NTPC dadri thermal report

NTPC Ltd

India’s largest power company, NTPC was set up in 1975 to accelerate power development in India. NTPC is emerging as a diversified power major with presence in the entire value chain of the power generation business. Apart from power generation, which is the mainstay of the company, NTPC has already ventured into consultancy, power trading, ash utilization and coal mining. NTPC ranked 317th in the ‘2009, Forbes Global 2000’ ranking of the World’s biggest companies. The total installed capacity of the company is 30, 144 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 naptha/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.

National Capital Power Station Dadri

The National Capital Power Station [NCPS] has the distinction of being the country's only three in one project ; consisting of Stage-I 840 MW; Stage-II 490MW ( and 490 MW under construction) of coal based units , 829 MW gas based modules , and a 1,500 MW H.V.D.C. converter station {under the operational control of P.G.C.I.L. since October '93}. The stage-II (490MW*2) coal based units are scheduled in 2010 to meet the common wealth games power requirement. The commercial operation of Stage-II Unit-V 490 MW has been declared w.e.f 31.01.2010. Also work for Stage-II UNIT-VI 490MW is under full swings. Besides the station has the largest switchyard in the country with a power handling capacity of 4,500 MW The station's capacity allocation is mainly concentrated in northern region of India . Spread over 2,465 acres , the station is situated on the Dadri -Dhaulana road [10 kms. off Dadri G.T. road , and 12 kms. off the National Highway # 24] . The route from New Delhi to NCPS is 60 kms. long and is about 25 kms. from GhaziabadThe station has the unique distinction of having Asia's first 100 percent dry ash extraction with transit ash storage silos and final storage place converted to an green ash mound . An Ash Technology park has also been set up to demonstrate the uses of ash which has become the point of attraction for the visitors.

USES OF COAL ASH

Dadri ash have been successfully used in the following applications . LAND FILLS ROAD EMBANKMENTS ROAD CONSTRUCTION PORTLAND POZZOLONA CEMENT BUILDING PRODUCTS CONCRETE

Use of Dadri ash in above applications have resulted in saving in terms of money , conservation of natural resources viz mother earth, lime stone, coal, sand, energy, land and water apart from reduction in CO2 emission and thus environment.

PRESENT SENARIO IN INDIA 65% of the total installed power generation is coal based. 230 - 250 million MT coal is being used every year. High ash contents vrying from 30 to 50%. 95 million MT ash generated every year. Ash generation likely to reach 170 million MT by 2010. Presently 65000 Acres of Land occupied by Ash Ponds.

The NCPS Dadri project has the unique distinction of having Asia's first 100 percent dry ash extraction with transit ash storage silos and final storage place converted to an green ash mound.

Ash can be collected in following categories: - DRY FLY ASH:-

Dry ash is collected from different rows of electrostatic precipitators. It is

available in two different grades of fineness in silos for use as resource material by different users

BOTTOM ASH:- Bottom ash collected from bottom of boiler and transported to hydro bins and then ash mound for use in Road Embankment.

CONDITIONED FLY ASH: - Conditioned fly ash is also available in Ash mound for use in Land fills and Ash Building prod

NTPC - A trend setter in the country has set up 100 % dry ash extraction cum disposal in the form os Ash Mound at NTPC Dadri . Ash mound has come out as the most viable alternative for ash disposal in an economic friendly way by minimum use of land and water.

ADVANTAGES OF ASH MOUND Less requirement of land only 1/3rd land requirement as compared to wet

disposal system. 375 acres of land is required as compared to 1000 acres for installed capacity

of 840 MW at Dadri. Only 1/50th water required in comparison to wet system Eliminates leaching effect. Separate storage of fly ash (PFA) and furnace bottom ash(FBA). Facilitates large scale utilization at later stage. The green ash mound can be used as a useful piece of land.

FEATURES OF ASH MOUND Ash mound covers area of 375 acres. Ultimate height 55 meters. Side slope 1:4 with haulage road at 15 m interval. Top most flat area 140 acres. Capacity of ash storage 53 million cum. Sufficient for running 840 MW for 40 years. Side slopes covered with green grass and plantations of trees . Beautiful green spot in the vicinity of power house.

National Capital Power Station - Coal

The coal-based station mainly meets power requirements of the National Capital Region [NCR] , and the northern grid . With the World Bank funding component , the capital cost of the units is Rs. 16.69 billion . There are four 210 MW coal based units. The units have a coal-fired boiler and a steam turbine each . The boiler design is also suitable for 100% operations with heavy furnace oil firing . For this , three storage tanks , each of capacity 15,000 kL , enough for 10 days continuous oil firing requirements have been provided for the boilers .

Coal Source:The coal is transported from the Piparwar block of mines of the North Karanpura Coalfields of Bihar , over a distance of about 1,200 kms. , by the Indian Railways bottom discharge , and Box 'N' type of wagons . The coal requirements for the four units is 15,000 M.T. each day , 3.67 million tonnes annually . The station has its' own 14 kms. Long rail track from the Dadri Railway Station , to the site , and a 6 km in-plant track , on electric traction.

National Capital Power Station - GasThe gas-based station at N.C.P.S. is the country's largest . It has two modules; each module consists of two gas turbines of 130.19 MW each with one waste heat recovery boiler and one steam turbine of 154.51 MW capacity . The power from this plant is allocated to Uttar Pradesh , and also to Delhi , Punjab , Jammu and Kashmir , Haryana , Himachal Pradesh and Rajasthan . The cost of gas based modules is Rs. 9.75 billion , which includes a German K.f. W. funding . The modules are fully commissioned . Gas turbines generate power at an efficiency of about 32% only , and to utilize the rest of this energy , a combined cycle system is adopted . The waste heat from the gas turbine exhaust is routed through the waste heat recovery boiler , and the steam thus generated is utilized in a conventional steam turbine to generate additional power . By this , the overall efficiency of fuel heat utilization reaches to about 48% .

Gas Source:The source of fuel for this plant is the reserves of South Bassein fields in South Tapi and mid Tapi delta in the Arabian Sea . The natural gas from South Bassein off shore fields is transported through a submarine pipeline to Hazira onshore terminal and then through the 1,700 kms. Long Hazira-Bijapur pipeline via Shahjanpur and Babrala , to the project . For the 829 MW project , the requirement is 3.00 million cubic meters per day (yearly average). It would be worthwhile to note that within a short span of less than 7 years , both the coal and gas based power cycle units/modules have been commissioned in a project . Both the projects have diverse modern technologies , with the latest process controls .

HVDC

This is a technological accomplishment in power by NTPC . Commissioned in December '90 , the system is the first commercial long distance HVDC link in India , and also the largest in Asia . The basic objective of the HVDC link is to transmit the power generated at the RhSTPP efficiently to the northern region , with significant reduction in transmission losses . It consists of two converter stations - one located at Rihand (RhSTPP) acting as a rectifier , and the other at Vidyutnagar (NCPP) as an inverter , involving a distance of about 900 kms. . These stations are connected by a +/- 500 kV HVDC line for transmission of 1,500 MW power from Rihand to Vidyutnagar . The overall HVDC system engineering was done by Asea Brown Boveri .

The special features of this HVDC line are that the entire system can be controlled either from RhSTPP or NCPP , depending on which station is selected as the master . The system has been handed over to the Power Grid Corporation of India , and is under their control since October 1993

DETAILS OF 220KV AND 400KV FEEDERS SOURCES

Sl.No. Line Name Capacity Remarks

1. Generator - 1 210 MW

Thermal Plant2. Generator - 2 210 MW

3. Generator - 3 210 MW

4. Generator - 4 210 MW

5. Generator - 1 131 MW

Gas Plant6. Generator - 2 131 MW

7. Generator - 3 131 MW

8. Generator - 4 131 MW

9. Generator – 5 (Steam) 146.5 MW

10. Generator – 6 (Steam) 146.5 MW

11. HVDC Feeder 1500 MW HVDC

TRANSMISSION LINES

Sl.No. Line Name Capacity States

1. Panipat - 1 500MW Haryana

2. Panipat - 2 600MW

3. Murad Nagar 500MW Utter Pradesh

4. Maler Kotla 500MW Puniab

5. Mandola - 1 750MW Delhi

6. Mandola - 2 750MW

7. Greator Noida 750MW Utter Pradesh

Delhi8. Maharani Bagh 750MW

2.2 SUB-STATION EQUIPMENTS

1. Bus-bar

2. Circuit Breaker

3. Earth Switch

4. Inter Connecting Transformer (I.C.T.)

5. Current Transformer (C.T)

6. Capacitive Voltage Transformer (C.V.T.)

7. Lightning Arrester

8. Protection Relay

10. Power Line Carrier Communication (PLCC)

Figure No. (5) Single line diagram for power flow

DADRI SWITCHYARD

Bus Coupler

Main Bus#2

Main Bus#1

Transfer Bus

Figure No. (6) Double Main and transfer bus arrangement

Transfer Bus Coupler

Feeder

BUS BAR SCHEME FOR 220KV SWITCHYARD

BUS BAR SCHEME FOR 400KV SWITCHYARD

Figure No.(8) : 400kV switchyard single line diagram

Feeder#2

ICT Feeder

Feeder#1

Bus#1

Bus#2

CIRCUIT BREAKER

Types of breakers operational at NTPC Dadri Switchyard

(1) 400kV Air blast circuit breaker

(2) 220kV SF6 filled circuit breaker.

SPECIFICATION OF AIR BLAST CIRCUIT BREAKER

Type DLYF420 nc4

Normal Voltage 420KV

Normal Current 2000A

Trip coil voltage 220V dc

Close coil voltage 220V dc

Frequency 50HZ

Short time Current 40KA 3Sec.

Breaking Current Sym. 40KA

Asym. 48 KA

R I L at 50HZ 630KV

Voltage switching impulse 1050

Operating pressure 27-31 Kg

Mass 3850 Kg

Make Hindustan Brown Boveri

SPECIFICATION OF SF6 GAS CIRCUIT BREAKER

SR. NO CIRCUIT BREAKER

1. CIRCUIT BREAKER TYPE ELF SL 4-1

2. SR. NUMBER 20000070

3. Month and year of Mfg. JANUARY - 2001

4. Voltage 245 KV

5. Normal current 1600/2500 AMP.

6. Lightning impulse with stand voltage 1050 KV

7. Switching impulse with stand voltage - KV

8. Short circuit breaking current 40 KA

9. Short time with stand current & duration 40 LA 1 Sec.

10. Line charging breaking current 125 AMP.

11. Operating sequence 0-0 3S - CO – 3Min- CO

12. First - pole - to - clear factor 1.3

13. Gas pressure SF6 at 200C (abs) 7.0 bar

14. Closing & opening device supply voltage 220 V DC

15. Auxiliary circuit supply voltage 240 V AC

16. Air pressure 20.5 bar

17. Frequency 50 Hz

18. Mass (approx) for 3 poles 4000 kg

INTERCONNECTING TRANSFORMER (ICT)

Power transformers are the backbone of the large grid. The power is generated

at the low voltage level and has to be carried to far away load centers. Typically

the power is generated at the Pit heads i.e power source like coal, water. It is

uneconomical carry the bulk power at low voltage levels. Depending upon the

requirement the voltage level is stepped upto the transmission level i.e 220 or

400kV. At higher voltages the transmission losses are less. Similarly at the

remote end the voltage is stepped down the distribution level. To accomplish the

task

Power transformers are installed and act as bi-directional element in the system.

At NTPC Dadri this task is carried out by bank of Single Phase 400/220kV

Interconnecting transformers. Autotransformers are used when transformation

ratio is between 1 and 2 and above 315MVA, due to size and weight constraints

all the transformers are single phases. Three such single phase transformers are

installed three phases to make One bank of transformer.

Three banks of transformers are installed to evacuate power from the 220kV

switchyard generated by 4X 210MW thermal Units.

All these transformers are star- star connected transformers with neutral solidly

grounded. A third winding called tertiary winding at much lower voltage i.e 33kV,

is also provide and is connected in delta to facilitate the flow of third harmonic

current to reduce the distortion in the output voltage.

To reduce the overall size of the transformer, the transformer is provided with Oil

forced and Air forced type cooling at its 100% rating. However, to save the

energy, the cooling system is controlled by the temperature of the winding.

The transformers are also equipped with On Load Tap Changer to meet the

change in voltage variation. Typically the Tap changer provides variation

between 10% of the nominal voltage i.e. 400kV with a variation of 0.5% at each

tap.

6.1 SPECIFICATIONS

Make CROMPTON GREAVES Ltd.

No. 3

Rating 167*3 = 500 MVA

Tap 17

No load Voltage KV (HV side)

400/√3

No load Voltage KV (IV side) 220/√3

No load Voltage KV (LV side) 33 KV

Line current Amp. (HV side) 289.25 , 433.88 , 723.13

Line current Amp. (IV side) 525.91, 788.87, 1314.78

Line current Amp. (LV side) 1688.48

Connection symbol YNaOd11 for 3 phase bank

Type of cooling ONAN / ONAF / OFAF

Frequency 50 Hz

Insulation level (HV) 1450kV

Insulation level (IV) 630kV

Insulation level (LV) 250kV

Temperature rise oil deg. c 350 above ambient

PROTECTION RELAYS

Relay is a device that detects the fault mostly in the high voltage circuits and

initiates the operation of the circuit breaker to isolate the defective section from

the rest of the circuit. Whenever fault occurs on the power system, the relay

detects that fault and closes the trip coil circuit. This results in the opening of the

circuit breaker, which disconnects the faulty circuit. Thus the relay ensures the

safety of the circuit equipment from damage, which the fault may cause.

PURPOSE OF PROTECTIVE RELAYING

The capital investment involved in a power system for the generation,

transmission and distribution of electrical power is so great that the proper

precautions must be taken to ensure that the equipment not only operates as

nearly as possible to peak efficiency, but also that it is protected from accidents.

The normal path of the electric current is from the power source through copper

conductors in the generators, transformers and transmission lines to the load and

it is confined to this path by insulation. The insulation however may be broken

down, either by the effect of temperature and age or by a physical accident, so

that the current then follows an abnormal path generally known as a short circuit

or fault. Whenever this occur the destructive capabilities of the enormous energy

in the power system may cause expensive damage to the equipment, severe

drop in the voltage and loss of revenue due to interruption of service. Such faults

may be made in frequent by good design of the power apparatus and lines and

the provision of protective devices, such as surge diverters and ground fault

neutralizers, but a certain number will occur inevitably due to lightening and

unforeseen accidental conditions.

The purpose of protective relays and relaying systems is to operate correct circuit

breaker so as to disconnect only the faulty equipment from the system as quickly

as possible, thus minimizing the trouble and damage caused by faults when they

do occurs. With all other equipment it is only possible to mitigate the effects of

short circuit by disconnecting the equipment as quickly as possible, so that the destructive

effects of the energy into the fault may be minimized.

UNDER VOLTAGE RELAY

Under voltage protection is provide for AC circuits, busbar, transformer, motor,

rectifier etc. Such protection is given by means of under voltage relay. The relay

coil is energized by voltage to be measured either directly or via a voltage

transformer.

9.3 OVER CURRENT RELAY

If a short circuit occurs the circuit impedance is reduced to a low value and

therefore a fault is accompanied by a large current, Over current protection is

that protection in which the relay pickup when the magnitude of current exceeds

the pickup level. The basic element in over current protection is an over current

relay. The over current relays are connected to the system normally by means of

CTs.

9.4 EARTH FAULT RELAY

Earth fault protection responds to single line to ground fault and double line to

ground faults. The current coil of the earth fault relay is connected either in

neutral to ground relay CT circuit. Core balance Cts are used for earth fault

protection.

9.5 DIFFERENTIAL RELAY

Differential protection responds to vector difference between two or more similar

quantities. In circulating current differential protections CTs are connected on

either side of the protected equipments. During the internal faults the difference

of secondary current flow through the relay coil. Differential protection is used for

protection of large transformer, generator, motors feeders and busbars.

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