Hunan Electric Power

Configuration Optimization and Performance Analysis of Supercritical Carbon Dioxide Power Generation and Energy Storage Integrated System

ZHU Guangming, CHEN Xun, HE Honghao, SUN Ruiqiang, XIE Guohong, YANG Yi, WANG Yangguang

2024, 44(4): 1-10. doi:10.3969/j.issn.1008-0198.2024.04.001

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To synergistically enhance the efficiency and flexibility of coal-fired power system, and promote the transformation of thermal power units, a scheme of using supercritical carbon dioxide (S-CO₂) working fluid to construct a coupling system of coal-fired power generation and pumped thermal electricity storage (“source-storage-integrated” system) is proposed. Based on the first and second laws of thermodynamics, the design and off-design calculation models of the integrated system are developed, and the potential of the flexibility improvement and the energy efficiency of the heat storage-release process are analyzed. The results show that by integrating pumped thermal electricity storage technology on the basis of S-CO₂ coal-fired power system, the minimum output power of the unit can be reduced from the original 30% rated load to zero, which greatly improves the peak regulation depth and operation flexibility. When 75% rated load is selected as the heat release condition, the output power can be increased by 23.59% of the rated load. In addition, the equivalent round-trip efficiency of the heat storage-release process of the integrated system is 78.64%. The sensitivity analysis of heat storage parameters shows that the optimal value range for the molten salt cold tank temperature is 405~420 ℃, and the value range for the atmospheric pressure water hot tank temperature is 70~75 ℃.

Dynamic Power Allocation Strategy for Hybrid Energy Storage System of Urban Rail Trains Based on Improved SAC Algorithm

HE Qingchen, QIN Bin

2024, 44(4): 11-19. doi:10.3969/j.issn.1008-0198.2024.04.002

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To smooth out voltage fluctuations in the traction network of urban rail trains, a power dynamic allocation strategy based on a soft actor-critic (SAC) with reinforcement learning is proposed based on the use of on-board supercapacitor and ground hybrid energy storage system. It is used to improve the energy-saving voltage stabilization characteristics of DC traction network and realize the life protection of on-board supercapacitor. Firstly, an urban rail train dynamics model is established, and the PEC-SAC algorithm is proposed to address the problems of long training time and slow convergence of SAC algorithm in urban rail dynamic power allocation. The algorithm combines prioritized experience replay, emphasizing recent experience and cosine annealing, and improves the learning rate by increasing the sampling probability of the recent experience and dynamically adjusting the learning rate, which improves the training efficiency and convergence speed. Then the state space, action space, and reward function are set up to realize that the train learns the optimal energy control strategy for the hybrid energy storage system in interaction with the simulation environment. The simulation platform is built through the joint simulation of MATLAB/Simulink and PYTHON, and the results show that the method improves the voltage stabilization by 0.36% and reduces the energy consumption by 4.52% compared to the SAC algorithm.

Parameter Identification Method for Battery Model Based on Bayesian Decision-Making

ZHANG Xingwei, SHAN Zhouping, LIU Lihong, LIU Luyu, ZHOU Kun, LENG Zhaojin

2024, 44(4): 20-26. doi:10.3969/j.issn.1008-0198.2024.04.003

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In order to balance the parameter estimation accuracy and computational complexity of the equivalent circuit model of battery module (BM), an identification method of BM equivalent circuit model based on Bayesian decision theory is proposed, considering the inconsistency of internal resistance, capacity and other parameters of single battery in BM, combined with the basic characteristics of series/parallel circuits. Bayesian information criterion is introduced to estimate the optimal model parameters. The simplified modeling method, the overall modeling method and the combined modeling method are used to build two parallel and two series connection of BM equivalent circuit models in MATLAB/Simulink, and the simulation and verification are carried out in the constant current discharge and dynamic stress test conditions. The results show that the combination modeling method based on third-order RC and polynomial function fitting terms of 3 has high accuracy, and the model error does not exceed 1.97% in the dynamic stress test condition, which verifies the validity and accuracy of the proposed method of identifying the model parameters of the BM model, and provides an effective method for solving the high-precision equivalent circuit model of multiple types of energy storage.

Analysis of Voltage Stability Capability of Dynamic Reactive Power Compensation Devices Supporting High Proportional New Energy Systems

ZHANG Ruiqi, LI Mengjiao, YANG Hongming, ZHAO Jian, XU Qiufei, ZHANG Shijie

2024, 44(4): 27-33. doi:10.3969/j.issn.1008-0198.2024.04.004

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In response to the voltage stability issue in high proportion new energy access areas, the characteristics of new energy output gap and weak transient reactive voltage regulation ability of new energy units are first considered. Starting from the penetration rate of new energy and the power grid strength of new energy access points, and the mechanism of voltage instability in high proportion new energy access areas is revealed. Then, the dynamic reactive power output characteristics of SVC, SVG, phase-shifting camera, and distributed phase-shifting camera are elaborated, and the support capabilities of four types of reactive power compensation devices in high proportion new energy scenarios are compared and analyzed. Distributed phase-shifting cameras have more advantages in supporting reactive voltage and suppressing overvoltage/undervoltage in new energy stations. Finally, taking the Xiangnan new energy access area as the research scenario, the support effect of reactive power compensation equipment under fault conditions with the same new energy penetration rate and different new energy penetration rates is analyzed to verify the correctness of the proposed viewpoint.

Calculation Method of Selecting Economic Cross-Section for Conductors in Wind Farms

YE Shishun, QU Junhui, SHU Dong, FAN Qiumin, WANG Tong, FANG Qilin

2024, 44(4): 34-39. doi:10.3969/j.issn.1008-0198.2024.04.005

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The traditional selection method is still used for the economic cross-section of wind farm conductors, and the different wind speeds in four seasons and morning and evening and the distinctive characteristics of wind farms with more power generation in winter, less power generation in summer, more power generation at night and less power generation during the day are not considered. In view of this, a method for calculating the maximum load loss hours of wind farms is proposed. Firstly, according to the method of minimizing the annual cost of the whole life cycle, the operation loss cost is comprehensively considered, and the influence of the maximum load loss hours of the wind farm on the economic cross-section of the wind farm conductor is emphatically studied. Then, the correspondence between the maximum load loss hours and the maximum load utilization hours is re-established through the actual power data of the wind farm. Then, with the help of the average ratio and the peak-to-valley difference ratio to describe the correlation between wind farms, the quantitative expression of the maximum load loss hours is given, and the economic cross-section of the conductor is calculated by using the minimum annual cost method of the whole life cycle. Combined with real-time data verification, the proposed method can guide the unbuilt wind farm to select the economic cross-section of the conductor.

An Online Estimation Method of Power Grid Equivalent Inertia Based on Augmented Recursive Least Squares

LIU Yonggang, WANG Jingwen, WU Jinbo, SUN Mingrui, LIAO Bangkun, WEN Yunfeng

2024, 44(4): 40-46. doi:10.3969/j.issn.1008-0198.2024.04.006

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In this paper, an online estimation method of equivalent inertia based on measurement data is proposed to solve the problem of equivalent inertia level perception under high proportion of non-synchronous power supply. Firstly, using the data of generator active power change and node frequency, auto regression and moving average model with exogenous input(ARMAX)model models active power-frequency dynamic changes in each region/whole power grid. Furthermore, the recursive extended least squares (RELS) algorithm is used to solve the unknown parameters in the ARMAX model, and the estimated values of the inertia constant of the system or region are identified. In addition, considering the inertia support provided by the interregional contact line, the coupling phenomenon of regional inertia through the contact line after unbalanced power disturbance is estimated and analyzed. Finally, based on the actual data of a provincial power grid, the correctness and effectiveness of the proposed method are verified by simulation tests, and the inertia support provided by the interconnecting regional lines is analyzed.

Effect of Corona Aging on Dielectric Properties of Nanocomposite PI Thin Films

ZHANG Liang, ZHANG Shumeng, CHEN Yijie, LIU Daosheng

2024, 44(4): 47-51. doi:10.3969/j.issn.1008-0198.2024.04.007

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High temperature superconducting amorphous alloy transformers, as low-temperature operating equipment, have energy-saving and consumption reducing functions. The low-temperature resistant polyimide (PI) film is selected as the main insulation material for high-temperature superconducting amorphous alloy transformers, the preparation process of PI film is improved , a corona aging system is built, and corona aging pretreatment on PI film is performed. A study is conducted on the dielectric properties of films pre-treated with corona aging, and it is found that the dielectric loss tangent of films pre-treated with corona aging in liquid nitrogen environment is lower than that in room temperature environment. When the mass fraction is less than or equal to 5%, the dielectric loss tangent of PI films filled with nanoparticles is smaller than that of the films before treatment.

Research on Calculation and Online Measurement of Wet Steam Condensation Flow in Last Stage of Steam Turbine

HAN Yanguang, ZHU Guangming, QIU Yingjun, QIAN Jiangbo, WANG Richeng, WU Shijie

2024, 44(4): 52-58. doi:10.3969/j.issn.1008-0198.2024.04.008

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Exhaust steam wetness is an important parameter that affects the efficiency and safe operation of steam turbine. Based on the research status at home and abroad, the microwave resonator is used to realize the on-line monitoring of steam turbine exhaust wetness. Then, the influence of the inlet and outlet parameters of the final stage of the steam turbine on the exhaust steam wetness is obtained through numerical simulation combined with the experimental data. The results show that the wetness of the microwave resonator is measured at 0.2m after the final stage of the turbine, and the results are similar to those obtained by the optical method after the interference of the resonator vibration and temperature change is excluded. The higher the subcooling degree of the inlet, the higher the wetness, and the higher the average wetness of the outlet of the rotor blade. With the increase of back pressure, the wetness will continue to decrease, and the average wetness at the outlet of the moving blade will also decrease. The research results can provide reference for the efficient and safe operation of steam turbines.

Predictive Current Control of Permanent Magnet Synchronous Motor Model Based on Fuzzy Sorting

ZHANG Xueyi, XIE Mu, LUO Zhaoxu, CHENG Zhun

2024, 44(4): 59-67. doi:10.3969/j.issn.1008-0198.2024.04.009

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Aiming at the problem of difficult design of cost function weight coefficients in model predictive current control of permanent magnet synchronous motor, a model predictive current control strategy based on fuzzy sorting method is proposed. First, the current errors and the switching frequency corresponding to different voltage vectors during the switching are sorted by the sorting method, thus eliminating the need to design the weigh coefficients. Since the control objectives are not exactly equal in importance, a sorting optimization method with variable gain coefficients is designed to adjust the importance of the control objectives by using the variable gain coefficients. Compared with the conventional weight coefficients, the variable gain coefficients have discrete segmentation characteristics, so their adjustment process can be effectively simplified. The variable gain coefficients are then dynamically optimized by means of fuzzy control to better adapt to the ever-changing operating conditions of the motor. Finally, the validity and feasibility of the method proposed in this paper is demonstrated by simulation and experimental results.

Experimental Study on Sulfate Removal from Reverse Osmosis Concentrated Water Using Ettringite Method

CHENG Jun

2024, 44(4): 68-72. doi:10.3969/j.issn.1008-0198.2024.04.010

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The removal efficiency of sulfate from reverse osmosis concentrated water by ettringite method is studied, and the effects of pH value, calcium sulfate ratio n(Ca/S), aluminum sulfate ratio n(Al/S), initial sulfate concentration and other factors on the reaction are explored. The results show that for reverse osmosis concentrated water with a mass concentration of sulfate of 1 015 mg/L, the removal rate of sulfate can be increased to over 80% through the ettringite method. The optimal process parameters are as follows:pH=12.0, n(Ca/S)=4,n(Al/S)=0.7. The ranking of the impact of the three factors on the experiment is as follows:pH>n(Al/S)>n(Ca/S),with pH being the key factor and playing a dominant role in the treatment effect, followed by aluminum content. This method has significant differences in treatment efficiency for wastewater with different initial sulfate concentration. Within the range of initial sulfate mass concentration of 1 090~1 550 mg/L, as the initial mass concentration of sulfate increases, the removal rate of sulfate gradually increases.The disadvantage of this method is that the mass concentration of residual calcium is relatively high, and subsequently residual calcium can be converted to calcium carbonate by adding sodium carbonate to achieve its resource utilization.

Precision Profiling Technology of Transformer Areas Clustering Based on VAE-Kmeans Algorithm

YU Zongchao, CHEN Zizi, WEN Ming, LUO Shuchen, WEI Dong, XIN Lijie

2024, 44(4): 73-83. doi:10.3969/j.issn.1008-0198.2024.04.011

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Building a precise portrait of electricity consumption in the substation area, depicting the load characteristics and electricity consumption patterns of the substation area, can provide precise guidance for refined load forecasting, load fluctuation analysis and tracing, and substation business scenarios. Therefore, this paper proposes a precision profiling technology of transformer areas clustering based on VAE(variational auto-encoder)-Kmeans algorithm. Firstly,VAE, Kmeans clustering and time series similarity algorithms are used to extract the typical curves of load for station areas and industries from multiple dimensions. Secondly, the most similar industry load is determined through comprehensive evaluation, and the corresponding portrait label is assigned to the transformer area. Finally, taking the relatively large residential transformer area as an example, a deep mining and accurate description strategy based on cluster analysis and decision tree algorithm are constructed, and 14 sets of accurate portrait categories of urban and rural residential transformer areas are formed, which provides a solid foundation for fine load forecasting and differentiated transformer operation and maintenance management strategies.

Oscillation Suppression of Grid-Forming VSC-HVDC System Based on Fixed-Time Sliding Mode Control

ZHU Sirui, WANG Canlin, ZHANG De, LI Yong, ZHOU Yang, WEN Ting

2024, 44(4): 84-92. doi:10.3969/j.issn.1008-0198.2024.04.012

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The grid-forming voltage source converter based high voltage direct current(VSC-HVDC)system is connected to the grid, which supports the voltage and frequency of the grid. This paper focuses on the oscillation problem caused by the receiving end grid of grid-forming VSC-HVDC system and proposes a fixed-time sliding mode control method to damp the oscillation. First, a mathematical model of the grid-forming VSC-HVDC system is established based on virtual synchronous generator control. Then, a nonlinear fixed time sliding mode control method is proposed for oscillation suppression control according to the sliding mode control and fixed time stability theory. Furthermore, Lyapunov theory proves that the proposed nonlinear fixed time sliding mode control can realize the restoration of stability of the grid-forming VSC-HVDC system within the fixed time. Finally, a simulation model of the grid-forming VSC-HVDC system is constituted on MATLAB/Simulink and the simulation results verify the validity and superiority of the proposed method in oscillation suppression.

A Passive Retrofit Method for Mechanical DC Circuit Breakers in Converter Station

WEN Yicheng, LI Hong, CHEN Gang, ZHANG Chaofeng, WEN Zhonghua

2024, 44(4): 93-99. doi:10.3969/j.issn.1008-0198.2024.04.013

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To address the complexity of the control and protection logic execution process and the high cost of device maintenance in mechanical active DC circuit breakers, the paper proposes a design method for passive transformation of mechanical DC circuit breaker in converter stations, which simplifies the logic related to DC circuit breakers in the control and protection system, cancels auxiliary disconnecting switches and charging devices, eliminates the need to build a reactor, and provides the required inductance by the stray inductors on the transfer circuit conductor. The upgrading of capacitors in accordance with the passive system design not only shortens the switching current conversion time and reduces the surge arrester conversion energy, but also improves the service life of capacitors and greatly reduces the DC circuit breaker failure rate. Finally, a DC system simulation platform is built using MATLAB/Simulink, and the simulation results are consistent with the theoretical analysis, which further verifies the correctness and effectiveness of the proposed DC circuit breaker passive transformation scheme.

Research on Characteristic Analysis and Parameter Adjustment Method for Cable Type Linear Thermal Fire Detector

TAN Fenglei, ZHANG Jun, GUO Yang, WANG Haiyang, XU Peng

2024, 44(4): 100-104. doi:10.3969/j.issn.1008-0198.2024.04.014

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A method of analyzing characteristics and adjusting parameters of cable type linear thermal fire detector is proposed to achieve performance status discrimination.Firstly,on the basis of studying the equivalent circuit of cable type linear thermal fire detector,the variation characteristics of insulation resistance of cable type linear thermal fire detectors with temperature and humidity is analyzed.Then a temperature resistance characteristic model for cable type linear thermal fire detector is established.A performance discrimination method is proposed,which divides cable type linear temperature fire detector into three states (excellent,good,and unqualified),and provides processing methods for these three states.Finally,a set of temperature resistance characteristic analysis device for cable type linear temperature fire detector is developed and it′s applied on site at a 1 000 kV ultra-high voltage substation.The results show that the device can accurately distinguish the performance status of cable type linear thermal fire detector,and significantly reduce false alarms during actual using.

Research on Route Planning of Adaptive UAV Inspection Considering Sag Variation of Transmission Lines

ZHANG Li, ZHOU Xueming, SHEN Yu, YAO Yao, FENG Zhiqiang

2024, 44(4): 105-111. doi:10.3969/j.issn.1008-0198.2024.04.015

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At present, UAV based precision inspection does not consider the influence of temperature on the sag of guide ground wire, which is difficult to operate in field and low inspection efficiency. To solve the above problems, this paper proposes an adaptive UAV inspection route planning technology considering the sag variation of transmission lines. Based on catenary equation, vectorization analysis and calculation are carried out on the point cloud data of the classified transmission lines, and the vectorized transmission lines have been obtained. Based on the discrete point data generated by interpolation, the waypoint spacing is calculated according to the camera parameters, photo distance, overlap rate and other parameters of the inspection UAV, and the adaptive UAV inspection route is generated. The flight test of patrol route with adaptive sag change of the transmission line is carried out. The test results show that the autonomous patrol route planning can be carried out by fully considering the sag change of the wire caused by temperature change, and the appropriate photo distance and photo overlap rate can be set, the texture and defect of guide ground wire can be clearly identified, and the image of overhead transmission wires and ground wires can be collected autonomously, completely and efficiently.

Optimized Design Study of Symmetrical Fork Pipe Structure and Hydraulic Characteristics

SHEN Yan, TANG Changchang, GUO Miao, WU Hao

2024, 44(4): 112-117. doi:10.3969/j.issn.1008-0198.2024.04.016

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Fork pipe structure is widely used in all kinds of water conservancy projects, its structural safety and hydraulic performance are the key to optimize the design, and both of them interact with each other, which will have an important impact on the comprehensive performance and operational safety of water conservancy projects. In this paper, the symmetrical fork pipe structure and hydraulic characteristics of a pumping and storage power station are optimized and designed, and the three-dimensional finite element method is used to carry out stress analysis on the initial design and optimization scheme of the fork pipe structure, and the calculation results show that the stress distribution on the waistline side of the fork pipe after optimization has been effectively improved compared with the initial design scheme. Based on the optimization of the turnpipe structure, the hydraulic model of the turnpipe with different bifurcation angles and rib width ratios is used to calculate and analyze the three-dimensional flow field under power generation and pumping conditions, and the bifurcation angles and rib width ratios of the turnpipe with better internal flow distributions and smaller head losses under all conditions are determined by orthogonal optimization strategy. It is found that the relationship between structural forces and hydraulic properties is not purely positive, and the optimal bifurcation angle of 75° and the rib width ratio of 0.30 are finally determined based on the orthogonal optimization idea to satisfy the structural safety and hydraulic performance.

Analysis of Impact and Countermeasures of Deterioration of Secondary Wiring Blocks in Capacitive Voltage Transformers on Pre-Test Data

LUO Zanchen, LU Yingjun, SONG Yunxiang, QIN Yan

2024, 44(4): 118-125. doi:10.3969/j.issn.1008-0198.2024.04.017

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The insulation degradation of the secondary terminal board of a capacitive voltage transformer can lead to large errors in the dielectric loss test data of the capacitive voltage divider, and can also cause the insulation resistance test of the intermediate transformer to fail. To address this issue, the basic principles of dielectric loss and the measurement principles of digital automatic dielectric loss meters are analyzed, an equivalent analysis circuit model for dielectric loss measurement are constructed, and the error data of dielectric loss tests for three types of capacitive voltage transformers(positive connection method, reverse connection method, and self-excited method)are calculated. The conclusion is that the positive connection method and self-excited method have larger errors, while the reverse connection method has smaller errors. Based on this, the optimal method can be guided for on-site use. The insulation structure characteristics of the intermediate transformer in capacitive voltage transformers is analyzed, and shielding method is used to measure the insulation resistance or dielectric loss of the secondary terminal board to determine the insulation condition of the secondary terminal board. Then, by measuring the dielectric loss of the primary winding of the intermediate transformer to the secondary winding, and combining the capacitance and dielectric loss data of the secondary terminal board, the dielectric loss value of the intermediate transformer winding can be calculated to accurately determine whether the insulation of the intermediate transformer is good.

Analysis and Research of GIS Transportation Vibration and Shock

CHEN Yu, XU Meng, GAO Yang, SHEN Fenghui, LIU Yuntong, LIU Dongyang

2024, 44(4): 126-131. doi:10.3969/j.issn.1008-0198.2024.04.018

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Taking a certain type of 126 kV GIS as the research object, the transportation vibration and shock characteristics are analyzed and studied. The three-dimensional solid structure model of GIS transportation unit is established, and the modal analysis and random vibration analysis with prestress under vibration conditions are carried out by using ANSYS Workbench software to obtain its natural frequency and mechanical strength of each component. The analysis results show that the maximum equivalent stress of the base is 153.5 MPa and the minimum safety factor is 1.53. The experimental research on the GIS transportation unit under abnormal shock conditions shows that the GIS equipment can still ensure good performance when the instantaneous shock acceleration reaches 6.7g, and the shock resistance is higher than the acceleration value required by the product is less than 3g standard. Through the analysis and research of GIS under vibration and shock conditions, the transportation performance of GIS is evaluated comprehensively, which has very important practical significance to ensure the transportation safety of GIS.

Fault Location of Distribution Networks Based on Combination of Quantum Computing and Ant Colony Algorithm

YANG Hailin, HUANG Cunqiang, TIAN Xu, AN Juan, ZHANG Shunzhen, BI Zhongqin

2024, 44(4): 132-137. doi:10.3969/j.issn.1008-0198.2024.04.019

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Aiming at the drawbacks of slow convergence speed and low success rate of intelligent optimization algorithms in dealing with fault location problems in distribution networks, a quantum ant colony algorithm based on the combination of quantum computing and ant colony algorithm is proposed for fault location in distribution networks. Firstly, considering the distortion and loss of information uploaded by the feeder terminal unit (FTU), a hierarchical positioning mathematical model is proposed that takes into account the false alarm information of FTU. Secondly, the basic principles and application schemes of quantum ant colony algorithm are introduced. Finally, simulation is conducted on MATLAB to verify the effectiveness of the quantum ant colony algorithm and the hierarchical localization mathematical model that takes into account FTU false alarm information.

Failure Analysis of Welded Joints on Water Wall in 1 000 MW Ultra Supercritical Units

LONG Huiguo, JING Xuechao, XIE Ameng

2024, 44(4): 138-142. doi:10.3969/j.issn.1008-0198.2024.04.020

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By observing the macroscopic and microscopic morphology of cracks,metallography,hardness,scanning electron microscopy, energy spectrum, and joint structure analysis, the failure reasons of welding seam cracks in the installation of the water-cooled wall of a 1 000 MW ultra supercritical unit boiler are studied. The results show that the gap at the root of the weld, the protrusion at the root of the weld, and their hardness exceed the standard, coarse weld microstructure and low melting point carbide phase segregation, weaken grain boundaries, and there are microcracks in the weld seam, which can be determined as welding hot cracks based on the analysis of the oxide phase inside the microcracks. Under the action of high temperature and high pressure stress during operation, crack propagation ultimately leads to cracking failure, and welding hot cracks are the main cause of this failure.

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