NTPC Training Report

INDUSTRIAL TRAINING

REPORT

CONTROL AND

INSTRUMENTATION

NTPC , SHAKTINAGAR

ACKNOWLEDGEMENT

I convey my gratitude and sincere acknowledgement to Mr

NIRMAL SHARMA (AGM, C&I DEPARTMENT) for his

kind permission, enabling me to undergo training at C&I LAB. I express my deep sense of gratitude to Mr S.KACHHWAHA (Manager) and Mr A.K.AHMED (Assistant Engineer) for his guidance and kind help extended to me in order to successfully complete my training by providing with adequate information & all required inputs.

I would like to thank them for providing me technical knowledge and

arranging introductory sessions for innovative and in depth understanding of the working procedures.

CONTENTS

TOPICS

•MAJOR C&I SYSTEMS i.e. SG & TG packages

•FUNCTIONS OF C&I DEPARTMENT

•ABOUT MAXDNA SYSTEMS USA

ABOUT NTPC

POWER GENERATION

Presently, NTPC generates power from Coal and Gas. With an installed capacity of 31,704 MW, NTPC is the largest power generating major in the country. It has also diversified into hydro power, coal mining, power equipment manufacturing, oil & gas exploration, power trading & distribution. With an increasing presence in the power value chain, NTPC is well on its way to becoming an “Integrated Power Major.” NTPC has been recently accorded ”MAHARATAN” Status by honourable GOVERNMENT OF INDIA.

While leading the nation’s power generation league, NTPC has remained committed to the environment. It continues to take various pro-active measures for protection of the environment and ecology around its projects.

NTPC was the first among power utilities in India to start Environment Impact Assessment (EIA) studies and reinforced it with Periodic Environmental Audits.

NTPC is the largest thermal power generating company of India .A Public sector Company wholly owned by government of India. It was incorporated in the year 1975 to accelerate power development in the country. Within a span of 30 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country. Contributing 26% of the country’s entire power generation. NTPC today lights up every fourth bulb in the country.With ambitious growth plans to become a 56000MW power company by 2017, NTPC the largest power utility of India has already diversified into hydro sector. 18 NTPC stations have already been accredited with the ISO 14001 certification. In keeping with its well focused environment protection policy, NTPC has set up a “Centre for Power Efficiency and Environmental protection” (CENPEEP) which functions as a resource centre for development and dissemination of latest technologies in environmental management. 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 32 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country.

Coal Stations

S.No Coal based State Commissioned Capacity_(MW) 1. Singrauli Uttar Pradesh 2,000 2. Korba Chattisgarh 2,100 3. Ramagundam Andhra Pradesh 2,600 4. Farakka West Bengal 1,600 5. Vindhyachal Madhya Pradesh 3,260@

6. Rihand Uttar Pradesh 2,000 7. Kahalgaon Bihar 840@

8. Dadri Uttar Pradesh 840 9. Talcher Kaniha Orissa 3,000 10. Unchahar Uttar Pradesh 840@

11. Talcher Thermal Orissa 460 12. Simhadri Andhra Pradesh 1,000 13. Tanda Uttar Pradesh 440

Total (Coal) 20,480

@Capacity presently under implementation Vindhyachal 1000 MW

Unchahar 210 MW

Gas/Liquid Fuel Stations

s.no Gas based State Commissioned Capacity_(MW) 14. Anta Rajasthan 413

15. Auraiya Uttar Pradesh 652 16. Kawas Gujarat 645 17. Dadri Uttar Pradesh 817 18. Jhanor-Gandhar Gujarat 648 19. Kayamkulam Kerala 350 20. Faridabad Haryana 430

Total (Gas) 3,955

Grand Total (Coal + Gas + JV) 23,749

ABOUT

NTPC SHAKTINAGAR

Shaktinagar Super Thermal Power station is one of the

most prestigious flagships of NTPC striving ahead to bridge the country generation gap especially in the western region. NTPC is the sixth largest thermal power generator in the world and the second most efficient utility in terms of capacity utilization based on data of 1998.

The station is located in Singrauli district in MP in the north-western side of the country. It has secured ISO 14001 and ISO 9002 certificate in the field of environment and power generation but also in various other fields. On November 2009, it made glorious achievement by ensuring production up to 3260 MW. By next few months, it adds 1000 MW more to its capacity (i.e. 4260 MW)

As a 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 Vindhyachal super thermal power project is one of the most prestigious flagships of NTPC striving ahead to bridge the country generation gap especially in the western region.

The station is located in Sidhi district in MP in the northwestern side of the country. It has secured ISO 14001 and ISO 9002 certificate in the field of environment and power generation but also in various other fields. On September 2002 it made glorious achievement by ensuring production up to 2260 MW. By next 06 months it adds 1000MW more to its capacity (3260MW). Work for Stage-III is going on in full swing. The erection work has been completed before scheduled.

TECHNICAL SPECIFICATION

ABOUT NTPC VINDHYACHAL

TYPE OF STATION - THERMAL

STATION CAPACITY - STAGE I 6 x 210 STAGE II 2 X 500 STAGE III 2 X 500 STAGE IV 2 X 500 (UNDER CONSTRUCTION) FUEL - COAL

COAL SOURCE - NIGHAI (NCL) TRANSPORTATION - BY RAIL

COOLING WATER SOURCE - RIHAND RESERVIOR

ASH DISPOSAL - RIHAND RESERVIOR CHIMNEY – FOR 210 MW PLANT – 210m FOR 500 MW PLANT – 265m

PLANT AREA - 90-200 ACRES

SOURCES FOR RAW MATERIALS

COAL SOURCE

Northern coalfields limited (NCL) mines at Dudhichua (7Km) and Nigahi (10Km) and Jayant (5Km).

FUEL OIL SOURCE

Indian oil corporation (IOC) COLD (customer operated lubricant and oil deposit) at Jayant.

WATER SOURCE

Discharge canal of Singrauli super thermal power station.

BENEFICIARY STATES

Madhya Pradesh, Chattisgarh, Maharastra, Gujarat, Daman & Diu and Dadar & Nagerhaveli.

BASIC POWER PLANT CYCLE

The thermal (steam) power plant uses a dual (vapor + liquid) phase cycle. It is a closed cycle to enable the working fluid (water) to be used again and again. The cycle used is “Ranking Cycle” modified to include super heating of steam, regenerative feed water heating and reheating of steam Figure 1A shows this cycle and is self explanatory.

WORKING OF A THERMAL

POWER PLANT

COAL TO STEAM

Coal from the coal wagons is unloaded in the coal handling plant. This Coal is transported up to the raw coal bunkers (1) with the help of belt conveyors. Coal is transported to Bowl Mills (3) by Coal feeders (2) the coal is pulverized in the Bowl Mill, where it is ground to a powder form. The mill consists of a round metallic table on which coal particles fall. This table is rotated with the help of a motor. There are three large steel rollers which are spaced 120 apart. When there is no coal, these rollers does not rotate but when the coal is fed to the table it packs up between roller and the table and this forces the rollers to rotate. Coal is crushed by the crushing action between the rollers and rotating table. This crushed coal is taken away to the furnace through coal pipes (4) with the help of hot and cold air mixture from P.A. Fan (5). P.A. Fan taken atmospheric

air, a part of which is sent to Air preheaters (7) for heating while a part goes directly to the mill for temperature control. Atmospheric air from F.D. Fan (18) is heated in the air heaters (7) and sent to the furnace (6) as combustion air. . Water from the boiler feed pump passes through economizer (8) and reaches the boiler drum (9). Water from the drum passes through down comers and goes to bottom ring header. Water from the bottom ring header is divided to all the four sides of the Furnace. Due to heat and the density difference the water rises up in the water wall tubes (12). Water is partly converted to steam as it rises up in the furnace. This steam and water mixture is again taken to the boiler drum (9) where the steam is separated from water. Water follows the same path while the steam is sent to super heaters for superheating. The super heaters are located inside the furnace and the steam is superheated (540°C) and finally it goes to turbine. Flue gases from the furnace is extracted by induced draft fan (14) which maintains balance draft in the furnace (-5 to -10mm of wcl) with forced draft fan (18). These flue gases emits their heat

energy to various super heaters in the pant house (15) and finally passes through air preheaters (7)and goes to electrostatic precipitator (16) where the ash particles are extracted. Electrostatic precipitator consists of metal plates which are electrically charged. Ash particles are attracted on to these plates, so that they do not pass through the chimney (17) to pollute the atmosphere. Regular mechanical hammers blows cause the accumulation of ash to fall to the bottom of the precipitator where they are collected in a hopper for disposal. This ash is mixed with water to form slurry and is pumped to ash pond.

As can be seen from figure 2, from the boiler, a steam pipe (1) conveys steam to the turbine through a stop valve (which can be used to shut off steam in an emergency) and through control valves (2) that automatically regulate the supply of steam to the turbine. Stop valve and control valves are located in a steam chest and a governor (3), driven from the main turbine shaft (4), operates the control valves to regulate the amount of steam used (This depends upon the speed of the turbine and the amount of electricity required from the generator).

Steam from the control valves enters the high pressure cylinder of the turbine, where it passes through a ring of stationary blades (5) fixed to the cylinder wall (6). These act as nozzles and direct the steam into a second. Ring of moving blades (7) mounted. On a disc secured to the turbine shaft. This second ring turns the shafts as a result of the force of the steam. The stationary and moving blades together constitute a ‘stage’ of the turbine and in practice many stages are necessary, so that the cylinder contains a number of rings of stationary blades with rings of moving blades arranged between them. The

steam passes through each stage in turn until it reaches the end of the high pressure cylinder and in its passage some of its heat energy is changed into mechanical energy.

The steam leaving the high pressure cylinder goes back to the boiler for reheating (8) and returns by a further pipe (9) to the intermediate pressure cylinder. Here it passes through another series of stationary and moving blades.

Finally, the steam is taken to the low pressure cylinders, each of which it enters at the centre (10) flowing outwards in opposite directions through the rows of turbine blades - an arrangement known as double flow - to the extremities of the cylinder. As the steam gives up its heat energy to drive the turbine, its temperature and pressure fall and it expands. Because of this expansion the blades are much larger and longer towards the low pressure ends of the turbine.

The turbine shaft usually rotates at 3,000 revolutions per minute. This speed is determined by the frequency of the electrical system used in this country and is the speed at

which a 2- pole generator must be driven to generate alternating current at a frequency of 50 cycles per second.

When as much energy as possible has been extracted from the steam it is exhausted directly to the condenser. This runs the length of the low pressure part of the turbine and may be beneath or on either side of it. The condenser consists of a large vessel containing some 20,000 tubes, each about 25mm in diameter. Cold water from the river, estuary, sea or cooling tower is circulated through these tubes and as the steam from the turbine passes round them it is rapidly condensed into water condensate. Because water has a much smaller comparative volume than steam, a vacuum is created in the condenser. This allows the steam to reduce down to pressure below that of the normal atmosphere and more energy can be utilized.

From the condenser, the condensate is pumped through low pressure heaters by the extraction pump, after which its pressure is raised to boiler pressure by the boiler feed

pump. It is passed through further feed heater to the economizer and the boiler for reconversion into steam. Where the cooling water for power stations is drawn from large rivers, estuaries or the coast, it can be returned directly to the source after use. Power status situated on smaller rivers and inland do not have such vast water resources available, so the cooling water is passed through cooling towers (where its heat is removed by evaporation) and re-used.

A power station generating 2,000,000 kilowatts (KW) of electricity requires about 2,27,500 cubic meters pf water an hour for cooling purposes. Where cooling towers are used, about one hundredth part of the cooling water evaporates and a certain amount is returned to its source to carry away any impurities that collect. Most of it

however is recirculated. .

The thermal power plant generates electricity using steam which is generated inside boiler by burning coal or oil.

Firstly, the coal is sent to the bunkers of a RC (Raw Coal) feeder from which it is sent to pulverisers at a controlled rate. The pulveriser has a grinder and three rollers at a distance of 2.5mm rotating in opposite directions. The powdered coal (of size less than or equal to 2.5mm) is sent to furnace through pipes. The coal is

fed in through pipes in four directions so as to maintain the temp. inside boiler homogeneous. The coal is sent to furnace with the help of PA fans (Primary Air Fans).

The igniter ignites the coal which is coming inside the furnace in such a way so that the direction of air through PA fan is tangent to an imaginary circle. This helps in making hot air in shape of a turbulent like structure which saves the furnace from damage due to uneven heating on any part of furnace.

Another fan called FD fan (Forced Draft Fan) is used for secondary air i.e. excess air required for combustion. The furnace walls have water pipes which absorb the heat of combustion and changes water to water vapour. The furnace has a goose shaped structure which saves the platen super heater pipes from melting due to direct heat produced from combustion of coal. The steam from down comer goes to drum which consists of a turbo separator. The steam and water gets separated out and the water is

sent to water walls through risers. The drum has an important role as it saves the turbine from water which causes corrosion and thus passes only dry steam.

The dry steam is then passed through LTSH (Low Temperature Super Heater) and then to platen super heater for gaining excess heat. This steam is sent to HPT (High Pressure Turbine) where it has a temp. of 540 degree Celsius and a pressure of 140-145 kg/cm2.

After doing work (rotating turbine) it has a temp. of 350 degree Celsius and a pressure of 40 kg/c m2 . This steam, CRH (Cold Reheat) is passed through reheater and then to final superheater and is called HRH (Hot Reheat). The steam now has a temp. of 540 degree Celsius and a pressure of 38 kg/c m2 and passed through IPT (Intermediate Pressure Turbine).

Then the steam is passed through LPT (Low Pressure Turbine) with 7.5-8 kg/cm2 and 350- 370 degree Celsius of temp. All the three turbines have a common shaft which is connected to generator from which electricity is produced. The steam is passed through cooled water in tubes where a pressure of 0.9 atm. is being maintained so that the steam flows in a single direction.

The cooled steam is collected in a large container called hot well decause the water droplets collected is still hot. This hot water is extracted through CEP (Condensate

Extraction Pump) to drain cooler where it has a temp. of 40 degree Celsius and a pressure of 22 kg/c m2 . This is passed through LP1 ,LP2 ,LP3 (Low Pressure heaters) with 50, 55 and 60 degree Celsius of temp. respectively. Now, it is passed from deareator where dissolved harmful gases such as sulphur dioxides are removed and then passed to feed water storage tank. The BFP’s (Boiler Feed Pump) are used to send this to HPH (High Pressure Heaters) at a pressure of 190-195 kg/cm2. The BFP consists of two parts namely booster pump and main pump. The HPH output is connected to economisers and then to drum. The above cycle repeats for generation of electricity.

TECHNICAL TERMINOLOGY

RC FEEDER

The function is to decide amount of coal (i.e. powdered coal) to be given in the furnace for heating.

Considering the case if the amount of coal given to furnace is more than required then as a result due to more heating more steam will be produced. Then due to more steam

more pressure will be generated. Here we use two types of valves:-1) Electromotive relief valve

2) Mechanical safety valve

Here when the pressure in the furnace is more than the set point then the valve get

opened and the steam is released in the atmosphere until the pressure drops to the set point and then the valve gets closed.

But steam loss is more in mechanical safety valve thus, electromotive relief valve is introduced.

BOILER LOAD INDEX

It is the index in which load of boiler is indicated.

Load of boiler means the amount of coal which is being burnt in the furnace.

FEEDER

The crushed raw coal is delivered from the bunkers to the individual, which in these feed the coal at a controlled rate to the pulverisers. In order to avoid overloading the pulverisation motor due to overfeeding and interrupting circuits should be used to reduce coal feed. If the motor become overloaded we start the coal feed again to make motor load normal.

PROCESS DELAY

Suddenly when there is pressure drop, then to raise the steam pressure to set point we have to give more amount of coal (to produce more steam). Now it takes time to raise the steam pressure after giving the coal to furnace (as it takes some time to produce steam). This time is taken is the delay generated known as process delay.

So process delay is the delay so as to have the steam pressure being raised to set point when we have to add coal in furnace due to pressure drop.

PRESSURE VARIATION

When there is a sudden pressure drop we can obviously say that there is pressure variation in the steam pressure from the set point (i.e. desired pressure).

LOAD CUTOFF

When the load of the boiler is more than the desired then this situation is dangerous.

Now to overcome this condition we use load cut-off which stops the connection of load and boiler i.e. cut-off of load is done for prevention.

There 2 types of pressure in consideration:-1) Throttle pressure

GRID BALANCING (Reduction of grid balancing)

1) RGMO – Restricted governing mode of control 2) FGMO – Free governing mode of control

Nowadays, RGMO is mostly used instead of FGMO. Now we consider the case when steam is given to the turbine, then steam does work and as a result turbine waves and thus rotor moves. The rotor waves at constant speed. Now initially steam does work mechanically and thus rotor moves. As a result magnetic field is generated. Due to thismagnetic field a current is generated and thus electricity is produced.

As the process starts from initial state we observe that it rises slowly and reaches to the set or desired point value.

LARGE VIDEO SCREEN (LVS)

It is the screen on which various parameters used in the process are displayed with their value.

ENGINEERING WORK STATION(EWS)

It is used by engineers to change/alter the limit or range of any instrument

TYPES OF FAN :

1)

Forced Draft (FD) Fan : Its function is to enable easy combustion of grounded coal in furnace. It sucks from the atmospheric air which gets heated in the air heaters and then sent to the boiler .It also supplies hot air to PA Fan if required as per the atmospheric conditions.

2)

Induced Draft (ID) Fan: The air heater receives heat from the boiler and hence the air accompanied there contains a huge amount of ash. This air is then passed through ESP and finally exhausted through the chimney with the help of ID fans.

3)

Primary Air (PA) Fan: Its function is to blow the crushes coal from ball mill to furnace through pipes. It operates using three type of air:- hot air, cold air and atmospheric air.

ELECTROSTATIC PRECIPITATOR

Here fly ash is separated from flue gas and then through ash hammering ash is collected and then passed through a system which is of two

types:-1) Wet system: - The dry ash is mixed with water to form slurry and then with ash slurry pump this slurry is sent to ash deck.

2) Dry fly ash system: - In this system no water is mixed with ash and the obtained Dry ash is given to cement / brick industries.

MAJOR

C&I

SYSTEMS

INCLUDED UNDER MAIN PLANT

i.e. SG & TG

The SG & TG C&I systems are based on state of the art of the microprocessor technology with CRT/KBD operation facilities. Operation through back up conventional

control devices is also possible. These C&I systems are procured under the respective main plant package i.e. SG/TG package.

THE SG-C&I SYSTEM

The SG-C&I system includes the following microprocessor based

systems:-1. Furnace safeguard supervisory system for purging, automatic firing, flame monitoring, sequential start-up and shut down of mills etc.

2. Secondary air damper control system 3. Auxiliary PDRS control system

4. Soot boiler control system 5. Coal feeder controls

7. Furnace temp. Probes Each of these functional blocks is provided as independent systems which are connected through redundant system bus to achieve integrated CRT/KBD operation & monitoring.

THE TG-C&I SYSTEM

The TG-C&I system includes the following functional

blocks:-1. EHG control system

2. Automatic Turbine Run Up System (ATRS) 3. HP-LP bypass control system

4. Turbine Stress Control System (TSCS) 5. Automatic Turbine Testing System (ATT) 6. Turbine protection system

7. Turbine Supervisory Instruments (TSI) Except for TSI, all other functional blocks are connected through redundant system bus to achieve integrated CRT/KBD operation & monitoring.

FUNCTIONS OF C&I

DEPARTMENT

Control and instrumentation in any process industry, can be compared to the nerve system in the human being. The way the nerve system controls the operation of various limbs of human beings, C&I in the same way controls and operates various motors, pumps, etc and thus helps us to achieve our targets.

C&I, as the name indicates, is a branch in engineering which deals with various measurement, indication, transmission and control in different technical field. The term instrument means “A device or combination of devices used directly or indirectly to measure and display a variable.” Instrumentation is a measurement of various parameters with comparison to set standards. In industries and process plants, Instrumentation makes use of various measuring components designed to suit the process and the purpose. As some of the big industries and process plant need to control different process variable from a remote distance control room, the further measuring, transmitting, indicating, recording and innovative.

The main work of C&I department is to observe, control and manipulate electrical as well as non-electrical quantities like temperature, pressure, vibrations etc. So first these signals are converted into digital signals by “A to D ” convertors. These are combinations of microprocessors and microcontrollers which contain certain logic coding and algorithm which convert analog signals to digital signals. C&I department governs the whole functioning and operation of power plant through the Central Control System (DDC-MIS) “Distributed Digital Control Monitoring and Information System”.

ABOUT MAXDNA SYSTEMS USA

The maxDNA Plant Automation System (PAS) is the latest version of Distributed control system developed by Metso Automation MAX Controls, US. MaxDNA works with the popular operating systems Microsoft Windows 2000/XP and Windows CE, along with high-speed switched Ethernet (maxNET) communications and Distributed Processing Units (DPUs), to give an open Architecture and reliable control system.

The maxDNA DDCMIS follows a multi-level hierarchy. The lowest or first level interacts with the actual plant by acquiring the parameters/status, and issuing the actuating signals/commands.

This is done by the I/O modules. The second level performs closed loop control and open loop control, which is accomplished through execution of atomic blocks by DPU in maxDNA. The operator console or the Operator’s Workstation (OWS), and the supervisory console or the Engineer’s Workstation (EWS), are at the third level. At the highest level, called Enterprise Management Network, engineers and managers have access to the entire system database.

MAXDNA software runs on popular Microsoft platforms. The attractive features of maxDNA software for the benefit of the engineer or operator

are:-1. High level object-oriented programming in Graphical User Interface(GUI)

2. Wide selection of standard library functions

3.Provision for user-defined multi-function expandability 4. User flexibility in assigning inputs/outputs

5. Unique address for I/O signals

Figure shows network connections of maxDNA systems.

CONCLUSION

I hereby affirm that the information given in this report is true to the best of my knowledge and is based on the training undergone at C&I department .This report fulfils the basic requirement under vocational training for undergraduates.

I again affirm that this report is fully made by me, Vidya Sagar and information provided is true to the best of my knowledge and belief.