33369999 Summer Training Project Report on NTPC by Prateek Jain VIT University

SUMMER TRAINING REPORT

12th July to 21st August

Submitted By:-

Chetan Anand B.Tech 3rdyear G.N.I.T College

Certificate

This is to certify that CHETAN ANAND, student of 2007-2011,Batch of \

Electronics & Instrumentation branch in 3rd year of Greater Noida

Institute of Technology, Greater Noida has successfully completed his

industrial training at Badarpur Thermal Power Station- NTPC, New Delhi

for six weeks from 12th july to 21st august 2010. He has completed the

whole training as per the training report submitted by him.

Training In-charge

Badarpur Thermal Power Station NTPC, Badarpur New Delhi.

Contents

1. Acknowledgement 2. About the Company3. NTPC Overview4. Thermal Power Plant

Introduction Operation Functioning

5. Electricity Generation Process 6. Control & Instrumentation 7. Switch Gear 8. Switch Yard

Acknowledgement

With profound respect and gratitude, I take the opportunity to convey my thanks to complete the training here. I express gratitude to the Program Manager and other faculty members of Control & Instrumentation Department of SELECT of Greater Noida Institute of Technology for providing this opportunity to undergo industrial training at National Thermal Power Corporation, Badarpur, New Delhi.

I do extend my heartfelt thanks to Ms. Rachna Singh Bhal for providing me this opportunity to be a part of this esteemed organization.

I am extremely grateful to Mr. G.D.Sharma, Superintendent of Im-Plant Training at BTPS-NTPC, Badarpur for his guidance during whole training.

I am extremely grateful to all the technical staff of BTPS-NTPC for their co-operation and guidance that helped me a lot during the course of training. I have learnt a lot working under them and I will always be indebted of them for this value addition in me.

Finally, I am indebted to all whosoever have contributed in this report work and friendly stay at Badarpur Thermal Power Station, Badarpur, New Delhi.

ABOUT THE COMPANY

CORPORATE VISION

“A world class integrated power major, powering India's growth with increasing global presence.”

CORE VALUES:

BCOMIT

B- Business ethics

C- Customer focus

O- Organizational & professional pride

M- Mutual respect & trust

I- Innovation & speed

T- Total quality for excellence

NTPC Limited is the largest thermal power generating company of India, Public Sector Company. It was incorporated in the year 1975 to accelerate power development in the country as a wholly owned company of the Government of India. At present, Government of India holds 89.5% of the total equity shares of the company and the balance 10.5% is held by FIIs, Domestic Banks, Public and others. Within a span of 31 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country.

NTPC's core business is engineering, construction and operation of power generating plants and providing consultancy to power utilities in India and abroad.

The total installed capacity of the company is 31134 MW (including JVs) with 15 coal based and 7 gas based stations, located across the country. In addition under JVs, 3 stations are coal based & another station uses naphtha/LNG as fuel. By 2017, the power generation portfolio is expected to have a diversified fuel mix with coal based capacity of around 53000 MW, 10000 MW through gas, 9000 MW through Hydro generation, about 2000 MW from nuclear sources and around 1000 MW from Renewable Energy Sources (RES). NTPC has adopted a multi-pronged growth strategy which includes capacity addition through green field projects, expansion of existing stations, joint ventures, subsidiaries and takeover of stations.

NTPC has been operating its plants at high efficiency levels. Although the company has 18.79% of the total national capacity it contributes 28.60% of total power generation due to its focus on high efficiency. NTPC’s share at 31 Mar 2001 of the total installed capacity of the country was 24.51% and it generated 29.68% of the power of the country in 2008-09. Every fourth home in India is lit by NTPC. 170.88BU of electricity was produced by its stations in the financial year 2005-2006. The Net Profit after Tax on March 31, 2006 was INR 58,202 million. Net Profit after Tax for the quarter ended June 30, 2006 was INR 15528 million, which is 18.65% more than for the same quarter in the previous financial year. 2005).

Pursuant to a special resolution passed by the Shareholders at the Company’s Annual General Meeting on September 23, 2005 and the approval of the Central Government under section 21 of the Companies Act, 1956, the name of the Company "National Thermal Power Corporation Limited" has been changed to "NTPC Limited" with effect from October 28, 2005. The primary reason for this is the company's foray into hydro and nuclear based power generation along with backward integration by coal mining.

A graphical overview

NTPC Limited

Type Public

Founded 1975

HeadquartersDelhi, India

Key peopleR S Sharma, Chairman & Managing Director

IndustryElectricity generation

Products Electricity

RevenueINR 416.37 billion (2008)

Net incomeINR 70.47 billion (2008)

Employees23867 (2006)

Website http://www.ntpc.co.in

STRATEGIES

JOURNEY OF NTPC

NTPC was set up in 1975 with 100% ownership by the Government of India. In the last 30 years, NTPC has grown into the largest power utility in India.

In 1997, Government of India granted NTPC status of “Navratna’ being one of the nine jewels of India, enhancing the powers to the Board of Directors.

NTPC became a listed company with majority Government ownership of 89.5%.NTPC becomes third largest by Market Capitalization of listed companies.

The company rechristened as NTPC Limited in line with its changing business portfolio and transforms itself from a thermal power utility to an integrated power utility.

National Thermal Power Corporation is the largest power generation company in India. Forbes Global 2000 for 2008 ranked it 411th in the world. National Thermal Power Corporation is the largest power generation company in India. Forbes Global 2000 for 2008 ranked it 317th in the world.

NTPC has also set up a plan to achieve a target of 50,000 MW generation capacity.

NTPC has embarked on plans to become a 75,000 MW company by 2017.

NTPC is the largest power utility in India, accounting for about 20% of India’s installed capacity.

BADARPUR THEMAL POWER PLANT

1975 1975

1997 1997

2005 2005

20042004

2008 2008

2009 2009

2017 2017

2012 2012

Introduction

Classification

Functioning

INTRODUCTION

Power Station (also referred to as generating station or power plant) is an industrial facility for the generation of electric power. Power plant is also used to refer to the engine in ships, aircraft and other large vehicles. Some prefer to use the term energy center because it more accurately describes what the plants do, which is the conversion of other forms of energy, like chemical energy, gravitational potential energy or heat energy into electrical energy. However, power plant is the most common term in the U.S., while elsewhere power station and power plant are both widely used, power station prevailing in many Commonwealth countries and especially in the United Kingdom.

At the center of nearly all power stations is a generator, a rotating machine that converts Mechanical energy into Electrical energy by creating relative motion between a magnetic field and a conductor. The energy source harnessed to turn the generator varies widely. It depends chiefly on what fuels are easily available and the types of technology that the power company has access to.

In thermal power stations, mechanical power is produced by a heat engine, which transforms Thermal energy (often from combustion of a fuel) into rotational energy. Most thermal power stations produce steam, and these are sometimes called steam power stations. About 80% of all electric power is generated by use of steam turbines. Not all thermal energy can be transformed to mechanical power, according to the second law of thermodynamics. Therefore, there is always heat lost to the environment. If this loss is employed as useful heat, for industrial processes or district heating, the power plant is referred to as a cogeneration power plant or CHP (combined heat-and-power) plant. In countries where district heating is common, there are dedicated heat plants called heat-only boiler stations. An important class of power stations in the Middle East uses by-product heat for desalination of water.

CLASSIFICATION

By fuel

• Nuclear power plants use a nuclear reactor's heat to operate a steam turbine generator.

• Fossil fuelled power plants may also use a steam turbine generator or in the case of natural gas fired plants may use a combustion turbine.

• Geothermal power plants use steam extracted from hot underground rocks.

• Renewable energy plants may be fuelled by waste from sugar cane, municipal solid waste, landfill methane, or other forms of biomass.

• In integrated steel mills, blast furnace exhaust gas is a low-cost, although low-energy density, fuel.• Waste heat from industrial processes is occasionally concentrated enough to use for power generation, usually in a steam boiler and turbine.

By prime mover

• Steam turbine plants use the dynamic pressure generated by expanding steam to turn the blades of a turbine. Almost all large non-hydro plants use this system.

• Gas turbine plants use the dynamic pressure from flowing gases to directly operate the turbine. Natural-gas fuelled turbine plants can start rapidly and so are used to supply "peak" energy during periods of high demand, though at higher cost than base-loaded plants. These may be comparatively small units, and sometimes completely unmanned, being remotely operated. This type was pioneered by the UK, Prince town being the world's first, commissioned in 1959.

• Combined cycle plants have both a gas turbine fired by natural gas, and a steam boiler and steam turbine which use the exhaust gas from the gas turbine to produce electricity. This greatly increases the overall efficiency of the plant, and many new base load power plants are combined cycle plants fired by natural gas.

• Internal combustion Reciprocating engines are used to provide power for isolated communities and are frequently used for small cogeneration plants. Hospitals, office buildings, industrial plants, and other critical facilities also use them to provide backup power in case of a power outage. These are usually fuelled by diesel oil, heavy oil, natural gas and landfill gas.

• Micro turbines, Sterling engine and internal combustion reciprocating engines are low cost solutions for using opportunity fuels, such as landfill gas, digester gas from water treatment plants and waste gas from oil production.

FUNCTIONING

In a thermal power plant, one of coal, oil or natural gas is used to heat the boiler to convert the water into steam. The steam is used to turn a turbine, which is connected to a generator. When the turbine turns, electricity is generated and given

as output by the generator, which is then supplied to the consumers through high-voltage power lines.

Process of a Thermal Power Plant

Detailed process of power generation in a thermal power plant:

1) Water intake: Firstly, water is taken into the boiler through a water source. If water is available in a plenty in the region, then the source is an open pond or river.

If water is scarce, then it is recycled and the same water is used over and over again.

2) Boiler heating: The boiler is heated with the help of oil, coal or natural gas. A furnace is used to heat the fuel and supply the heat produced to the boiler. The increase in temperature helps in the transformation of water into steam.

3) Steam Turbine: The steam generated in the boiler is sent through a steam turbine. The turbine has blades that rotate when high velocity steam flows across them. This rotation of turbine blades is used to generate electricity.

4) Generator: A generator is connected to the steam turbine. When the turbine rotates, the generator produces electricity which is then passed on to the power distribution systems.

5) Special mountings: There is some other equipment like the economizer and air pre-heater.An economizer uses the heat from the exhaust gases to heat the feed water. An air pre-heater heats the air sent into the combustion chamber to improve the efficiency of the combustion process.

6) Ash collection system: There is a separate residue and ash collection system in place to collect all the waste materials from the combustion process and to prevent them from escaping into the atmosphere.Apart from this, there are various other monitoring systems and instruments in place to keep track of the functioning of all the devices. This prevents any hazards from taking place in the plant.

OPERATION

• Introduction• Steam Generator or Boiler• Steam Turbine• Electric Generator• Condenser

IntroductionThe operating performance of NTPC has been considerably above the national average. The availability factor for coal stations has increased from 85.03 % in 1997-98 to 90.09 % in 2006-07, which compares favourably with international

standards. The PLF has increased from 75.2% in 1997-98 to 89.4% during the year 2006-07 which is the highest since the inception of NTPC.

In Badarpur Thermal Power Station, steam is produced and used to spin a turbine that operates a generator. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser; this is known as a Rankine cycle. Shown here is a diagram of a conventional thermal power plant, which uses coal, oil, or natural gas as fuel to boil water to produce the steam. The electricity generated at the plant is sent to consumers through high-voltage power lines.The Badarpur Thermal Power Plant has Steam Turbine-Driven Generators which has a collective capacity of 705MW. The fuel being used is Coal which is supplied from the Jharia Coal Field in Jharkhand.Water supply is given from the Agra Canal.

Table: Capacity of Badarpur Thermal Power Station, (BTPS) New Delhi

There are basically three main units of a thermal power plant:

1. Steam Generator or Boiler

2. Steam Turbine

3. Electric Generator

We have discussed about the processes of electrical generation further. A complete detailed description of two (except 2) units is given further.

Coal is conveyed (14) from an external stack and ground to a very fine powder by large metal spheres in the pulverised fuel mill (16). There it is mixed with preheated air (24) driven by the forced draught fan (20). The hot air-fuel mixture is forced at high pressure into the boiler where it rapidly ignites. Water of a high purity flows vertically up the tube-lined walls of the boiler, where it turns into steam, and is passed to the boiler drum, where steam is separated from any remaining water. The steam passes through a manifold in the roof of the drum into the pendant super heater (19) where its temperature and pressure increase rapidly to around 200 bar and 540°C,

sufficient to make the tube walls glow a dull red. The steam is piped to the high pressure turbine (11), the first of a three-stage turbine process. A steam governor valve (10) allows for both manual control of the turbine and automatic set-point following. The steam is exhausted from the high pressure turbine, and reduced in both pressure and temperature, is returned to the boiler reheater (21). The reheated steam is then passed to the intermediate pressure turbine (9), and from there passed directly to the low pressure turbine set (6). The exiting steam, now a little above its boiling point, is brought into thermal contact with cold water (pumped in from theCooling tower) in the condenser (8), where it condenses rapidly back into water, creating near vacuum-like conditions inside the condensor chest. The condensed water is then passed by a feed pump (7) through a deaerator (12), and pre-warmed, first in a feed heater (13) powered by steam drawn from the high pressure set, and then in the economiser (23), before being returnedto the boiler drum. The cooling water from the condensor is sprayed inside a cooling tower (1), creating a highly visible plume of water vapour, before being pumped back to the condensor (8) in cooling water cycle. The three turbine sets are sometimes coupled on the same shaft as the three-phase electrical generator (5) which generates an intermediate level voltage (typically 20-25 kV). This is stepped up by the unit transformer (4) to a voltage more suitable for transmission (typically 250-500 kV) and is sent out onto the three-phase transmission system (3). Exhaust gas from the boiler is drawn by the induced draft fan (26) through an electrostatic precipitator (25) and is then vented through the chimney stack (27).

Steam Generator/Boiler

The boiler is a rectangular furnace about 50 ft (15 m) on a side and 130 ft (40 m) tall. Its walls are made of a web of high pressure steel tubes about 2.3 inches (60 mm) in diameter. Pulverized coal is air-blown into the furnace from fuel nozzles at the four corners and it rapidly burns, forming a large fireball at the center. The thermal radiation of the fireball heats the waterthat circulates through the boiler tubes near the boiler perimeter. The water circulation rate in the boiler is three to four times the throughput and is typically driven by pumps. As the water in the boiler circulates it absorbs heat and changes into steam at 700 °F (370 °C) and 3,200 psi (22.1MPa). It is separated from the water inside a drum at the top of the furnace. The saturated steam is introduced into superheat pendant tubes that hang in the hottest part of the combustion gases as they exit the furnace. Here the steam is superheated to 1,000 °F (540 °C) to prepare it for the turbine. The steam generating boiler has to produce steam at the high purity, pressure and temperature required for the steam turbine that drives the electrical generator. The generator includes the economizer, the steam drum, the chemical dosing equipment, and the furnace with its steam generating tubes and the superheater coils. Necessary safety valves are located at suitable points to avoid excessive boiler pressure. The air and flue gas path equipment include: forced draft (FD) fan, air preheater (APH), boiler furnace, induced draft (ID) fan, fly ash collectors (electrostatic precipitator or baghouse) and the flue gas stack.

For units over about 210 MW capacity, redundancy of key components is provided by installing duplicates of the FD fan, APH, fly ash collectors and ID fan with isolating dampers. On some units of about 60 MW, two boilers per unit may instead be provided.

Schematic diagram of a coal-fired power plant steam generator

Boiler Furnace and Steam Drum:Once water inside the boiler or steam generator, the process of adding the latent heat of vaporization or enthalpy is underway. The boiler transfers energy to the water by the chemical reaction of burning some type of fuel.The water enters the boiler through a section in the convection pass called the economizer. From the economizer it passes to the steam drum. Once the water enters the steam drum it goes down the down comers to the lower inlet water wall headers. From the inlet headers the water rises through the water walls and is eventually turned into steam due to the heat being generated bythe burners located on the front and rear water walls (typically). As the water is turned into steam/vapour in the water walls, the steam/vapour once again enters the steam drum. The steam/vapour is passed through a series of steam and water separators and then dryers inside the steam drum. The steam separators and dryers remove the water droplets from the steam and the cycle through the water walls is repeated. This process is known as natural circulation. The boiler furnace auxiliary equipment

includes coal feed nozzles and igniter guns, soot blowers, water lancing and observation ports (in the furnace walls) for observation of the furnace interior. Furnace explosions due to any accumulation of combustible gases after a tripout are avoided by flushing out such gases from the combustion zone before igniting the coal. The steam drum (as well as the superheater coils and headers) have air vents and drains needed for initial start-up. The steam drum has an internal device that removes moisture from the wet steam entering the drum from the steam generating tubes. The dry steam then flows into the superheater coils. Geothermal plants need no boiler since they use naturally occurring steam sources. Heat exchangers may be used where the geothermal steam is very corrosive or contains excessive suspended solids. Nuclear plants also boil water to raise steam, either directly passing the working steam through the reactor or else using an intermediate heat exchanger.As the steam is conditioned by the drying equipment inside the drum, it is piped from the upper drum area into an elaborate set up of tubing in different areas of the boiler. The areas known as superheater and reheater. The steam vapour picks up energy and its temperature is now superheated above the saturation temperature. The superheated steam is then piped through the main steam lines to the valves of the high pressure turbine.

Re-heaters:The function of the re-heater is to increase the temperature of the steamto 5400C thereby increasing the heat content of the stem. This is only employed in the 210MW units because of the greater demand for heat energy.

Economizer : Economizer reheats the boiler feed water before it is introduced into the drum by reusing the heat from the flue gases. This particular accessory increases the efficiency of the boiler. Steam enters at 247OC and leaves at 278OC. The water in the economizer flows in the upward direction thereby giving heat to the boiler feed water.

Electrostatic Precipitator: These are generally two plate type located between the boiler and the chimney. The precipitator is arranged for horizontal gas flow and is constructed with welded steel casing.

Boiler ParametersStem Temperature (in degree Celsius)1. Stem entering horizontal SH 3402. Stem leaving horizontal SH 4343. Stem entering final SH 5154. Stem leaving final SH 540

Design Parameters1. Capacity of boiler 700T/hrs2. Stem temperature leaving 540oC3. Pressure at SH outlet 137 kg/cm2

STEAM TURBINE

A steam turbine converts the heat energy of steam into mechanical energy and drives the generator. It uses the principle that the steam from a small opening attains high velocity. The velocity attained during expansion depends on the initial and final heat content of the steam. This difference between initial and final heat content represents the heat energy converted into kinetic energy.In the 210MW units there are three types of turbine. High Pressure Turbine(HPT) which works from super heated stem at 540oC, the stem after losing its energy is the again re-heated and is feed to Intermediate Pressure Turbine(IPT), the steam coming out of the IPT is then feed to Low Pressure Turbine(LPT). These turbine rotated around 3000 rpm(usually 2930-2970).

TURBINE AUXILLARIES

De-aerator:This component removes oxygen, carbon dioxide(CO2), ammonia(NH3) and other corrosive gases that are dissolved in the water to be sent to the boiler. The main function of the de-aerator is to minimize the amount of oxygen in the water so that there may be minimal corrosion in the boiler internals where the water has to flow through .

A steam generating boiler requires that the boiler feed water should be devoid of air and other dissolved gases, particularly corrosive ones, in order to avoid corrosion of the metal. Generally, power stations use a de-aerator to provide for the removal of air and other dissolved gases from the boiler feed water. A de-aerator typically includes a vertical, domed deaeration section mounted on top of a horizontal cylindrical vessel which serves as the de-aerated boiler feed water storage tank.

Boiler Feed Water De-aerator

There are many different designs for a de-aerator and the designs will vary from one manufacturer to another. The adjacent diagram depicts a typical conventional trayed de-aerator. If operated properly, most de-aerator manufacturers will guarantee that oxygen in the deaerated water will not exceed 7 ppb by weight (0.005 cm3/L).

Ejector:There are two 100% capacity ejectors whose purpose is to evacuate air and others non-condensing gases from condenser and maintain vacuum in the condenser, stem from de-aerator with 11 atm. headers as working medium for ejectors.

Electric GeneratorThe three turbine and the generator is connected with a single common shaft. So when the shaft is rotated magnetic flux changes thus producing electricity.The steam turbine-driven generators have auxiliary systems enabling them to work satisfactorily and safely. The steam turbine generator being rotating equipment generally has a heavy, large diameter shaft. The shaft therefore requires not only supports but also has to be kept in position while running. To minimize the frictional resistance to the rotation, the shaft has a number of bearings. The bearing shells, in which the shaft rotates, are lined with a low friction material like Babbitt metal. Oil lubrication is provided to further reduce the friction between shaft and bearing surface and to limit the heat generated.

Generator Reading (UCB-5)

1. Station battery volt 240V2. Turbine speed 2937 rpm3. Hydrogen purity 97.874. Generator 210MW5. Generator current 7900A6. Generator frequency 49Hz7. Field current 204x10A8. Field voltage 220V9. Stator water conductivity 280k-ohm-cm

Generator (210MW)

1. Maximum constant KVA rating 2470002. Maximum constant KW rating 2100003. Rated power factor 15.75 kv4. Rated terminal voltage 0.85pf in lag5. Rated speed 3000 rpm6. Stator current 9050A7. Stator volt 15750 v8. Direction of rotation anticlockwise

Rotor Cooling

1. Hydrogen Pressure 4.5 kg/cm2

2. Purity 97%3. Gas Volume 66m3

Stator Cooling

1. Water Pressure 3.5 kg/cm2

2. Quantity of water 130 m3/hr

CondenserThe surface condenser is a shell and tube heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from the low pressure turbine enters the shell where it is cooled and converted to condensate (water) by flowing over the tubes as shown in the adjacent diagram. Such condensers use steam ejectors or rotary motor-driven exhausters for continuous removal of air and gases from the steam side to maintain vacuum. A Typical Water Cooled CondenserFor best efficiency, the temperature in the condenser must be kept as low as practical in order to achieve the lowest possible pressure in the condensing steam. Since the condenser temperature can almost always be kept significantly below 100 C where the vapour pressure of water is much less than atmospheric pressure, the condenser generally works under vacuum. Thus leaks of noncondensible air into the closed loop must be prevented. Plants operating in hot climates may have to reduce output if their source of condenser cooling water becomes warmer; unfortunately this usually coincides with periods of high electrical demand for air conditioning. The condenser generally uses either circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once-through water from a

river, lake or ocean.

A typical water cooled condensor

Auxiliary Systems

Oil System:An auxiliary oil system pump is used to supply oil at the start-up of the steam turbine generator. It supplies the hydraulic oil system required for steam turbine's main inlet steam stop valve, the governing control valves, the bearing and seal oil systems, the relevant hydraulic relays and other mechanisms. At a preset speed of the turbine during start-ups, a pump driven by the turbine main shaft takes over the functions of the auxiliary system.

Generator Heat Dissipation:The electricity generator requires cooling to dissipate the heat that it generates. While small units may be cooled by air drawn through filters at the inlet, larger units generally require special cooling arrangements. Hydrogen gas cooling, in an oil-sealed casing, is used because it has the highest known heat transfer coefficient of any gas and for its low viscosity which reduces windage losses. This system requires special handling during start-up, with air in the chamber first displaced by carbon dioxide before filling with hydrogen. This ensures that the highly flammable hydrogen does not mix with oxygen in the air. The hydrogen pressure inside the casing is maintained slightly higher than atmospheric pressure to avoid outside air ingress. The hydrogen must be sealed against outward leakage where the shaft emerges from the casing. Mechanical seals around the shaft are installed with a very small annular gap to avoid rubbing between the shaft and the seals. Seal oil is used to prevent the hydrogen gas leakage to atmosphere. The generator also uses water cooling. Since the generator coils are at a potential of about 15.75kV and water is conductive, an insulating barrier such as Teflon is used to interconnect the water line and the generator high voltage windings. Demineralised water of low conductivity is used.

Generator High Voltage System : The generator voltage ranges from 10.5 kV in smaller units to 15.75 kV in larger units. The generator high voltage leads are normally large aluminum channels because of their high current as compared to the cables used in smaller machines. They are enclosed in well-grounded aluminum bus ducts and are supported on suitable insulators. The generator high voltage channels are connected to step-up transformers for connecting to a high voltage electrical substation (of the order of 220 kV) for further transmission by the local power grid. The necessary protection and metering devices are included for the high voltage leads. Thus, the steam

turbine generator and the transformer form one unit. In smaller units, generating at 10.5kV, a breaker is provided to connect it to a common 10.5 kV bus system.

Other Systems

Monitoring and Alarm systemMost of the power plant’s operational controls are automatic. However, at times, manual intervention may be required. Thus, the plant is provided with monitors and alarm systems that alert the plant operators when certain operating parameters are seriously deviating from their normal range.

Battery Supplied Emergency Lighting & Communication:A central battery system consisting of lead acid cell units is provided to supply emergency electric power, when needed, to essential items such as the power plant's control systems, communication systems, turbine lube oil pumps, and emergency lighting. This is essential for safe, damage-free shutdown of the units in an emergency situation.

CONTROL AND INSTRUMENTATION

This division basically calibrates various instruments and takes care of any faults occur in any of the auxiliaries in the plant.

This department is the brain of the plant because from the relays to transmitters followed by the electronic computation chipsets and recorders and lastly the controlling circuitry, all fall under this.

Instrumentation can be well defined as a technology of using instruments to measure and control the physical and chhemical properties of a material.Control and instrumentation has following labs:

1. Manometry lab

2. Protection and interlocks lab

3. Automation lab

4. Pyrometry Lab

Pressure measurement

Temperature measurement

Flow measurement

Control valves

5. Water treatment plant

6. Furnaces Safety Supervisory System Lab

Manometry lab

Transmitters - Transmitter is used for pressure measurements of gases and liquids, its working principle is that the input pressure is converted into electrostatic capacitance and from there it is conditioned and amplified. It gives an output of 4-20 ma DC. It can be mounted on a pipe or a wall. For liquid or steam measurement transmitters is mounted below main process piping and for gas measurement transmitter is placed above pipe.

Manometer - It’s a tube which is bent, in U shape. It is filled with a liquid. This device corresponds to a difference in pressure across the two limbs.

Bourden Pressure Gauge - It’s an oval section tube. Its one end is fixed. It is provided with a pointer to indicate the pressure on a calibrated scale. It is of two types : (a) Spiral type : for low pressure measurement and (b) Helical type : for high pressure measurement

Protection and Interlock Lab

Interlocking : It is basically interconnecting two or more equipments so that if one equipments fails other one can perform the tasks. This type of interdependence is also created so that equipments connected together are started and shut down in the specific sequence to avoid damage. For protection of equipments tripping are provided for all the equipments. Tripping can be considered as the series of instructions connected through OR GATE. When The main equipments of this lab are relay and circuit breakers. Some of the instrument uses for protection are:

RELAY : It is a protective device. It can detect wrong condition in electrical circuits by constantly measuring the electrical quantities flowing under normal and faulty conditions. Some of the electrical quantities are voltage, current, phase angle and velocity.

FUSES : It is a short piece of metal inserted in the circuit, which melts when heavy current flows through it and thus breaks the circuit. Usually silver is used as a fuse material because: a) The coefficient of expansion of silver is very small. As a result no critical fatigue occurs and thus the continuous full capacity normal current ratings are assured for the long time. b) The conductivity of the silver is unimpaired by the surges of the current that produces temperatures just near the melting point. c) Silver fusible elements can be raised from normal operating temperature to vaporization quicker than any other material because of its comparatively low specific heat.

Miniature Circuit Breaker : They are used with combination of the control circuits to. a) Enable the staring of plant and distributors. b) Protect the circuit in case of a fault. In consists of current carrying contacts, one movable and other fixed. When a fault occurs the contacts separate and are is stuck between them. There are three types of –

MANUAL TRIP THERMAL TRIP SHORT CIRCUIT TRIP.

Protection and Interlock System :

1. HIGH TENSION CONTROL CIRCUIT: For high tension system the control system are excited by separate D.C supply. For starting the circuit conditions should be in series with the starting coil of the equipment to energize it. Because if even a single condition is not true then system will not start. 2. LOW TENSION CONTROL CIRCUIT: For low tension system the control circuits are directly excited from the 0.415 KV A.C supply. The same circuit achieves both excitation and tripping. Hence the tripping coil is provided for emergency tripping if the interconnection fails.

Automation Lab

This lab deals in automating the existing equipment and feeding routes. Earlier, the old technology dealt with only (DAS) Data Acquisition System and came to be known as primary systems. The modern technology or the secondary systems are coupled with (MIS) Management Information System. But this lab universally applies the pressure measuring instruments as the controlling force. However, the relays are also provided but they are used only for protection and interlocks.This lab deals in automating the equipment and feeding routes. The automatic control system provide safe peration under all plant disturbances and component faliures.This lab universally applies the pressure measuring instruments as the controlling force. Once the control circuit can easily be designed with single chip having multiple. In the plant all control instruments are excited by 24V DC supply(4-20mA).The systems installed here in BTPS are old Russion systems these are ACS(Automatic Controll System) which are slowly being replaced by DCS(Digital Controll System ). In the present ACS system mosy of the decision making has to be done manually like opening or closing of any pressure valve.

Pyrometry Lab

Liquid in glass thermometer - Mercury in the glass thermometer boils at 340 degree Celsius which limits the range of temperature that can be measured. It is L shaped thermometer which is designed to reach all inaccessible places.

Ultra violet censor - This device is used in furnace and it measures the intensity of ultra violet rays there and according to the wave generated which directly indicates the temperature in the furnace.

Thermocouples - This device is based on SEEBACK and PELTIER effect. It comprises of two junctions at different temperature. Then the emf is induced in the circuit due to the flow of electrons. This is an important part in the plant.

RTD(Resistance temperature detector) - It performs the function of thermocouple basically but the difference is of a resistance. In this due to the change in the resistance the temperature difference is measured. In this lab, also the measuring devices can be calibrated in the oil bath or just boiling water (for low range devices) and in small furnace (for high range devices).

PRESSURE MEASUREMENT:

Pressure can be monitored by three types of basic mechanisms

Switches Gauges Transmitter type

For gauges we use Bourden tubes : The Bourdon Tube is a non liquid pressure measurement device. It is widely used in applications where inexpensive static pressure measurements are needed.

A typical Bourdon tube contains a curved tube that is open to external pressure input on one end and is coupled mechanically to an indicating needle on the other end, as shown schematically below.

Typical Bourdon Tube Pressure Gages

For Switches pressure swithes are used and they can be used for digital means of monitoring as swith being ON is referred as high and being OFF is as low.All the monitored data is converted to either Current or Voltage parameter.The Plant standard for current and voltage are as under

Voltage : 0 – 10 Volts range Current : 4 – 20 milliAmperes

We use 4mA as the lower value so as to check for disturbances and wire breaks.Accuracy of such systems is very high .

ACCURACY : + - 0.1 %The whole system used is SCADA based.Programmable Logic Circuits ( PLCs) are used in the process as they are the heardt of Instrumentation .

PressureElectricity

Start Level low Pressure in line Level High

High level pump Electricity

Stop Pressure

Electricity

BASIC PRESSURE CONTROL MECHANISM

TEMPERATURE MESUREMENT:

HL switch

LL switch

AND

OR

We can use Thernocouples or RTDs for temperature monitoringNormally RTDs are used for low temperatures.

Thermocoupkle selection depends upon two factors:

Temperature Range Accuracy Required

Normally used Thermocouple is K Type Thermocouple: Chromel (Nickel-Chromium Alloy) / Alumel (Nickel-Aluminium Alloy)This is the most commonly used general purpose thermocouple. It is inexpensive and, owing to its popularity, available in a wide variety of probes. They are available in the −200 °C to +1200 °C range. Sensitivity is approximately 41 µV/°C.

RTDs are also used but not in protection systems due to vibrational errors.

We pass a constant curre t through the RTD. So that if R changes then the Voltage also changes RTDs used in Industries are Pt100 and Pt1000

Pt100 : 0 0C – 100 Ω ( 1 Ω = 2.5 0C )Pt1000 : 0 0C - 1000ΩPt1000 is used for higher accuracyThe gauges used for Temperature measurements are mercury filled Temperature gauges. For Analog medium thermocouples are used And for Digital medium Switches are used which are basically mercury switches.

FLOW MEASUREMENT:

Flow measurement does not signify much and is measured just for metering purposes and for monitoring the processes

ROTAMETERS:A Rotameter is a device that measures the flow rate of liquid or gas in a closed tube. It is occasionally misspelled as 'rotometer'.

It belongs to a class of meters called variable area meters, which measure flow rate by allowing the cross sectional area the fluid travels through to vary, causing some measurable effect.A rotameter consists of a tapered tube, typically made of glass, with a float inside that is pushed up by flow and pulled down by gravity. At a higher flow rate more area (between the float and the tube) is needed to accommodate the flow, so the float rises. Floats are made in many different shapes, with spheres and spherical ellipses being the most common. The float is shaped so that it rotates axially as the fluid passes. This allows you to tell if the float is stuck since it will only rotate if it is not. For Digital measurements Flap system is used. For Analog measurements we can use the following methods :

Flowmeters Venurimeters / Orifice meters Turbines Massflow meters ( oil level ) Ultrasonic Flow meters Magnetic Flowmeter ( water level )

Selection of flow meter depends upon the purpose , accuracy and liquid to be measured so different types of meters used.Turbine type are the simplest of all.They work on the principle that on each rotation of the turbine a pulse is generated and that pulse is counted to get the flow rate.

VENTURIMETERS :

Referring to the diagram, using Bernoulli's equation in the special case of incompressible fluids (such as the approximation of a water jet), the theoretical pressure drop at the constriction would be given by (ρ/2)(v2

2 - v12).

And we know that rate of flow is given by:Flow = k √ (D.P)Where DP is Differential Presure or the Pressure Drop.

CONTROL VALVES:

A valve is a device that regulates the flow of substances (either gases, fluidized solids, slurries, or liquids) by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but usually are discussed separately.

Valves are used in a variety of applications including industrial, military, commercial, residential, transportation. Plumbing valves are the most obvious in everyday life, but many more are used.

Some valves are driven by pressure only, they are mainly used for safety purposes in steam engines and domestic heating or cooking appliances. Others are used in a controlled way, like in Otto cycle engines driven by a camshaft, where they play a major role in engine cycle control.

Many valves are controlled manually with a handle attached to the valve stem. If the handle is turned a quarter of a full turn (90°) between operating positions, the valve is called a quarter-turn valve. Butterfly valves, ball valves, and plug valves are often quarter-turn valves. Valves can also be controlled by devices called actuators attached to the stem. They can be electromechanical actuators such as an electric motor or solenoid, pneumatic actuators which are controlled by air pressure, or hydraulic actuators which are controlled by the pressure of a liquid such as oil or water.

So there are basically three types of valves that are used in power industries besides the handle valves. They are :

Pneumatic Valves – they are air or gas controlled which is compressed to turn or move them

Hydraulic valves – they utilize oil in place of Air as oil has better compression

Motorised valves – these valves are controlled by electric motors

Water Treatment Plant

Since there is continuous withdrawal of steam and continuous return of condensate to the boiler, losses due to blow-down and leakages have to be made up for so as to maintain the desired water level in the boiler steam drum. For this, continuous make-up water is added to the boiler water system. The impurities in the raw water input to the plant generally consist of calcium and magnesium salts which impart hardness to the water. Hardness in the make-up water to the boiler will form deposits on the tube water surfaces which will lead to overheating and failure of the tubes. Thus, the salts have to be removed from the water and that is done by a Water Treatment Plant or Demineralised Water (DM).

A DM plant generally consists of cation, anion and mixed bed exchangers. The final water from this process consists essentially of hydrogen ions and hydroxide ions which is the chemical composition of pure water. The DM water, being very pure, becomes highly corrosive once it absorbs oxygen from the atmosphere because of its very high affinity for oxygen absorption. The capacity of the DM plant is dictated by the type and quantity of salts in the raw water input. However, some storage is essential as the DM plant may be down for maintenance. For this purpose, a storage tank is installed from which DM water is continuously withdrawn for boiler make-up. The storage tank for DM water is made from materials not affected by corrosive water, such as PVC. The piping and valves are generally of stainless steel. Sometimes, a steam blanketing arrangement or stainless steel doughnut float is provided on top of the water in the tank to avoid contact with atmospheric air. DM water make-up is generally added at the steam space of the surface condenser (i.e., the vacuum side). This arrangement not only sprays the water but also DM water gets deaerated, with the dissolved gases being removed by the ejector of the condenser itself.

FURNACE SAFEGUARD SUPERVISORY SYSTEM

FSSS is also called as Burner Management System (BMS). It is a microprocessor based programmable logic controller of proven design incorporating all protection facilities required for such system. Main objective of FSSS is to ensure safety of the boiler.

The 95 MW boilers are indirect type boilers. Fire takes place in front and in rear side. That’s why it’s called front and rear type boiler. The 210 MW boilers are direct type boilers (which mean that HSD is in direct contact with coal) firing takes place from the corner. Thus it is also known as corner type boiler.

IGNITER SYSTEM

Igniter system is an automatic system, it takes the charge from 110kv and this spark is brought in front of the oil guns, which spray aerated HSD on the coal for coal combustion. There is a 5 minute delay cycle before igniting, this is to evacuate or burn the HSD. This method is known as PURGING.

PRESSURE SWITCH

Pressure switches are the devices that make or break a circuit. When pressure is applied, the switch under the switch gets pressed which is attached to a relay that makes or break the circuit. Time delay can also be included in sensing the pressure with the help of pressure valves.

1. Manual valves (tap)2. Motorized valves (actuator) – works on motor action3. Pneumatic valve (actuator) _ works due to pressure of compressed air4. Hydraulic valve

SWITCHGEARThe term switchgear, used in association with the electric power system, or grid, refers to the combination of electrical disconnects, fuses and/or circuit breakers

used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream. Switchgear is already a plural, much like the software term code/codes, and is never used as switchgears.The very earliest central power stations used simple open knife switches, mounted on insulating panels of marble or asbestos. Power levels and voltages rapidly escalated, making open manually-operated switches too dangerous to use for anything other than isolation of a de-energized circuit. Oil-filled equipment allowed arc energy to be contained and safely controlled. By the early 20th century, a switchgear line-up would be a metal-enclosed structure with electrically-operated switching elements, using oil circuit breakers. Today, oil-filled equipment has largely been replaced by air-blast, vacuum, or SF6 equipment, allowing large currents and power levels to be safely controlled by automatic equipment incorporating digital controls, protection, metering and communications.Typically switchgear in substations is located on both the high voltage and the low voltage side of large power transformers. The switchgear located on the low voltage side of the transformers in distribution type substations, now are typically located in what is called a Power Distribution Center (PDC). Inside this building are typically smaller, medium-voltage (~15kV) circuit breakers feeding the distribution system. Also contained inside these Power Control Centers are various relays, meters, and other communication equipment allowing for intelligent control of the substation.For industrial applications, a transformer and switchgear line-up may be combined in one housing, called a unit substation.

HousingSwitchgear for low voltages may be entirely enclosed within a building. For transmission levels of voltage (high voltages over 66 kV), often switchgear will be mounted outdoors and insulated by air, though this requires a large amount of space. Gas- [or oil- or vacuum-] insulated switchgear used for transmission-level voltages saves space, although it has a higher equipment cost.At small substations, switches may be manually operated, but at important switching stations on the transmission network all devices have motor operators to allow for remote control.A piece of switchgear may be a simple open air isolator switch or it may be insulated by some other substance. An effective although more costly form of switchgear is "gas insulated switchgear" (GIS), where the conductors and contacts are insulated by pressurized (SF6) sulfur hexafluoride gas. Other common types are oil [or vacuum] insulated switchgear.

Circuit breakers are a special type of switchgear that are able to interrupt fault currents. Their construction allows them to interrupt fault currents of many hundreds or thousands of amps. The quenching of the arc when the contacts open requires careful design, and falls into four types:Oil circuit breakers rely upon vaporisation of some of the oil to blast a jet of oil through the arc.Gas (SF6) circuit breakers sometimes stretch the arc using a magnetic field, and then rely upon the dielectric strength of the SF6 to quench the stretched arc.Vacuum circuit breakers have minimal arcing (as there is nothing to ionise other than the contact material), so the arc quenches when it is stretched a very small amount (<2-3 mm). Vacuum circuit breakers are frequently used in modern medium-voltage switchgear to 35,000 volts.Air circuit breakers may use compressed air to blow out the arc, or alternatively, the contacts are rapidly swung into a small sealed chamber, the escaping of the displaced air thus blowing out the arc.Circuit breakers are usually able to terminate all current flow very quickly: typically between 30 ms and 150 ms depending upon the age and construction of the device.A single line-up may incorporate several different types of devices, for example, air-insulated bus, vacuum circuit breakers, and manually-operated switches may all exist in the same row of cubicles.Ratings, design, specifications and details of switchgear are set by a multitude of standards. In North America mostly IEEE and ANSI standards are used, much of the rest of the world uses IEC standards, sometimes with local national derivatives or variations.Functions One of the basic functions of switchgear is protection, which is interruption of short-circuit and overload fault currents while maintaining service to unaffected circuits. Switchgear also provides isolation of circuits from power supplies. Switchgear also is used to enhance system availability by allowing more than one source to feed a load.To help ensure safe operation sequences of switchgear, trapped key interlocking provides predefined scenarios of operation. James Harry Castell invented this technique in 1922. For example, if only one of two sources of supply is permitted to be connected at a given time, the interlock scheme may require that the first switch must be opened to release a key that will allow closing the second switch. Complex schemes are possible.

SWITCHYARDSwitchyard forms an integral part of any power plant i.e. Industrial CPP, Thermal Power Utilities, Gas Turbines based power plants or Hydel power plants. These

power plants have their main plant equipment integral controls (Boiler / Turbine / Gas Turbine / Hydro Turbine) as well as plant DCS System (BoP / Station C & I). While the entire power plant is integrated at the DCS level, true unification is achieved by incorporating / integrating switchyard controls (SCADA) also in the plant DCS.NTPC has incorporated switchyard SCADA on IBS hardware (Multibus compatible) and integrated with main plant DCS in a few projects. With the Technical Collaboration Agreement for the state-of-the art max DNA system, NTPC is now well position to provide this unification on the same platform as the plant level DCS system.The Supervisory control and data acquisition system (SCADA) of switchyard consists of Operator Stations, Engineer's Stations, Historical Storage, Computers and associated peripherals and the switchyard bay control systems interconnected through a high speed network . The system constitutes several operator work stations and engineer's work station with high resolution Color display monitors, touch screen, function key board, mouse, track ball and printers.The system collects digital and analog information available throughout the plant and presents information in various graphic displays, alarms, logs, reports. The operator can perform control via CRT.