratings are 6, 16, 32, and 63 amperes. The breaking or rupturing capacity is of the order of 4k A for 2 and 4ampere fuses the 16k A for 63 A fuses. D-type cartridge fuse have none of the drawbacks of the rewireable fuses. Their operation is reliable. Coordination and discrimination to a reasonable extent and achieved with them. B) Link type Cartridge or High Rupturing Capacity (HRC) Where large number of concentrations of powers is concerned, as in the modern distribution system, it is essential that fuses should have a definite known breaking capacity and also this breaking capacity should have a high value. High rupturing capacity cartridge fuse, commonly called HRC cartridge fuses , have been designed and developed after intensive research by manufactures and supply engineers in his direction. The usual fusing factor for the link fuses is 1.45. the fuses for special applications may have as low as a fusing factor as 1.2. The specifications for medium voltage HRC link fuses are covered under IS KNIFE BLAD TYPE HRC FUSE It can be replaced on a live circuit at no load with the help of a special Insulated fuse puller. BOLTED TYPE HRC LINK FUSE  It has two conducting plates on either ends. These are bolted on the plates of the fuse base. Such a fuse needs an additional switch so that the fuse can be taken out without getting a shock. Preferred ratings of HRC fuses are 2 ,4, 6, 10, 16, 25, 30, 50, 63, 80, 100,125, 160, 200, 250, 320, 400, 500 ,630, 800, 1000 and 1,250 amperes Circuit Breaker  A circuit breaker is an automatically operated basic function is to detect a fault condition and, by interrupting continuity, to immediately once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city. Earth Leakage Circuit Breaker  E earth leakage circuit breaker is used for the protection n against electrical leakage in t he circuit of 50Hz or 60Hz, rated voltage single-phase 240V, 3-phase 415V, rated current up to 60A When somebody gets an electric shock or the residual current of the circuit exceeds the fixe value, the ELCB can cut off the power within the time of 0.1s automatically protecting the personal safety and preventing the equipment from the fault resulted from the residual current. With this function, the ELCB can protect the circuit against overload and short circuit or can be used for the unfrequent switchover of the circuit under normal conditions. It conforms to IEC 61009 standard. Miniature Circuit Breaker  A MCB is a mechanical switching device which is capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and automatically breaking currents under specified abnormal circuit conditions such as those of short circuit. In short, MCB is a device for overload and short circuit protection. They are used in residential & commercial areas. Just like we spend time to make a thorough check before buying appliances like washing machines or refrigerators, we must also research about MCBs. Also, if you are still using a fuse then you must replace it with MCB. High Voltage circuit Breaker  April- May Class X Thermal Power Plant Introduction Electricity is produced at a an electric power plant. Some fuel source, such as coal, oil, natural gas, or nuclear energy produces heat. The heat is used to boil water to create steam. The steam under high pressure is used to spin a turbine. The spinning turbine interacts with a system of magnets to produce electricity. The electricity is transmitted as moving electrons through a series of wires to homes and business. Working Principle We used coals as fuel for the generation of heat energy. As the water in the Boiler evaporated due to the intense heat, it becomes high-pressurized steams. -And the steams are passing through a conduit (there is a turbine at the other end of the tunnel), it forces its way through the Turbine, thus  rotating the Turbine. (As the steams are high-pressurized, the Turbine will rotate very fast.) -The Turbine is connected to a Generator via a coupler. As the Turbine is rotating (from the force of the steams), electrical energy is being produced. -After the steams have passed through the turbine, it enters a Condenser. The Condenser has got a cooling agent (namely seawater) and the steam will go through the cooling agent via a pipe. The steam thus changes back to its liquid form and returns to the Boiler. -And the whole process repeats. 
List of Major Thermal Power Plants in India 
Nuclear Power station:  Nuclear power plants use the amazing power of the atom to generate electricity with a very low fuel cost and much less pollution than fossil fuel plants. However, the planning, building, and operating of a nuclear power plant is a long, costly, and very complex process. When the idea for nuclear power plants first came out, the Atomic Energy Commission (AEC) claimed that it would be a cheap way of generating electricity. Compared with fossil fuel power plants, nuclear power plants use very little fuel, so the cost is small, but it is made up for in other areas. The AEC was wrong. In fact, today, nuclear power plants cost just as much to build and run as coal plants do. Principle: When the nucleus of an atom is split, nuclear  a fuel called uranium, a relatively common material. Energy is released from uranium when an atom is split by a neutron. The uranium atom is split into two and as this happens energy is released in the form of radiation and heat. This nuclear reaction is called the fission process How Does a Nuclear Power Plant Work  Nuclear power plants are powered by Uranium. In a process known as nuclear fission, uranium atoms are split to produce large amount of energy which is eventually converted to heat. The enormous amount of heat created, boils the water to produce steam, which is used to rotate turbines. These turbines in-turn spin the shaft of the generator. As the generator gets into action, the coils of wire within the generator are spun in a magnetic field to produce electricity. A nuclear reactor maintains and controls the nuclear reaction within the plant to produce energy. There are various types of nuclear reactors, such as Pressurized Water Reactor (PWR), Boiling Water Reactor (BWR), Pressurized Heavy Water Reactor (PHWR), Advanced Gas-cooled Reactor (AGR), etc. Location of Nuclear Power Plants in India
Comming up Nuclear Plants in India
April-May Class XII Study of Electrical Motor Electric motors, both ac motors and dc motors, come in many shapes and sizes. Some are standardized electric motors for general-purpose applications. Other  electric motors are intended for specific tasks. In any case, electric motors should be selected to satisfy the dynamic requirements of the machines on which they are applied without exceeding rated electric motor temperature. Thus, the first and most important step in electric motor selection is determining load characteristics -- torque and speed versus time. Electric motor selection is also based on mission goals, power available, and cost. An induction machine is the most simple electrical machine from constructional point of view, in most of the cases. It can be classified into motor and generator.Induction machines work on induction principle, in other words it depends on Faraday's law of induction (i.e. when a conductor moves in a magnetic field, it gets some voltage(induced voltage). this voltage can set up current if construction permits and can set up its own magnetic field.). In this case it should be noted that moving in a magnetic field actually  makes the magnetic flux changing to the moving conductor(actually seems to be changing, from the view point of one who is moving), and this changing magnetic field causes voltage and current to be induced on the moving body.But if the magnetic filed is itself changing in nature, then it can induce voltage on a stationary conductor. This is the case for induction motor and generator. Motor remains stationary(rotor of the motor), a changing voltage (i.e. magnetic flux) is supplied to the stator and hence the rotor get some induced voltage because it remains stationary in changing magnetic field. This rotor voltage creates rotor current and rotor magnetic field(rotor flux), this rotor flux try to catch stator flux and thus rotor starts to rotate. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
