Meeting the Challenges of the New Millennium:*
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Show Generator Theory General Overview and Typical System from Training CD
SR489
SR489
Blown VT Fuses
32 Reverse Power
PTs on Low Side
PTs on High Side
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 amounts of damage
Very secure
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!
SR489
Directional Supervision under saturation conditions
Distance Backup Protection
Backup for primary line protection
Configurable Reach and Angle Distance Characteristic
100% Stator Ground Protection
Voltage Restraint increasing sensitivity under low voltage conditions
Frequency Protection
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
SR489