Analysis and Solution of Frequency Instability of Diesel Generator
As a kind of power supply unit, diesel generator requires its power output and frequency to be within a reasonable range. In actual applications, large frequency fluctuations of diesel generators are rare, and small fluctuations are more common. There are many reasons for the instability of the diesel generator frequency caused by tracing the source. To improve this problem, it is necessary to analyze the various causes that may occur, so that such failures can be quickly and accurately resolved in actual work. Based on my own work experience, the author believes that the problem should be analyzed from the following aspects through actual case analysis. 1 Reasons for Frequency Instability of Diesel Generator Sets There are many reasons for the frequency instability of diesel generator sets. We analyze the reason to speculate in a scientific and reasonable way, and also analyze based on actual conditions and work experience. Through the formula protection mode of the generator frequency and the speed of the prime mover, while optimizing the organization and management, and strengthening the technical means of maintenance and repair of the high-speed rail machinery and equipment, it can not only complete the routine maintenance of the high-speed rail machinery and equipment, but also when sudden failures occur It is necessary to organize manpower and allocate resources in a timely manner to ensure the normal operation of the high-speed rail to the greatest extent. 4.2 Strengthening the technical means and responsibility consciousness of technical personnel In the final analysis, the maintenance of high-speed railway machinery and equipment needs to rely on the technical level and practical experience of technical personnel to complete. Therefore, strengthening the personal ability of the technical staff of high-speed rail machinery and equipment maintenance is a basic work that needs to be continued for a long time. To this end, China needs to increase the training of high-speed rail technical personnel. First, more detailed and specialized high-speed railway technology majors need to be established in colleges and universities, and more talents with both theoretical knowledge and practical ability can be delivered to the front line of railway work; then, railway bureaus need to retrain skills for current employees. In order to continuously improve its technical capabilities, in the face of new models and new equipment, it is necessary to increase training in a targeted manner so that any model and equipment will be repaired by someone. In the face of the "iron rice bowl" thinking of some railway employees, railway bureaus need to introduce competition mechanisms, such as performance appraisal system and last elimination system, to give incentives to employees who work hard, and to employees who do n’t care. punishment. This can improve the sense of urgency of technical personnel, help them develop a sense of responsibility and crisis, increase their enthusiasm for active learning and self-reinforcement, and ensure that they can seriously and smoothly complete high-speed rail machinery and equipment management and maintenance tasks. 4.3 Standardize the management and maintenance of high-speed railway machinery and equipment market relationship: f = p6n0 It can be seen that the working frequency f of the diesel generator set has a greater correlation with the rotor speed n and the number of pole pairs p. Therefore, when the frequency of the diesel generator is unstable, it should be the first Considering the rotor speed and the number of pairs of magnetic poles, when the number of pairs of magnetic poles is fixed, the factor that affects frequency is the speed. Based on the statistical analysis of the faults of the diesel generator set of Fujian 121 Geological Group for many years, the author summarizes several of the most common fault points, and uses actual cases to explain the reasons and solutions for the unstable frequency of the diesel generator set. 1.1 The case introduced a four-stroke diesel generator set of type GF-100. Its diesel engine model is TBD226B-6D, the motor model is TFW2-250L-4, the rated speed is 1500r / min, the rated power is 100kW, and the rated voltage is 400V. . In the actual operation of the unit, the quality and maintenance efficiency of the low-frequency diesel machinery and equipment of the diesel generator set have not only affected the economic income of the railway operating agencies, but also the protection of people's lives and property. To ensure that high-speed trains do not have accidents, not only rely on high-quality machinery and equipment, but also excellent maintenance methods. China's high-speed rail equipment market is at the stage of construction and development. Therefore, loopholes in laws and regulations may appear, which will allow some bad businesses with luck to take advantage of it. However, with the continuous improvement of standardized management measures in the high-speed rail equipment market in China, the loopholes will be blocked and bad businesses will be expelled from the market. To this end, relevant national departments need to issue corresponding policies as soon as possible to regulate the market. At the same time, when railway equipment management departments are outsourcing equipment procurement and maintenance work, they need to brighten their eyes, identify bad businesses, and purchase equipment that meets national standards. This can ensure the safety of train operations and the smooth progress of maintenance. Reference Library  Huang Xinji. Research on Comprehensive Maintenance System of High-speed Railway [J]. Railway Survey and Design, 2005, 6 (1).  Xue Xuewei, Wang Gang. Construction machinery promotes China ’s railway construction for 60 years [J]. Construction Machinery Technology and Management, 2009 (09) aid  Yang Lan. The Wuhan-Guangzhou High-speed Railway officially opened to the traffic of the Yishanhe Intelligent Rotary Drilling Rig [J]. Journal of Transportation World (Jianyang. Machinery), 2010 ( 01) Aid  Liu Chaoying. Taking the safety of high-speed rail as the core and taking management innovation as a means to advance the electrical work to a new level. A report at the 2011 National Railway Work Conference [J]. Railway Communication Signals, 2011 (02) Assisting Internal Combustion Engine & Parts · 159 · Stability phenomenon, the fluctuation range of the frequency indicator is large, the power operation of each cylinder of diesel is uneven, and there is a clear phenomenon of "parking". After the diesel generator set is loaded, The frequency pointer fluctuates. 1.2 Analysis of Common Causes 1.2.1 Oil Road Problems Oil road problems are mainly manifested in four aspects. The first is pipeline cracks, that is, oil pipelines are damaged, and cracks cause oil transmission to be irregular, and the tightness is reduced. The second is that the oil tank level is too low, which causes air and impurities to be mixed into the fuel. The oil does not meet the needs of the fuel tank, and other impurities are mixed in. Once again, the filter in the oil circuit is clogged. The filter in the oil circuit has not been cleaned for a long time, and dust and impurities have blocked the passage, causing the oil to flow smoothly. Fourth, the fuel line leaks oil, which will lead to insufficient fuel supply for the entire generator. The above oil circuit problems are common problems that cause the frequency of diesel generators to be unstable. Failure of the oil circuit will directly lead to poor oil supply and the speed of the generator will decline, which will cause frequency instability. 1.2.2 Fuel injection pump failure Fuel injection pump failure is an important cause of frequency instability. When the fuel injection pump has inflexible fuel supply rods, and the elasticity of the governing spring is lowered, it will cause the fuel supply of each cylinder of the diesel generator to become unstable. Equilibrium then causes a change in speed, which in turn causes a change in frequency. 1.2.3 Injector failure Injector failure is mainly due to natural wear. Due to the complex location of the injector, the possibility of human injury is small. When the diesel generator set runs for a long time, the impurities in the fuel may be Attached to the needle valve coupler, and then caused by the flow of the oil to cause the adverse reaction of the fuel injection, the fuel injection quantity of the fuel injector will change, and the speed will change, which will cause frequency instability. 1.2.4 Speed sensor measurement Distortion sensor plays the role of control induction. The speed sensor in diesel generators is a magnetoelectric sensor. This type of sensor is prone to electromagnetic reactions and is sensitive to electromagnetic phenomena. It is not prone to failure when it is properly maintained and repaired. However, if there is no maintenance for a long time, dust in the air will collect in the gap of the sensor, causing the sensor to malfunction, and the display data will have a large error or distortion. 1.2.5 Failure of the speed control system The speed control system is a stability maintenance system, which directly affects the operating status of the diesel generator. If the speed control system fails, it may affect the overall control of the speed control system, and the oil speed will be affected. The frequency of the generator set will also be unstable. 2 Solving strategies for frequency instability faults of diesel generator sets 2.1 Judging the causes of generator set failures In order to improve the actual problems of four-stroke diesel generator sets of model DK-100, the causes of their failures need to be judged first. First, start with the more familiar and stable aspects, that is, first consider the problem of the diesel engine, remove the injector of the diesel engine from the unit, and then perform the atomization experiment. The experimental results prove that the condition of the injector is good and does not affect normal use. In order to further verify this idea, the fuel injection pump was disassembled and replaced with another generator in good working condition for testing. The test results were all normal, indicating that the fault of the generator set had nothing to do with the fuel injection pump, and the oil circuit and fuel injection pump were basically excluded. Problems with the fuel tank. Then make a fault judgment on the speed control system of the generator set, remove the sensors of the speed control system and replace them with normal sensors, and the unit's fault is still there. In the state of power generation and shutdown, the voltage input and output of the short-circuited controller and actuator are normal, and the actuator and fuel pump gear of the entire unit are intact, so the cause of the failure of the four-stroke diesel generator set of model JH30 It is that the electronic governor adjusts the differential and the gain tuning fails. Through the above analysis, it is not difficult to find that the cause of the problem affecting the frequency of the diesel generator set is changeable. The adjustment and repair of the fuel injection pump and the sensor are relatively simple, and the maintenance of the electronic governor is more difficult. The troubleshooting is analyzed. 2.2 Speed setting of the electronic governor First, the speed setting of the electronic governor should be performed in accordance with the principle of idle speed adjustment. When the diesel generator is started, it is necessary to pay close attention to the speed of the generator. When deviations in the speed of the diesel engine are found, , Immediately readjust the low-speed setting potentiometer to restore the data to the original setting. The adjustment method of the low-speed setting potentiometer is roughly to increase the speed by adjusting clockwise, and decrease the speed by adjusting counterclockwise. The method is simple and easy to operate, as long as the value is restored to a reasonable idle speed. Then restart the switch of the diesel generator set to increase the idle speed, observe the operation of the tachometer, and let the speed reach the level of the rated speed. When the idling value is adjusted, you still need to pay close attention to the operation of the electronic governor. As long as the fluctuation range exceeds 0.25%, the next step is to maintain stability. 2.3 Speed dynamic index adjustment Speed dynamic index adjustment is performed on the basis of stability adjustment. The dynamic indicators of the speed regulation system include instantaneous speed regulation and stabilization time. When the electronic speed governor of a diesel generator fails, the adjustment differential, Gain to adjust the electronic governor, and then look for the best operating point of the speed dynamic index. This working point can be found by using a stable line near the gain as a primitive, adjusting it clockwise to the three o'clock direction of the potentiometer, and then turning on the diesel generator set switch until the high-frequency fluctuation of the diesel engine speed and adjusting the differential counterclockwise. Help the diesel generator run smoothly. 2.4 Steady-state speed adjustment Adjusting the steady-state speed is to reduce the speed of the electronic governor. Manually adjust to reduce the error of the electronic governor. First observe the conditions of the steady-state speed adjustment clockwise. If clockwise The adjustment leads to an increase in the adjustment rate. During the adjustment, first set a designated operating point according to the potentiometer. Observe the operating changes during no-load and load during the period, and adjust the value of the steady-state adjustment rate according to the actual situation. This operation requires Repeat until the error is within a reasonable range. 3 Conclusion In summary, the diesel generator set is related to the entire power generation device and power generation operation, so we must always pay attention to the frequency operation of the generator set, and repair problems in time. Through the analysis of this paper, it is found that there are many reasons that affect the frequency of the generator set. In addition to the common mechanical and component failures, the electronic governor is also an important factor that affects the frequency change. Therefore, the staff must repeat the basis of mastering the electronic governor. Debug the generator set and maintain the normal operation of the generator set. At the same time, daily inspections and regular maintenance are required to prevent problems before they occur. Only in this way can the stable operation of the diesel generator set be truly achieved. Reference Library  Xu Xuewu. Cummins diesel generator frequency instability failure analysis and equipment management and maintenance, 2012 (4): 19-20.  Guo Fuyuan. Application of fault tree theory in remote diagnosis system Research [D]. Dalian: Dalian University of Technology, 2007.  Lu Xinxiang, Xu Jianliang. Judgment and Elimination of Faults in Electronic Governors [J]. Mobile Power & Vehicles, 2008 (2): 40-44.