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gas turbine generator set operation and maintenance
- 1. Turbine Generator Sets AGENDA Generator Basics break Voltage regulator break Generator operation
- 3. Generator Basics Electricity can be obtained from magnetism, and magnetism can be produced from Electricity used on generator excitation system creates voltage in generator stator windings and output terminals Creating eddy current in generator core Is causing armature reaction
- 4. Generator Basics In 1831, an English physicist named FARADAY discovered that an emf could be produced in a wire loop moved into a magnetic field and a magnetic field is created around a current-carrying conductor
- 5. Generator Basics This method is not very efficient because air is resistant to flux line
- 6. Generator Basics With an Iron or steel core
- 8. Generator Basics Mechanical/Electrical Degrees Relationship F = P x RPM /120 P = number of pole RPM = revolution per minutes F = frequency in Hertz
- 9. Generator Basics More Power at little increase in cost
- 10. Generator Basics
- 11. Generator Basics The generator output voltage is controlled by controlling the electromagnetic field of the pole : a controlled DC current is circulating in windings
- 12. Generator Basics Distributed windings Spread out the windings around the periphery of the stator to minimize the abrupt change in the field strength as pole rotates over the winding slot Skewing Slot noise results from the rotor passing by the coil slots and suddenly increases the effective air gap. A method of reducing the effect of this sudden change is to apply a skew to the slot. Laminated Stator Core To reduce Eddy current losses, Stator is composed mainly of thin, high- grade steel silicone laminations
- 13. Generator Basics Fractional pitch winding To eliminate the effects of the third harmonic plus the other triplen (9, 15, etc)
- 14. Generator Basics
- 15. Generator Basics
- 16. Generator Basics
- 20. Elf120000 Generator Basics Xd reactance is important r is usually not significant Xd during steady operation If a fault occurs Xd becomes: first X’’d ( Subtransient ) 0 to 6 cycles then X’d (Transient ) 6 cycles to 5 seconds Equivalent circuit of a “perfect generator”
- 21. Elf120000 Generator Basics Harmonics Distortion Fourier, a French Mathematician Theorem states that any waveform can be broken down into a summation of a fundamental frequency and harmonics of the fundamental frequency. THD % ( Total Harmonics Distortion ) Can be applied on Voltage or Current Usually around 3 % content caused by the generator itself
- 22. Elf120000 Generator Basics Harmonics Distortion What are the symptoms? Erratic operation of control and protective relays Faulty readings frequency meter. Over heating and high current pulse, etc... What is causing harmonics? UPS, Battery chargers, SCR’s or Thyrister, saturated transformers, etc… What can be done? Increase conductor and connector size Derate existing overloaded transformer and add additional ones or replace them with bigger ones Re-distribute load to balance harmonics Increase size of the generator
- 23. Elf120000 Generator Basics Harmonics Distortion MOBIL JADE EQUATORIAL GUINEA
- 27. Elf120000 Voltage regulator Static Voltage Regulator
- 28. Elf120000 Voltage regulator Static Voltage Regulator
- 29. Voltage regulator Static Voltage Regulator TYPICAL POWER STAGE
- 30. Voltage regulator Static Voltage Regulator Adjust the stability potentiometer for stability EFFECTS OF STABILITY LOOP
- 31. Voltage regulator Static Voltage Regulator Adjust voltage stability at no load higher gain because less saturated
- 32. Voltage regulator Digital Excitation Control System DECS 15
- 33. Voltage regulator Digital Excitation Control System
- 34. Voltage regulator Digital Excitation Control System SCALING CIRCUIT AND A/D CONVERTER
- 35. Voltage regulator Digital Excitation Control System SCALING CIRCUIT AND A/D CONVERTER
- 36. Voltage regulator Digital Excitation Control System DIGITAL CONTROLLER REFERENCE INPUT Uses a Digital word stored in its RAM This word can be adjust • via local controls • remotely mounted raise/lower switch • other portion of the program during under-frequency, parallel operation, VAr or PF controllers, ...
- 37. Voltage regulator Digital Excitation Control System D/A CONVERTER AND POWER STAGE
- 38. Voltage regulator Digital Excitation Control System
- 39. Voltage regulator Analog versus Digital + Process the signal continuously with infinite resolution + cost - Component aging or temperature drift an affect performance of analog circuitry - hardwired solutions: upgrade difficult - good performance but limited adjustments - Process signal in discrete time intervals - sensitive to harmonics + Performance essentially similar to their analog counterparts + once signal is converted into digital format accuracy not affected by age or temperature + programmable: upgrade easy + multiple stability parameter can allow precise matching + remote control easy + remote communication capability trough serial ports + event recording
- 41. Generator operation Island mode LOAD LOAD LOAD GENERATOR #1 GENERATOR #2 Load Share Indicates Energy Flow Path
- 42. Generator operation Island mode Different Type of load
- 43. Inductive load are said to accept reactive power Capacitors are said to supply reactive power S = Apparent Power VA Q = Reactive Power VAR P = Real Power Watt PF = Power Factor = P/S Generator operation Island mode AN ELECTRICAL MOTOR IS AN INDUCTIVE LOAD, IT IS THE MOST COMMON LOAD GENERATOR ARE THEREFORE USUALLY OPERATING WITH A LAG POWER FACTOR Different Type of load
- 44. Generator operation Island mode Parallel operation, DC analogy
- 45. Generator operation Island mode Parallel operation, DC analogy
- 46. Generator operation Island mode Parallel operation, DC analogy
- 47. In the DC Analogy with, only voltage had to be controlled for proper load sharing To parallel AC generators, both variables must be controlled properly • torque applied to the generator to share real power KW • excitation to control and share reactive power KVAR Generator operation Island mode
- 48. Generator operation Island mode Bus Voltage and Frequency are set by the Generator Set. Load determines power output and power factor - Generator(s) must deliver requested load - If capacity is exceeded system will shutdown Control Available - Frequency (Speed Isoch) - Voltage (Voltage Droop 2 units or more, Voltage Isoch if 1 unit) - Load Sharing (Speed Isoch) - Reactive Load Sharing (Voltage Droop) - Base Loading (Speed Droop) - Synchronization
- 49. Generator operation Island mode Parallel operation, Real load sharing purpose: Prevent load swapping between units Load all units in the system proportionally. CASE 1: Automatic: all generators are in speed isochronous mode, load share lines are connected. CASE 2: Manual: Some generators are in speed droop mode, others are in speed isochronous mode. Unit in speed droop mode is base loaded. Units in isochronous mode take the swing load proportionally if load share lines are connected.
- 50. Generator operation Island mode LSM LOAD SHARE ERROR = (LOAD SHARE INPUT VOLTAGE) / (LOAD SHARE FULL SCALE VOLTAGE) - ACTUAL POWER / MAXIMUM POWER LOADSETPT NPTLEADLAG - + TO MIN SELECTOR See also LSM EDM 154
- 51. Generator operation Island mode Parallel operation, Reactive load sharing purpose: Prevent power factor drift between units Share reactive load between all units proportionally. All generators are in voltage droop mode
- 52. Generator operation Island mode USED by SOLAR
- 56. Generator operation Island mode CCT (CROSS CURRENT TRANSFORMER) 663 - Should deliver 3 to 5 amps at rated load - Phase relationship of CCT to voltage regulator must be correct or the system will not parallel properly >for 3 phase sensing CCT must be in line E2 >for 1 phase sensing CCT must be in the line not supplying sensing voltage to voltage regulator. - To check CCT direction apply inductive load and switch from voltage ISOCH to voltage DROOP -----> Voltage should DROOP -----> if Voltage rises instead of drooping reverse CCT sensing leads
- 57. LOAD LOAD LOAD GENERATOR #1 GENERATOR #2 UTILITY kW kW Export Import Plant Process Indicates Energy Flow Path Generator operation Grid mode
- 58. Generator operation Grid mode Bus Voltage and Frequency are set by the Grid. Operator determines power output and power factor of the generator set. If Generator is run in Speed Isoch without an output power control scheme the generator will either offload and trip on reverse power or it will T5 top Control Available kW (Speed Isoch) Import/Export (Speed Isoch) Process (Speed Isoch) Power Factor Synchronization Base Loading (Speed Droop)
- 59. Generator operation Grid mode LOAD LOAD LOAD GENERATOR #1 GENERATOR #2 UTILITY kW kW Export Import Plant Process Feedback Measurement Point Indicates Energy Flow Path The kW output of the generator is controlled to a preset value Usage: To limit the heat output of the turbine To limit the fuel usage To limit emissions
- 60. Generator operation Grid mode LOAD LOAD LOAD GENERATOR #1 GENERATOR #2 UTILITY kW kW Export Import Plant Process Feedback Measurement Point IMPORT CONTROL The kW output of the generator is regulated to maintain a minimum of imported power. Usage: -To prevent the export of power during periods when the customer load is less than the turbine capacity or to ensure a limited amount of kW is imported when there is a lot of demand. EXPORT CONTROL The kW output of the generator is regulated to maintain a maximum of exported power. Usage: -To sell power to utility companies.
- 61. Generator operation Grid mode LOAD LOAD LOAD GENERATOR #1 GENERATOR #2 UTILITY kW kW Export Import Plant Process Feedback Measurement Point The power output of the generator is regulated to maintain a required Process that utilizes the heat of the turbine Usage: To control steam pressure (Direct Process) To maintain a constant heat flow (Direct Process) To control Inlet Turbine Pressure (Inverse Process)
- 62. Generator operation synchronizing = 2 f V (%) = (V1 - V2 )/ 100 V1 (%) <= 1% f = (f1 - f2) < = 0.1 Hz =(1 - 2)< = 10 Acceptance window > = 0.5 seconds V1 sin (1t + 1) Indicates Breaker is Closed Indicates Breaker is Open LOAD V2 sin (2t + 2) {Oncoming Generator} V1 sin (1t + 1)
- 63. Generator operation synchronizing SYNCHRONIZATION -1.1 -0.6 -0.1 0.4 0.9 Time % Volt Main Bus Oncoming Generator Amplitude Difference Frequency Difference Phase Difference CONDITIONS MET (WINDOW FOR CLOSING)
- 64. QUESTIONS?