OPERATION OF HYDRO POWER STATION

 OPERATION OF HYDRO POWER STATION

                                                                              

1.0  INTRODUCTION

 

Operation of Hydropower plant involves understanding of operation of hydraulic features and equipments. All features may not be included in every plant and will depend on type of plant water source, turbine & generator installed and power evacuation arrangement and will generally consists of following:-

 

1.1 CIVIL & HYDRAULIC STRUCTURE

 

• Lake/pond/river/canal as main water source

• Dam/Diversion weir/Diversion barrage

• Head regulator

• Power channel/tunnel

• Desilting arrangements

• Fore Bay

• Bye pass/Spillway

• Trash racks

• Intake Gates with Hoist

• Siphon intake

• Surge Tanks/Spilling pipes

• Penstocks

 

1.2 POWER HOUSE

 

(i) Mechanical

• Main inlet valve (Butterfly/Spherical valve)

• Bye pass valve

• Inlet bend and branching pipes

• Drain valve

• Pressure reducing valve for cooling water system

• Cooling water system

• Turbine and its auxiliaries

• Draft tube

• Draft tube gates

• Governor, associated OPU and guide apparatus

• Station auxiliaries such as:-

(i) EOT cranes/hoists

(ii) Station compressor

(iii) Drainage & Dewatering system

      (iv) D.G. Set

 

 

(ii) Electrical

• Hydro generator and auxiliaries

• AVR & Excitation system

• Generator protection/relay and control panel

• A.C. auxiliary supply

• D.C. control supply, batteries & battery charger

• TG start up panel

• Synchronizing panel

• Generator transformer

• Station transformer

• Unit auxiliary transformer (if applicable)

     • Relay and control panel

 

1.3 SWITCHYARD

 

• Switchyard structure

• VCBs/SF6 circuit breakers and Isolators

• CTs

• PTs

• LA

• Line side Isolator

• Surge counters

• Outgoing lines

 

1.4 OTHER SYSTEMS

 

• Lighting system, emergency lighting

• Station earthing, lightening protection

• Communication system

• Fire fighting and hydrant system

• Safety tagging & safety interlocks

 

2.0  GUIDELINES FOR OPERATION OF POWER PLANT

 

      Operation of power plant shall have two elements:-

• Water operation

• Operation of Power Plant

 

2.1 WATER OPERATION

 

Just like operation of Turbine Generator set or a transformer, efficient water operation forms an important part of hydro power plant be it large storage plant or small run of river plant. Water operation means operation of following systems of the hydro plant in such a manner that efficiency of plant is maximum. It is generally reflected in   kWH/ Cumec

 

.

2.1.1 Catchment Area

 

The area gives the runoff into the lake/pond/river during rainy season. Run off rate cubic m/mm should be known to operator to adjust generation accordingly.

 

2.1.2 Lake/Storage/Pond

 

The operation of lake based plant means keeping the level such that during rainy

season the over flow chances are minimum. In case of diversion type plants it is

essential to keep the gates during flood conditions open to avoid flooding and lower them only when rain is low or over. In such plant it is essential to check that there is no leakage from the gates or stop log gates. If operator notes that the leakage is more, he should pass on his observation to higher authorities to ensure corrective measures in the interest of having more generation.

 

2.1.3 Run of River Type Plants

 

Availability of water is more important factor in operation of hydro power plants. It is therefore, essential to generate continuously to its full capacity during monsoon season. Failure of a machine during monsoon can cause a substantial generation loss. All operation staff must, therefore, be very vigilant during this period. In lean season diversion barrage gates/diversion weir gates are checked for leakage, corrective measures are taken as soon as possible so that there may not be any generation loss on his account

 

2.1.4 Power Channel/Duct/Canal

 

The operation of open channel/duct is critical to water operation and efficiency of plant. Depending upon the length, condition of lining, head on head regulator, time required discharge to reach fore bay and to the machine. As per this discharge guide vane opening is calculated. Any time delay or change in opening will affect water reaching the TG unit causing change in generation. The time taken by water to reach the turbine will depend on many factors and only experience will make the operator perfect

.

2.1.5 Fore bay

 

Fore bay is a essential part of any water conductor system with open channel. It  serves the purpose of connecting penstocks with gates and acts as tank. It takes care of small variation in generation, water supply and acts as desilting basin. The operation of fore bay is important during picking up load and at the time of tripping of machines. Actual over flow, through bye pass, is always recorded to calculate water wasted during over flow, especially during lean season.

 

 

 

 

2.2 OPERATION OF POWER STATION

 

The operation of power station requires that its staff is trained and well versed with all necessary technical as well as basic trouble shooting knowledge. As a   to bring out some details of operating a HEP, the following checks are to

be made before starting of machine:-

 

• Shut down clearance

• Water restriction, if any

• Permission from ALDC

• Permission from nearest grid substation

• Proper working of

􀂾 Communication system

􀂾 AC Power

􀂾 DC Power

􀂾 Firefighting system

􀂾 Cooling water system

􀂾 Drainage & dewatering system

􀂾 H.S. lubrication system

􀂾 L.P. & H.P. compressed air system

􀂾 Protection system

 

2.2.1 Check List for Starting of Machine

 

The staff responsible for the operation should be well conversant with technical

details and importance of following:-

• Intake gates, bye pass gates, draft tube gates & fore bay

• Inlet valves

• Turbine

• Generator

• Generator Transformers

• Switchyard

• Synchronizing with grid

• Shut down of machine

• Emergency shutdown of machine

• Importance of log sheets

 

2.2.2 Mechanical

 

On Intake

• Check bye pass gate are not mechanically locked and all valves are in okay

    position

• Check position of intake gate

• Check position of stop log gates

• Check filling line valve of penstock

• Check supply to gates is O.K.

 

Inside P.S.

(i) Inlet valve:-

• AC power for pump operation

• HP compressed air

• Locking pin position

• Level and pressure in OPU

 

(ii) Others:-

    (a) Check valves:

• Check spiral drain valve is closed

• Check D.T. drain valve is closed

• Position of strainer valves ensure water flowing in cooling pipes

• Gland seal valve open

• Air seal valve closed

• Top cover drain system okay

          (b) Check levels:

• Pressure accumulator (OPU)

• Turbine Guide bearing

• Lower Guide bearing

• Upper Guide bearing

• Thrust bearing

          (c) Check pressures:

• Spiral casing

• OPU

• Stator cooling water pressure

• Thrust bearing, UGB, LGB

• Sealing water pressure

• Servo motor Pr. Gauge

• Air pressure (brakes)

         (d) Check working of systems

• Top cover drain

• Oil leakage unit

• Oil cooling unit

• Oil pressure unit

• Brakes

• Position of CO2 batteries

• Guide vane lock on or off

• Check jacking/de-jacking of m/c

• Check flow relays

• Check emergency slide valve reset

• Check working of ventilation system

• D.C. System

• Grid Power

• DG Set power

              • Event logger & Disturbance logger

             

2.2.3 Electrical

 

        Check list of Generator

• Brake system

         • Cooling water for bearings

• Generator fire fighting, if applicable

• AVR condition

• DC supply for field flashing

• Oil levels in bearings

• IR values

• Jack position

• H.P. lubrication system

• Check earth link for bus duct/XLPE cables

 

     Check list for Transformers

• Cooling water system

• Firefighting system

• Transformer cooling oil pump position

• Buccholz relay

• Oil level in conservator

• Colour of silica gel

• IR of winding and core

• BDV of oil

Check list for Switchyard

• Compressed air in case ABCBs are used

• SF6 gas pressure in case of SF6 breaker

• Earthing switch position

• Isolator position – close

• Breaker position – off

• Line isolator position

 

2.2.4 Operations

 

       (i) Inlet Valve Opening

• Put oil pumps on ‘auto’ mode

• Open compressed air valve, if applicable

• Open bye pass manual valve

• Give opening command to bypass auto valve

• Check water pressure for equalizing

• Give opening command to inlet valve

• When inlet valve is fully open oil pumps must be stopped

 

 

 

      (ii) Turbine Operation

• Put oil pumps on auto mode

• Check availability of Nitrogen cylinder and check pressure of the same

• Open cooling water for bearings

• Open shaft seal water

• Put brake on auto mode

• Release lock pin

• Fix GV opening limit

• Put machine on auto mode

 

   (iii) Generator Operation

• AVR on manual mode

• Cooling water for transformer on

• Oil circulation of transformer on

• Keep fire fighting system alert

• On D.C. supply for excitation flashing

• At 30% of generator voltage D.C. supply from battery cuts

        • Now generator excitation supply

 

.

 (iv)  Synchronization

 

   (a) Synchronization checks

• Line protection

• PLCC

• Give clearance for line back charging

• Close line isolators

• Close line breakers

• Now circuit is charged up to switchyard from remote end

• Start machine on auto mode

 

     (b) Synchronization

• Close field breaker

• Now m/c will run at rated speed and rated voltage

• Check line voltage & frequency

• Check generator voltage & frequency

• Reduce or increase generator voltage & frequency to match with line

   voltage & frequency.

• At equal line & generator voltage and frequency, close generator

   breaker.

• Now generator is synchronized with grid.

• Take minimum prescribed load immediately

 

   

 

 (c) Checks after synchronizing and taking load

• Unit control board supply is changed to unit Aux. Transformers.

• Transformer “Motor for Cooling Water Supply” started.

• All parameters in control room are matching and correct.

• General check up of machine and other unit auxiliaries at all floors.

 

2.2.5 Checks at the Time of Shift Change Over (Machine Running on Load)

 

(i) Turbine & Governor

􀂾 Check Temperature of following

- Thrust bearing

- Upper guide bearing

- Lower guide bearing

             􀂾 Check following in normal working condition

- Cooling water flow and pressure of all bearings at inlet & outlet

- Sealing water flow and pressure

- Stator cooling flow and pressure, if stator air coolers are provided

- Grease pump

􀂾 Check oil level in housings of all bearings

􀂾 Check if, there is vibration or abnormal sound in OPU pumps

􀂾 Check grease in the container of centralized grease lubrication system

              􀂾 Check working of following

- OPU pump 1 & 2

- OLU pump

- Drainage pump & dewatering pumps

- Governor compressor

- General purpose compress

- Ejector system for top cover drains

- Cooling water strainers

􀂾 Check sealing water pressure & air seal pressure

􀂾 Check running and vibration of machine and ensure nothing is  abnormal

􀂾 Check working of top cover drainage system

􀂾 Check water, oil and air flow indicators

              􀂾 Check physical appearance of various system such as man holes, valves indicators etc.

􀂾 Check G.V. Servomotor stroke & R.B. angle is normal

􀂾 Check general housekeeping is in order and all panels, mountings on

                   wall is clean and in order.

 

         (ii) Generator, AVR & Excitation System

􀂾 Watch running and vibration of machine and ensure nothing is

      abnormal.

􀂾 Check for any sparking from the brush of slip ring, if applicable for

    SEE only

 

􀂾 Check temperatures of winding & core. Ensure that these are within

    limit.

􀂾 Check that all instruments and indicators mounted on unit control

     board, governor panel and AVR & excitation panel are in OK

                   condition.

􀂾 Check all indication lamps are glowing.

􀂾 Check with test push button that all fault indication lamps are OK.

􀂾 Physical check of all sub distribution boards installed in P.S.

􀂾 Check all inlet exhaust fans are working.

􀂾 Check all batteries are physically in good condition.

􀂾 Check battery chargers are in normal working conditions.

􀂾 Check for any abnormality, sound, chattering in bus duct, generator

     barrel, neutral cubicle.

􀂾 Check all AC supply boards installed in Power House are okay.

􀂾 Check air conditioning plant is working satisfactorily.

 

        (iii) Control room

􀂾 Check that all parameters indicated on various panel are matching.

􀂾 Check all indicating lamps are glowing. Also check annunciations are

    OK.

􀂾 Check movement of all pointers & reset them.

􀂾 Check all instruments mounted on panels are in working order.

􀂾 Check all facias & relays are reset.

􀂾 Check rear of all panels and mounting on this side for OK condition.

􀂾 Check emergency lighting system is OK.

􀂾 Check position of circuit breakers for outgoing lines.

􀂾 Check grid voltage & frequency.

(iv) L.T. room

􀂾 Check all indication lamps are glowing.

􀂾 Have general look on instruments and relays mounted on board.

􀂾 Check various switches are in correct position.

􀂾 Check whether supply to various distribution boards are OK

.

       (v) DC Distribution Board, Battery Charger & Battery sets

􀂾 Check D.C. voltage is correct.

􀂾 Check D.C. supply is healthy by making momentarily float off. This

     would ensure that batteries are connected with load.

􀂾 Check both batteries are on float.

􀂾 Check all the switches on DC board are in correct position.

􀂾 Check that both chargers are functioning correctly.

􀂾 Check all cells of battery bank are healthy. Their sp. Gravity and cell

     voltage is correct.

 

          (vi) Main Transformers

􀂾 See that oil level is OK & there is no leakage from anywhere.

􀂾 Check that oil pressure and water pressure are normal.

􀂾 Check that oil temperature and winding temperature are normal.

􀂾 Check silica gel colour is normal.

􀂾 See that oil and water flow indicators are normal.

􀂾 Carry out following checks for healthy condition of Mulsifyre system:

     - Compressor

      - Power

􀂾 Oil level in conservator is normal.

(vii) Switchyard

􀂾 Have general look at switchyard including bus bars, jumpers etc. Ensure

     that there is no sparking anywhere and everything is in order.

􀂾 Check compressed air system in case of ABCB is OK, if provided.

􀂾 Check SF6 gas pressure in case of SF6 breaker.

􀂾 Check position of all breakers, isolators & line isolator and cast a look

    on all CTs, PTs, LAs, Surge counters, wave traps and coupling

    capacitor and ensure that everything is in order.

 

         (viii) Routine maintenance to be carried out during each shift

- Cleaning of all panels, instruments and equipment installed in power

    station.

- Oiling and greasing of all equipment as per instructions.

- Topping up of oil in bearings, OPU sump.

- Replacement of lamps, fuses etc.

- Cleaning of trash racks.

- Inspection of fore bay, bye pass gates, intake gates.

- Any other work as assigned.

- Work carried out during each shift shall be logged in daily in control

    room logbook.

 

 

Safety Precautions and Practices in Operating and Maintenance

 

•  No unsafe operation will ever be permitted. Feedback regarding unsafe operation /condition should be taken into consideration with proper spirit and review should be made to avoid accidents.

 

• Interlocks should not be by-passed unless it is very essential. Written permissions should be obtained from the superintendent/ in charge of the station. Extra precaution should be taken by all the parties during such cases.

 

• Equipment are designed for certain operating conditions, it should be operated within prescribed operations limits. Overstressing of the equipment should be for minimum possible time with minimum percentage of overloading. This will avoid damage to the equipment.

 

 

 

• Operation and Maintenance staff should be familiar with the station layout and

   Operations limits of different equipment such as breakers, transformers, isolators CTs, PTs, etc. A person should be allowed to operate or take over the equipment only after he has acquired adequate knowledge of the equipment.

 

• Operation should be carried out as per Operations Instructions. This will help in carrying out operations safely and maintaining uniformity. In case of any

   modifications/ change in the layout operating instructions should be reviewed.

 

• Booklets/ manufacturer’s instructions for different equipment should be available and should be referred to before taking out equipment for maintenance.

 

• It is the responsibility of the supervisor to interpret correctly and explain safety rules and regulations to all the persons concerned and ensures that they thoroughly understand the same.

 

• Breach of safety rules should be suitably dealt with.

 

• Only authorized persons shall be allowed to carry out operation and maintenance.

• Supervisor shall guard against the use of defective safety appliances, tools,    and materials.

 

• In case of any emergency, in which quick action is necessary, in order to safeguard personals or property, only authorized persons will take necessary action. Under no circumstances attempt shall be made to carryout operations which are not safe.

 

• All persons must use the standard protective equipment intended for the job

.

• All protective equipment should be periodically tested.

 

• Metal ladders should not be used in switchyard.

 

• Adequate number of first aid and firefighting equipment shall be maintained.

 

• First aid and artificial respiration chart shall be exhibited. Every person shall be familiar with the same.

 

• Every person shall be familiar and should know how to operate firefighting

   equipment, so that fire can be extinguished promptly thus minimizing damage

.

• In the event of the fire on electrical installation, the affected part shall be immediately switched off and isolated from all the sources.

 

• Use HRC fuses only with proper capacity.

 

• While opening isolator confirm that it is not carrying load current. Similarly isolator should not be closed on load.

 

• Underrated circuit breakers should not be used to clear the fault.

 

• No breaker should be operated beyond stipulated operating duty.

• While working on the breaker, its operating mechanism should be de-energized such as discharging spring, releasing air pressure etc.

 

• Transformer should be discharged and grounded from all sides (windings). Neutral grounding of the transformer should not be treated as grounding.

 

• Current transformer secondary should never to be left open circuited.

 

• After cutting out capacitor bank, it should be allowed to discharge through discharge PT for about 10 minutes. The bank should be grounded with hot stick before commencing the work.

 

• ASKAREL compound used in capacitor bank as a dielectric is very toxic and harmful. Hence, should be handled with great care.

 

• Apparatus, frame work and other non-current carrying metal parts associated with power system are to be effectively grounded.

 

• Lighting arresters shall be grounded independently.

 

• Isolating switches provided for Generators and synchronous condensers and other rotating machines should never be opened when connected to any voltage source even when the machine is carrying no load.

 

• The areas should be cordoned off indicating location of work on the particular

  equipment.

 

• Use of safety tags must be ensured while allowing shut down for maintenance on some part/ equipment.

 

 

 

 

 

 

 

 

 

 

6.0 GUIDELINES FOR DOCUMENTATION

 

Documentation

 

Documentation at all levels of work done is necessity for any references and analysis of data/information in future as and when required.

 

Roll of operation staff is very important in registering all valid information operatin parameters such as temperature, vibrations, pressure, generation voltage and current etc. in the operation log books and shift registers.

 

Every event should clearly mention frequency, voltage, MVAR, MW, MWH at the

instant with other necessary data e.g. alarms, annunciations temperatures, fore bay

Levels/reservoir levels, inflows etc. as may be necessary from case to case.

 

 

Any tripping event should be clearly noted with relevant details, such as relay

operation details, disturbance recorders and event logger print outs. Restoration activities after every tripping should be reported with details of preventive action taken or to be taken based on certain conditions. This information should be presented in prescribed format, should be checked on daily basis by Engineer concerned, who will check and authenticate the same for future use.

 

For maintenance also similar registers are maintained giving details of maintenance

activities at different frequencies such as daily, monthly, annual etc. or break down

maintenance.

 

Results of test and measurements carried out during maintenance should be tabulated in standard formats and this should include the commissioning and acceptable values are applicable for proper comparison and planning remedial action.