What are the tripping parameters of turbine

Tripping parameters of turbine and related logic’s

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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