GB/T 44079-2024Code for operation of solar power tower plant (English PDF)

3 Terms and definitions

The receiver peak flux density is defined as the maximum radiant flux density received by the absorbing surface of the receiver; a note gives its unit as watts per square metre.

A cold start-up is defined as a start-up in which the gauge pressure on the steam and water side of the drum of the steam generation system is zero and the temperature is close to ambient. A hot start-up is a start-up in which that temperature is above 250 °C.

Four operating modes are defined. The collector and thermal storage mode is the mode in which the collector system, the heat transfer system and the thermal storage system are in operation while the heat exchange system and the steam turbine generator system are not. The power generation from thermal storage mode is the mode in which the thermal storage system, the heat exchange system and the steam turbine generator system are in operation while the collector and heat transfer systems are not. The collection, storage and power generation mode is the mode in which the collector system, the heat transfer, storage and heat exchange systems and the steam turbine generator system are all in operation. The anti-freezing mode is the mode in which the collector system and the storage and heat exchange systems are shut down for a long period and the molten salt is prevented from solidifying.

The terms and definitions of GB/T 40104 and GB/T 51307 also apply.

4 Basic provisions

4.1 Before the plant is put into operation, the selection of equipment and the configuration of the systems are to meet the requirements of GB/T 51307.

4.2 Before the plant is put into operation, the grid connection dispatch agreement and the power purchase and sale contract are to have been signed, and the grid connection technical requirements are to meet GB/T 28566 and GB/T 40103.

4.3 Before the plant is put into operation, an operating code is to be prepared and management systems drawn up, namely the duty management system, the daily management rules, the work ticket system, the operation ticket system, the shift handover system, the equipment patrol inspection system, the periodic testing and rotation system for equipment, the equipment defect management system, the operation analysis system, the training management system, the fire safety system, the technical document management system, the anti-accident measure plan, the labour protection measure plan and the emergency plan for accidents.

4.4 Operating staff are to have received pre-job training and obtained the corresponding certificate of qualification, to be in a state of health that meets the conditions for the post, to be familiar with the requirements of electrical safety work, and to have mastered the technical requirements, the methods of operation and the methods of fault handling of a solar power tower plant.

4.5 to 4.7 The operation, patrol inspection, routine maintenance, abnormal operation and fault handling of the step-up substation and of the high and low voltage electrical equipment, the secondary equipment and the common equipment are to meet DL/T 969. The operation, patrol inspection, routine maintenance, abnormal operation and fault handling of the electrical lines are to meet DL/T 1253. The operation of the dispatch automation equipment is to meet GB/T 31464 and DL/T 516.

4.8 and 4.9 The plant is to choose among the collector and thermal storage mode, the power generation from thermal storage mode, the collection, storage and power generation mode and the anti-freezing mode according to the meteorological conditions, the dispatch requirements, the system configuration and the operating state. After the plant is put into operation, equipment operating records are to be established, the operating condition of the equipment and the handling of abnormal operation and faults recorded and reported, and the operating data collected and analysed in good time.

5 Monitoring and operation

5.1 During operation, the state of the equipment, the operation of the production equipment and the adjustment of the parameters are to be monitored. The operation of equipment under the jurisdiction of the grid dispatch is to have the permission of the dispatch body. The load of the unit is to be controlled according to the planned curve issued by the dispatch body, the control indices meeting GB/T 40103.

5.2 The monitoring of the plant is to include the irradiance, ambient temperature, ambient humidity, wind speed, wind direction and cloud monitoring data; the operating mode of the plant; the grid voltage and frequency; the operating state of the heliostat field; the temperature of each panel of the receiver, the level of the inlet and outlet buffer tanks and the change of the inlet and outlet molten salt temperature; the pressure, temperature and pump state of the heat transfer system; the tank wall temperature, foundation temperature, expansion indication, cooling fan state, molten salt temperature and level of the storage system; the pressure, temperature and level of the heat exchange system together with the main steam flow and the temperature and pressure of the reheat steam; the operating state of the electric tracing and electric heating systems; the turbine back pressure and low pressure cylinder exhaust temperature, the steam pressure and temperature at the high pressure cylinder exhaust and at each regenerative extraction stage, and the turbine speed and differential expansion; the active and reactive power, voltage, current and frequency of the generator, the stator and rotor winding temperature and the stator core temperature, and the inlet water temperature, pressure and flow and the outlet water temperature of the generator cooler; the metal temperature of the thrust and support bearings of the turbine generator set, the vibration of the shaft and bearing pedestals, the axial displacement, the inlet and return oil temperature of each bearing, and the rotor vibration and eccentricity; the state of the electrical equipment; the state, bearing temperature, speed, pressure, flow, current and vibration of the rotating machines; the state of the valves and actuators; the state of the fire protection and fire detection alarm; the fault, accident and protection actuation signals; the real-time monitoring of the video surveillance system; and the parameters of the other auxiliary systems that need to be monitored. Alarm information found by the operating staff is to be acknowledged in good time.

5.3.1 The operations are to include the start-up, operation and shutdown of the collector and heat transfer systems, of the storage and heat exchange systems and of the steam turbine generator set.

5.3.2 For the collector and heat transfer systems, the checks before start-up are to include that the meteorological conditions meet the start-up requirements; that the station service power system is running normally; that the storage system is ready to receive molten salt; that the uninterruptible alternating current supply, the meteorological observation device and the infrared imager of the heliostat field are running normally; that the working indication signals of the heliostat field control network communication are correct; that the receiver and heliostat control systems are running normally; that the instruments, the equipment state and the parameter display are normal and the relevant protections are in service, the protections of the main systems and equipment being given in Annex A; that the main control system is working normally, the main analogue control systems being given in Annex B; that the electric tracing and electric heating systems are running normally under automatic control and the temperature meets the conditions for filling the system with salt; that the level of the low temperature molten salt tank meets the requirements for start-up and for operation on load; that the valve positions are correct and their drives normal; and that the compressed air system is running normally. The start-up operations are to include putting the electric tracing and electric heating of the collector and heat transfer systems into service; putting the heliostats into service and preheating the receiver; putting the receiver compressed air system into service; starting the receiver molten salt circulating pump so that the receiver begins to fill with salt; and adjusting the molten salt flow so that the receiver molten salt circulation is established.

5.3.2 (continued) The operating actions are to include adjusting the flow of the receiver molten salt circulating pump so that the level of the inlet buffer tank is controlled; adjusting the number of heliostats in operation or the flow between the circuits so that the receiver outlet molten salt temperature is controlled and the temperature difference between the circuit outlets is lowered; operating the valves according to the receiver outlet molten salt temperature so that the salt flow is switched to the low or the high temperature tank; and keeping the receiver peak flux density within the technical requirements of the receiver when the heliostat field is adjusted. The shutdown actions are to include reducing the number of focusing heliostats; adjusting the flow of the receiver molten salt pump so that the cooling rate of the panels meets the technical requirements of the receiver; switching the downcomer salt flow to the low temperature tank at a suitable time according to the receiver outlet temperature; keeping the receiver inlet molten salt flow not less than the minimum safe operating flow; opening the receiver drain valve so that the receiver is drained; adjusting the number of heliostats in service after draining so that the panel cooling rate meets the technical requirements; and withdrawing the heliostats from tracking.

5.3.3 For the storage and heat exchange systems, the checks before start-up are to include that the electric tracing and electric heating of the equipment are running normally; that the system equipment is intact, the valve positions correct and the drives normal; that the instruments, the equipment state and the parameter display are normal and the protections in service, the protection items being given in Annex A; that the control system is working normally, the main analogue control systems being given in Annex B; that the level of the high temperature molten salt tank meets the needs of unit start-up and operation on load; that the water treatment, dosing and sampling systems are working normally; that the compressed air, fire protection, industrial water, circulating water and other common systems are running normally; and that all the tests before start-up have passed. The hot start-up actions are to include checking that the drum level is normal and the water quality qualified and confirming that the drum is under heat and pressure preservation; choosing, according to the pressure parameters of the heat exchange system, the temperature at which the high temperature molten salt circulating pump and the tempering pump mix the salt for filling the system; and adjusting the output of the feedwater heater or the feedwater flow so that the preheater inlet feedwater temperature meets the technical requirements. The cold start-up actions are to include starting the feedwater pump so that the drum begins to fill, putting the feedwater heating system into service after the cold flushing of the system is qualified and, once the normal level is reached, starting the circulating pump so that steam and water circulation begins, the rate of rise of the drum saturation temperature and the temperature difference between any two points of the drum wall meeting the technical requirements of the equipment; raising the temperature and pressure of the heat exchange system to the set parameters and, once the hot flushing is qualified, starting the tempering pump so that the system is filled with salt, the rate of temperature change meeting the technical requirements; and starting the high temperature molten salt circulating pump, the rate of temperature rise of the mixed salt meeting the technical requirements.

5.3.3 (continued) The operating actions are to include controlling the load by the opening of the turbine governing valve when the unit runs at rated load and adjusting the flow of the high temperature molten salt circulating pump so that the pressure before the turbine inlet valve stays stable; opening the governing valve fully when the unit runs in sliding pressure mode and adjusting that flow to the same end; adjusting the feedwater flow, the drum level preferably being kept at the zero mark with a normal fluctuation range of 0 mm to 50 mm; and adjusting the molten salt flow and temperature so that the terminal temperature difference of the heat exchanger meets the technical requirements. The shutdown actions are to include starting the tempering pump so that the salt is mixed according to the required rate of temperature fall of the heat exchange system; putting the feedwater heating equipment into service according to the required feedwater temperature; shutting down the turbine once the steam pressure and temperature of the heat exchange system have fallen to the shutdown parameters and the load to the minimum the turbine permits; stopping the high temperature molten salt circulating pump and the tempering pump; and cutting off the external steam source, stopping the feedwater pump and the filling of the drum, and holding the temperature, pressure and drum level of the heat exchange system.

5.3.4 For the steam turbine generator set, the checks before start-up cover the integrity of the systems and equipment, the valve positions and their drives, the quality of the steam and water, the instruments, audible and visual alarms, equipment state and parameter display and the main protections of the unit, the main control system, the tests before start-up, the barring operation and its continuous running time with restart of the count after an interruption, the supply of gland steam with the rotor on barring, the thorough draining and warming of the gland steam supply and return lines, the order of putting the gland sealing system into service before the vacuum system in a turbine with axial exhaust so that there is no oil leakage at the oil deflector behind the intermediate and low pressure rotors, the running of the gland steam condenser fan so that the condenser is under slight negative pressure, the matching of the gland steam temperature with the metal surface temperature of the rotor gland region within the permitted deviation, the establishment and holding of vacuum before rolling, the confirmation that the automatic, interlock and protection functions are normal and in service before the bypass is put into use, the correct service and normal indication of the measuring, signal, protection and interlock devices, the qualified insulation of the stator and rotor, the normal working of the excitation and cooling systems, and the normal measured parameters and appearance of the bearings and the enclosed busbar.

5.3.4 (continued) The start-up actions are to include that at start-up the pressure and temperature of the main and reheat steam before the main stop valve meet the technical requirements of the equipment and the superheat of the main and reheat steam is not lower than 56 °C; that after rolling the barring gear is confirmed to have disengaged normally; that during rolling the trip and friction test is carried out as the technical requirements of the equipment demand, the internal sound of the turbine being listened to carefully and the absence of friction in the flow path and at the oil deflectors and the normal oil return of each bearing confirmed, together with the normal action of the turbine interlocks, before the speed is raised, the rate of rise being set as the technical requirements demand; that during rolling the friction and collision between the moving and stationary parts, the vibration of the shaft and bearings, abnormal bearing metal temperature and the jumping, sticking or poor contact of the brushes on the collector or slip ring are checked; that the warming time, warming speed and warming temperature follow the start-up curve of the unit, the critical speed range being passed through quickly, the main, reheat and gland steam temperatures being controlled during warming, the differential expansion of the turbine being strictly kept within the prescribed value and the warming effect being judged from the cylinder expansion; that during rolling the differential expansion, vibration, bearing metal temperature, lubricating oil pressure and temperature, steam and metal wall temperature and other parameters are monitored and the unit tripped at once if a prescribed value is exceeded; that after the unit has reached 3 000 r/min and run stably and a full check has proved normal, the relevant tests may be carried out as the technical requirements of the equipment demand; that the bearing oil flow temperature and bearing metal temperature are checked, the generator and cooling system being checked in a closed cooling system with air leakage points marked and dealt with in good time, the water pressure, flow and leak detector being checked on a water-cooled generator and the hydrogen pressure and seal oil pressure on a hydrogen-cooled generator; that before the voltage is raised the three-phase stator current is zero or close to zero, the field flashing being carried out once the generator has reached rated speed, after which the balance of the three-phase voltage and its not exceeding the rated value are checked, together with the agreement of the field current and field voltage with the no-load rated values, the cause being ascertained where the difference is large; that where automatic synchronizing is used the difference between the generator frequency and the system frequency is within 1 Hz before the automatic synchronizer is put into service; and that after the unit is connected to the grid the rate of increase of active load is governed by the turbine, the rate of increase of stator and rotor current of an indirectly cooled turbine generator being unrestricted while for a directly cooled machine the rate of growth of active load meets the technical requirements of the equipment.

5.3.4 (continued) The operating actions are to include warming at the initial load after grid connection, the initial load and the warming time following the start-up curve; monitoring the temperature rise of the generator cooling medium, the core temperature, the winding temperature and the working condition of the brushes and the excitation device while load is added; controlling the rate of load rise and the rate of change of the main and reheat steam parameters as the start-up curve requires; keeping the rate of load change within the technical requirements in constant pressure operation and in sliding pressure operation; and confirming that the corresponding drain valves are closed once the load has risen to the prescribed value. The shutdown actions are to include the normal trial running of the alternating and direct current lubricating oil pumps and the jacking oil pump before shutdown; the transfer of the station service supply to the standby source before shutdown for a unit without an outlet circuit breaker and the station service transfer test for a unit with one; the adjustment of the main and reheat steam temperature and pressure within the technical requirements during shutdown; the opening of the drain valves at the corresponding load; the lowering of the active and reactive load of the generator to the minimum before disconnection, after which the shutdown operation is carried out and the fall of the turbine speed checked; the breaking of vacuum when the speed has fallen to the value the technical requirements give, the high temperature and high pressure drain valves to the exhaust device being closed in good time after the vacuum is broken; the stopping of the gland steam supply only after the vacuum has reached zero; the immediate engagement of the barring gear once the speed has reached zero, the coasting time of the rotor being recorded and analysed; and the stopping of barring once the metal temperature of the turbine has fallen to the value the technical requirements give.

6 Patrol inspection

6.1 Operating staff are to patrol at the prescribed times and along the prescribed route. They are to deal with the defects and hidden dangers found during the patrol. Where equipment is monitored as abnormal, a patrol inspection of that equipment is to be organized at once. The records of the patrols are to be counted, analysed and reported. In abnormal weather the patrol period is to be shortened, and after the abnormal weather has ended a patrol is to be organized in good time.

6.2 The content and the period of the patrol inspection of the main systems and equipment of the plant are to meet Annex C. The settlement and deformation of the receiver tower and of the storage tanks are to be inspected periodically.

7 Abnormal operation and fault handling

7.1 Where the equipment of the plant runs abnormally, the operating staff are to strengthen the monitoring and the patrol inspection.

7.2 Where a fault occurs, the operating staff are to take the corresponding measures at once so that the fault does not spread.

7.3 Abnormal operation and fault handling at the plant are to be reported according to the dispatch jurisdiction over the equipment and following the requirements of the grid dispatch.

7.4 Where a fault occurs in the operation of the main systems and equipment of the plant, it is to be handled by the methods given in Annex D.

7.5 After an abnormality or a fault has been dealt with, the operating staff are to record in good time the name of the equipment concerned, the phenomenon, the method of handling and the restoration of operation, and to file the record as required.

7.6 After the fault handling is complete a test is to be carried out, and equipment that concerns the grid is to be reported to the grid dispatch body before being put back into operation.

A Annexes A and B (informative) Protection items and analogue control systems

Table A.1 lists the protection items of the main systems and equipment by system. For the collector and heat transfer system the items are the low level protection of the inlet buffer tank, the fault protection of the level gauges of the inlet and outlet buffer tanks, the fault protection of the inlet flow signal of any circuit, the fault protection of the outlet temperature of any circuit, the low pressure protection of the high pressure compressed air of the inlet buffer tank, the over-temperature protection of the receiver panels, the fault-open protection of the bypass valve, the communication interruption protection of the heliostat field network and the wind speed protection of the heliostat field. For the storage and heat exchange system they are the all-stop protection of the high temperature molten salt circulating pumps, the high and the low drum level protection, the low level protection of the molten salt storage tank, the water side leakage protection of the heat exchange system and the low inlet water temperature protection of the preheater. For the steam turbine generator system they are the mechanical and the electrical overspeed protection, the axial displacement protection, the low vacuum protection, the low lubricating oil pressure protection, the low fire resistant oil pressure protection, the bearing vibration protection, the differential expansion protection, the high bearing metal temperature and the high thrust bearing temperature protection, the master interlock protection, the fault protection of the digital electro-hydraulic control system, the low pressure ratio protection of the high pressure cylinder, the high exhaust temperature protection of the high and of the low pressure cylinder, the low oil level protection of the lubricating oil tank and of the fire resistant oil tank, and the protection of the generator stator cooling system.

Table B.1 lists the main analogue control systems by process system. For the collector and heat transfer system they are the level control of the inlet and of the outlet buffer tank, the receiver inlet flow and outlet temperature control, the high pressure compressed air pressure control, the heliostat field control and the electric heating and electric tracing control. For the storage and heat exchange system they are the high temperature molten salt flow and level control, the tempering low temperature molten salt control, the forced water circulation control of the drum and the electric heating and electric tracing control. For the steam turbine generator system they are the turbine governing control, the turbine hydraulic servo, the level control of the deaerator and the heaters, the feedwater pump control, the high and low pressure bypass control, the gland steam pressure and temperature control, the lubricating oil and fire resistant oil temperature control, the closed and open circulating cooling water temperature control and the drain control.

Table C.1 fixes the content and the period of the patrol inspection of the main systems and equipment. For the collector and heat transfer system it covers the heliostat, checked daily for the agreement of the actual position with the commanded position, for loose fixing screws, for the completeness and cleanliness of the mirror surface, for loose frame screws and for frame deformation; the heliostat drive and tracking system, checked daily for fastener bolts, sensor condition, oil leakage and seepage of the drive parts, abnormal running sound, abnormality of the working and standby power supplies, abnormality of the network communication and closure of the control cabinet; the meteorological observation device, checked daily for the fixing of the device to the ground, abnormality of its sensors and data logger, abnormality of its power supply and the cleanliness of the image collection lens and the pyranometer; and the receiver, checked daily for the integrity of the external upper and lower guard plates, for internal ambient temperature, light leakage and odour, for internal lighting and for leakage, deformation, loss of paint colour and peeling of the outer panels. For the storage and heat exchange system it covers the molten salt storage tank, checked once per shift for leakage of the shell, the completeness of its insulation and deformation; the steam generation system equipment, checked two to three times per shift for the local expansion indication, the completeness of the insulation and leakage of the equipment body; and the piping, valves and pipe supports and hangers, checked two to three times per shift for expansion, leakage, the completeness of the insulation and looseness or deformation of the supports and hangers. The remainder of Table C.1 and the whole of Table D.1, which gives the faults of the main systems and equipment and the methods of handling them, run beyond the extracted text available and their contents are not reproduced here.