Turbine Governing system

Key Points

Ø  Governing- Regulation of Turbine Speed under No Load and Varying Load

Ø  Others Works: CV Actuation/ Initial Run-up & Synchronization/ Load Variation to meet Grid Freq

Ø  500 MW KWU: Throttle Governed Machine

Ø  2 Governors , EHC and HG connected in Parallel: Only One at a time through Hyd Minimum slection

Ø  CVs Open according to Secondary oil Pressure

Ø  Between 100 MW  to 525 MW , Load variation done by HPCV throttling

Hydraulic Governor

Ø  Only one control Loop: Speed controller

Ø  Machine Speed: measured & Indicated by Primary Oil Pressure

Ø  Range of Speed Control : 2800-3210 rpm

Ø  Speed Regulation Range( Droop) of HG= 7%

Ø  HG acts as a Back-up to EHG

Ø  HG Cannot be isolated Mechanically

Ø  HG is the Primary Governor of KWU turbine

Electro-Hydraulic Governor

Ø  EHG has 3 control loops for speed, Load, Pressure

Ø  EHG enhance Turbine life by TSE

Ø  Faster Response and Precise Frequency control

Ø  Actual Speed Measured by Hall Probes

Ø  Range of speed Control : 0-3210 rpm

Ø  Speed Regulation( Droop) can be changed from 2.5% to 8% in step of 0.5% on Load, Usual setting: 5%

Ø  EHG Can be mechanically isolated by closing secondary oil from local

RTS:

Ø  Running condition: De-energized(Drain : closed), Tripping condition: Energized( Drain : Open)

Ø  Running: Control Oil àTo Trip Gear

Ø  Tripped Condition: Control Oil Path Locked & Trip oil from Trip Gear àDrained through Drain Port

Ø  02 in Nos in Series

Turbine Trip Gear

Ø  Main Protection Mechanism | 02 in Nos

Ø  Control OilàRTSàControl OilàTrip Gear spoolà Spool MovementàTrip Oil (from top) & Aux Trip Oil ( From Bottom)

Ø  Aux Trip Oil Keeps Spool in Lifted Position

Ø  Aux Trip Oil is connected to hydraulic Safety Devices: Over-speed, Low Vacuum & Thrust Bearing Trip Devices

SLLD

Ø  Resets Turbine after Tripping

Ø  Opens : SVs and Release CVs for Opening

Ø  AT 0% starting Device:

Bellows compressed ( CVs Closed)

Aux start up Oil Resets Trip Devices

Start up oil Resets SVs ( ESVs & IVs)

Ø  Raising starting Device:

Start-up Oil & aux start-up Oil circuits drained

ESV Opens at 42% and IVs open at 56%

Speeder Gear

Ø  Bellow + Spring

Ø  Bellow compression controlled by

Starting Device Position

Speeder Gear Position ( alerts Spring Tension)

Primary Oil Pressure

Ø  Draining /closing of oil drains happens through Aux FUP connected through link with speeder Gear

Test Valves

Ø  HP/IP SVs receive Trip Oil Through their Test valves

Ø  Port Opening for start-up oil and Trip Oil

Ø  Resets SVs after Turbine Tripping

Ø  Test valve can be operated with Handwheel

Working of Governing system

Control OilàStarting DeviceàAux Start-Up oil àTrip GearàHydraulic Protection Devices

                                                   àStart-Up oil àTrip GearàESVs

                                                                (Speeder Gear linked with Starting Device)

Trip Oil àAux FUP(movement according to SG)àAux secondary Oil à Input to Hydraulic Converter

Control Oil + Aux Sec OilàHydraulic converterà(trip oil àFUPs)àHP/IP Secondary oil to CVs