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GSECL Electrical branch Training Report

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GSECL Electrical branch Training Report

  1. 1. Electrical branch Training Report Training Center: GSECL, Gandhinagar College: VGEC, Chandkheda
  2. 2.  Report prepared by: • Yagnik Utsav P. • College Enrollment no. 100170109053 • Guided by : • Shri M. L. Upadhyay (Ex. C.E., GSECL, Gandhinagar) • Shri M. B. Patel (S.E., efficiency department, GSECL, Gandhinagar) • Shri R. R. Valand (Switchyard, GSECL, Gandhinagar) • Shri N. L. Patel (GSECL, Gandhinagar)
  3. 3. General Information about TPS • A TPS(Thermal Power Plant) is a electricity generating station which uses coal as the fuel to generate heat. The heat produced is then given to the boiler which produces steam. This steam is then given to the HP turbines and utilized to run the shaft. The shaft of turbine is mechanically coupled to the alternator which converts mechanical energy to the electrical energy. The diagram about a TPS is as below. All TPS work on the Rankine cycle. Normally, such TPS have efficiency of the range 30-35%.
  4. 4. Diagram of a Coal based TPS
  5. 5. About GSECL, Gandhinagar • GSECL, Gandhinagar (The Gandhinagar Thermal Power Station) is a Coal Based Power Station. It is on the bank of Sabarmati River. There are two units of 120 MW each (Unit no. 1 & 2), three units of 210 MW each (Unit no. 3, 4 & 5) with a total installed capacity of 870 MW. • All the above units are of BHEL make. Commissioning dates of unit no. 1 to 5 are 13.03.1977, 10.04.1977, 20.03.1990, 20.07.1991 and 17.03.1998 respectively.
  6. 6. Departments Of Training • Switchyard • CPEM • EMD-2
  7. 7. Switchyard  For Transmission and Controlling • Generator • Transformers • G.T.(Generating Transformer) • S.T.(Station Transformer) • Auxiliary Transformer • Current Transformer • Wave teff • Isolator • Terminal box for selection of isolator  For Protection and Measurement • Post insulator • SF6 circuit breaker • Potential transformers • Surge / Lightening arrester • Earth wire • Earth electrodes • Current Voltage transformer
  8. 8. About Switchyard • We can consider switchyard as the electrically starting end or finishing end of the power station. If the power is generated in the station and it is transmitted to the outer stations than it can be referred as end point. After generation , the voltages are stepped up using GTs and then given to the bus no 1 and transmitted to the selected line using isolators. • If the power is received then it can be referred as starting end. The high voltage received from buses is stepped down by STs and then utilized for running auxiliaries
  9. 9. For Transmission and Controlling  Generator • At GSECL, Gandhinagr, the total installed capacity is 870MW. • There are total 5 generators in the plant. Generator 1 and 2 are 120MW and 2,3 and 4 are 210 MW generators. • All generators are BHEL make.
  10. 10.  Transformers
  11. 11. GT(Generating transformer) • GSECL, Gandhinagar has 5 GTs of 140 MVA capacity. They provide 220 kV by stepping up 13.8 kV/15.75 kV which is received from generator. • When power is generated in the generator, respective GTs are used to step up the 13.8 kV to 220 kV. The GT is then connected to the current transformer
  12. 12. ST(Station transformer) • GSECL, Gandhinagar has 5 STs of 22.5 MVA capacity. They provide 7 kV by stepping down 220 kV which is received from bus bars. • When generator is in off position and the power is not generated, the respective STs are operated to run the auxiliaries.
  13. 13. Unit Auxiliary Transformers • When synchronization goes above 70%, the power plant uses its own power to run auxiliaries. • GSECL, Gandhinagar has auxiliary transformers of 15 MVA. • They step down voltage from 15.75 kV to 7 kV or 6 kV. All UATs are tap changer transformers.
  14. 14.  Current transformers • CTs are useful to reduce the current so that it remains below a certain limit to reduce the copper and corona losses. • Here, switchyard has 1000:1 ratio CTs. • Specifications : Parameter Rating Highest system voltage 245kV Rated primary current 1500kA Frequency 50Hz Insulation level 480/1050kV S.T. current 20kA/3sec
  15. 15.  Wave teff • Wave teff is an instrument which controls the frequency of power transmission so that it doesn’t give disturbance to the neighboring communication lines. • It is a cylindrical caged instrument. • Specification : Parameter Rating Inductance 0.5 mH Frequency band 150-500 kHz Ir 1250 A Short circuit current 3.5 kA
  16. 16.  Isolator • Isolator is a switch which connects bus bar to outer transmission line. It is an “off load” device. • We can select required isolator to conduct by using a terminal box which works by a bidirectional motor. • Isolator is made open when line requires maintenance and servicing. • Isolator is also called as “disconnector” or “disconnect switch”.
  17. 17. Figure of the Isolators
  18. 18. For protection and measurement  Post insulator • It is used to give required ground clearance to the conductor so that hazardous effect is avoided due to high voltage being carried by the conductor. • The length and size of disc depends upon our required voltage rating and conductor parameters.
  19. 19. Figure for Post insulator
  20. 20.  SF6 circuit breaker • At GSECL, Gandhinagar, all circuit breakers are SF6 circuit breakers. • They are connected after CTs to provide protection to the grid and buses A and B. • As the name suggests, in these circuit breakers the quenching medium is SF6 air which is pumped in the airtight cabinets so that their pressure remains 20.5 bar.
  21. 21. Specifications of SF6 circuit breaker Parameter Rating Voltage 245 kV Normal current 2000 A Lightening impulse voltage withstand 1050 kV Short time withstand current and duration 40 kA & 3 sec First pole to clear factor 1.3 Closing and opening device supply voltage 220 V dc Gas pressure SF6 / 20⁰ C 7.0 bar
  22. 22. Picture of the SF6 circuit breaker
  23. 23.  Potential transformer • PTs are useful for measuring bus voltages by reducing the values of high voltages to the meter range. • In this way PTs protect the measuring devices from high voltages. • We can use PT of the required range to step down the high voltage and bring it to the measuring range. • At GSECL, Gandhinagar, PT steps down voltage from 220 kV to 110 V for measurement
  24. 24.  Surge arrester • The purpose of surge arrester is to divert damaging lightening-induced transients safely to ground through property changes to its varistor in parallel arrangement to the conductor inside the unit. • Also called a surge protection device (SPD) or transient voltage surge suppressor (TVSS), they are only designed to protect against electrical transients resulting from the lightning flash
  25. 25. Pictures of Surge arrester
  26. 26.  Earth wire • An earth wire is run along transmission line at the top of the tower so that an earth fault doesn’t damage the transmission tower.  Earth electrodes • Earth electrodes are given to the outer surface of the apparatus to make human safe from fatal current due to earth faults.
  27. 27. Current Voltage transformer • The CVT are used to measure current and voltages on the line. • Ratings of CVT at GSECL, Gandhinagar : Parameter Rating Rated voltage 220/1.73 kV Total burden 100 VA Highest system voltage 245 kV Nominal capacitance 400 pF Frequency 50 Hz
  28. 28. Ariel view of a switchyard
  29. 29. CPEM • CPEM is the short form of Coal Plant Electrical Maintenance
  30. 30. Path of Coal in storage yard • The coal extracted from the mines is brought to the TPS through train or any other transport. • At GSECL, the coal from Bihar, Jharkhand and other eastern states is brought in train. • The train is emptied in the big conveyer belt by tipplertippler.
  31. 31. About Tippler • Tippler is a motor driven assembly which empties train wagon by rotating it 180 degrees. • Its motors are 6.6 kV motors and are operated by operator when four arms of tippler holds the vagon. • At GSECL, it can empty a wagon within 10 seconds after motors are operated. GSECL, Gandhinaagr has 3 tippler units.
  32. 32. Picture of Wagon tippler
  33. 33. Path of Coal in storage yard • After coal has been emptied from wagon, it falls on apron feeder. • Apron feeder is a mechanism moving on the shafts and return roller. The whole structure is kept on a main frame. • It can manage flow of stones or powder materials like coal.
  34. 34. Figure of Apron feeder
  35. 35. Roller magnetic separator • It is a mechanism in which metal parts are removed from coal so that crusher inlet has only coal content. • If metal parts are not removed from coal than crusher might get mechanically locked or even damaged while operating. • It is called as IMS(inductive magnetic separator) as it uses induction motors in rollers. Motors are 415 V motors.
  36. 36. Path of Coal in storage yard • After metal parts have been removed from coal, if coal is in form of big stones than it is given to the crusher unit. • Crushers are 6.6 kV motors having hammer on their surfaces so that they can break stones of coal in to small parts. • GSECL, Gandhinagar has 4 crusher units.
  37. 37. Picture and diagram of Crusher
  38. 38. Path of Coal in storage yard  Concept of Pulverization of coal • The concept of burning coal that has been pulverized into a fine powder stems from the belief that if the coal is made fine enough, it will burn almost as easily and efficiently as a gas. • The feeding rate of coal according to the boiler demand and the amount of air available for drying and transporting the pulverized coal fuel is controlled by computers. Pieces of coal are crushed between balls or cylindrical rollers that move between two tracks or "races."
  39. 39. Pulverization of coal • The raw coal is then fed into the pulverizer along with air heated to about 650 degrees F from the boiler. As the coal gets crushed by the rolling action, the hot air dries it and blows the usable fine coal powder out to be used as fuel. • The powdered coal from the pulverizer is directly blown to a burner in the boiler. The burner mixes the powdered coal in the air suspension with additional pre-heated combustion air and forces it out of a nozzle similar in action to fuel being atomized by a fuel injector in modern cars. Under operating conditions, there is enough heat in the combustion zone to ignite all the incoming fuel.
  40. 40. Figure of Pulverized coal burner
  41. 41. Diagram of an coal handling plant
  42. 42. EMD • EMD is the short form of Electrical Maintenance Department. • This department deals with replacement and repairing of electrical equipments used in different departments of power plant.
  43. 43. Care to be taken • Performing maintenance on electrical equipment can be hazardous. Electrical and mechanical energy can cause injury and death if not managed properly. • Complete, accurate, and current documentation is essential to an effective maintenance program. Whether performing preventive, predictive, condition-based, or reliability-centered maintenance, keeping track of equipment condition and maintenance—performed and planned—is critical.
  44. 44. Critical equipment as any system, asset, or component whose failure could cause: • Loss of transmission capability or reduction in capacity • Serious personnel injury or violation of a safety regulation • An environmental hazard resulting in harm to the public, environment, or damage to public property
  45. 45. Frequencies of maintenance • Weekly: Calendar week (Sunday to Saturday) • Monthly: Calendar month (first day through the last day of the month) • Quarterly: A calendar quarter consisting of 3 calendar months • Semi-annually: Six calendar months • Annually: A calendar year (January 1 through December 31) • Multiyear: Multiple calendar years (e.g., 5-year – January 1, 2011, through December 31, 2015) • It is up to the individual office to document the tolerances associated with these stated frequencies. • Many offices use the concept of a maintenance season to describe the timeframe. A maintenance season will be considered the period of time from October 1 of the current year through May 31 of the following year.
  46. 46. Electrical Equipment Maintenance  Annunciators and Alarms • Annunciators and alarms provide essential plant condition status information to O&M personnel. Two aspects must be considered: 1. Correct operation of annunciator and alarm devices 2. Integrity of the annunciator and alarm circuits Maintenance or Test Recommended Interval Operational test Weekly Functional test 2 years
  47. 47.  lightening Arresters • Lightning or surge arresters provide protection for important equipment from high energy surges. These arresters are static devices that require fairly infrequent maintenance. • Most maintenance must take place while the associated circuit is de-energized. • However, crucial visual inspections and infrared (IR) scans can take place while energized. Maintenance or Test Recommended Interval Visual inspection Semi-annually Clean insulator and check integrity of connections 6 years Insulation test (Double test – power frequency dielectric loss, direct current [dc] insulation resistance, power factor 6 years
  48. 48.  Batteries, Battery Chargers, and Battery Monitoring Systems • Battery systems provide “last resort” power for performing communication, alarm, control, and protective functions (relaying and breaker tripping) when other sources of power fail. • Battery system maintenance should have highest priority. • Computerized, online battery monitoring systems can be installed to supplement a maintenance program and reduce costs. • Battery chargers require regular maintenance as well.
  49. 49. • Maintenance Schedule – Flooded, Wet Cell, Lead Acid etc Batteries Maintenance or Test Recommended Interval Battery float voltage (charger meter) Weekly Visual inspection Monthly Check accuracy of charger meter Monthly Cell float voltage pilot cells with meter Monthly Cell float voltage all cells Quarterly Specific gravity pilot cells Monthly Specific gravity (10 percent [%] of all cells) Quarterly Specific gravity all cells Annually Temperature (pilot cell) Monthly Temperature (10% of all cells) Quarterly Connection resistance (this may be checked by IR scan while loaded) Annually Capacity testing 5 years Safety equipment inspection Monthly
  50. 50.  Bushings • Bushings are critical components of medium and high voltage circuit breakers and transformers. • Bushing maintenance usually is conducted at the same time maintenance is performed on the circuit breaker or transformer, or at least during an outage on that equipment.
  51. 51.  Buswork, Enclosures, and Insulators • Buswork conducts current from one part of the powerplant or switchyard to another. Buswork usually is constructed of flat or round copper or aluminum busbar and can be either isolated-phase or nonsegregated. • Except for infrared scanning, bus maintenance must be conducted de- energized. Standoff buswork insulators provide isolation of “live” power circuits from ground and other circuits. Failure of insulators will cause a power system fault and a forced outage. Maintenance or Test Recommended Interval Check integrity of connections 6 yrs Check and clean enclosures 6 yrs Insulation test 6 yrs
  52. 52.  Power Cables – Energized at 2 kV and Above • Periodic maintenance tests are needed during the life of the cable to determine whether or not there has been significant insulation deterioration due to operational or environmental conditions. • High potential tests (hipot) effectively reduce inservice failures from faults of the cable or its accessories. When done properly, maintenance tests can detect problems in cables that are approaching failure without accelerating the deterioration process. • Except for infrared scanning, de-energize the cable circuit before maintenance. Maintenance or Test Recommended Interval Insulation test 5 yrs Insulating oil – dissolved gas analysis (DGA), physical, and chemical tests Annually
  53. 53.  Circuit Breakers • Circuit breakers interrupt electrical current to stop power flow both for switching operations and during fault conditions. • Molded case circuit breakers located in low voltage distribution panels are typically 125 to 250 volts direct current (Vdc); 120, 208, 240, 277, and 480 volts alternating current (Vac); or used for control, protection, and auxiliary power. These molded case breakers should not be loaded more than 80% of the rated value unless the breaker is specified as a continuous type capable of being loaded to 100%. • Medium voltage circuit breakers generally are located in station-service metal clad switchgear or in separate enclosures as unit breakers. Examples are 4,160-Vac station service and 11.95- and 13.8-kV unit breakers. These breakers may be air, air blast, vacuum, or SF6 . • High voltage circuit breakers are located in separate breaker enclosures, either indoors or outdoors. These are oil, air-blast, or SF6 breakers. Examples are 115- and 230-kV breakers located in the switchyard.
  54. 54.  Medium and High Voltage SF6 Breaker Maintenance Schedule Maintenance or Test Recommended Interval Preventive maintenance (external inspection) Annually Record gas pressure and temperature; compare with tolerances and prior readings Monthly Record operations counter Monthly Visual inspection Monthly Check contact wear 6 years Check foundation, grounds, paint 6 years Check external screws, bolts, electrical terminals tight Annually
  55. 55.  Coupling Capacitors • Coupling capacitor/voltage transformers (CCVTs) are instrument transformers that provide a path for communications, metering, control, and relaying equipment without allowing power system frequency energy to pass. • These are static devices requiring relatively little maintenance. Except for infrared scanning, maintenance must be conducted with equipment de-energized. • This equipment normally is oil-filled and must be checked for oil leaks.
  56. 56. • Thus, EMD department looks after all needs of maintenance and replacements. • Figure of Thermal imaging camera
  57. 57. An overview of coal based TPS
  58. 58. THANK YOU