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Protection Systems for Power generators
The document outlines an agenda for a presentation on protection systems for power generators held by AGCC from 1-3pm on November 1, 2014. The agenda includes: a welcome speech at 1pm, introduction of the speaker at 1:10pm, a fault analysis detail session at 1:15pm, a tea break at 1:50pm, a presentation on generator protection systems from 2-2:40pm, a question and answer section from 2:40-3pm, and ending the presentation at 3pm. The rest of the document provides details on generator protection including common protection functions, wiring diagrams, and an example.
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Protection Systems for Power generators
- 1. by Nicholas Naing ProtectionSystems for the Power Generators
- 2. Index Agenta : 1Nov 2014 1 p.m ~ 3 p.m “AGGC” 1.00 p.m : Welcome Speech by AGCC CEO 1.10 p.m : Introduction to the Speaker 1.15 p.m : Fault Analysis Detail 1.50 p.m : Tea Break 2.00 p.m : Protection Systems for Power Generators 2.40 p.m : Question and Answer Section 3.00 p.m : End of Presentation
- 3. Index Generator Protection What aGenerator looks like
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- 5. Index Why Upgrade? Generatorand Transformer Existing generator and transformer protection (more than 5 years or non-digital) may: – Cause protection security issues Tripping on through-faults, external faults, swings, load encroachment and energizing – May lack comprehensive monitoring and communications capabilities Not provide valuable forensic info that can lead to rapid restoration – Not be up to ANSI/IEEE Standards! Insurance, Asset Reliability and Personal Liability Issues C37-102: Guide for the Protection of Synchronous Generators C37.91: Guide for Transformer Protection
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- 7. Index Show Generator TheoryGeneral Overview and Typical System from Training CD
- 8. Index Generator Protection Internal andExternal Short Circuits The "Wild" Power System G Exciter Stator Ground Stator Phase System Ground System Phase
- 9. Index Generator Protection Review –Abnormal Operating Conditions Loss of Synchronism Abnormal Frequency Overexcitation Field Loss Inadvertent Energizing Breaker Failure Loss of Prime Mover Power Blown VT Fuses Open Circuits
- 10. Index Generator Protection Abnormal OperatingConditions The "Wild" Power System G Exciter Loss of Field Loss of Field Overexcitation Overexcitation Overexcitation Open Circuits Loss of Synchronism Inadvertent Energizing, Pole Flashover Abnormal Frequency Abnormal Frequency Breaker Failure Reverse Power Over Power
- 11. Index Small Machine Protection IEEEBuff Book Small – up to 1 MW to 600V, 500 kVA if >600V 32 Reverse Power 40 Loss of Excitation 51V voltage restraint 51G Ground overcurrent 87 Differential
- 12. Index Small Machine Protection IEEEBuff Book Medium – up to 12.5 MW 32 Reverse Power 40 Loss of Excitation 46 Negative Sequence 51V voltage restraint 51G Ground overcurrent 87 Differential
- 13. Index Small Machine Protection IEEEBuff Book Large – up to 50 MW 32 Reverse Power 40 Loss of Excitation 46 Negative Sequence 49 Thermal Overload 51V voltage restraint 51G Ground overcurrent 64 Ground Relay 87 Differential
- 14. Index Unit Connected, High ZGrounded Large Machine Protection IEEE C37.102 32 Reverse Power 40 Loss of Excitation 46 Negative Sequence 49 Thermal Overload 51V voltage restraint 51G Ground overcurrent 64 Ground Relay 87 Differential
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- 16. Index Protection Functions Protection FunctionsInclude: • Generator Stator Differential • Backup Distance Protection • 100% Stator Ground • Generator Unbalance • Loss of Excitation • Accidental Energization • Breaker Fail • Phase Overcurrent – Voltage Restraint • Neutral Inst. / Timed Overcurrent • Neg. Sequence Overcurrent • Under / Over Voltage • Under / Over Frequency • Generator Thermal Model
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- 18. Index Generator Protection withGSU Wrap PTs on Low Side
- 19. IndexGenerator Protection withGSU Wrap PTs on High Side
- 20. IndexGenerator Protection PTs onLow Side
- 21. Index Desirable Attributes -Generator – Reverse Power (32) Should be sensitive to 0.05 pu to properly detect motoring in large steam turbines Existing E/M and Static relays not sensitive enough May cause shutdown difficulties – Negative Sequence (46) Should be sensitive to low values to detect open poles/conductors on system after GSU Existing E/M and Static relays not sensitive enough Long time low level events may cause excessive rotor heating, thermal tripping and damage rotor – 100% Stator Ground (59N / 59D) Protects all of the stator winding Existing schemes typically only see 90% Stop low level fault near neutral from degrading into a high level fault and causing large
- 22. Index Desirable Attributes -Generator Inadvertent Energizing (50/27) – High speed tripping of unit after breaker accidentally closed on dead machine, also pole flashover prior to syncing Most existing schemes do not incorporate – Many schemes fail due to complexity (reliance on breaker auxiliary switches, yard distance relays, etc. – If breaker is not tripped rapidly, mechanical and electric damage can occur to machine in fractions of a second! – Pole flashovers must be cleared by high speed breaker failure, as the breaker is open!
- 23. Index Line – Groundfaults – Delta Connected Generator
- 24. Index Line – Groundfaults – Wye Connected Generator
- 25. Index Protection Functions Generator StatorDifferential • Stator Phase Differential • Dual Slope Percent Restraint Operating Characteristic • Directional Supervision under saturation conditionsDistance Backup Protection • 2 or 3 Zone Mho Distance Protection • Backup for primary line protection • Configurable Reach and Angle Distance Characteristic 100% Stator Ground Protection • 95% Fundamental OverVoltage • 15% Third Harmonic UnderVoltage Dual Slope Phase Differential Two Zone Distance Backup
- 26. Index Protection Functions Voltage RestraintOvercurrent Undervoltage Trip Curves Voltage Protection • Phase Overvoltage • Phase Undervoltage • Neutral Overvoltage (fundamental) • Neutral Undervoltage (3rd Harmonic) • Voltage Phase ReversalCurrent Protection • Phase, Ground and Negative Sequence Overcurrent Tripping • IEC, ANSI , IAC and Customizable Overcurrent Curves • Voltage Restraint increasing sensitivity under low voltage conditionsFrequency Protection • Overfrequency • Underfrequency
- 27. Index Protection Functions Loss ofExcitation Thermal Protection • Generator Thermal Model • RTD Alarming and Tripping • RTD Biased Thermal Model Inadvertent Energization • Prevents Accidentally Closing a Stopped Generator onto a Live Line • Armed when Generator is Offline and Voltage is below a pre-set level Loss of Excitation (show Training CD) • Uses Impedance Circle for loss of excitation detection • 2 Zones for fault detection and control Volt/Hertz (Overexcitation) • Detects changes in the Volts/Hertz ratio of the generator or associated transformer Thermal Model – Voltage Dependant Overload Curves
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- 34. Index Agenda : 1Nov 2014 1 p.m ~ 3 p.m “AGCC” THANK YOU.