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La5C2001 What are systematic errors, random errors, and negligence errors? Answer: Systematic error is a measurement error that remains constant or changes in a predictable manner across multiple measurements of the same quantity. Random error, also known as accidental error, is an error in which the absolute value and sign of the error change in an unpredictable manner during multiple measurements of the same quantity. Negligible error refers to the error that exceeds what is expected under specified conditions. What are the common methods used to eliminate systematic errors in La5C2002? Answer: Systematic error plays an important role in measurement errors; it determines the accuracy of the measurement. Systematic errors follow certain patterns, and different experimental methods must be employed to eliminate them based on these patterns. Common methods include: (1) Methods for eliminating known systematic errors include: ① Introducing correction values ； ②Eliminate the factors that cause errors ； ③Substitution method ； ④Substitution method ； ⑤Positive and negative error compensation method. (2) The symmetric observation method can be used to eliminate system errors with a linear variation. What are the application areas of the La5C2003 shock wave oscillator? (Please mention 5.) Answer: Communication, broadcasting, television, industry, agriculture, biomedicine, etc. What are the differences in the characteristics of AC and DC amplifiers in La5C2004? Answer: An AC amplifier cannot amplify DC signals. A DC amplifier can amplify DC signals, but the amplification of AC components is easily overwhelmed by the DC component. La5C2005 What is an operational amplifier? Answer: It is a directly coupled amplifier with a high gain level and deep negative feedback; through an input network or feedback network composed of linear or nonlinear components, various digital processing operations can be performed on the input signal. What are the main requirements for a power amplifier in La5C2006? Answer: A power amplifier is required to have sufficient power output, low distortion, high efficiency, and matched impedance. La5C2007 What is the holding current of a thyristor? Answer: The holding current refers to the minimum anode current required to maintain the thyristor in the on state. In the La5C3008 single-phase half-wave rectifier circuit, what is the reverse voltage (maximum value) of the diode? Compared to a full-wave rectifier circuit, which one withstands a higher reverse voltage? Which has a higher utilization rate for power transformers? Answer: In a single-phase half-wave rectifier circuit, the reverse voltage (maximum value) of the diode is √2U2, which is the amplitude of the AC supply (the effective value of the AC voltage output on the secondary side of the transformer). In both circuits, the diodes are subjected to the same reverse voltage. The power transformer in a full-wave rectifier circuit has high efficiency. La5C3009 Please briefly explain the working principle of the filtering capacitor in a rectifier circuit. Answer: The function of the filtering capacitor is to ensure that the voltage output after filtering is a stable DC voltage. Its working principle is such that the capacitor charges when the rectified voltage is higher than the capacitor voltage, and it discharges when the rectified voltage is lower than the capacitor voltage; through this process of charging and discharging, the output voltage remains relatively stable. What are the characteristics of the La5C3010 bistable circuit? Answer: A bistable circuit has two characteristics: (1) The circuit has two stable states ； (2) The circuit can transition from one stable state to another only under the action of an external trigger signal. La5C3011 What is the phenomenon of mutual inductance? What laws govern the magnitude and direction of the mutual induction emf? Answer: The phenomenon in which a change in current in one winding induces an electromotive force in another winding is called mutual inductance. The magnitude and direction of the mutual induction emf are governed by Faraday’s law of electromagnetic induction and Lenz’s law, respectively. La5C3012 Please explain what the conditions are for parallel operation of three-phase power transformers What are the consequences if it is not met? Answer: (1) Parallel connection conditions: identical phase sequence, identical turns ratio, identical wiring group, and equal short-circuit impedance. (3) If the first three conditions are not met, large circulating currents will be generated between the transformers operating in parallel, leading to the destruction of the transformers ； If the fourth parameter is not the same, it will lead to uneven load distribution among the transformers during operation, affecting the efficiency of their parallel operation as well as their total capacity. La5C3013: Why are medium and large DC motors not allowed to start directly? What starting methods are generally used during startup? Answer: When a DC motor is started directly, the back EMF is zero at the moment of starting; therefore, the starting current is the terminal voltage divided by the armature resistance. Due to the low armature resistance, the starting current during direct starting is generally 10 to 20 times the rated current. Such a high current can cause severe damage to the motor itself, the power grid, and the mechanical transmission system, and may even destroy the motor. Generally, two methods are used: reduced-voltage starting and starting by inserting a resistor in the armature circuit. La5C3014 Please briefly explain the reasons for core heating in transformers and the methods to reduce such heating. Answer: The main reasons for the heating of the transformer core are hysteresis loss, eddy current loss, and the heat conducted by the windings. To reduce the heating of the core, it is necessary to strengthen cooling, use silicon steel sheets with better magnetization properties, and increase the resistance between the silicon steel sheets. Is the effective value of La5C3015’s positive fluctuation value the same as its average value? Why? Answer: The effective value of a sinusoidal quantity is not its average value. Because the effective value equals the average of the squares of the instantaneous values over one cycle, and it produces the same amount of heat as a direct current of the same value applied to the same resistor, whereas the average of the instantaneous values is zero. La5C3016: Please briefly explain how the phase difference of coherent waves at the same frequency is calculated, and whether it is related to time Answer: The phase difference between positive sinusoids of the same frequency is equal to their initial phase difference, and it is independent of time. La5C3017 What is the relationship between electrical power and electrical energy? Does a higher electric power mean more electrical energy? Answer: Electrical energy is the integral of electrical power over time (or electrical power indicates the rate at which electrical energy changes). The greater the electrical power, the larger the electrical energy is not necessarily. La5C3018 What is the time constant of an RC circuit? How does its size affect the circuit’s response? Answer: The time constant of an RC circuit is the product of R and C. The larger the time constant, the slower the response; conversely, the smaller it is, the faster the response. What are the main parameters of the La5C4019 diode? Answer: The main parameters of a diode are as follows: (1) Maximum rectifying current ； (2) Reverse current ； (3) Operating frequency ； (4) Maximum reverse operating voltage. La2C2020 What conditions must be met for two three-phase transformers to operate in parallel? Answer: For two three-phase transformers to operate in parallel, the following conditions must be met: (1) The phase sequence must be the same ； (2) Same group ； (3) Equal transformation ratio ； (4) The short-circuit impedances are equal. How will the gain and passband change when La2C3021’s N-pole amplification circuit is connected in series? Answer: The magnification increases while the passband narrows. Lb5C1022: What is a composite control system? Answer: A composite control system refers to a control system in which open-loop control and closed-loop control are used in combination. Lb5C2023 What is regulator parameter tuning? Answer: After the regulator is connected to the actual system, determining its proportional band, integral time, and derivative time is what constitutes regulator parameter tuning. Lb5C2024 What is an open-loop control system? Answer: An open-loop control system is one in which the output of the system has no influence on the system’s control action; in other words, there is no closed loop in the signal relationship between the control device and the controlled object. Lb5C2025 What is coordinated control? Answer: Coordinated control is a good approach for load control of unit systems; it utilizes the coordinated operation of the turbine and boiler to achieve power control of the unit, and it is a control method based on feedforward-feedback control. What are the components of the Lb5C3026 thermal measurement instrument? What is the function of each part? Answer: Thermal measuring instruments consist of a sensing element, an intermediate element, and a display element. The sensor is in direct contact with the object being measured; it detects changes in the parameters of that object and converts the signals related to these parameters into signals that are suitable for measurement and display. The middleware transmits the signals output by the sensing element directly to the display element, or amplifies and converts them into signals suitable for the display elements. The display element reflects to the observer the value and changes of the parameter being measured. Lb5C3027: What are the common components used for temperature measurement? Answer: The commonly used ones include: thermal resistors, thermocouples, bimetallic thermometers, and expansion thermometers. Lb5C3028 Please describe the applicable conditions for standard throttling devices. Answer: Standard throttling devices are suitable for: ① the flow rate of single-phase, homogeneous fluids in circular pipes ； ②The fluid fills the pipeline; no phase change or impurity precipitation occurs within a certain distance before and after the throttling element, and the flow velocity is below the speed of sound ； ③The flow is non-pulsating; the fluid stream before passing through the throttling element is parallel to the pipe axis, with no rotational flow allowed ； ④The flow regime is typically developing turbulence. What are the two components of the Lb5C3029 automatic adjustment system? What are the most common basic components that make up an automatic control system? Answer: (1) The automatic control system consists of two parts: the controlled object and the control device. (2) The most common basic elements that make up an automatic control system are: first-order inertial element, proportional element, integral element, differential element, and delay element. Lb5C4030 What is an intelligent transmitter? What are its features? Answer: An intelligent transmitter is a transmitter equipped with a microprocessor. Compared with traditional transmitters, it has the following main features: (1) High accuracy, generally ranging from ±0.1% to ±0.15%. (2) It has software signal processing capabilities and good linearity. (3) It has temperature and pressure compensation functions. (4) Large range adjustment capability. (5) Remote transmission, adjustment range, diagnosis, and communication. (6) High reliability and low maintenance requirements. What components does the Lb5C4031 pneumatic control instrument consist of? Answer: Pneumatic control instruments mainly consist of pneumatic transmitters, pneumatic controllers, pneumatic display instruments, and pneumatic actuators. What two functions should the Lb5C4032 bypass control system have? Answer: To meet the functional requirements of the bypass system, the bypass control system should possess the following two functions: First is the automatic adjustment function under normal conditions, which adjusts the pressure and temperature of the steam in the bypass system based on fixed or variable values. Secondly is the automatic protection function in abnormal situations, where it is necessary to quickly open or close the bypass valve in order to protect the operating equipment. Lb5C5033 What is a closed-loop control system? Answer: A closed-loop control system, also known as a feedback control system, is one in which the output of the system has a direct impact on the system’s regulatory actions. That is, a closed loop formed in the signal relationship between the control device and the controlled object. Lb4C2034 What is the air consumption of pneumatic instruments? Answer: The amount of working gas consumed by each pneumatic instrument per unit of time is called the gas consumption of that instrument, with L/h being the commonly used unit. When fluid flows through a control valve, what are the various types of effects it has on the valve spool? Answer: When fluid passes through a control valve, its flow direction exerts two effects on the valve core: one is to cause the valve to tend to open, and valve cores with such a structure are called flow-open type valve cores ； Another type is one that causes the valve to tend to close; the valve core of this type of structure is called a flow-blocking valve core. Lb4C3036 What does bypass mean? What does 30% bypass mean? Answer: A special pipeline through which the new steam and reheat steam generated by the boiler can enter the condenser directly, without passing through the turbine, when necessary, is called a bypass. The steam flow rate that can pass through the bypass is 30% of the rated flow rate, which is referred to as 30% bypass. Lb4C3037 What is integral separation? What is its role in process control? Answer: Integral separation is a special algorithm for programmable regulators; that is, when there is a large deviation in the system (as determined by logical judgment), the integral term does not function, and only the proportional and derivative terms are active. However, when the system deviation is small (the process variable is close to the setpoint), the integral term becomes active. By using integral separation, deviations can be rapidly eliminated in cases of large offsets, preventing overshoot in the system; at the same time, it shortens the transition time and improves the quality of regulation. What components can the Lb4C3038 TF-900 type of assembled instrument be divided into based on its functions? Answer: The TF-900 type of assembled instruments can be classified into 9 major categories of components based on their functions, namely conversion, regulation, calculation, control, setting, display, operation, power supply, and auxiliary functions; there are a total of 108 different models in these categories. Lb4C3039 What is redundancy? What is redundancy checking? Answer: Redundancy means repetition. In computer terminology, redundancy refers to the intentional duplication or partial duplication of circuits or information in order to reduce the probability of failures in computer systems or communication systems. Redundancy checking is accomplished by verifying whether the digit combination is valid, using redundant bits known as parity bits to detect errors caused by the computer. The specific approach is to calculate the redundancy code of the output data from the redundancy code of the input data, and then compare it with the redundancy code of the result to determine whether they are identical. In this type of redundancy code, an odd number is selected when the adder circuit uses an even number. Redundant checking is generally used in arithmetic circuits. What are the main functions of the Lb4C3040 FSSS (Boiler Safety Monitoring System)? Answer: To prevent the accumulation of explosive mixtures of fuel and air in any part of the boiler during the startup, shutdown, and operation of the boiler, to avoid damage to the steam generator or equipment in the combustion system, while continuously monitoring a range of parameters and enabling rapid response to abnormal operating conditions. This is the basis for the startup, operation, and shutdown procedures of power plant equipment. What aspects should be focused on in the quality management work of team Lb4C3041? Answer: ① Regularly conduct ideological education on the principle of “quality first” among all the construction workers in the class ； ②Organize the whole class to study construction drawings, equipment specifications, quality standards, process procedures, quality inspection methods, etc ； ③Organize workers to train in basic skills ； ④Verify the drawings and check the quality of materials and equipment as well as their certificates of conformity ； ⑤Adhere to the correct construction procedures and maintain a clean and orderly construction site ； ⑥Organize self-inspections and mutual inspections, leverage the role of team quality supervisors, and fill out construction and acceptance technical records in a timely and thorough manner ； ⑦For the weak links in the construction process, a quality improvement plan is formulated to define the goals for enhancing quality ； ⑧Establish and improve QC teams to achieve \"full participation in quality management\". What does the “4C” technology refer to in the Lb4C3042 distributed control system? Answer: Control technology (CONTROL), computing technology (COMPUTER), communication technology (COMMUNICATION), and image display technology (CRT). What are the most common network topologies for Lb4C3043 DCS, and what structural approaches are used to improve the reliability of such systems? Answer: The most common network topologies for DCS are star, bus, and ring. To improve its operational reliability, a redundancy-based structure is often employed, with the main structural approaches including an automatic backup system formed by multiple units and a manual backup method. What are the static characteristics of the commonly used control valve Lb4C3044? Answer: There are 4 common types of static characteristics for control valves: ① Linear characteristic ； ②equal probability property ； ③Parabolic properties ； Quick open feature. Under what conditions does the low-pressure bypass isolation valve close rapidly to protect the condenser? Answer: In the following situations: ① High condenser pressure ； ②High condenser temperature ； ③**Low pressure ； ④Main fuel trip. The low-pressure bypass isolation valve closes rapidly to protect the condenser. LB3C2046 What is the ideal flow characteristic of a control valve? Answer: The static characteristics of a control valve, namely the ideal flow characteristic, refer to the relationship between the relative flow rate of the medium (the ratio of the actual flow rate to the rated flow rate) and the relative opening degree of the valve, when the pressure difference across the valve remains constant. LB3C2047 What is voltage transformation operation mode? Answer: The variable pressure operation mode refers to the situation where the set value of main steam pressure determined by the control system changes according to the load; that is, at high loads, the set value for steam pressure is higher ； At low load, the steam pressure setpoint is low; during operation, the control system maintains the steam pressure at this setpoint, which in turn varies with the load. LB3C3048 How to perform operation and maintenance of the water supply control system? Answer: ① After the water supply control system is put into automatic operation, enhanced supervision and maintenance are necessary ； ②Conduct thorough on-site inspections of all components of the control system daily, and address any issues found promptly ； ③Various disturbance tests on the control system should be conducted regularly, with proper experimental records kept ； ④Regularly flush the sampling pipeline. LB3C3049 The handling of field I/O by DCS can be divided into local I/O and remote I/O; explain the differences and relationships between the two Answer: Difference: Short-distance I/O involves introducing process variables directly into the computer via signal cables, which transmit analog signals. Remote I/O enables field I/O through remote terminal units; a connection and signal exchange are established between the remote terminal units and the computer via communication lines, with the communication cables transmitting digital signals. Relationship: Both are required to complete the data collection of process variables at the site. What are the main functions of the LB3C3050 DEH control system? Answer: The DEH control system primarily has the following functions: ① Automatic startup function ； ②Automatic load control function ； ③Manual operation function ； ④Over-speed protection function ； ⑤Automatic emergency shutdown function. LB2C3051: Briefly describe the function of the measurement bridge in a diffused silicon pressure transmitter Answer: The measurement bridge of a diffused silicon pressure transmitter serves three main functions: ① To obtain a linear output from the transmitter ； ②Favorable for environmental temperature compensation ； ③By changing the value of the feedback resistor, it is possible to adjust the output sensitivity of the transmitter and change the pressure measurement range. What does “two tickets and three systems” refer to in the LC5C2052 Power Safety Regulations? Answer: “Two tickets” refer to: ① Operation ticket ； ②Work order. “The “three systems” refer to: ① a system for regular periodic inspections of equipment ； ②Shift handover system ； ③Regular switching system for redundant devices. What are the components of the comprehensive quality system for LC3C3053? Answer: The key components of a total quality management system include: quality policy, quality objectives, quality system, quality planning, quality costs, quality improvement, quality culture, and quality audits. What are the objectives and tasks of on-site quality management for LC2C2054? Answer: The goal of on-site quality management is to produce products that meet design requirements or to provide services that comply with quality standards, that is, to ensure and improve conformity quality. The tasks of on-site quality management fall into 4 aspects: prevention of quality defects ； Maintenance of quality ； Improvement in quality ； Evaluation of quality. What is the scope of technology for thermal instruments and control devices LC2C2055? Answer: ① Thermal parameter detection, display, and recording system ； ②Automatic control system ； ③Protection interlock and process signal system ； ④Sequential control system ； ⑤Measurement standards and devices. LC2C2056 What is the concept and role of “5S” in total quality management? Answer: The concept is: ① Organize ； ②Rectify ； ③cleaning ； ④Clean ； ⑤Literacy. Its functions are: ① To create a positive corporate image ； ②Improve work efficiency ； ③Work safety ； ④Reduce waste. What are the main elements of the LC2C3057 comprehensive quality management system? Answer: As an organic whole, the components of total quality management mainly include: quality policy, quality objectives, quality system, quality planning, quality costs, quality improvement, quality culture, and quality audits. The interrelationship between them not only constitutes total quality management as a cohesive whole but also reflects its scientific nature and advancement. LC2C3058: What are the principles behind fully functional power management? Answer: It is based on the following principles: ① System principle ； ②The principle of whole and part combination ； ③Feedback principle ； ④Closure principle ； ⑤Principle of operation ； ⑥Principle of elasticity ； ⑦Principles of the rule of law. LC2C3059 What is the role of a quality management team? Answer: The roles of a quality management team are: ① It helps to change old management habits. ②It facilitates the development of approaches to overall employee management. ③It helps to promote activities aimed at improving product quality. ④It facilitates the dissemination of modern management ideas and methods. ⑤It helps to generate more economic benefits. ⑥It helps to promote the development of spiritual civilization. JD5C3060: What are the methods for starting and ending an arc during welding? Answer: There are the friction method and the tapping method for starting an arc ； There are the transfer method and the stacking method for arc termination. JD5C4061 Discuss the main reasons for the breakage of saw blades during cutting Answer: The reasons are: ① The saw blade is installed too tightly or too loosely ； ②The workpiece is shaking or loose ； ③The saw cut is skewed ； ④Forceful correction after the saw seam becomes skewed ； ⑤Too much pressure when sawing ； ⑥The saw blade is caught in the saw gap ； ⑦After the saw blade breaks, a new one cuts in from the original cut. JD2C1062: Briefly explain the difference in response speed between an asynchronous binary up-counter and a synchronous binary up-counter, and why Answer: Asynchronous counters have a slower response speed; when the interval between signal pulse inputs is shorter than the total conversion period, the counter cannot function. The reason is that the carry signals of asynchronous counters are transmitted stage by stage; the counting speed is influenced by both the transmission delay time of the flip-flops and the number of flip-flops. The total conversion time equals the product of these two factors, which thus **reduces** the switching speed of asynchronous counters. JE5C1063 What are the basic operating principles of industrial regulators? Answer: The basic operation modes of industrial regulators include proportional (P) control, proportional-integral (PI) control, and proportional-integral-differential (PID) control. JE5C1064 What are the tuning parameters of a PID automatic regulator? Answer: There are three tuning parameters: proportional band, integral time, and derivative time. JE5C2065 What is a base-type instrument? What are its features? Answer: A base-type instrument refers to an instrument that integrates functions such as detection, display, and regulation (transmission), and is usually capable of being installed on-site. Its features are: ① Integration and concentration, as it brings all the necessary functional components together in a single instrument; with just a control valve added, it can form a control system. ②The system has a simple structure and is easy to use and maintain. ③The disadvantages are its simple functionality, which makes it unsuitable for constructing complex control systems; it is also bulky and has relatively low precision. JE5C2066 What is two-wire system? What are the advantages of two-wire systems? Answer: Two-wire system refers to the fact that there are only two wires connecting the field transmitter to the instruments in the control room; these two wires serve both as power lines and signal lines. Compared to the four-wire system, its advantages are: ① it can save a large amount of cable and installation costs. ②It is beneficial for safety and explosion prevention. JE5C2067 What are the static and dynamic characteristics of a link? Answer: The relationship between the input signal and the output signal of a system when they are in equilibrium is known as the static characteristics, while the relationship between them when they are in a state of change is known as the dynamic characteristics. JE5C2068 What are the “forward” and “reverse” actions of a regulator? Answer: If the output value of the regulator increases as the positive deviation value increases, it has a “positive” effect ； The output value of the regulator decreases as the positive deviation value increases, which is a “negative” effect. JE5C3069 What are the technical requirements for wiring inside the panel? Answer: The basic technical requirements for wiring inside the panel are: to carry out work according to the diagrams and to ensure correct wiring ； Secure connection with good contact ； The insulation and wires are not damaged ； The wiring is neat, clear, and aesthetically pleasing. JE5C3070: What are the main systems of a drum boiler installation? Answer: The main control systems for drum boiler units include the feedwater control system, the main steam temperature control system, and the combustion control system of the drum boiler. JE5C3071 What are the basic forms of the adjustment process? (In the case of step perturbations) Answer: There are 4 forms: ① Aperiodic process. These can be further divided into two forms: those with monotonic variation and those with a single peak value. ②Attenuated oscillation process. ③Isochoric process. After the disturbance to the control system, a new equilibrium cannot be reached, and both the controlled quantity and the control action undergo oscillations of equal amplitude. This condition is called “boundary stability”. ④Divergent oscillation process. JE5C3072 What is the function of a valve position transmitter? Answer: The function of the valve position transmitter is to linearly convert the angle of rotation (0–90 degrees) of the output shaft of the pneumatic actuator into a 4–20 mA DC signal, which is used to indicate the valve position and to provide positional feedback for the system. Therefore, the valve position transmitter must have sufficient linearity and linear range in order to enable the actuator’s output shaft to move in close accordance with the regulator’s output signal. JE5C3073 What is the measurement principle of a throttling device in brief? Answer: When the fluid filling the pipe flows through a throttling device within the pipe, the flow stream undergoes local contraction at the throttling element, which increases the flow velocity and reduces the static pressure; as a result, a static pressure difference is created before and after the throttling element. The greater the fluid flow rate, the greater the pressure difference generated before and after the throttling element. Therefore, the flow rate of the fluid as it passes through the throttling device can be determined by measuring this pressure difference. This measurement method is based on the law of conservation of energy and the equation of continuity for flow. JE5C3074 What are the main functions of an electric actuator? Answer: Electric actuators generally have the following functions: enabling manual remote operation ； Enable seamless manual/automatic switching. JE5C3075 What are the maintenance tasks for force balance transmitters? Answer: The items include: general inspection ； Inspection of the mechanical parts of the transmitter ； Transmitter sealing check. JE5C3076 How should the various thermal connection pipelines be inspected? Answer: The main thing to check is the pipelines, namely whether there are any misconnections, blockages, or leaks in the steam, air, and water pipelines. JE5C3077 How should on-site inspections be carried out for thermal control circuits? Answer: All connections in the control circuit must be inspected to verify that they meet the requirements specified in the drawings, that there are no misconnections, that the insulation between wires and against ground meets the specified standards, and that the wire connections are in good contact. JE5C3078 What is disturbance-free switching of a control loop system? Answer: Switching a control system from manual to automatic, or from automatic to manual, should not affect the change (jump) in the regulator’s output. This mutual switching between manual and automatic modes does not affect the operation of the regulator output, and is referred to as bidirectional disturbance-free switching. Only when switching from manual to automatic or from automatic to manual is there no disruption, which is referred to as a one-way seamless switch. JE5C3079 Briefly describe the tasks that should be carried out before installing the sampling pipeline Answer: The following tasks should be carried out before installing the sampling tube: inspection of the pipeline material and specifications ； Visual inspection of the catheter ； Cleaning inside the catheter. JE5C3080 Discuss the technical requirements for the maintenance and installation of actuators Answer: Generally, the following technical requirements apply: ① The mechanical parts of the actuator should move smoothly, without any looseness or sticking. ②The electrical insulation of the actuator must be satisfactory; it should operate smoothly during power-on testing, and there should be no fluctuations in the opening indication. ③Pneumatic actuators shall undergo leak tests and relevant protection tests (such as those with triple-break protection), and shall comply with relevant regulations. ④The actuator should have clear on/off direction indicators ； The rotation direction of their handwheels should be consistent; generally, clockwise is designated as “off” and counterclockwise as “on”. JE5C4081 Whenever a fire is detected, any organization or individual should promptly and accurately report it to the authorities and actively participate in efforts to extinguish the fire. What are the key points of reporting a fire, and what does each point entail? Answer: There are 4 items, which are: the location of the fire, the intensity of the fire, the materials burning and their approximate quantity, and the name and phone number of the person who reported the fire. JE5C4082: The DKJ electric actuator is in its designated position, and the number of oscillations exceeds 1.5 cycles – how should this be handled? Answer: Adjust the W1 stability potentiometer to stabilize it, but be careful not to overdo it, as this could result in too low amplifier sensitivity or no output. JE5C4083 How to perform zero point migration for the 1151 transmitter? Answer: The steps for zero migration of the 1151 transmitter are as follows: ① First, adjust one of them to the desired value before performing the migration. ②Perform zero shift using the lower limit value of the measurement; enter the pressure corresponding to this lower limit, and adjust it with the zero adjustment potentiometer so that the output is 4 mA. ③Recheck at full scale, and make fine adjustments if necessary. ④If the migration amount is large, first switch the transmitter’s migration switch (connector) to the positive or negative migration position (determined by the direction of migration), then apply the lower measurement limit pressure and use the zero adjustment potentiometer to set the output at 4 mA. JE5C4084 How to conduct a test on the output current stability of a DTL regulator? Answer: 1. Set the integration time to the maximum, the differentiation time to the minimum, and the proportional band to 100% ； 2. By changing the input signal to obtain any desired output value, the output jitter should not exceed 0.05 mA. JE5C4085 What are the requirements for removing the automatic pressure control system of the deaerator? Answer: 1. Under stable operating conditions, the deaerator pressure exceeds the alarm value. 2. When the control valve is fully open yet the pressure continues to drop, or when the control valve is fully closed yet the pressure continues to rise. 3. The operation mode of the deaerator has changed, failing to meet the requirements for automatic control. JE5C4086: What are the components of the B-series pneumatic base-type control instrument? Answer: The B-series pneumatic base-type control instrument is mainly composed of components such as the measuring element, setting mechanism, differential mechanism, two-stage power amplifier, air switch, feedback mechanism, manual operation mechanism, alarm device, and valve position indicator. JE5C4087: What are the components that make up the TFT-060/B type adjustment assembly? Answer: The principle block diagram is omitted; it consists of a deviation circuit, proportional-differential circuits, proportional-integral operation circuits, as well as an automatic/manual switching circuit and an output limiting circuit. JE5C4088 What are the main turbine protection items? Answer: The main ones include: condenser vacuum low protection, lubricating oil pressure low protection, main engine overspeed protection, rotor axial displacement protection, and high-pressure heater water level protection. What are the requirements for the tightness of pneumatic instrument signal pipelines for JE5C4089? Answer: The signal pipelines of pneumatic instruments must not leak. In the event of a leak, it will affect the proper operation of the instruments and their associated systems. Therefore, a leak test is required after installation or maintenance. According to the technical specifications for the construction and acceptance of power generation facilities, a tightness test must be carried out at a working pressure of 1.5 (150 kPa), with the requirement that the pressure drop within 5 minutes shall not exceed 0.5% (750 Pa). What are the performance indicators used to evaluate the regulating system for JE5C4090? Answer: To measure and compare the performance of control systems, several characteristic values on the transition curve are commonly used as performance indicators, namely the steady-state error y(∞) of the controlled variable, the maximum dynamic error ymax, the time required for the control process ts, and the overshoot σp of the controlled variable. JE5C4091: How to calibrate the scale error of the proportional band of the DTL regulator? Answer: ① The proportional band is set at the measured scale value Ps; by changing the input current Ii, the corresponding output current is Io (not exceeding 10 mA). The measured value of the proportional band, Ps, is calculated using the following formula: Ps = 100% × Ii/Io. ② Five points are selected within the usual range of the proportional band (including the 100% point), calibration is performed 2–3 times, and finally the Ps-Pr curve is drawn based on the average values. ③The relative error of the proportional band scale should not exceed ±25%. What important role does the JE5C4092 adjustment mechanism play in automatic control systems? Answer: The regulating mechanism is one of the components of an automatic control system. In typical thermal automatic control systems, it is used to regulate the flow of substances or energy into and out of the process being controlled, thereby enabling the automatic adjustment of various thermal parameters in industrial production processes. A well-designed automatic control system can still experience problems or even fail to function if the operating characteristics of its control mechanism are poor or if its adjustable range is insufficient. Practice has shown that poor regulation quality of the control system or failures in the control system are often caused by problems with the control mechanism. What issues should be considered when selecting the size validator for JE5C4093? Answer: Size value selectors generally have 4 input channels; during verification, these channels should be connected to separate signal sources (in other words, 4 signal sources are required), and each channel must be verified individually. When verifying the selection performance, a certain signal must be applied to all 4 channels; this issue is particularly important when evaluating the selection performance of the low-value selector. If a channel has no input signal, the output of the minimizer is zero. What is the function of the JE5C4094 pneumatic valve positioner? How does it work? Answer: In situations where the operating conditions of the actuator are poor but high quality is required, pneumatic valve positioners are used in combination with pneumatic actuators to form a closed-loop system. The principle of negative feedback is utilized to improve accuracy, sensitivity, and stability, thereby enabling the valve to determine its opening degree precisely based on the input control signal. A pneumatic valve positioner is a pressure-displacement feedback system that operates on the principle of displacement balance. What principles should be followed when adjusting the combustion control system of JE5C4095? Answer: It mainly follows the following three principles: 1. Tuning is primarily carried out on the basis of coordinated operation of the three sub-regulation systems for fuel volume, air supply volume, and exhaust air volume. 2. The correlation coefficients in the control system are generally determined based on the principle of steady-state proportioning, to ensure that the fuel volume, supply air volume, and exhaust air volume maintain an appropriate proportional relationship. 3. In the combustion control system, excessive overshoot is not allowed for the three control variables (fuel volume, air supply volume, and exhaust air volume) as well as the three process variables to be controlled (steam pressure, excess air coefficient, and furnace pressure) during dynamic operations. What is the main function of the turbine and boiler actual load command processing module in JE5C4096 for unit load control? Answer: The main functions include: 1. Rapid restoration of the actual load command for the unit. 2. Forced increase/decrease of the actual unit load command. 3. Automatic/manual control switching for the turbine load command. 4. Maintenance of the actual load command for the turbine and boiler. JE5C5097: How to adjust the insensitive zone of the servo amplifier? Answer: The common method is to adjust the amplification factor of the amplifier by modifying the depth of negative feedback, in order to adjust its insensitive region. First, adjust the trim potentiometer W2 in the magnetic amplifier. When the actuator oscillates, the insensitive zone should be increased. If the oscillation still cannot be eliminated, the resistance of the feedback loop can be reduced to increase the depth of negative feedback ； Or reduce the offset resistance to increase the offset current and deepen the saturation state of the magnetic amplifier core ； The resistance at the output of the magnetic amplifier can also be adjusted to reduce the effective voltage value of the input flip-flop. Can a \"stall\" condition in the JE5C5098 angular travel electric actuator damage the motor? Why? Answer: When a motor is in a \"stall\" condition, the current flowing through the stator windings is as high as the starting current. Over time, excessive temperature rise can cause the motor to burn out. However, the actuator motor reduces the starting current by increasing the rotor resistance; it features both a sufficient starting torque and the ability to keep the temperature rise within specified limits even under prolonged \"stall\" conditions, so the motor will not be damaged as a result of stall in electric actuators. What is the function of the phase-splitting capacitor CD in the JE5C5099 DKJ actuator? What might happen when a CD is damaged? Answer: The phase separation capacitor CD enables an 90-degree phase difference to be created between the alternating voltage in the stator winding connected in series with it and the alternating voltage in another stator winding, thereby generating a combined rotating magnetic field that produces a starting torque to make the rotor rotate. Its direction of rotation depends on which stator winding the phase-splitting capacitor is connected in series with. Therefore, the function of the phase-splitting capacitor CD is, first, to generate a starting torque, and second, to change the direction of rotation. If the CD circuit is broken, a composite rotating magnetic field cannot be generated, and thus no starting torque is produced; the motor will not start. If the CD is short-circuited, current of the same phase flows through both windings of the motor simultaneously, causing the motor to be in an electrical braking state and preventing it from rotating. How to distinguish whether JE5C5100 is oscillating due to an electric actuator or an oscillation in the control system? Answer: For the entire control system, oscillations in electric actuators represent small-loop oscillations, while the control system itself experiences large-loop oscillations; there are differences between them in terms of phenomena and characteristics. Observationally, when the actuator oscillates, the pointer of the valve position indicator fluctuates up and down, whereas there are no significant changes in the parameter being regulated or in the output of the regulator. When the control system oscillates, in addition to the oscillation of the actuator itself, the output of the controller exhibits regular oscillations as a result of fluctuations in the process variable being controlled. In terms of characteristics, the actuator oscillates at a high frequency with a short period. The oscillation frequency of the control system is low and its period is long; the oscillation frequencies of the controlled variable, the controller output, and the actuator are essentially the same. What are the steps for determining the tuning parameter δa1 of the secondary regulator using the critical proportionality method in the JE5C5101 cascade control system? Answer: The steps are as follows: ① Put the main and auxiliary circuits into closed-loop operation; set the parameters of the main regulator to δa2=100%, Ti=, Td=0, and set the parameters of the auxiliary regulator to any value. ②Change the proportional band δa1 of the secondary regulator so that the secondary loop exhibits undamped oscillations, and record the proportional band δa1* at this point. ③The setting value of the secondary regulator is δa1=2δa1*. What are the features of the JE5C5102 cascade control system? Answer: The cascade control system has the following characteristics: ① A cascade control system can be equivalent to a single-loop control system, with the secondary loop of the cascade system becoming part of the equivalent controlled object; therefore, it is considered a single-loop control system that improves the dynamic properties of the controlled object. ②Due to the presence of the secondary loop, the operating frequency of the control system has increased significantly. ③It improved the ability to suppress interference entering the secondary circuit. ④Since the secondary loop is a fast-following system, it endows the cascade control system with a certain degree of adaptability. What does the ascension speed ε of the JE4C2103 object refer to? Answer: ε refers to the maximum rate of change of the measured quantity under a unit step disturbance. What does the time constant T of the JE4C2104 object refer to? Answer: The time constant T of an object is an important parameter that indicates the time required for the measured quantity to complete its change process after being perturbed; it is a parameter that represents the inertia of the object. The larger T is, the greater the inertia of the object. What are the characteristics of the proportional control effect of JE4C2105? Answer: The advantage of proportional action is fast response. Its output reflects changes in the input without delay, which is the most fundamental control function. The disadvantage is that there is a static deviation in the controlled quantity after adjustment is completed. What are the adjustment types available for the JE4C2106 KMM regulator? Answer: There are 4 types: Type 0 regulation, Type 1 regulation, Type 2 regulation, and Type 3 regulation. In the input circuit of the JE4C3107 DBW temperature transmitter, what is the main function of the bridge circuit? Answer: The main functions of a bridge circuit are to achieve automatic compensation for the cold junction temperature of thermocouples ； Zero-point migration ； Thermocouple open circuit alarm ； Implement instrument self-check. JE4C3108: What tracking control method is used between the low-pressure bypass **valve and the low-pressure bypass steam valve? Answer: A proportional tracking control method is adopted. When the low-pressure bypass valve is opened, **the valve will track according to a set proportional coefficient, and pressure and temperature corrections for this proportional coefficient have been taken into account in the system design. As the steam pressure and temperature at the outlet of the low-pressure bypass valve increase, the proportional coefficient increases in a certain manner, thereby increasing the amount of flow through the valve and maintaining the steam temperature at its lower value at the outlet of the low-pressure bypass valve. What are the accuracy calibration items for the JE4C3109 regulator? Answer: 1. Manual operation error test. 2. Tuning of the closed-loop tracking error of the electric regulator ； Adjustment of the control point deviation for pneumatic regulators. 3. Proportional band, integral time, and derivative time scale error tests. 4. When there are additional mechanisms, the motion error of those mechanisms should be adjusted. JE4C3110 What measures can be taken to reduce the steam temperature when the amount of water used for temperature reduction has been increased to its maximum and the temperature of the superheated steam remains high? Answer: 1. Adjust the boiler combustion to lower the position of the flame center. 2. Reduce the excess air volume within the allowable range. 3. Appropriately reduce the boiler’s evaporation rate. How can JE4C3111 achieve automatic tracking of a cascade control system? Answer: A cascade control system has two controllers, and it is necessary to address the issue of automatic tracking for these two controllers. Generally speaking, the secondary regulator is directly related to the actuator; it must track the position of the actuator (or the valve position signal) so as to avoid disturbances when the secondary regulation circuit is activated first. The setpoint of the secondary regulator is the output of the primary regulator; when it is in balance with the intermediate controlled parameter, the secondary regulator does not operate. Therefore, the primary regulator should track a signal that keeps the input of the secondary regulator in a balanced state at all times. For example, in a cascade steam temperature control system, the main regulator can monitor the steam temperature after the desuperheater, while the secondary regulator can monitor the opening degree of the desuperheating valve. What is the task of JE4C3112 in regulating the temperature of superheated steam? Answer: The task of regulating the temperature of superheated steam is to maintain the steam temperature at the outlet of the superheater within acceptable limits, to ensure that the wall temperature of the superheater tubes does not exceed the permitted operating temperature, and to supply the turbine with qualified superheated steam, thereby ensuring the safe and economical operation of the main equipment. What is the task of automatic combustion control in a drum boiler JE4C3113? Answer: The tasks of automatic combustion control in a drum boiler are: 1. Maintain a constant steam pressure ； 2. Ensure the economic efficiency of the combustion process ； 3. Adjust the exhaust air volume to match the supply air volume, in order to keep the negative pressure in the furnace within the allowable range. JE4C3114 Why are pure integral controllers rarely used in industrial production? Answer: The characteristic of integral action is that as long as there is a deviation, the output will keep increasing over time, and the actuator will continue to operate until the deviation is eliminated; thus, integral action can eliminate static error. Pure integral action can easily lead to excessive adjustment actions, causing the adjustment process to oscillate repeatedly or even diverge; therefore, pure integral controllers are rarely used in industrial production. They can only be employed when the dynamic characteristics of the system being regulated are favorable. JE4C3115 What is full-range water level adjustment? Answer: Full-range regulation of the boiler water level means that automatic control is used throughout the entire process of the boiler, from water filling, recirculation, pressure building, operation under load, normal operation, to shutdown. What tests should be conducted on JE4C3116 before the temperature automatic control system is put into use? Answer: Before being put into use, the automatic temperature control system should undergo tests on the dynamic characteristics of the superheated steam temperature, tests on the dynamic characteristics of the reheat steam temperature, and tests on the characteristics of the desuperheating water control valve. What are the two different structural formats of the main control system for the JE4C3117 unit at present? Answer: One structural approach is to form an independent control system using the various functional components of the main control system, while the other control systems of the unit operate in a manner similar to conventional systems, capable of receiving commands from the main control system ； Another structural approach is to place the various functional components of the main control system within the control systems of the turbine and boiler, resulting in no separate main control system in terms of structure. JE4C3118: In what applications are programmable regulators commonly used? Answer: Given the characteristics of programmable regulators, they are commonly used in the following situations and applications: 1. Complex control systems that require extensive control and computation. 2. Systems for which electric unit combination instruments and assembled instruments are not suitable. 3. Renovation of control systems using old equipment. 4. Projects prepared for the transition to a distributed control system. JE4C3119 What is alarm hysteresis in the PID operation data table of the KMM programmable regulator? How should it be set? Answer: Alarm lag refers to the delay required to eliminate an alarm. The lag amount is set as a percentage of the full scale (the range is 0.0%–100%). If the full range of the temperature measurement system is 0–100°C, the alarm threshold is set at 70°C, and the alarm delay is 10%, then the alarm should be disabled when the temperature drops from 70°C to 60°C. JE4C3120 What should be noted when using a spare manual unit? Answer: When using a backup manual unit, the following two points should generally be noted: 1. The power supply for the backup manual unit and that of the regulator should preferably be separated, with a dedicated fuse installed. 2. When inserting or removing a spare manual unit while the regulator is powered on, it is necessary to cut off the power supply to the spare manual unit. JE4C3121: What should be done when it is necessary to remove the DFQ-2200 type manual operator during operation and replace it with a V187MA-E type programmable regulator? Answer: 1. First, set the manual/auto switch of the regulator to the manual position, then plug the regulator into the input socket; at this point, the output of the controller should remain unchanged. 2. Turn the manual knob on the regulator itself to make the regulator’s output match that of the hand controller, thereby performing the alignment operation. 3. Set the manual/auto switch on the controller to automatic; at this point, the output of the controller is controlled by the controls on the regulator, allowing the DFC-2200 controller to be removed. JE4C3122 Why is the differential law generally not used for regulating pressure and flow? And is the regulation of temperature and composition mostly based on differential laws? Answer: For regulated parameters such as pressure and flow rate, the time constant T0 of their control loops is small; hence, even slight disturbances can cause rapid changes in these parameters. If a differential control strategy is used, it can easily lead to oscillations in the instrumentation system, which has a significant impact on the quality of regulation. If T0 is very small, using a negative derivative can yield good results. For adjustable parameters such as temperature and composition, the time constants of both the measurement channels and the control channels are large; as a result, even in the presence of slight disturbances, the changes in these parameters occur slowly, allowing the use of differential laws. By utilizing differentiation and leading action, the inertia of the parameter being regulated can be overcome, thereby improving the quality of regulation. JE4C3123: What conditions are required to put the water level control system of a drum boiler into operation? Answer: Generally, the following conditions must be met before work can begin: 1. The boiler is operating properly and is in a condition to supply steam to the turbine; it is advisable for the turbine’s load to be above 50%. 2. The main water supply pipeline is in normal operating condition. 3. The drum level gauge, steam flow meter, and feedwater flow meter are operating properly, with accurate readings and clear records. 4. The drum level signal and protection device are put into operation. 5. The equipment of the drum water level control system is in good condition and the parameter settings are correct. JE4C3124 When integral saturation of the regulator is detected on-site, what methods can be used to eliminate it as quickly as possible? Answer: The best way to eliminate integral saturation is to switch the regulator from automatic to manual mode. At this point, the manual current is applied to the integration capacitor, causing the regulator’s output to track the manual current and quickly eliminating integration saturation. Frequently switching the regulator from automatic to manual is also not good, as it can cause disturbances to the control system. At this point, some measures to counter integral saturation can be taken, or a regulator with integral saturation protection functionality can be used. JE4C4125: When calibrating differential pressure (pressure) transmitters, sometimes when there is a large sudden change in the input signal, the normally indicated output current can suddenly drop to zero. What is the reason for this? Answer: This is because the distance between the aluminum sheet and the detection coil has been set too small, causing the high-frequency oscillator to operate at the edge of the operating range on its characteristic curve. When the input signal suddenly increases, the aluminum sheet is detected to adhere abruptly to the detection coil; as a result, the high-frequency oscillator stops oscillating, the transmitter’s output becomes zero, the current flowing through the feedback coil is zero, the feedback force disappears, and the aluminum sheet remains in contact with the detection coil. Therefore, when making adjustments, it is essential to pay attention to the initial distance between the aluminum sheet and the detection coil. JE4C4126 What functions does the MZ－III adjustment component have? Answer: The regulation component is the core element of a regulation system. In addition to the conventional P, PI, and PID continuous regulation functions, it also possesses additional features such as resistance to integral saturation, the ability to incorporate feedforward signals, and parameter control signals. JE4C4127: Which digital filtering method is suitable for temperature signals? Answer: Under normal circumstances, temperature signals change slowly. The main interferences at the site are pulse disturbances such as those caused by switches and motor startups; such disturbances do not occur very frequently, so the median filtering method can be used. JE4C4128 What are the requirements for grounding the shielding layer of shielded wires (or shielded cables)? Why? Answer: The shielding layer should be grounded at one end and left ungrounded at the other; the grounding point can be located at the electronic device or at the sensing element, depending on the desired anti-interference effect. If both sides are grounded, a circuit is formed between the shielding layer and the ground, and common-mode interference signals will enter the electronic device through the distributed capacitance between the wires and the shielding layer, thereby causing interference ； With one end grounded and maintaining the same potential as only one side, while a circuit is formed between the shielding layer and the ground, no interference signals can enter the electronic device, thereby preventing the intrusion of common-mode interference voltages from the ground. JE4C4129 Under what circumstances should the main steam pressure control system before the turbine in a DC boiler be removed? Answer: 1. The control system operates unstably, with the main steam pressure deviating from the set value by more than ±0.3 MPa. 2. A fault has occurred in the control mechanism of the turbine speed control system. 3. The boiler or steam turbine is not operating properly. 4. Deactivate the protection and interlocking devices. JF4C4130: The DKJ electric actuator can only operate in one direction; when the polarity of the input signal is changed, the actuator does not move. Please analyze the cause of this fault Answer: 1. Check the wiring from the amplifier to the motor; if one of the wires is broken, this phenomenon will occur. 2. When the polarity of the input signal changes, alternating pulses should appear at the two trigger poles. If there is no pulse on one side, the reasons are: (1) the transistor is broken down ； (2) The unit crystal transistor BT31F is open-circuited or broken down; in this case, no pulse is generated, and one of the thyristors will not conduct. JE3C2131 What are the advantages and disadvantages of pneumatic instruments? Answer: The advantages of pneumatic instruments are: reliable operation, fire and explosion resistance, easy maintenance, low cost, and strong resistance to external interference. The disadvantages are: slow transmission speed, short transmission distance, complex origin device, and inconvenient connection to industrial control computers. JE3C2132 Why is it necessary to ensure a minimum flow rate for the boiler feed water pump? Answer: The boiler feed water pump is one of the important auxiliary equipment in thermal power plants. When the flow rate of the boiler feed water pump is lower than the required minimum flow rate, the feed water passing through the pump will vaporize locally, resulting in cavitation that can damage the pump; therefore, it is essential to ensure a minimum flow rate for the boiler feed water pump. JE3C3133 What are the main differences between the DDZ-III type instruments and the DDZ-II type instruments? Answer: There are 5 main features: 1. It uses linear integrated circuits. 2. The international standard signal system is adopted; the signals transmitted on-site are 4–20 mA DC, while the signals used for communication in the control room are 1–5 V DC. The signal current and voltage are converted to a resistance of 250 ohms. 3. Centralized and unified power supply: a power supply box provides 24V DC power to each unit, with batteries available as a backup power source. 4. It has a reasonable structure and diverse functions. 5. It can form a safe spark-type explosion-proof system. JE3C3135 How to put the feedwater regulator into automatic mode on-site? Answer: When the adjusted parameter approaches the set value, the system is switched to automatic operation, and the changes in water level are monitored based on the drum water level. If the adjustment process slows down or the deviation becomes large, the corresponding tuning parameters should be modified. When an anomaly occurs, the automatic mode should be disabled immediately for further inspection. JE3C3136: What are the various functional modules of a programmable regulator? Answer: Function modules are the software of programmable regulators; they are sub-routine segments that possess certain computing and processing functions. In programmable regulators, function modules can be classified into the following categories based on their roles: 1. Computing function modules ； 2. Control function module ； 3. Input/Output Function Module ； 4. Sequence control module. JE3C3137 What does the three-break self-locking protection for electric signal pneumatic long-stroke actuators refer to? Answer: The three-break self-locking protection means that when the working gas supply is interrupted, the power supply is interrupted, or the signal is interrupted, the rotation angle of the actuator’s output arm remains at its original position. During self-locking, the air paths leading to the upper and lower cylinders are severed, preventing the piston from moving and thus providing protection. JE3C3138: Which feedback signals are received by the digital controller of the DEH control system? Answer: The digital controller receives three feedback signals: the unit’s speed, the generator’s power, and the pressure at the control stage. JE3C3139 In the boiler steam temperature control system, why is it necessary to use the steam temperature signal after the desuperheater as the lead signal? Answer: Using the steam temperature signal after the desuperheater as a local feedback signal allows for the detection of disturbances through various dynamic relationships; it serves as an indirect measurement signal, and it can reflect the effects of desuperheating water disruptions earlier than the main steam temperature. JE3C3140 What is a differential-leading PID controller? Answer: A PID regulator with differential leading actually uses the measured value as a reference, which can reduce the lag of the measurement signal and help improve the quality of regulation. JE3C4141 What is the main function of the load requirement command processing module in the unit load control? Answer: The main functions are as follows: 1. Under normal conditions, the load is adjusted by ADS or the operators, and load request commands are generated through rate limitation ； 2. Grid frequency regulation under normal conditions ； 3. Manual setting of variable load rate limit ； 4. Manual setting of the maximum and minimum load of the unit ； 5. During rapid return, rapid shutdown, forced rise/fall, and main fuel trip, the load requirement command shall track the actual boiler load command. JE3C4142 What is the main function of the control strategy generation module in the unit load control? Answer: The main functions include: 1. Implementing a coordinated control method ； 2. Implement boiler follow mode ； 3. Implement the turbine follow mode ； 4. Implement the basic operation mode ； 5. Achieve constant-pressure operation mode ； 6. Implement the sliding pressure operation mode. JE3C4143: What are the components of the DTL-331 regulator, and what is the method for achieving proportional operation? Answer: The DTL-331 regulator is a PID-type regulator with an independent differential channel; it consists of an input circuit, a differential input channel, a modulation amplifier, a feedback circuit, and a limiting circuit. The method to achieve proportional operation is to short-circuit the integration capacitor in the feedback loop, set the integration resistor to its maximum value, open-circuit the differentiation capacitor, and short-circuit the differentiation resistor. JE3C4144: What might be the cause of “-6.9” or “6.9” appearing on the display of the KMM programmable regulator? Answer: This situation usually occurs when the analog input signal overflows (either below 4 mA or above 20 mA), or there is a fault in the regulator’s own analog input sampling or analog-to-digital conversion circuitry. For the former case, it is possible to further check whether the transmitter’s output is normal ； For the latter case, the corresponding components need to be replaced. JE3C4145 What conditions are required to put the temperature control system into operation? Answer: Generally, the following conditions must be met before starting work: 1. The furnace is operating normally, and the temperature of the superheated steam has reached the rated operating temperature ； 2. The unit load is above 60%, and the temperature of the reheat steam reaches the rated operating parameters ； 3. The cooling water control valve has sufficient tuning margin ； 4. The superheated steam temperature gauge and the reheat steam temperature gauge give accurate readings with clear recordings ； 5. The equipment of the temperature control system is in good condition, and the parameter settings are correct. JE3C4146 When replacing the control system using a DDZ-II instrument with a programmable regulator, what problems need to be addressed primarily? Answer: When replacing the control system using DDZ-II type instruments with programmable regulators, the transmitters and actuators are generally retained. The main issues that need to be addressed are: 1. The signal conversion problem between the II type instruments and the programmable regulators ； 2. Programmable regulators generally only have soft controls and no hard controls; therefore, hard control switches must be added to the operator panel to improve the reliability of the system. JE2C2147 What does the control software configuration generally include? Answer: It includes the following aspects: 1. Determine the type of algorithmic function blocks based on the block diagram of the process control system. 2. Specify the input and output signals for the function block. 3. Indicate the method of signal processing. 4. Enter the parameters required for the function block, etc. JE2C3148 What are the main reasons for errors when using a balanced container to measure the water level in a steam drum? Answer: 1. During operation, when the pressure in the steam drum changes, it causes changes in the density of saturated water and saturated steam, resulting in errors in the differential pressure output. 2. The design calculations for the balance compensation pipe are based on the condition where the water level is at zero, and deviations of the boiler from this zero level during operation can cause measurement errors. 3. When the drum pressure drops suddenly, the condensate in the positive pressure chamber may evaporate, resulting in abnormal instrument readings. JE2C3149: What are the calibration items for the electrical signal pneumatic stroke actuator (Type ZSLD-A)? Answer: The calibration items are as follows: 1. General inspection. 2. Check the direction of action. 3. Calibration of basic error and return error. 4. Calibration of the insensitive zone (dead zone). 5. No-load full-stroke time calibration. 6. Self-locking performance calibration. 7. Changes in air source pressure affect the test. JE2C3150: Should the air volume signal be subject to temperature correction? Answer: The air volume signal in the air supply control system is generally taken from the inlet duct of the air supply fan. Due to the large difference in temperatures between winter and summer, the inlet air temperature also varies significantly; under the same pressure difference, the mass flow rate differs greatly, hence temperature correction is necessary. If the air flow sampling device is located at the outlet of the air preheater, calculations must be done based on the highest and lowest temperatures of the air; temperature corrections may not be necessary if the required accuracy level is met. At the same time, the air leakage loss of the preheater can also be ignored. JE2C3151 Why is it necessary to perform dynamic correction on the load command signal? Answer: For unit plants equipped with an intermediate reheater, the volume lag of the intermediate reheater results in a certain degree of inertia in the power changes of the middle and low-pressure cylinders. This is unfavorable for the turbine to operate under load, as well as for grid frequency regulation. To improve the turbine’s ability to adapt to changes in load, the load command signal is dynamically adjusted when the load requirements change, causing the turbine’s inlet valve to open (or close) more, before reaching an appropriate opening degree in a certain manner to meet the demands of the changing load. JE2C3152 How to calibrate a control valve with a valve positioner? Answer: Generally, a valve positioner and a control valve are integrated as one unit. During verification, the method is the same as that for verifying control valves; it is only necessary to verify the relationship between the input signal and the valve stem displacement. As for what the output of the locator is and how it relates to the input signal, this can be ignored. JF2C2153: What are the main tasks of the major overhaul standard items? Answer: 1. Conduct a thorough inspection, cleaning, measurement, and repair. 2. Eliminate defects in equipment and systems. 3. Conduct regular monitoring, testing, and evaluation, and replace components that have reached their expiration date and require periodic replacement. 4. General inspection work within the “four types” of supervision (pay attention to aging issues in generator sets that have been in operation for over 150,000 hours). JF2C2154 What is the significance of implementing coordinated control for unit systems? Answer: 1. From the perspective of the entire power grid, achieving coordinated control of individual generating units contributes to the safe and economic operation of the grid. 2. In terms of the individual units, achieving coordinated control ensures the stability of the main operating parameters of these units, as well as the effectiveness of their monitoring and protection functions, thereby enhancing the safety of their operation during significant changes in load. 3. It enables coordinated control, reduces operations, and lowers the workload for operators. 4. Achieving coordinated control can reduce deviations in operating parameters, improve the quality of regulation, and enhance the economic efficiency of the unit. It can also improve the efficiency of boilers and turbines. JF2C3155 What are the activity steps of a quality management team? Answer: 1. Select a topic 2. Conduct a status survey 3. Set target values 4. Analyze the causes 5. Formulate countermeasures 6. Implement the countermeasures 7. Check the effectiveness 8. Consolidate the measures 9. Plan for the next steps.