Turbine unit bearing temperature error tripping cause and solution

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Turbine unit bearing temperature error tripping cause and solution

Source: China Bearing Network Time: 2014-06-23

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1 Foreword Bikou Hydropower Station is equipped with three mixed-flow hydroelectric generating units with a capacity of 100MW; it is produced by Harbin Electric Machinery Factory.
The temperature measurement system of the unit was originally selected for ratiometric temperature measurement equipment; it was switched by reed switch contact; because of its low reliability; it affected the supervision of the temperature of each part of the unit and the normal meter reading of the operating personnel; taking into account the unit temperature and computer The demand for the monitoring system; from the end of 1996; the implementation of the temperature monitoring circuit of the three units in contact with the computer monitoring system was modified; the DAS-IA/B series multi-function inspection instrument produced by Hefei University of Technology High Technology Industrial Company was selected. The operating conditions are usually; there are several times when the appearance is abnormal and the communication is stopped, the anti-interference ability is poor, and the appearance is poor; and the wiring touch is bad and the line is broken, causing the temperature to rise sharply. Together, because the temperature measurement point is in the strong electromagnetic environment of the generator. In the middle; some temperature measurement points often show the appearance of high-limit alarms; and the inspection instrument can not remove the disturbance signal; bring a lot of alarms to the server of the monitoring system; cause the server to crash when severe.
2 Bearing temperature error tripping edge analysis
August 30, 2001; 1# unit with 100MW load operation. In operation, the 1# unit temperature inspection instrument showed the appearance of abnormal temperature; the maintenance personnel after the operation ticket; the stator temperature measurement circuit was viewed. After the person opens the defective stator coil resistance thermometer 02 terminal; the maintenance personnel touches the common terminal with the multimeter test pen; when another watch is used to prepare to touch the measured resistance value of the turned-open 02 terminal; the "1F water machine" light word is presented. Row; outlet switch 2201DL trip; emergency stop solenoid valve action; unit active load to "0"; view for "1F bearing temperature overheating measures" microcomputer monitoring matter appears as: 1F water guide + X direction, -X direction, +Y direction, -Y direction resistance type temperature 骤 sudden change "high limit alarm" are 124. 5 ° C, 77. 3 ° C, 79. 5 ° C, 79 ° 2 ° C (initiation stop: 65 ° C). And view the 1F water Inflated large thermometer indications are: 40°C in +X direction, 43°C in +Y direction, 37°C in -X direction, and 41°C in -Y direction.
After the incident, immediately analyze and find the incident. Because the common terminal of the unit temperature measurement circuit is loose; when the maintenance personnel touch the common terminal with the meter of the multimeter (the other end has not touched the terminal); the looseness of the terminal causes the resistance value to occur. The temperature value collected by the temperature inspection instrument exceeds the setting value of the 65°C stop of the unit's event; the water machine protection measures to jump open the outlet switch; the unit's load rejection event stops. Then repeated simulation experiments (measurement resistance short circuit, The temperature measuring resistor is open, the common end is disconnected, and the common terminal is loose.) When the temperature measuring resistor is short-circuited, the temperature measuring resistor is open, and the common terminal is disconnected, the output temperature value of the patrol instrument is zero; no temperature rise occurs. The analysis of the results obtained and the printed trend chart show that as long as the public end is loose, the temperature will increase due to the enthalpy; this is consistent with the appearance of the incident. Therefore, the reason for acknowledging the incident is that the common terminal is in operation. Loose; caused by the sharp rise in temperature values.
In the microcomputer monitoring system; the bearing temperature trip circuit selects the trip command from the logic circuit after reading the data from the temperature inspection instrument; the method of driving the relay to the unit outlet switch; this method has the following defects in operation: (1) temperature The data read on the patrol instrument is more (60 points in total); the temperature value of the stator coil is greatly disturbed by the magnetic field of the generator; the drift of the collected temperature value occurs; the appearance of the banned point has an attack; Difficult to overcome the influence of the on-site disturbance signal, (2) the temperature display and the amount of control are read from the temperature inspection instrument. 庋 露 露 妊 妊 煲 煲 煲 煲 煲 煲 煲 ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) When a certain defect occurs, it is required to stop the temperature inspection instrument; it will form an exit of all temperature protection.
3 Renovation plan for temperature trip circuit
3.1 The main contents of the temperature measurement circuit transformation include: adding a temperature control cabinet next to the machine; separating the original water guide bearing, thrust bearing and upper bearing temperature control loop from the temperature inspection instrument; adding XMT-800 number to each machine Three controllers; independently perform temperature collection and resolution functions; announce trip orders.
3.2 Replace the temperature measuring resistor; except the stator temperature package can not be replaced; still use the copper resistance Cu53 to measure the temperature; the other uses the platinum resistance Pt100 to measure the temperature. The temperature preservation is selected by Anhui Hefei University of Technology High Technology Industrial Company. XMT-800 digital display controller; make up for the DSA-I inspection instrument simple misoperation, anti-interference and other defects; the operation is marked for more than a year; the controller is safe and reliable; high precision.
3. 3 The temperature measurement point for the stop is selected by double temperature measurement component; one input microcomputer temperature measurement controller; one input local control unit (LCU). The temperature of the microcomputer is only high at two points. The action stops; and a time limit is added to the logic loop to distinguish the false signal (because the rise of the bearing temperature is a process of successive changes; it should not be a sudden change); greatly improving the robustness of the insurance measures.
4 Several issues that should be paid attention to during the transformation process
4.1 Transforming the bearing temperature trip circuit; selecting an independent temperature trip control loop; the temperature trip detector is separated from the patrol instrument; under the condition that the original number of points is unchanged; using the original shaft swell large thermometer device hole for processing Install a thermometer with a length of 200mm; Φ10. The temperature of the three major bearings of the thrust, upper guide and water guide are independently led to their respective temperature controllers (measured at 8 o'clock); The switch module of the ground unit. Add the control splicing of each bearing on the trip circuit; this is convenient for the maintenance personnel to view a thermometer without affecting other temperature measuring points; the temperature trip of the circuit can be temporarily withdrawn; After rehabilitation, the normal operation method can eliminate the mutual interference between the measuring points.
4. 2 Reasonably place the orientation of the thermometer; the lead wire of the thermometer is made of oil-resistant and temperature-resistant twisted-pair shielded cable; the shielding layer is firmly grounded in the disk. The terminals must be strong; especially the common terminals need to be strong; Interfere with each other.
3.4 After the end of the device, the circuit of all resistance thermometers should be viewed and tested; the open circuit, short circuit and grounding appearance cannot be presented.
4.4 When the temperature of the tile surface changes; because the sensor can not be directly detected; but it is detected after the conduction of the tile body; this is not only a large hysteresis; and there is also temperature decay. Therefore, the device of the thermometer needs to touch the tile as much as possible. surface.
4. 5 The temperature trip circuit transformation can only be contacted with the overhaul of the unit.
5 Conclusion After the above improvement; 2# unit officially put into operation on February 6, 2002 until July 31, 2004; has been safely operated for more than two years. Reaching the need for safe and reliable operation; clarifying the bearing temperature trip circuit The transformation is successful.

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