Operation of hydro power plants

The presentation will give you brief idea about the operation of hydro power plant which includes pre-check conditions, starting and stopping sequences, loading of unit, emergency stopping, parameter monitoring and control.

1. Operation of Hydro Power Plants Dinesh Prasad [email protected]

2. Topics to be covered Pre-check conditions Starting & Stopping sequences Loading of unit Emergency Stopping Parameter monitoring and control

3. Layout of Presentation Unit Operation Control Pre-Check Conditions Starting Sequence Parameter Monitoring & Control Stopping Sequence Emergency Stopping

4. Unit Operation Control(1) Manual control Semi-automatic control Fully automatic control Offsite supervisory control

5. Unit Operation Control(2) Manual Control:- In this type of control, the chain of the pre- starting checks, starting , synchronizing, loading and stopping is selected and performed in turn by hand whether mechanically or by push buttons.

6. Unit Operation Control(3) Semi-automatic control:- In this type of control, from a single manual starting impulse a unit may be brought to the ready to synchronize condition by the automatic selection , performance, and providing of a sequence of controls . Likewise a similar stopping impulse completely shutdown the unit. Synchronizing and loading control remain manual functions from the local and remote control , points.

7. Unit Operation Control(4) Fully automatic control:- In this type of control, means are provided for running up, automatically synchronizing and loading up to a predetermined quantity on receipt of a single starting impulse. Subsequent manual variations of loading and excitation may be provided as a remote control function. The corresponding stopping impulse will cause the load to be reduced, the unit to be disconnected from the bus bars and the turbine to be shutdown completely.

8. Unit Operation Control(5) Offsite supervisory control:- Starting, stopping, switch closing or opening and other functions initiated from a remote point, together with indications of successful operations of voltage and load control and of the repetition of alarm conditions at the remote control point. The equipment is ancillary to either semiautomatic or fully automatic unit control.

9. Unit Operation Control(6) Control Hierarchy of Hydro-electric Plants:- Control category Subcategory Remarks Location Local Control is local at the controlled equipment or within sight of the equipment. Centralized Control is remote from the controlled equipment, but within the plant. Offsite Control location is remote from the project. Mode Manual Each operation needs a separate and discrete initiation; could be applicable to any of the three locations. Automatic Several operations are precipitated by a single initiation; could be applicable to any of the three locations Operation (Supervision) Attended Operator is available at all times to initiate control action Un-attended Operation staff is not normally available at the project site

10. Pre-check conditions(1) There is no work-permit , outstanding. Intake gate fully open. Draft tube gate is fully open. Protective devices reset. Wicket gates closed.

11. Pre-check conditions(2) Control supply(Generally DC) to Unit control Board(UCB), Control & Metering Relay(CMR) Panel, Excitation system, Governor cubicle etc. are healthy. AC supply to UCB, CMR and all unit auxiliaries are made ON. Governor in automatic position . OPU Pressure is normal. Oil level in the lubrication system normal.

12. Pre-check conditions(3) Compressed air system normal . Brake pressure is normal. Cooling water supply to bearing coolers & shaft seal is healthy. Guide vane servomotor lock is released. Space heaters of generator are OFF. Generator/GT Circuit Breaker is open. All temporary earthling arrangements are removed off live conductors/wires.

13. Pre-check conditions(4) All earth switches in Generator/GT bay of switchyard are open. Generator brakes are released. Generator field breaker is open. Water level normal.

14. Pre-check conditions(5) Many of the above checks and operations may be built up in the starting interlocks and starting sequence. These variations are to be checked with particular Power Station.

15. Unit Operation Sequence Unit operation sequence refers to the safe operation of machine in a particular sequence, without any damage to plant and its associated equipment's, thereby giving birth to successful generation. Starting sequence Stopping sequence

16. Starting Sequence(1) 4 steps :- Generally opens the main inlet valve & start unit auxiliaries. The turbine is started and brought up to speed no load and field breaker is closed. The paralleling of the unit is carried out & unit is synchronized with generator bus by closing the Generator/GT circuit breaker. Loading of the unit is carried out up to a preset value.

17. Starting Sequence(2) Starting the Unit :- Ready to start signal appears in control room Start command is given. Inlet valve opening sequence starts By pass valve opens Spiral casing pressurized Inlet valve opens By pass valve closed. H.P . oil injection pump starts.

18. Starting Sequence(3) Cooling Water flow to bearings, stator coolers and transformer cooler starts and cooling water established relay energized. Open command given to guide vane limiter. Guide vanes open to start position. Machine starts rolling. Machine speed reaches 80%.

19. Starting Sequence(4) Governor starts functioning. Machine speed reaches 90%. Generator Field excitation starts. Generator Voltage reaches normal. Machine ready to synchronize. Note down the starting time of machine.

20. Starting Sequence(5) Synchronization of Unit :- Inform RLDC and receiving-end about synchronization. Check that Bus selection isolator is in close position. Check that Bus Bar is charged. Make the synchronizing selector switch on. Match voltage & frequency of the Generator with that of the grid.

21. Starting Sequence(6) Make synchro-scope indicator start rotating in clock-wise direction at a very slow speed. Close Circuit Breaker at 11o’clock position of synchro-scope indicator. Increase the Power Generation by Power Raise/ Lower switch. Note down the synchronization time of the unit.

22. Parameter monitoring and control(1) Attend any alarm appearing in control room Identify critical points of the Power station Like :- Temperature of bearings. Temperature of Stator. Temperature of Generator Transformers . Cooling water flow in shaft seal different bearings, stator air cooler, transformer cooler and running of pumps, choking of coolers.

23. Parameter monitoring and control(2) Leakage water level in turbine pit. Running of drainage/dewatering pumps. Voltage at HV Bus and reactive Power flow. Stator & field currents. OPU Pressure and oil level in OPU Pressure tank (should not be high) Oil level in bearings. Machine vibrations. Abnormal sound from the machine.

24. Parameter monitoring and control(3) Take hourly reading of Tail water level. Obtain hourly reading of Dam water level from Dam Control Room. Fill up hourly log sheet for various parameters of the machine. Co-ordinate with RLDC and Remote end for any shutdown of machine/ line and major change in generation.

25. Stopping Sequence(1) Inform RLDC and receiving end. Reduce the load of the machine slowly. When load is reduced around 10-15% of full load, open the generator C.B. Check that C.B. has opened. Give stop command Generator C.B. opens if not open already. Generator Field breaker opens and closing starts.

26. Stopping Sequence(2) Guide vane is closed. Machine retards. The bearing H.P. oil pump starts, At 25% of rated speed, Generator Brakes are applied. Machine comes to stand still. H.P. Oil pump stops. Generator Brakes released.

27. Stopping Sequence(3) Cooling water to stator, transformer and bearings is closed. G.V. servomotor is locked. Generator Isolation (EHV) is opened Make a record of time of opening of Generator C.B. and stopping of machine.

28. Emergency Stopping(1) TRIPPING OF MACHINE ON FAULT(1):- Protection relay operates  Trip Relay operates. Generator C.B. is opened. Generator Field breaker is opened. Closing command is given to guide vanes and inlet valve. Stop sequence starts as in case of manual stopping of the machine. Note down the operated protection relays, flags after ensuring that machine has stopped.

29. Emergency Stopping(2) TRIPPING OF MACHINE ON FAULT(2):- Take print out of Sequential Event Recorder. In case of tripping of lines/load throw-off, communicate with remote end and get information about operation of relays at receiving end. Also take print out of Sequential Event Recorder (SER) & Fault Disturbance Recorder. Intimate maintenance staff giving as much detail as known.

30. Emergency Stopping(3) Increase in water level inside Power House :- Raise Alarm. Intimate Project In charge. Try to stop the source of leakage water. If the leakage is from the machine immediately close the intake gate after opening the generator circuit breaker and giving stop command to the machine. Ensure that Power Supply to Drainage & Dewatering pumps is not shut down. Run the available drainage / dewatering pumps or any other available pumps to pump out the water.

31. Emergency Stopping(4) Fire:- Raise Alarm. If fire is in the machine or Transformer Give stop command. Release CO 2 or water through mulsi fire system as per the provision . Intimate fire station. Try to isolate other equipment from the source of fire.

32. Thank You