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The overspeed module voltage is less than the minimum working voltage, the anti-interference is poor, and the probability of misoperation is large; after the overspeed protection misoperation, the safety chain action is triggered, the pitch system has not completed the paddle collection, the fan has overspeed, and the tower has violent vibration instability and collapse the tower.
Analysis report of the collapse of the tower of the No. 18 fan
1. Tower down incident
On December 18, 2021, the No. 18 wind turbine of a wind farm in Heilongjiang had a tower reversal incident. The company's production department, a company, the Electric Power Research Institute, and the host manufacturer quickly rushed to the scene and set up a technical team to carry out incident investigation and analysis. The first scene of the upside-down tower is photographed in Figures 1-1 and 1-2.
Figure 1-118 fan after the tower collapse site situation
Figure 1-218 After the inverted tower of the No. 3 section of the wind turbine deformation morphology
2. Introduction to wind farms
The total construction scale of a wind farm in Heilongjiang is 99MW, which is built in two phases. The first phase installed 33 single-machine capacity 1.5MW units, with a total installed capacity of 49.5MW, put into operation on September 24, 2009, all withdrew from the warranty on December 31, 2015, and outsourced the internal maintenance and inspection of the depot; the second phase installed a single-machine capacity of 1.5MW units, with a total installed capacity of 49.5MW, all put into production in 2012, and all of them withdrew from the warranty on August 24, 2020; both phases of the project have been connected to the remote centralized control platform, and the operation and inspection mode adopts the mode of independent operation and maintenance and maintenance outsourcing The No. 18 wind turbine is the first phase of a wind farm in Heilongjiang.
3. Overview of equipment testing and transformation
In July 2020, the first phase of a wind farm in Heilongjiang conducted 100% non-destructive flaw detection on the high-strength bolts of wind turbines 19 and 26, and the test results were qualified. In June 2021, 33 wind turbines were transformed for low-voltage ride-through and overspeed active yaw. On October 25, 2021, the fixed inspection of wind turbine No. 18 was completed, and no abnormalities were found.
In July 2021, a wind farm in Heilongjiang conducted 100% non-destructive flaw detection on the high-strength bolts of the second phase of wind turbines 35 and 59, and the test results were qualified.
4. The incident
Operation of the unit before the event on December 18: the weather is clear, the average wind speed of the whole field in the first phase is 10m/s, the load is 40MW, and the power is not limited; the first phase of the 110kVI. busbar is running normally, the No. 1 main transformer is running normally, the 35kVI. busbar is running normally, the No. 1 grounding is normal, the No. 1 reactive power compensation device is overhauled, the 35kV3501, 3502, 3503, 3504, 3505, 3506, 3507 collector lines are running normally; the first phase of the wind turbine is running 31 units. Unit 11 and Unit 20 failed to stop, and the average wind speed of Unit 18 was 10.89m/s, the instantaneous wind speed was 9.06m/s, and the load was 1531kW.
At 8:00 on December 18, the on-duty personnel of the remote centralized control center monitored and found that unit 18 of the first phase of a wind farm in Heilongjiang alarmed, and when viewing the fault information of unit 18, units 1 to 18 lost their communication connection, and immediately notified the on-site personnel to troubleshoot and deal with it.
At 8:00, the on-site duty officer heard the SCADA alarm in the central control room, ready to view the wind turbine fault information and operation data, suddenly the No. 1 to No. 18 wind turbine lost the communication connection, at this time the duty chief received the remote centralized control center inspection instructions, immediately reviewed the historical data, found that the unit has overspeeding, immediately reported to the field manager and contacted the local vacancy elimination working group (is processing the Unit 11 pitch motor overcurrent elimination) to check the situation.
At 8:08, the on-site vacancy elimination working group arrived at the No. 18 fan position and found that the No. 18 unit had reversed the tower, and the bolts at the connection between the fan foundation ring and the first stage tower were all disengaged, and the unit as a whole fell to the mid-hillside (see Figure 1-1, 1-2).
Immediately use the walkie-talkie to report this situation to the wind farm director, the wind farm director inquired about the scene situation, arrange the duty chief to transfer the Operation of the No. 3 Collector Line 3503 where the No. 18 wind turbine is located (the operation is completed at 8:15).
Arrange safety personnel to set up a safety cordon around the foundation of Wind Turbine No. 18, and arrange for people to stay behind on the spot to prevent unrelated personnel from straying into the danger area.
At 8:14, the director of a wind farm in Heilongjiang reported to the deputy general manager of the company's production. The on-site attendant retrieved the SCADA data of the wind turbine, and the record showed that the No. 18 wind turbine reported "tower emergency shutdown (first out)", "safety chain emergency stop", "spindle overspeed module tight stop", "spindle soft overspeed tight stop", "tower 1, 2 or so limit", "transmission chain 1, 2 or so limit" and other faults.
After the incident, the Heilongjiang Provincial Company launched an emergency plan, and the directly subordinate unit set up an incident investigation team to carry out investigation and analysis work, and simultaneously carried out related matters such as the demolition and repair of the wind turbines in the upside-down tower.
5. On-site inspection
5.1 Document Review
Analysts from the Electric Power Research Institute consulted the wind farm production management, work records and other information, as detailed in Table 5-1.
Through the consultation, the on-site documents are complete.
Table 5-1 Field Documents
5.2 SCADA Data Collection
The incident analysts of the Electric Power Research Institute collected SCADA data from wind turbine No. 18 and SCADA data from adjacent wind turbines, as detailed in Table 5-2.
5.3 Data Analysis
5.3.1 Time Correction
After on-site investigation, it was found that the computer clock function of the wind farm was displayed incorrectly, according to the clock correction result, the actual starting time of the overspeed fault was 08:00:08 on December 18, 2021 (the system record time was 07:27:50 on December 18, 2021), all the analysis in this report is based on the revised time, see Figure 5-1.
Figure 5-1 Screenshot of the fault situation after the failure of the unit
5.3.2 Event Restore
Before 08:00 on December 18, Wind Turbine No. 18 was in the state of rated power operation, with an average wind speed of 0.89m/s for 10 minutes, an instantaneous wind speed of 9.06m/s, a load of 1531kW, and a stable change in wind speed and wind direction.
At 08:00:08 on December 18, the main circuit breaker of the wind turbine jumped away, and the SCADA system of the unit first reported the emergency shutdown fault of the tower base, and at the same time reported the tight stop of the spindle overspeed module and the tight stop of the safety chain (see Figure 5-1).
The main control performs the emergency shutdown procedure, at this time the blade is not closed, the speed of the fan rises rapidly after it is off the grid, and at 08:00:38, the generator speed rises to 4480r/min. 08:00:52 to 01:03 sec to report the transmission chain up and down amplitude 2 level overrun, the transmission chain left and right amplitude 2 level overrun, the tower left and right amplitude 2 level overrun and other vibration overrun fault, the fan overspeed after the yaw motor started, due to the speed is too fast, the torque is too large, the yaw motor overload, 08:00:54 s yaw motor 13 thermal trip, 08:01:08 s report shutdown failure emergency yaw fault, see Figure 5-2, 5-3.
Figure 5-2 The speed change of the propeller blade and generator after the No. 18 fan of the SCADA system performs the emergency shutdown procedure
Figure 5-3 SCADA system No. 18 fan performs emergency shutdown program transmission chain and vibration tower movement
At 08:08 on December 18, the on-site shortage elimination working group arrived at the No. 18 fan position and found that the No. 18 unit had collapsed the tower, the bolts at the connection between the fan foundation ring and the first stage tower were all disengaged, and the unit as a whole fell to the mid-hillside, see Figure 1-1, 1-2.
View the No. 28 fan in situ video surveillance playback (the No. 28 fan in-situ video surveillance can see the general operating status of the No. 18 wind in the distance, other fan video surveillance can not see the whole picture), found that the No. 18 fan inverted tower before the impeller speed gradually rises, a blade breaks, the fan tower tilts, and finally completely collapses, see Figure 5-4, 5-5, 5-6.
Fig. 5-418 Fan has been broken before the blade breaks after speeding
Fig. 5-518 fan is collapsing the tower after speeding
Fig. 5-618 fan after speeding completely inverted the front of the tower
5.3.3 Run data analysis
At 14:03 on December 22, under the joint witness of the Electric Power Research Institute, wind farm personnel and main engine manufacturers, the tower base front machine was retrieved on the spot.
5.3.3.1 "Tower Base Emergency Shutdown" Signal Analysis
Check the SCADA system and tower front of Unit 18 data, scada system displays "tower emergency shutdown" fault information, but there is no such fault information in the fan PLC and tower front, see Figure 5-7. The No. 30 fan was extracted to do the spindle overspeed trigger safety chain action test, and it was found that the SCADA system reported "safety chain tight stop", "spindle overspeed module tight stop", "tower emergency shutdown" fault information, and showed that the tower base emergency stop was the first fault, but the tower front machine also did not report the "tower emergency stop" fault information, see Figure 5-8, Figure 5-9.
After on-site inspection, the fault information is caused by the error in the mapping of the SCADA system and the PLC point table of the fan during the network-related transformation process: "0" represents the normal state, and "1" represents the action state. The Tower Base Emergency Shutdown signal status should be set to "0", but the actual setting is "1". When the spindle overspeed module action starts the safety chain, the spindle overspeed signal state becomes "1", at this time the tower base emergency stop is not really moved, but because the tower base emergency stop signal is set to "1" (see Figure 5-10), when the "spindle speeding" and other faults are reported, the PLC first receives the tower base emergency stop "1" signal, and then successively receives the spindle speeding action and other signals. Therefore, when the overspeed module and other protective actions, the SCADA system will be accompanied by the "tower emergency shutdown" information and the first fault. After inspection, it was confirmed that the first phase of 33 wind turbines had this error.
After the technical personnel of the main engine manufacturer corrected and upgraded the SCADA system of the first phase of the 33 wind turbine, they once again tested the overspeed safety chain of the spindle of the No. 30 fan, and the SCADA system was consistent with the fault report of the on-site front-mounted machine, and the fault signal of the emergency shutdown of the tower base was not reported, as detailed in Figure 5-11. Fan No. 23 was sampled for overspeed testing, and the results were the same as that of Fan No. 30.
Conclusion: "Tower emergency shutdown" is an accidental signal caused by the setting error of the SCADA system, which is not related to the current wind turbine tower collapse incident.
Fig. 5-7 Differences between the unit faults recorded by the SCADA system of the No. 18 fan and the tower-based front-end machine
Figure 5-83 SCADA system fault log situation after overspeed safety chain test of Fan No. 0
Figure 5-9 The failure of the front aircraft in the cabin after the overspeed safety chain test of the No. 30 fan shows the situation
Figure 5-10 The state of the tower base emergency stop signal after the speeding safety chain action of the No. 18 fan
Figure 5-11 SCADA and front machine failure display after the 30-gauge fan spindle overspeed safety chain test after the upgrade of the SCADA system
5.3.3.2 Spindle overspeed module action analysis
According to the snapshot data of the Front Machine of the No. 18 fan before and after the event on December 18, 2021, the change curve of the spindle speed and the spindle overspeed state table drawn, it was found that the actual speed of the wind spindle at the trigger time of the "spindle overspeed module tight stop" was 19.05rpm, see Figure 5-12, and did not reach the "spindle overspeed module emergency stop (B200_7)" given by the manufacturer. Fault trigger condition (speed exceeding 23.1rpm trigger), spindle protection action value is less than the fault trigger logic value given by the manufacturer, see Figure 5-13.
After communicating with the on-site personnel of the wind farm, after the network-related transformation of the 33 wind turbines in the first phase, except for the spindle speed of units 4 and 5, which was limited to 18rpm and did not occur, the other 31 units had the spindle overspeed module operation, accumulating 182 times, and all the wind farm technicians in Heilongjiang checked and confirmed that all of them were mishandled. Retrieving some of the operation records failures, it was found that the spindle speeding module action occurred at full load, and the spindle speed was around 19rpm. In response to the spindle overspeed report failure, the company sent a letter to the main engine manufacturer on June 28, 2021, and the main engine manufacturer did not respond to this problem. On August 20, 2021, a letter was sent again at the acceptance meeting of the network-related transformation to request the handling of this fault, and as of now, no response has been made, as detailed in Annexes 1 and 2.
Figure 5-12 Storage of fault log of tower front machine
Fig. 5-13 Spindle soft and hard speeding fault trigger logic table
According to the analysis, in this tower reversal incident, the No. 18 fan reported that the "spindle overspeed module is tightly stopped" without meeting the trigger conditions, which caused the safety chain action, which is the spindle overspeed protection mismanagement.
The factory date of the Spindle Overspeed Module of the No. 18 fan is March 7, 2011, check the spindle overspeed module DN2131 pulse relay related information, the technical parameters in the DN2131 specification, the working voltage range is 24V±10% (21.6V ~ 26.4V).
At the scene, no. 14 with more faults of "spindle overspeed module" was selected, No. 17 with a general number of faults, and No. 29 fan overspeed module (DN2131) with fewer faults were selected for action testing. First of all, the DN2131 speed monitoring and protection module configuration display software is used to read the overspeed module setting value of 10Hz, which can determine that the overspeed module setting value is consistent with the manual knob setting value, and eliminate the possibility that the manual rotation setting value is not cured into the module. Using the square wave generator to simulate the speed pulse of the fan, each module did three action tests, and the results of the 9 tests showed that the modules could accurately move at a set value of 10Hz (equivalent to 2400rpm for the high-speed axis). When the pulse signal amplitude of the tachymetry probe is lower than 17.6VDC, the module fails to judge the acquired frequency value, whether the frequency is higher than 10Hz or less than 10Hz, the speeding module does not move, because it is not a mishandling, so it will not be further discussed.
Check the design drawing of the on-site safety chain power supply module and the on-site configuration and find that the auxiliary devices such as the optical transceiver and the tower-based pre-machine are connected to the field power supply system, and the safety chain power supply fails to achieve independent power supply; the power of the overspeed module 24V power supply module is 120W, the optical transceiver power is 24W, and the pre-powered machine is 23W.
On-site selection of No. 28 fan to measure the safety chain power supply module and loop voltage, the measuring instrument is a multimeter and oscilloscope, the oscilloscope signal input terminal test point selects the spindle overspeed module MS22.1 power terminal 2, see accessories, the measurement point of the multimeter is at each node of the safety chain. The test found that: the power supply 24V starting voltage steady-state value is 23.8V, the test overspeed module MS22.1 power terminal 2 voltage steady-state value is 20.4V (less than the minimum working voltage of 21.6V), the interference signal is weak, see Figure 5-14; start the wind turbine to simulate the normal operation state, test the spindle overspeed module MS22.1 power terminal 2, the oscilloscope shows that the voltage value fluctuates within 20.4V±2V, indicating that there is an objective source of interference at the scene, see Figure 5-15. 5-16; After multiple simulation tests, the overspeed module has misoperation in the working voltage range of 17-18V, see Figure 5-17; the remaining transformation units in the wind field are randomly inspected to carry out the same test, and the working voltage of the overspeed module is found to be in a low-voltage state.
Figure 5-14 The minimum voltage of the quiescent loop is 20.4V and the interference situation
Fig. 5-15 24V voltage fluctuation diagram after grid connection
Fig. 5-16 24V voltage fluctuation diagram at the moment of grid connection
Figure 5-17 overspeed module test test
Through the static and dynamic operation test data, it can be seen that the electromagnetic field of the generator system is the interference power source of the overspeed module 24V working voltage, and the electromagnetic field generated by the wind turbine at the grid connection moment and after the grid connection operation reaches ±2V to the speeding module 24V power supply interference value. Due to safety reasons, the site did not carry out high-speed interference voltage test, such as under the rated number of revolutions to test the interference voltage value must be ≥ 2V. The most recent snapshot log of Fan No. 18 shows:
On November 24, 13:00, the overspeeding malfunction was successful, at this time the spindle speed was 19.0rpm, and the machine was in the rated power operation state, indicating that the electromagnetic field under the rated power working conditions of the generator system had the greatest interference with the 24V power supply of the overspeed module. Spot check no. 30 fan found that on December 14 and December 15, the speed protection module was mismanaged once, and the corresponding spindle speed was 19.05rpm and 19.01rpm, respectively.
Conclusion: The Safety Chain Action caused by the No. 18 fan reporting "spindle overspeed module tight stop" when the trigger conditions are not met, which is the misoperation of the spindle overspeed protection; the anti-interference resistance of the wind turbine spindle overspeed module is reduced after the 24V voltage is reduced, and the misoperation phenomenon occurs frequently.
5.3.3.3 The blade was not returned to the paddle in time
The propeller power supply during the normal operation of the fan is used to change the pitch or the paddle collection power supply during normal shutdown, and the accident shutdown is considered when the safety chain is started, and the paddle collection power supply is switched to the battery. On the morning of December 25, after the completion of the safety measures, under the joint witness of the company, the Electric Power Research Institute and the manufacturer, the inspection in the wheel hub of the No. 18 fan found that the factory time of the paddle 1 battery was partly 2015, part was 2016, and the battery factory time of the paddle 2 and paddle 3 was 2016 (the main engine manufacturer specified that the battery replacement cycle was 3.5 years); the battery voltage was measured on the spot, and the paddle 1, 2 and 3 voltages were 0V, 10V and 0V, indicating that the battery was in a capacityless state.
View the drawings (see appendix), the 6K1 contactor and 6K2 contactor when the battery is powered are the key electrical components: the 6K1 contactor is the electric main loop component of the paddle motor when the battery is powered, only its main contact is connected, the motor can turn the paddle; the 6K2 contactor is powered by the battery When the paddle motor bearing brake device is powered, the electric main loop component of the paddle motor bearing brake device, only its main contact is connected, the brake device can be released, otherwise the brake device will hold the paddle motor to death so that it cannot turn the paddle.
(1) The No. 1 paddle blade was not returned to the paddle in time for analysis
The Storage Data of the No. 1 Paddle Tower Base Pre-machine is plotted into a curve (Figure 5-18) and analyzed to find: 7:46:33 (time before correction) The No. 1 paddle motor starts, the starting current is about 22 amperes, and it drops smoothly, the blade angle does not change, it has been in the 0 degree position, after 40 seconds, the motor current drops to about 6 amperes, at this time the paddle pitch angle begins to change, and quickly reaches the 70 degree position (the battery pitch rate is the fastest 20 degrees / s). The 6K2 contactor was tested, and it was found that the main contact was sometimes connected and sometimes not connected during the action, and after disassembly, it was found that there was a main contact burning and melting phenomenon, see Figure 5-19.
Therefore, the analysis and judgment: when the accident paddle collection signal is issued, the 6K1 contactor is absorbed, and the No. 1 motor has a current, but due to the poor contact caused by the burning and melting of the main contact of the contactor caused by the lack of power at this time, the brake device is locked, resulting in the paddle motor cannot be rotated, and the blade angle is unchanged; due to the performance of the battery itself, after about 40 seconds, the battery voltage falls to about 80V (contactor trip action voltage), the 6K1 contactor is released, the DC motor is powered off; the battery voltage rises after stopping the power supply. The 6K1 contactor is re-absorbed, and at this time, the 6K2 contactor is in the suction and conduction state, the brake device is electrified and released, and the blade is quickly retracted; after the blade is retracted to about 70 degrees, it is terminated due to the battery power finally exhausted, and the accident paddle collection system stops working. The reason for the melting of the 6K2 contactor: The biggest difference between DC and AC is that the AC arc crosses the zero point and the DC arc is not zero, when the contactor is broken, the DC arc is not more than zero, and the contactor is easily damaged when the contactor is frequently operated.
View the record of the no. 18 wind turbine's paddle collection action, from April 19 to November 24, a total of 15 oar collections occurred, see the figure below.
Fig. 5-18 No. 1 paddle motor current and paddle moment angle curve (right vertical coordinate unit is amperes)
Fig. 5-19 No. 18 fan blade 1 contactor 6K2 main contact melting
(2) The No. 2 paddle blade was not returned to the paddle in time for analysis
The storage data of the No. 2 paddle tower base machine is plotted as a curve (Figure 5-20, the left vertical coordinate unit is ampere) and the analysis can be found: 7:46:33 (time before correction) The current of the No. 2 motor is zero, the paddle receiving motor is not powered on and rotated, and the blade angle is maintained at about 3.8 degrees. After disassembling the No. 2 6K1 contactor, it was found that the core of the coil had a protruding part, resulting in its inability to absorb, so the main contact could not be connected, and the paddle retractor motor was not energized and rotated; measuring the 6K1 contactor coil, it was found that its DC resistance was 189 ohms less than the other two rotor blades that were not damaged by the 6K1 contactor coil, and the coil of the protruding part of the iron core had changed color and had a burning smell (see Figure 5-21), and it was judged that the No. 2 paddle blade 6K1 contactor coil was short-passed by the heat and caused the deformation to bulge and could not be absorbed, which eventually led to the paddle motor not moving.
Fig. 5-20 Rotor motor current and paddle moment angle curve of No. 2 paddle motor (left vertical coordinate unit is ampere)
Fig. 5-21 No. 18 fan blade 2 contactor 6K1 after disassembly the iron core protrudes
(3) The No. 3 paddle blade was not returned to the paddle in time for analysis
The storage data of the No. 3 paddle tower base machine is plotted into a curve (Figure 5-22, the left vertical coordinate unit is ampere) and analyzed, it can be found that: 7:46:33 (time before correction) The No. 3 paddle motor starts, the starting current is about 27 amperes, and it drops smoothly, the blade angle does not change, and it has been in the 0 degree position. From the size of the DC motor starting current, it can be seen that the capacity of the No. 3 paddle blade is larger than that of the No. 1 battery. The 6K2 contactor was tested, and it was found that the main contact was sometimes connected and sometimes not connected during the action, and after disassembly, it was found that there was a phenomenon of main contact melting, see Figure 5-23.
Therefore, the analysis and judgment: when the accident paddle collection signal is issued, the 6K1 contactor is absorbed, and the No. 1 motor has a current, but due to the poor contact caused by the burning and melting of the contactor 6K2, the contact is not energized at this time, and the brake device is locked, resulting in the paddle motor cannot be rotated, and the blade angle is unchanged; for example, the battery capacity of the No. 3 paddle blade is also the same as the Capacity of the No. 1 paddle, or slightly lower than the capacity of the No. 1 paddle battery, when the battery voltage falls to only about 80 volts, the battery paddle main contactor 6K1 will also be disconnected. The battery voltage rises and then absorbs, the brake contactor 6K2 is absorbed, the brake device is energized and opened, and the motor is energized to turn and turn the paddle. Because the capacity of the No. 3 battery is larger than the capacity of the No. 1 battery, there is no process of disconnection and suction, the brake device cannot be opened, and the motor cannot turn the paddle.
Fig. 5-22 Rotor motor current and blade angle curve of No. 3 propeller variable motor (left vertical coordinate unit is ampere)
Figure 5-23 No. 18 fan blade 3 contactor 6K2 main contact melting
Conclusion: The main contact of the contactor 6K2 of the paddle blade 1 and 3 is burned and melted, resulting in the brake device not being energized, and the motor is locked and unable to rotate the paddle; the short circuit heating of the rotor blade 2 contactor 6K1 part of the coil causes the deformation and protrusion of the iron core, the contactor cannot be absorbed, and the DC motor cannot be energized to rotate the paddle.
5.4 Comprehensive analysis
Comprehensive on-site inspection, data analysis and on-site testing, comprehensive analysis believes that: the overspeed module voltage is less than the minimum working voltage, the anti-interference is poor, the probability of misoperation is larger; after the overspeed protection misoperation, the safety chain action is triggered, the pitch system has not completed the oar collection, the fan has overspeed, and the tower has violent vibration instability and collapse. In this event, the cause logic of the tower collapse process event is shown in Figure 5-24:
Fig. 5-24 Cause logic diagram of the inverted tower process event
6. The main problems exposed
6.1 The implementation of technical measures for equipment accident prevention of the group company is not effective. The "Safety Technical Measures for Wind Turbines" and the "Key Requirements for Technical Prevention of Wind Power (Photovoltaic) Equipment" clearly require that "the power supply of the safety chain should be set independently, and it is forbidden to connect other uses of power supplies in parallel", and the wind turbines of a wind farm in Heilongjiang will connect the communication conversion module, man-machine exchange interface and data memory to the safety chain power supply, which does not meet the requirements of countermeasures and is not rectified in time, and there are long-term safety hazards.
6.2 Equipment defect management is not standardized. A total of 31 units of the 33 wind turbines in the first phase of a wind farm in Heilongjiang have frequently reported spindle speeding faults in the past six months, with a number of 182 times, which have not attracted enough attention, have not been analyzed in time to find the cause, only a simple inspection is reset and started, and the safety hazards have not been eliminated in time.
6.3 Regular maintenance management is not in place. The equipment operation was not analyzed as required before the maintenance, and frequent faults such as the overspeed of the spindle of the unit and the rejection of the pitch contactor were not included in the maintenance plan, and the relevant safety hazards were not dealt with in time.
6.4 The technical transformation work is not strictly controlled. In June 2021, after the wind farm completed the low-voltage ride-through and yaw protection transformation, the partial fault point table and clock of the unit PLC and SCADA system did not correspond, the self-test parameters of the pitch backup power supply were set incorrectly, and the acceptance was not found in time.
6.5 Other Issues
(1) Technical precautions require that "in the case of normal power supply of the working power supply of the pitch system, priority should be given to the use of the working power supply to perform the pitch action". The first phase of the wind turbine of a wind farm in Heilongjiang gave priority to the use of backup power supply after the safety chain was triggered, which did not meet the requirements of countermeasures.
(2) The maintenance and maintenance procedures of wind turbines in a wind farm in Heilongjiang are not perfect, and the relevant backup power supply and safety chain test requirements are not clear。
(3) The technical supervision work is not comprehensive and meticulous. The internal resistance (capacity) of the pitch battery (supercapacitor) was not tested at least once a year as required, and only the backup supply voltage was measured, and the operating state of the pitch battery could not be grasped in time. Problems such as the main control cannot monitor the temperature of the pitch battery and the insufficient power capacity of the tower main control UPS cannot be found in time.
7. Precautionary measures
7.1 Immediately carry out the investigation and management of hidden dangers of wind turbine flying vehicles。 In strict accordance with the requirements of the wind turbine fault classification management, attaches great importance to and seriously treats every fault and alarm reported by the wind turbine SCADA system. Focus on checking whether the safety chain of the wind turbine is complete, whether each node can be correctly triggered, whether there is no backup power supply guarantee for the power supply of the pitch system, whether there is internal resistance, voltage, capacity, and discharge time of the lead-acid battery of the pitch system that does not meet the requirements, and whether there is a stuck phenomenon in the mechanical structure of the pitch system.
7.2 Strengthen maintenance management. Immediately revise the maintenance management system, improve the maintenance items and standards, and include the maintenance of important electrical circuit contactors, relays, and battery heating systems in the regular maintenance plan. Strengthen the training of inspection and maintenance personnel, improve the skill level of personnel, ensure that the inspection and elimination of defects is in place, and timely discover and eliminate hidden dangers of equipment.
7.3 Strengthen the investigation and rectification of hidden dangers. Carry out the rectification of the safety chain power supply circuit, the safety chain circuit must be independently powered, and mixed power supply is strictly prohibited. Immediately carry out the investigation of hidden dangers of the unit, focusing on the comprehensive investigation and test of the wind turbine safety chain protection circuit, electrical protection, battery power supply, lightning protection performance, etc., to ensure that the safety chain and battery power supply are accurate and reliable, and the equipment is safe and reliable. In view of the problems such as not having the pitch power switching function and battery status monitoring, we will continue to promote the DC to AC project of the pitch system to achieve the protection function. Whether there is an irrelevant load access unit control system UPS, the requirements are still not met, and the UPS should be upgraded and increased.
7.4 Strengthen defect management. Wind turbine safety chain failures or frequent failures, it is strictly forbidden to reset and restart simply processing, and it is necessary to comprehensively inspect and deal with them in a timely manner; timely analysis and find the root causes, timely take effective measures to eliminate the occurrence of failure expansion caused by untimely and incorrect treatment; strengthen defect closed-loop management, strictly implement the defect management system, and put an end to the occurrence of long-term non-elimination of defects and long-term sick operation of fans。
7.5 Deeply absorb the lessons of this incident. Take one example and three, in light of the previous occurrence of personal and equipment incidents, expose the problems and preventive measures, immediately organize the investigation, carefully sort out the problems in the equipment itself and management, rectify the problems found in a timely manner, avoid similar incidents, and increase the timely function of the system.
7.6 Standardize the management of fan technical transformation work, unify SCADA data format and fan fault coding.
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