Index
This Seminar is Proudly Sponsored by :TRUST SYNERGY INTERNATIONAL
by Nicholas Naing
GENERATOR PROTECTION SYSTEM
Index
1.00 p.m : Welcome Speech by YTU Electrical Power Department Head
1.10 p.m : Introduction to the Speaker
1.15 p.m : Generator Protection Systems
1.50 p.m : Tea Break
2.00 p.m : Protection Functions Detail
2.40 p.m : Question and Answer Section
3.00 p.m : End of Presentation
Agenta : 13th JAN 2016 , 1 p.m ~ 3 p.m , YTU
IndexOverview Generator Abnormal Operating Conditions
Loss of SynchronismAbnormal FrequencyOver excitationField LossInadvertent EnergizingBreaker FailureLoss of Prime Mover PowerBlown VT FusesOpen Circuits
Index
The "Wild"PowerSystem
G
Exciter
Loss of FieldLoss of Field
Overexcitation
Overexcitation
Overexcitation
OpenCircuits
Loss ofSynchronism
InadvertentEnergizing,Pole Flashover
AbnormalFrequency
AbnormalFrequency
BreakerFailure
ReversePower
OverPower
What Really happened ?
IndexWhat Really happened ?
The "Wild"PowerSystem
G
Exciter
StatorGround
StatorPhase
SystemGround
SystemPhase
IndexProtection Functions
• 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• RTD Temperature• Overexcitation – Volts/Hertz
IndexSmall Generator Protection (IEEE)
32 Reverse Power
40 Loss of Excitation
51V voltage restraint
51G Ground overcurrent
87 Differential
Small Size – up to 1 MW
IndexMedium Generator Protection (IEEE)
Medium Size – up to 12.5 MW
32 Reverse Power
40 Loss of Excitation
46 Negative Sequence
51V voltage restraint
51G Ground overcurrent
87 Differential
IndexLarge Generator Protection (IEEE)
Large Size – 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
IndexLarge Generator Protection (IEEE)
Large Size – above 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
IndexSample Generator Protection Relay Wiring
IndexSample Generator Protection Relay Wiring
IndexSample Generator Protection Relay Wiring
IndexSample Generator Protection Relay Wiring
Index
binary w. cable supervision inputs
Three-phase V AC(110-690V AC)
Three-phase I AC
MPU pickup/Dig. running/Ana. running
Crank Start prepare Run/stop coil
Three multi inputs: PT 100/1000, (0)4..20mA, VDO, 0..40V
Emergency stop
Start enable
Sample Generator Protection with Relay
Index
16 diesel generators15 diesel generators & 1 emergency generator8 bustie breakers2 shaft generators2 shore connectionsWrapped busbar possibillity
Sample Generators Parallel Setup
IndexBreak
IndexDesirable Attributes of Generator
Protection ANSI number Levels Standard
Phase sequence voltage 47 1 ×
Generator reverse power (2×) 32 2 ×
Generator overcurrent (4×) 50 4 ×
Voltage-dependent overcurrent 51V 1 ×
Fast overcurrent (2×) 51 2 ×
Generator overvoltage (2×) 59 2 ×
Generator undervoltage (3×) 27 3 ×
Generator overfrequency (3×) 81 3 ×
Generator underfrequency (3×) 81 3 ×
Busbar overvoltage (3×) 59B 3 ×
Busbar undervoltage (4×) 27B 4 ×
Busbar overfrequency (3×) 81B 3 ×
Busbar underfrequency (4×) 81B 4 ×
Generator overload (5×) 32 5 ×
Current/voltage unbalance 60 1 ×
Over excitation 24 1 ×
Loss of excitation 40 1 ×
Alarm relay 74 1 ×
Trip of non-essential load 3 3 groups
IndexGenerator Management Relay Sample
IndexProtection Functions
Generator Stator Differential (87)• Stator Phase Differential• Dual Slope Percent Restraint Operating
Characteristic • Directional Supervision under saturation
conditionsDistance Protection (21/21N)• set based in percentages of the line
impedances• zone 1 is 80% of the impedance of the
line in order to not reach the remote end, the
• zone 2 can be set at 120% of the impedance of the line in order to dependably overreach the line,
• zone 3 sometimes are disabled or set to cover an adjacent line.
IndexProtection Functions
Over Excitation ( 24 )
IndexProtection FunctionsVoltage Protection (59)
• Phase Overvoltage• Phase Undervoltage• Neutral Overvoltage (fundamental)• Neutral Undervoltage (3rd Harmonic)• Voltage Phase Reversal
Voltage Restraint OvercurrentUndervoltage Trip Curves
IndexProtection FunctionsCurrent Protection (50)
• Phase, Ground and Negative Sequence Overcurrent Tripping
• IEC, ANSI , IAC and Customizable Overcurrent Curves
• Voltage Restraint increasing sensitivity under low voltage conditions
IndexProtection Functions
Frequency Protection (81)• Overfrequency (81O)• Underfrequency (81U)
100% Stator Ground Protection (59N/59D)
Protects all of the stator windingExisting schemes typically only see 90%Stop low level fault near neutral from degrading into a high level fault and causing large amounts of damage
IndexProtection Functions
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 enoughMay cause shutdown difficulties
Negative Sequence (46)Should be sensitive to low values to detect open poles/conductors on system after
GSUExisting E/M and Static relays not sensitive enough
Long time low level events may cause excessive rotor heating, thermal tripping and damage rotor
IndexProtection FunctionsVolt/Hertz (Overexcitation) (40)
• Detects changes in the Volts/Hertz ratio of the generator or associated transformer
Loss of Excitation
Loss of Excitation (24)• Uses Impedance Circle for loss of excitation detection
• 2 Zones for fault detection and control
IndexProtection Functions
Thermal Protection (49 )• Generator Thermal Model• RTD Alarming and Tripping• RTD Biased Thermal Model
Thermal Model – Voltage Dependen Overload Curves
IndexProtection Functions
Inadvertent Energizing (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!
IndexProtection Relay Actions
IndexProtection Relay Actions
IndexCommon Problems
Index
Index
THANK YOU