Cause Analysis and Treatment of Shaking and Repeated Breaking of High Voltage Adjusting Door in Power Plant

Abstract: The reason analysis and treatment information for the shaking and repeated breakage of the high-pressure regulating door of the power plant are provided by the excellent flowmeter and flowmeter manufacturers and quotation manufacturers. 1. Overview Zhejiang Huaneng Changxing Power Plant #5 is an N125-135/535/535 ultra-high pressure, intermediate reheat condensing steam turbine produced by Shanghai Steam Turbine Plant. It was installed and put into operation in August 1992. The original #5 steam turbine speed control system was a full hydraulic speed control system from May to June 2001. More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following is the analysis and treatment article details of the reason for the shaking and repeated fractures of the high-pressure regulating door of the power plant. 1. Overview of Zhejiang Huaneng Changxing Power Plant #5 is the N125-135/535/535 ultra-high pressure, intermediate reheat condensing steam turbine produced by Shanghai Steam Turbine Plant, which was installed and put into operation in August 1992. The original #5 steam turbine speed control system is a full hydraulic speed control system. From May to June 2001, the original speed control system was transformed with the DEH-IIIA high-pressure fire-resistant fuel pure electric control system of Xinhua Control Engineering Company. After the transformation of the unit control system, the degree of automation has been greatly improved, the response time of the system is fast, and the control precision is high. However, from February to June 2002, five LVDTs of the #3 high-profile door were broken. In May 2002, the high-profile door shook at a specific position, which seriously threatened the safe operation of the unit. 2. A brief description of the shaking of the high-voltage control door of the #5 machine and the fracture of the LVDT of the #3 high-voltage control door At about 22:37 on February 2, 2002, the output of the #5 machine was 125MW, coordinated control, and the #3 high-profile door LVDT2 signal suddenly rose from 0V to The maximum value of 4.04V, the VCC card is selected high, so that the 4.04V fault signal is input to the servo valve and compared with the control command at that time. The output of the servo valve forces the #3 gate to close quickly. After the load drops to 115MW, due to the actual load of the unit and the There is a deviation between the target values. After the calculation of the DEH software, when the #3 gate has been falsely opened, the #4 gate is opened to maintain the balance between the load target value and the given value. On April 10, 2002, the morning inspection found that the LVDT1 signal of gate #3 was 0V, and the signal of LVDT2 was about 1.4V. It was judged that the LVDT1 signal of gate #3 was faulty. Around May 1, 2002, when the load of the #5 unit went up and down, the door swayed greatly, especially the LVDT2 signal of the #3 door had jumps when the control command did not change. On-site inspection, the actual position of door #3 shakes greatly, and because the LVDT1 of door #3 has been shielded, in order to ensure the stable operation of unit #5, it is decided to forcibly close door #3. Before the LVDT of door #3 is replaced, only #1 and #2 , #4 tune gate participates in adjustment. 3. Analysis of the reason for the shaking of the high-pressure regulating door of the #5 machine and the fracture of the LVDT of the #3 high-pressure regulating door For the DEH control system, the shaking of the regulating door is a common fault. Generally speaking, it is caused by the following reasons: 1. The vibration of the servo valve causes the regulating door to fail. Shaking; 2. The control parameters do not match, the thermal signal is faulty; 3. The valve stem of the speed control valve vibrates; The servo valve filter element is blocked, the main valve core of the servo valve is stuck, and the valve port of the servo valve is worn. Because the DEH control system of our factory has not been put into use for a long time, and our factory has strict control of oil quality (all indicators of anti-fuel oil are within the required range), it should be said that the possibility of oil quality is very small. At the same time, we found that the wobbling phenomenon of the high-pressure gate is related to the specific position of the #3 gate. Therefore, we focus on the search for other factors, and do not easily replace the servo valve. The thermal control and maintenance personnel checked the control parameters and thermal signals during the troubleshooting process, and found no abnormality. Analyzing the shaking of #1 and #2 regulating doors when the #5 machine is lifting the load, we can find two phenomena: 1. The shaking of the #1 and #2 high-pressure regulating doors is related to the specific load (the opening degree is 48%--50%). , 2. It is related to the opening of the #3 door (0-10%) and the state of the LVDT. On April 30, 2002, we found that the #1 and #2 doors of the #5 machine shook when the load was lifted. At the same time, on May 5, 2002, we found that one LVDT of the #3 door had been broken (the other one had already been shielded) , After the replacement of the #3 adjustable door LVDT on May 14, 2002, the shaking phenomenon of #1 and #2 adjustable doors no longer occurs when the load is lifted. On April 30, 2002, the shaking of the #1 and #2 gates occurred at about 100MW. The opening of the #1 and #2 gates was about 48%, while the opening of the #3 gate was 0-10%. #3 When the door is about to be opened but not opened, the total valve flow characteristic is just at the inflection point, and the flow here varies greatly. At the same time, because one LVDT of the #3 gate is shielded and the other LVDT is broken, when the load of the unit is stable, the two broken ends of the broken LVDT are just not disengaged (in a fragile stable state), and the gate feedback does not change. When the unit load is adjusted, the two ends of the broken LVDT are disconnected, resulting in a change in the linear relationship between the feedback of the #3 door and the actual opening degree, which further aggravates the change in flow rate, making the system unable to perform accurate adjustment, resulting in vibration, caused by This caused the door to vibrate.

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