Judgment method for vacuum drop of steam turbine condenser

Abstract

The invention provides a method for judging vacuum drop of a steam turbine condenser, which relates to the technical field of thermal power generation and comprises the following steps of: acquiring related operation data of the steam turbine condenser, including current values of roots pumps on high and low backpressure sides, exhaust steam temperatures of high and low condensers, sparse expansion temperatures, circulating water pressure and condenser water levels; calculating the current change rate of the roots pump and the difference value of each related parameter; preliminarily judging the vacuum drop condition according to a preset threshold value, and calculating the vacuum drop probability in combination with a probability calculation model; outputting a judgment result according to the calculated vacuum drop probability, and sending out an alarm signal when the probability exceeds a set alarm threshold value; the invention aims to provide the vacuum drop judgment method based on multi-parameter comprehensive judgment and probability analysis, so as to solve the problems in the prior art, improve the reliability and effectiveness of monitoring the running state of the steam turbine condenser and ensure the safe and economical running of a thermal generator set.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power generation, and in particular to a method for judging whether a steam turbine condenser has a vacuum drop. Background Art

[0002] The steam turbine condenser is one of the key equipment in the thermal power generation system. Its performance directly affects the economy and safety of the entire unit. The main function of the condenser is to establish and maintain a high vacuum at the exhaust port of the steam turbine, so that the exhaust steam of the steam turbine condenses into water at a lower pressure, thereby improving the work capacity of the steam turbine and increasing the power generation efficiency. With the continuous development of steam turbine technology, the performance requirements for condensers are also increasing. Modern condensers are constantly innovating in design and manufacturing, using advanced heat exchange tube materials and structural forms to improve heat exchange efficiency. For example, the use of high-performance materials such as stainless steel heat exchange tubes and titanium alloy heat exchange tubes has effectively enhanced the corrosion resistance and heat transfer performance of the heat exchange tubes. New tube bundle arrangements, such as double-pass and triple-pass, optimize the flow path of steam in the condenser and improve the heat exchange effect. At the same time, the vacuum system of the condenser has also been continuously improved and perfected, using more efficient vacuum pump units and sealing technologies to ensure that the condenser can maintain a stable vacuum level. However, existing methods for determining condenser vacuum drop mostly rely on monitoring a single parameter or a few parameters, and lack the ability to conduct comprehensive analysis and probability calculations on multiple related operating parameters. This makes it impossible to accurately assess the impact of changes in each parameter on the possibility of vacuum drop, making it difficult to provide comprehensive and accurate vacuum drop determination results. Therefore, there is an urgent need in the art for a method for determining whether the vacuum of a steam turbine condenser has dropped to solve the above-mentioned problem. Summary of the Invention

[0003] The present invention provides a method for determining whether a steam turbine condenser has lost vacuum, aiming to solve the problems existing in the above-mentioned prior art, improve the reliability and effectiveness of monitoring the operating status of the steam turbine condenser, and ensure the safe and economical operation of the thermal power generating set.

[0004] The present invention provides a method for determining whether a steam turbine condenser has a vacuum drop, comprising: Step 1: Collect relevant operating data of the steam turbine condenser, including: Roots pump current value, expansion temperature, exhaust temperature, circulating water pressure and condenser water level; Step 2: Calculate the current change rate of the Roots pump and the difference of relevant parameters; Step 3: Preliminarily judge the vacuum drop situation based on the pre-set threshold value, and calculate the vacuum drop probability in combination with the probability calculation model; Step 4: Output the judgment result based on the calculated vacuum drop probability, and issue an alarm signal when the probability exceeds the set alarm threshold.

[0005] According to a method for determining a decrease in the vacuum of a steam turbine condenser provided by the present invention, the step of collecting relevant operating data of the steam turbine condenser comprises: Set the data collection time interval to The total collection time is , number of collections ; Real-time acquisition of the current value of the Roots pump on the high back pressure side within the acquisition time and the current value of the Roots pump on the low back pressure side , high condenser exhaust temperature and low condenser exhaust temperature , high condenser expansion temperature and low condenser expansion temperature , high condenser circulating water pressure and low condenser circulating water pressure , condenser water level ; The collected data is filtered to remove abnormal fluctuation values.

[0006] According to a method for determining a decrease in the vacuum of a steam turbine condenser provided by the present invention, the step of calculating the current change rate of the Roots pump and the difference between the relevant parameters includes: Calculate the current change rate of the Roots pump on the high back pressure side , the calculation formula is: ; in, is the current value of the Roots pump on the high back pressure side collected for the i-th time, is the current value of the Roots pump on the initial high back pressure side; is the current value of the Roots pump on the high back pressure side collected for the i-1th time; Calculate the current change rate of the Roots pump on the low back pressure side , the calculation formula is: ; in, is the current value of the Roots pump on the low back pressure side collected for the i-th time, is the current value of the Roots pump on the initial low back pressure side; is the current value of the Roots pump on the low back pressure side collected for the i-1th time; Calculate the exhaust temperature difference of the condenser , ; Calculate the condenser's expansion temperature difference , ; Calculate the circulating water pressure difference of the condenser , .

[0007] According to a method for determining vacuum drop in a steam turbine condenser provided by the present invention, the process of preliminarily determining the vacuum drop according to a preset threshold value includes: Preset the Roots pump current change rate threshold , exhaust temperature difference threshold , sparse expansion temperature difference threshold , circulating water pressure difference threshold and condenser water level threshold ; When both satisfy or 、 、 、 、 When the vacuum drops, it is preliminarily judged that there is a vacuum drop; At the same time, if When , it is preliminarily judged that there is a vacuum drop on the high back pressure side; like When , it is preliminarily judged that there is a vacuum drop on the low back pressure side.

[0008] According to a method for determining vacuum drop in a steam turbine condenser provided by the present invention, the process of calculating the probability of vacuum drop in combination with a probability calculation model includes: When it is preliminarily determined that there is a vacuum drop on the high back pressure side, the first probability calculation model is used to calculate the vacuum drop probability on the high back pressure side; When it is preliminarily determined that there is a vacuum drop on the low back pressure side, the second probability calculation model is used to calculate the vacuum drop probability on the low back pressure side; The first probability calculation model and the second probability calculation model are respectively: ; ; in, is the vacuum drop probability on the high back pressure side, is the probability of vacuum drop on the low back pressure side; is the maximum value of the Roots pump current change rate under extreme fault conditions, The upper limit of the difference between the exhaust steam temperature under extreme fault conditions and normal operation; is the weight coefficient of the Roots pump current change rate, is the exhaust temperature difference weight coefficient.

[0009] According to a method for judging the vacuum drop of a steam turbine condenser provided by the present invention, the weight coefficient of the current change rate of the Roots pump is and exhaust steam temperature difference weight coefficient The calculation process is: Calculate the weight coefficient of the current change rate of the Roots pump , the calculation formula is: ; in, It is the upper limit of the difference between the current change rate of the Roots pump under normal operation and extreme fault conditions; It is the lower limit of the difference between the current change rate of the Roots pump in normal operation and extreme fault conditions; The upper limit of the difference between the exhaust steam temperature under extreme fault conditions and normal operation; The lower limit of the difference between the exhaust steam temperature under extreme fault conditions and normal operation; is the average value of the Roots pump current change rate calculated based on the current collected data, is the average value of exhaust steam temperature difference calculated based on the current collected data; Calculate the exhaust steam temperature difference weight coefficient , .

[0010] According to a method for determining vacuum drop in a steam turbine condenser provided by the present invention, the process of outputting a determination result based on the calculated vacuum drop probability and issuing an alarm signal when the probability exceeds a set alarm threshold comprises: Pre-set alarm probability threshold ; then , represent or Generate an alarm signal on the corresponding side and record the current vacuum drop probability value for subsequent trend analysis.

[0011] According to a method for judging the vacuum drop of a steam turbine condenser provided by the present invention, the alarm probability threshold Determined based on field testing and dynamic adjustments.

[0012] Compared with the prior art, the present invention has the following advantages: This application collects multiple relevant operating data, including the current values of the Roots pumps on the high and low back pressure sides, the exhaust temperature, expansion temperature, circulating water pressure and condenser water level of the high and low condensers, and conducts comprehensive analysis to more comprehensively reflect the working status of the condenser, avoiding the limitations of single parameter judgment; This application calculates the rate of change of the Roots pump current and the difference between various related parameters, and makes a judgment based on a pre-set threshold. At the same time, it combines the probability calculation model to calculate the vacuum drop probability, which can more accurately judge the vacuum drop situation and reduce the possibility of misjudgment. This application can promptly detect early signs of vacuum system failure, effectively monitor and judge slight vacuum drop trends, and help take measures in advance to prevent further development of failures; This application fully considers the intrinsic relationship between multiple related parameters, such as the Roots pump current change rate, exhaust temperature difference, expansion temperature difference, circulating water pressure difference, etc., accurately evaluates the impact of changes in various parameters on the possibility of vacuum drop, and provides more comprehensive and accurate vacuum drop judgment results; the alarm probability threshold is determined through on-site testing and dynamic adjustment, which is more in line with actual operating conditions, thereby improving the accuracy and reliability of the alarm.

[0013] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 The present invention provides a flow chart of a method for determining whether a steam turbine condenser has lost vacuum. DETAILED DESCRIPTION

[0016] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0017] Example 1: The embodiment of the present invention provides a method for judging the vacuum drop of a steam turbine condenser. Figure 1 ,include: Step 1: Collect relevant operating data of the steam turbine condenser, including: Roots pump current value, expansion temperature, exhaust temperature, circulating water pressure and condenser water level; Step 2: Calculate the current change rate of the Roots pump and the difference of relevant parameters; Step 3: Preliminarily judge the vacuum drop situation based on the pre-set threshold value, and calculate the vacuum drop probability in combination with the probability calculation model; Step 4: Output the judgment result based on the calculated vacuum drop probability, and issue an alarm signal when the probability exceeds the set alarm threshold.

[0018] The principle and beneficial effects of this embodiment are as follows: The condenser is equipped with a large number of copper tubes and is fed with circulating cooling water. When the exhaust steam from the turbine contacts the outer surface of the condenser's copper tubes, it is cooled by the water flowing within the tubes, releasing latent heat of vaporization and turning into condensed water. This latent heat is continuously transferred through the copper tube walls to the circulating cooling water and carried away. In this way, the exhaust steam is continuously condensed through the condenser. As the exhaust steam is cooled, its specific volume decreases dramatically, creating a high vacuum inside the condenser below the turbine exhaust port. The condenser's true density has a significant impact on the unit's operational safety and thermal economy. During unit operation, deterioration of the condenser's operating condition will directly lead to increased turbine heat and steam consumption, and reduced output. In addition, a drop in vacuum can cause the turbine's exhaust temperature to rise, turbine bearing center deviation, and, in severe cases, turbine vibration. At present, in order to save energy, most power plants use Roots vacuum pumps to replace water ring vacuum pumps to maintain the vacuum of the unit during normal operation. When the Roots pump is running, the more the pressure is increased, the flow rate does not increase much, and the shaft power increases rapidly. When the amount of air leakage increases, the pressure of the Roots pump increases and the current increases. This embodiment ensures real-time monitoring of the condenser's operating status by collecting key parameters such as the Roots pump current, exhaust temperature, expansion temperature, circulating water pressure, and condenser water level in real time. Calculating the Roots pump current change rate and the difference between related parameters helps more accurately reflect the changing trend of vacuum. The probability of vacuum drop is assessed using pre-set thresholds and a probability calculation model. This method not only considers the changes in individual parameters but also comprehensively considers the interactions between multiple parameters, improving the reliability of the diagnostic results. A judgment result is output based on the calculated vacuum drop probability, and an alarm signal is issued when the probability exceeds the set alarm threshold. This allows operators to receive warnings before a significant vacuum drop occurs, allowing them to prepare for response and avoid efficiency reduction or equipment damage caused by insufficient vacuum. It also reduces unnecessary downtime and inspections, as alarms are only triggered when there is clear evidence of a risk of vacuum drop. This helps improve the operational efficiency of the power plant and reduce maintenance costs. By promptly detecting and addressing condenser vacuum problems, safety incidents caused by insufficient vacuum can be effectively prevented, ensuring the safe operation of the power plant.

[0019] In order to further optimize the above embodiment, the steps of collecting relevant operating data of the steam turbine condenser include: Set the data collection time interval to The total collection time is , number of collections ; Real-time acquisition of the Roots pump current value on the high back pressure side within the acquisition time and the current value of the Roots pump on the low back pressure side , high condenser exhaust temperature and low condenser exhaust temperature , high condenser expansion temperature and low condenser expansion temperature , high condenser circulating water pressure and low condenser circulating water pressure , condenser water level ; The collected data is filtered to remove abnormal fluctuation values.

[0020] It should be noted that the rate and period of change of various parameters during the operation of the steam turbine condenser should be taken into consideration; for example, the current of the Roots pump may change relatively quickly, while the water level of the condenser may change relatively slowly; for parameters that change quickly, such as current, the collection time interval should be shorter, such as 1-5 seconds, to accurately capture their dynamic changes; for parameters that change slowly, such as water level, the collection time interval can be appropriately extended to 10-30 seconds; the total time must cover various possible operating conditions of the equipment, generally set to 30-60 minutes, to ensure that sufficient data samples can be collected to reflect the operation of the equipment under different states; the number of collections is calculated based on the time interval and the total time. For example, if the time interval is 2 seconds and the total time is 30 minutes, the number of collections is 900 times; Shorter collection intervals and more collection times will generate a large amount of data, requiring strong data processing capabilities. Therefore, a reasonable balance should be struck between data volume and processing difficulty while ensuring accurate monitoring of the equipment's operating status. If data processing capabilities are limited, the interval can be appropriately extended or the total time can be shortened, but this must not affect the accuracy of critical situations such as vacuum drop. Use a high-precision current transformer to collect the current value of the Roots pump. Its accuracy should reach ±0.5% or above to ensure the accuracy of current measurement. The current transformer should be installed on the power line of the Roots pump, close to the pump body to reduce the impact of line loss on the measurement results. At the same time, the current transformer must be shielded to prevent external electromagnetic interference from affecting the measurement accuracy. For exhaust and expansion temperatures, armored thermocouples are used as temperature sensors. The temperature measurement range of the thermocouple should meet the condenser operating temperature requirements, generally -50°C to +500°C, with an accuracy of no less than ±1°C. The sensor should be installed on the corresponding pipe or container of the condenser to ensure accurate measurement of steam or water temperature. During installation, ensure that the temperature measuring end of the thermocouple is in full contact with the measured medium. It can be fixed by welding or threading, and insulation measures should be taken to reduce measurement errors caused by heat loss. Pressure collection: Use a high-precision pressure transmitter to measure the circulating water pressure, with an accuracy requirement of ±0.2% FS or higher. Install the pressure transmitter on the circulating water pipeline, open a pressure tapping hole on the pipeline, and tightly connect the pressure tapping port of the pressure transmitter to the pressure tapping hole to ensure accurate pressure measurement. The pressure tapping hole should be perpendicular to the inner wall of the pipeline and have a moderate aperture to avoid excessive resistance to the water flow or the generation of vortices that affect the measurement results. At the same time, the pressure transmitter should be regularly calibrated and maintained to ensure its long-term stable operation. Water level acquisition: Use a differential pressure level gauge or ultrasonic level gauge to measure the condenser water level. A differential pressure level gauge calculates the water level by measuring the static pressure difference of the liquid, with a measurement accuracy of ±2mm. An ultrasonic level gauge uses the principle of ultrasonic reflection to measure the water level, with an accuracy of approximately ±5mm. The level gauge should be installed in a suitable position on the condenser to ensure accurate measurement of water level changes. For differential pressure level gauges, pay attention to the installation height and sealing of the pressure sampling pipes on the positive and negative pressure sides. Ultrasonic level gauges should be installed away from locations where there is steam interference or obstacles that may affect ultrasonic propagation. Use a mean filter algorithm: calculate the average value of a set of collected data (such as 5-10 consecutive data points), and use this average value as the filtered data at the current moment; this algorithm is simple and effective, and can effectively smooth out random fluctuations in the data; for example, for filtering the current value of a Roots pump, five current values are collected continuously, namely 10.1A, 10.2A, 9.9A, 10.0A, and 10.3A, and their average value is (10.1+10.2+9.9+10.0+10.3) / 5=10.1A, so the filtered current value is 10.1A; the mean filter algorithm can be implemented in the data acquisition system by writing a simple calculation program. After each new data is collected, it is added to the data queue and the average value of the data in the queue is calculated as the output; Adopt the median filtering algorithm: sort the collected data by size and take the middle value as the filtered data; this algorithm has a good effect on removing pulse interference; for example, for a set of exhaust temperature data of 40.1℃, 40.5℃, 41.0℃, 39.8℃, 40.3℃, the sorted data are 39.8℃, 40.1℃, 40.3℃, 40.5℃, 41.0℃, and the middle value 40.3℃ is the filtered temperature value; when implementing the median filtering algorithm, it is necessary to establish a sorting and middle value function module in the data acquisition system. After each new data is collected, the data sequence is updated and sorted, and the middle value is taken as the filtering result; in actual application, according to the characteristics of the data and the type of interference, the appropriate filtering algorithm can be selected or multiple filtering algorithms can be used in combination to achieve the best filtering effect, ensure the accuracy and stability of the collected data, and provide a reliable data basis for subsequent vacuum drop judgment.

[0021] To further optimize the above embodiment, the steps of calculating the current change rate of the Roots pump and the difference between the relevant parameters include: Calculate the current change rate of the Roots pump on the high back pressure side , the calculation formula is: ; in, is the current value of the Roots pump on the high back pressure side collected for the i-th time, is the current value of the Roots pump on the initial high back pressure side; is the current value of the Roots pump on the high back pressure side collected for the i-1th time; Calculate the current change rate of the Roots pump on the low back pressure side , the calculation formula is: ; in, is the current value of the Roots pump on the low back pressure side collected for the i-th time, is the current value of the Roots pump on the initial low back pressure side; is the current value of the Roots pump on the low back pressure side collected for the i-1th time; Calculate the exhaust temperature difference of the condenser , ; Calculate the condenser's expansion temperature difference , ; Calculate the circulating water pressure difference of the condenser , .

[0022] It should be noted that the initial high back pressure side Roots pump current value and the initial low back pressure side Roots pump current value Represents the initial operating current of the Roots pump on the high back pressure side and the low back pressure side when data collection begins; the difference 、 、 The calculation results are based on the average value of all collected data.

[0023] To further optimize the above embodiment, the process of preliminarily determining the vacuum drop condition based on a preset threshold value includes: Preset the Roots pump current change rate threshold , exhaust temperature difference threshold , sparse expansion temperature difference threshold , circulating water pressure difference threshold and condenser water level threshold ; When both satisfy or 、 、 、 、 When the vacuum drops, it is preliminarily judged that there is a vacuum drop; At the same time, if When , it is preliminarily judged that there is a vacuum drop on the high back pressure side; like When , it is preliminarily judged that there is a vacuum drop on the low back pressure side.

[0024] It should be noted that the current change rate threshold of the Roots pump is determined as follows: First, based on the performance curve and theoretical model of the Roots pump, the theoretical range of the current change rate under different vacuum degrees is analyzed. For example, when the Roots pump is operating at normal vacuum, the current change rate is small, and as the vacuum degree decreases, the current change rate will gradually increase. Combined with the technical information provided by the Roots pump manufacturer and the actual operating experience data accumulated in similar steam turbine condenser systems, a preliminary threshold range is determined. Generally speaking, the initial setting can be around 1.5-2.5 times the average value of the normal operating current change rate. Then, through actual testing and debugging, optimization is carried out. Under the normal operating state of the steam turbine condenser, the current change rate of the Roots pump is observed. If it is within the set threshold range and the equipment is operating stably, it can be used as a reference. If misjudgment or missed judgment occurs, the threshold is adjusted appropriately. For example, if the current change rate frequently approaches the threshold during normal operation but the actual vacuum of the equipment is normal, the threshold can be appropriately increased. If it is found that the current change rate does not reach the threshold when the vacuum decreases and no alarm is issued in time, the threshold can be appropriately lowered. Different operating conditions, such as turbine load and circulating water temperature, will affect the current change rate of the Roots pump. Under low-load operation, the current change rate of the Roots pump is relatively low; under high load or high circulating water temperature, the current change rate may increase. Therefore, it is necessary to test different typical operating conditions, obtain corresponding current change rate data, and determine a reasonable threshold value applicable to various operating conditions after comprehensive analysis. For example, in the high temperature of summer when the circulating water temperature is high, the current change rate of the Roots pump may be 10%-20% higher than in winter. This seasonal variation factor must be taken into account when determining the threshold value to ensure that the threshold value can effectively detect vacuum drop under normal operating conditions and avoid misjudgment under special operating conditions. Exhaust steam temperature difference threshold is determined by: Based on the condensation heat transfer principle of steam turbine exhaust within the condenser, the theoretical exhaust temperature and the range of the exhaust temperature difference between the two sides are calculated under normal vacuum conditions and different steam flow rates and circulating water parameters. For example, under ideal vacuum conditions, the exhaust steam can be fully cooled, and the difference in exhaust temperature between the upper and lower condensers is small, generally not exceeding 3-5°C. When the vacuum decreases, the exhaust temperature increases, and the difference increases. Using a thermodynamic calculation model, combined with the actual condenser structure and operating parameters, a theoretical upper threshold for the exhaust temperature difference is determined. During actual turbine operation, continuously monitor the difference between the high and low condenser exhaust temperatures, and record changes in these values under different operating conditions. In particular, observe fluctuations in the exhaust temperature difference during equipment startup, shutdown, and load changes. If, under certain operating conditions, the exhaust temperature difference exceeds the set threshold but the vacuum is normal, this may be due to other factors (such as uneven local heat load). In this case, the threshold needs to be appropriately adjusted. Generally, through statistical analysis of long-term operating data, the maximum exhaust temperature difference under normal operation and stable vacuum conditions, plus a certain safety margin (e.g., 1-2°C), is used as the final threshold. Determination of the sparse-diffusion temperature difference threshold: Study the steam-water mixing and heat transfer process within the evacuation chamber to understand the relationship between evacuation temperature and factors such as condenser vacuum, drain flow rate, and pressure. Under normal vacuum conditions, the temperature difference between the high and low condenser evacuations is relatively stable, generally within a range of 1-3°C. When the vacuum drops, this may affect drain flow and heat transfer, causing the evacuation temperature difference to change. Through theoretical analysis and simulation calculations, determine the approximate range of the evacuation temperature difference threshold. During turbine operation, closely monitor changes in the evacuation-expansion temperature difference and compare and analyze it with the condenser vacuum and other operating parameters. If the evacuation-expansion temperature difference is found to be lower than the set threshold in some cases but the vacuum is normal, or if the evacuation-expansion temperature difference does not achieve the expected change when the vacuum decreases, the threshold needs to be adjusted. Based on the distribution of actual operating data, a value that accurately reflects the relationship between vacuum decrease and evacuation-expansion temperature difference can be selected as the threshold. For example, the minimum evacuation-expansion temperature difference during normal operation minus a certain margin (such as 0.5-1°C) can be used as the lower threshold to ensure timely triggering of judgment when the vacuum decreases. Method for determining the circulating water pressure difference threshold: Analyze the impact of factors such as the circulating water system's pipe resistance and pump performance on the circulating water pressure in the high and low condensers. During normal operation, the pressure difference between the high and low condensers is primarily determined by factors such as the pipe layout and water flow distribution. It is generally stable, ranging from 0.05 to 0.15 MPa. When the vacuum drops, it may cause changes in the water flow state within the circulating water system, leading to pressure difference fluctuations. Determine a reasonable pressure difference threshold range through hydraulic calculations and actual operation monitoring of the circulating water system. During turbine operation, observe changes in the circulating water pressure differential, especially when the circulating water quality changes or the circulating water pump is switched. If the pressure differential is found to be close to the threshold under certain normal operating conditions, which may easily lead to misjudgment, the threshold can be appropriately raised. If the pressure differential does not change significantly when the vacuum drops and is not detected in time, the threshold can be appropriately lowered. Through continuous adjustment, ensure that the threshold can accurately reflect the relationship between the circulating water pressure differential and the condenser vacuum state, thereby ensuring the reliability of equipment operation. Condenser water level threshold determination method: According to the condenser's design specifications, understand the permissible water level range for normal operation. Generally speaking, a high condenser water level may flood the heat exchange tubes, affecting vacuum formation, while a low water level may allow steam to enter the vacuum pump, disrupting the vacuum. For example, the design permissible water level range is -0.5m to +0.5m. Considering a certain safety margin, the water level threshold can be set between -0.3m and +0.3m. During actual operation, evaluate the impact of different water levels on condenser vacuum and equipment safety; if it is found that the water level is close to the upper or lower limit but the equipment can still operate normally for a period of time, the threshold range can be appropriately relaxed; if a slight change in water level has a significant impact on the vacuum, the threshold range should be narrowed to ensure timely detection of abnormal water levels that may affect the vacuum and ensure the safe and stable operation of the turbine condenser.

[0025] Furthermore, when the Roots pump is maintaining the vacuum in the condenser, when the vacuum drops, the amount of air leaking in increases, and the Roots pump requires more power to maintain the vacuum, which causes its current to rise. The threshold value of the current change rate of the Roots pump is set because the current change rate can intuitively reflect the changes in the load of the Roots pump. If the current change rate exceeds the threshold, it means that the working state of the Roots pump has changed significantly. It is likely that the vacuum degree of the condenser has dropped, causing the Roots pump to process more gas, thereby consuming more power and increasing the current. For example, during normal operation, the current of the Roots pump is relatively stable. When the vacuum begins to drop and air continues to leak in, the Roots pump needs to speed up or increase the working intensity to extract the excess gas. The current will rise rapidly accordingly. Exceeding the set threshold indicates that there may be a vacuum drop.

[0026] The function of the condenser is to cool the turbine exhaust steam and condense it into water. Under good vacuum conditions, the exhaust steam is adequately cooled, and the difference in exhaust temperature between the high and low condensers should be within a reasonable range. When the vacuum decreases, the exhaust steam cooling effect deteriorates, the specific volume of the steam cannot be effectively reduced, and the exhaust temperature rises. By setting a threshold for the exhaust temperature difference, when the absolute value of the difference between the high and low condenser exhaust temperatures exceeds this threshold, it indicates a significant deviation in the exhaust steam temperatures on both sides. This may be due to insufficient cooling of the exhaust steam on one side due to a drop in vacuum on that side, resulting in an increase in temperature, indicating a possible problem with the overall vacuum status of the condenser.

[0027] The expansion chamber is part of the condenser drain system, and its temperature fluctuations are related to the condenser vacuum state. Under normal circumstances, the difference between the high and low condenser expansion chamber temperatures should be relatively stable and within a certain range. If the vacuum drops, it may affect the drain flow and heat transfer process, causing abnormal changes in the expansion chamber temperature. Set a threshold for the expansion chamber temperature difference. When the absolute value of the difference between the high and low condenser expansion chamber temperatures falls below this threshold, it is possible that the vacuum drop has affected the normal operation of the drain system, reducing the difference in expansion chamber temperatures. This can also serve as an auxiliary basis for determining whether the vacuum has dropped.

[0028] Circulating water plays a key role in removing the latent heat of steam condensation in the condenser, and its pressure stability is crucial to ensuring the cooling effect. During normal operation, the difference in circulating water pressure between the high and low condensers should be within a reasonable range. When the vacuum drops, it may cause pressure fluctuations in the circulating water system, such as changes in local resistance, causing the difference in circulating water pressure between the high and low condensers to change. Set a circulating water pressure difference threshold. When the absolute value of the difference in circulating water pressure between the high and low condensers is less than the threshold, it indicates that there has been an abnormal change in the circulating water system pressure, which may be due to a series of chain reactions caused by the vacuum drop, thereby assisting in judging the vacuum status of the condenser.

[0029] A condenser water level that is too high or too low can affect its vacuum performance. A high water level can partially submerge heat exchange tubes, reducing the heat exchange area and hindering steam condensation, leading to a drop in vacuum. A low water level can allow steam to directly enter the vacuum pump, disrupting its normal operation and also affecting the vacuum level. A condenser water level threshold is set. When the absolute value of the condenser water level falls below this threshold, it indicates an abnormal water level, which may be associated with a drop in vacuum and can serve as a reference for determining a drop in vacuum.

[0030] When the current change rate of the Roots pump on the high-back-pressure side exceeds the threshold, it indicates that the operating status of the Roots pump on this side has changed significantly. Since the change in the Roots pump current is closely related to the vacuum level, in this case, it is likely that the vacuum in the condenser on the high-back-pressure side has dropped, causing the load on the Roots pump on this side to increase and the current to rise significantly. Therefore, it is preliminarily determined that there is a vacuum drop on the high-back-pressure side. Similarly, when the current change rate of the Roots pump on the low-back-pressure side exceeds the threshold, it indicates that the operating condition of the Roots pump on the low-back-pressure side has changed significantly. It is likely that the vacuum in the condenser on the low-back-pressure side has dropped, causing the Roots pump on the low-back-pressure side to require more power to maintain the vacuum, resulting in an increase in current. Therefore, it is preliminarily determined that there is a vacuum drop on the low-back-pressure side.

[0031] To further optimize the above embodiment, the process of calculating the vacuum drop probability in combination with the probability calculation model includes: When it is preliminarily determined that there is a vacuum drop on the high back pressure side, the first probability calculation model is used to calculate the vacuum drop probability on the high back pressure side; When it is preliminarily determined that there is a vacuum drop on the low back pressure side, the second probability calculation model is used to calculate the vacuum drop probability on the low back pressure side; The first probability calculation model and the second probability calculation model are: ; ; in, is the vacuum drop probability on the high back pressure side, is the vacuum drop probability on the low back pressure side; is the maximum value of the Roots pump current change rate under extreme fault conditions, The upper limit of the difference between the exhaust steam temperature under extreme fault conditions and normal operation; is the weight coefficient of the Roots pump current change rate, is the exhaust temperature difference weight coefficient.

[0032] Roots pump current change rate weight coefficient and exhaust steam temperature difference weight coefficient The calculation process is: Calculate the weight coefficient of the current change rate of the Roots pump , the calculation formula is: ; in, It is the upper limit of the difference between the current change rate of the Roots pump under normal operation and extreme fault conditions; It is the lower limit of the difference between the current change rate of the Roots pump in normal operation and extreme fault conditions; The upper limit of the difference between the exhaust steam temperature under extreme fault conditions and normal operation; The lower limit of the difference between the exhaust steam temperature under extreme fault conditions and normal operation; is the average value of the Roots pump current change rate calculated based on the current collected data, is the average value of exhaust steam temperature difference calculated based on the current collected data; Calculate the exhaust steam temperature difference weight coefficient , .

[0033] It should be noted that the upper or lower limit of each difference is determined based on the actual operating equipment, and the acquisition method is existing technical means, which will not be elaborated in detail.

[0034] To further optimize the above embodiment, the process of outputting a judgment result based on the calculated vacuum drop probability and issuing an alarm signal when the probability exceeds a set alarm threshold includes: Pre-set alarm probability threshold ; then , represent or , generate an alarm signal on the corresponding side, and record the current vacuum drop probability value for subsequent trend analysis.

[0035] It should be noted that the alarm probability threshold Determined based on field testing and dynamic adjustments.

[0036] The on-site testing and dynamic adjustment process is: Start the debugging phase test: During the startup and commissioning process after the steam turbine condenser is installed, a series of vacuum drop simulation tests are conducted. By manually controlling factors that affect vacuum (such as gradually increasing the amount of air leakage), the changes in various parameters at different vacuum drop levels are recorded, along with the corresponding calculated probability values. Based on this test data, a vacuum drop probability curve is plotted, observing the trend of probability values as the vacuum drop level changes, thereby determining an appropriate alarm probability threshold. During this process, it is important to ensure that the test conditions are as close as possible to actual operating conditions to obtain accurate and reliable data.

[0037] Initial operation monitoring and optimization: During the initial stages of formal unit operation, closely monitor the condenser's operating parameters and the calculated vacuum drop probability. Although the equipment is operating normally during this phase, various practical factors (such as equipment running-in and environmental changes) may cause some deviations from theoretical expectations. Based on actual operating data, further optimize and adjust the alarm probability threshold. If the calculated probability value frequently approaches or exceeds the initially set threshold in certain circumstances, but actual equipment operation is not significantly affected, the threshold can be appropriately raised. Conversely, if the vacuum drop problem is found to have an adverse impact on equipment operation even at a lower probability value, the threshold should be lowered.

[0038] Long-term running data statistics and updates: As units operate over time, they accumulate a large amount of operational data. This data is regularly statistically analyzed, including the distribution of vacuum drop probabilities under different seasons and load conditions. Based on these long-term operational data, the alarm probability threshold is dynamically updated. For example, if the calculated probability value for the same vacuum drop level changes with equipment aging, or if long-term changes in the operating environment (such as rising circulating water temperatures due to rising temperatures) are observed, the alarm probability threshold needs to be adjusted accordingly to ensure it accurately reflects the actual operating status of the equipment and issues alarm signals promptly and effectively.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for determining whether a steam turbine condenser has a vacuum drop, characterized in that: include: Step 1: Collect relevant operating data of the steam turbine condenser, including: Roots pump current value, expansion temperature, exhaust temperature, circulating water pressure and condenser water level; Step 2: Calculate the current change rate of the Roots pump and the difference of relevant parameters; Step 3: Preliminarily judge the vacuum drop situation based on the pre-set threshold value, and calculate the vacuum drop probability in combination with the probability calculation model; Step 4: Output the judgment result based on the calculated vacuum drop probability, and issue an alarm signal when the probability exceeds the set alarm threshold.

2. The method for judging whether a steam turbine condenser has a vacuum drop according to claim 1, wherein: The step of collecting relevant operation data of the steam turbine condenser includes: Set the data collection time interval to The total collection time is , number of collections ; Real-time acquisition of the current value of the Roots pump on the high back pressure side within the acquisition time and the current value of the Roots pump on the low back pressure side , high condenser exhaust temperature and low condenser exhaust temperature , high condenser expansion temperature and low condenser expansion temperature , high condenser circulating water pressure and low condenser circulating water pressure , condenser water level ; The collected data is filtered to remove abnormal fluctuation values.

3. The method for judging whether a steam turbine condenser has a vacuum drop according to claim 2, wherein: The step of calculating the current change rate of the Roots pump and the difference between the relevant parameters includes: Calculate the current change rate of the Roots pump on the high back pressure side , the calculation formula is: ； in, is the current value of the Roots pump on the high back pressure side collected for the i-th time, is the current value of the Roots pump on the initial high back pressure side; is the current value of the Roots pump on the high back pressure side collected for the i-1th time; Calculate the current change rate of the Roots pump on the low back pressure side , the calculation formula is: ； in, is the current value of the Roots pump on the low back pressure side collected for the i-th time, is the current value of the Roots pump on the initial low back pressure side; is the current value of the Roots pump on the low back pressure side collected for the i-1th time; Calculate the exhaust temperature difference of the condenser , ; Calculate the condenser's expansion temperature difference , ; Calculate the circulating water pressure difference of the condenser , .

4. The method for judging whether a steam turbine condenser has a vacuum drop according to claim 3, wherein: The process of preliminarily judging the vacuum drop condition based on the preset threshold value includes: Preset the Roots pump current change rate threshold , exhaust temperature difference threshold , sparse expansion temperature difference threshold , circulating water pressure difference threshold and condenser water level threshold ; When both satisfy or 、 、 、 、 When the vacuum drops, it is preliminarily judged that there is a vacuum drop; At the same time, if When , it is preliminarily judged that there is a vacuum drop on the high back pressure side; like When , it is preliminarily judged that there is a vacuum drop on the low back pressure side.

5. The method for judging whether the steam turbine condenser vacuum drops according to claim 4, characterized in that: The process of calculating the vacuum drop probability by combining the probability calculation model includes: When it is preliminarily determined that there is a vacuum drop on the high back pressure side, the first probability calculation model is used to calculate the vacuum drop probability on the high back pressure side; When it is preliminarily determined that there is a vacuum drop on the low back pressure side, the second probability calculation model is used to calculate the vacuum drop probability on the low back pressure side; The first probability calculation model and the second probability calculation model are respectively: ； ； in, is the vacuum drop probability on the high back pressure side, is the vacuum drop probability on the low back pressure side; is the maximum value of the Roots pump current change rate under extreme fault conditions, The upper limit of the difference between the exhaust steam temperature under extreme fault conditions and normal operation; is the weight coefficient of the Roots pump current change rate, is the exhaust temperature difference weight coefficient.

6. The method for judging the vacuum drop of a steam turbine condenser according to claim 5, characterized in that: The weight coefficient of the Roots pump current change rate and exhaust steam temperature difference weight coefficient The calculation process is: Calculate the weight coefficient of the current change rate of the Roots pump , the calculation formula is: ； in, It is the upper limit of the difference between the current change rate of the Roots pump under normal operation and extreme fault conditions; It is the lower limit of the difference between the current change rate of the Roots pump in normal operation and extreme fault conditions; The upper limit of the difference between the exhaust steam temperature under extreme fault conditions and normal operation; The lower limit of the difference between the exhaust steam temperature under extreme fault conditions and normal operation; is the average value of the Roots pump current change rate calculated based on the current collected data, is the average value of exhaust steam temperature difference calculated based on the current collected data; Calculate the exhaust steam temperature difference weight coefficient , .

7. The method for determining whether a steam turbine condenser has a vacuum drop according to claim 6, wherein: The process of outputting a judgment result based on the calculated vacuum drop probability and issuing an alarm signal when the probability exceeds a set alarm threshold includes: Pre-set alarm probability threshold ; then , represent or , generate an alarm signal on the corresponding side and record the current vacuum drop probability value.

8. The method for judging whether the steam turbine condenser vacuum drops according to claim 7, characterized in that: The alarm probability threshold Determined based on field testing and dynamic adjustments.

Images