What are the tripping parameters of turbine

DCS Control Systems
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Tripping parameters of turbine and related logic’s

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By Interlocks, we are ensuring the safety of Steam turbine and its accessories.
Steam turbine and generator together have hell a lot of interlocks for the safety and reliability of the units. I’ll try to cover the major one,

All these interlocks are usually based on the supervisory probes/sensors provided by OEM to make sure the turbine parameters should not jump the safe limits. And if they act, they either trip the machine or shutdown it.

  • Bearing Vibration - Probes are provided on almost every bearings for measuring bearing vibration (sensor type- displacement/velocity/or Acceleration) and they trip the machine in case high vibration crosses specific limits.
  • Bearing temperature. - High temp. Alarm and then Trip.
  • Differential Expansion (It indicates the relative expansion of Turbine casing and Turbine rotor - Will have trip limits on both +Ve and -Ve side) and Absolute Expansion (Measures the expansion of casing relative to Bearing pedestal ).
  • Lube Oil temperature - Alarm - Not trip usually.
  • Lube Oil Pressure- Low pressure trip.
  • Steam parameters - Low steam flow and temperature- Trip.
  • Vacuum deterioration- High Exhaust Pressure-Low Vacuum - Trip.
  • High Hotwell level - Trip.
  • Overspeed - Trip (Usually 3 or 6 sensors - Voting logic - 2 out of 3/ 4 out of 6).
  • High Exhaust temperature - Trip.
  • If Both CEPs (Condensate Extraction pump ) are unavailable - Trip.
  • If Both Vacuum pumps are unavailable - Trip.
  • If upstream Steam source (Boiler or HRSG) Trips - ST Trip.
  • Control/Hydraulic oil pressure ( Operating the Main steam stop and control valves ) Low- Trip

Author : Bhola Shanker

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