Table of Content

25 June 2020, Volume 42 Issue 6

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Optimized method on distributed reactive power compensation in lowvoltage distribution network based on interval power flow calculation

CHEN Hongyan，TANG Zhiguo，CHEN Qi，WANG Yongxu，WU Luming

2020, 42(6):  1-5. 

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The circuits are radially distributed in lowvoltage distribution network.The loads are unevenly distributed and of great uncertain change,and the voltage of terminal nodes is low.Thus,an optimization method on distributed reactive power compensation in lowvoltage distribution network based on interval power flow calculation is presented.The interval calculation is introduced based on NewtonRaphson power flow calculation model,and affine arithmetic is used in its convergence algorithm.The scope of reactive power shortage is calculated by interval power flow algorithm.The capacity and quantity of distributed capacitor banks of a lowvoltage power distribution network was determined by calculation and analysis.It is proved that he proposed method can improve the voltage quality of distribution networks effectively with great load fluctuations.

Operation region partition for hydraulic turbine generator units based on stability test data

WANG Lijie，WANG Hongteng，SUN Bo

2020, 42(6):  6-9. 

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The stability of hydraulic turbine generator units is the key to the safe operation of hydropower stations.Stability indicators, such as vibration, swing, pressure fluctuation and so on, were obtained by a stability test under full head. The operation status of a unit in a hydropower station under full head was analyzed to find out whether the stability indicators met the standards. Fine partition of full-load operation region under full head was made combining the actual status of the power plants, which provides scientific basis for safe, efficient and stable operation of power plants.

一起电子互感器异常引发的复杂发展性故障分析及改进

WU Luming，XUE Mingjun，CHEN Qi，WANG Yongxu，TANG Zhiguo，CHEN Hongyan1,2

2020, 42(6):  10-15. 

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With the rising of smart substations, electronic transformers have been widely used in relay protections, but their defects are gradually exposed. A complex developing fault caused by abnormal electronic transformer was introduced, and the process and reasons for this failure were analyzed. By analyzing the abnormal sampling visit (SV) criterion and solutions for different protections on site, the operation of protection devices after the fault was detailed and discussed.It is believed that the reliability of the current electronic transformer needs to be further improved. On this basis, an optimization scheme for phase selection logic in the line protection is proposed and be proved to be feasible by a simulation test. The scheme can be applied in complex developing faults to improve the reliability of smart substations

Water quality control technology for circulating cooling water taking soft water as source

NIU Ben

2020, 42(6):  16-21. 

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To ensure the water saving and operation safety of units at the same time, the optimal treatment scheme and operation condition of circulating cooling water were sought for. According to the characteristics of circulating cooling water taking soft water as supplement, the performance of four scale and corrosion inhibitors was studied by limit carbonate alkalinity method, weightloss method and dynamic simulated test. In the dynamic simulated test, “1/2Ca2++JDM”value which replaced the traditional ΔA value was used to adjust the sewage discharge in the circulating water system, and the corrosion of the concrete of cooling tower immersed in the circulating water with high SO42- content was observed. Being soaked in circulating water for 20days, the morphology of specimens remained unchanged, and the SO42- content of the solution was stable. The results show that QJ has excellent corrosion and scale inhibition performance, and is suitable for the circulating cooling water system taking soft water as supplement.It is feasible to prevent scaling in circulating water system by controlling “1/2Ca2++JDM” value, and SO42- shows no significant erosion on cement and aggregate in concrete when circulating water is of high cycle of concentration.

Design and application of intelligent algaeblocking equipment for water conveyance main canal

SHANG Liyang，FAN Suxiang，ZHANG Zhiyong，YU Penghui，HE Yong，JI Yanru

2020, 42(6):  22-24. 

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To solve the algae pollution in the main canal of  SouthtoNorth Water Diversion  Middle Route Project,a new intelligent algaeblocking equipment for the main canal  was designed based on the first generation algaeblocking equipment, which included filter driving device, lifting device and control system. This equipment realized fullsection continuous algaeblocking  with  adjustable depth. Considering the large and irregular current force impacted on the equipment in water, a static finite element analysis was carried out on the filter installation frame. The results showed that the equipped met the requirements of strength and stiffness. After the running of the intelligent algaeblocking equipment in Zhengzhou section of SouthtoNorth Water Diversion Middle Route Project,the algaeblocking effect has been good, the water quality has been improved.The equipment is of good application prospects.

Research on energysaving optimization for mediumspeed mill pulverizing systems

ZHANG Hailong，YANG Guangrui，JING Xinjing，XING Leqiang，LIU Chao，DANG Lijun

2020, 42(6):  25-30. 

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As the vigorous development of renewable energy,coalfired power plants are facing severe challenge in energy saving and consumption reduction. In order to reduce the energy consumption of pulverizing systems, intensive study was made on consumption reduction by controlling thetemperature at mill outlet and optimizing primary air pressure，and thecoupling relationship between the two controlling strategies. The optimal optimization strategy was determined after theoretical analysis. The optimization test was carried out fromcontrollingthe temperature at mill outlet tooptimizing the primary air pressure. The temperature at mill out goes up to 80℃ after the test, and the primary air pressure can be controlled at 6.5,8.0 and 9.0kPa respectively under the load of 300, 450 and 600MW.The curve of primary air pressure changing with the load is given. After the optimization, the coal consumption of the unit can be reduced by 0.38g/(kW·h).The optimization is of good economic benefits, and can provide reference for energy saving for pulverizing systems.

Setting for design parameters of a wet plume treatment project 

YANG Pengfei，WU Chong，ZHANG Xiqian，WANG Kailiang，ZHANG Qi

2020, 42(6):  31-34. 

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Since 2017,the treatment on gypsum rain and wet plume from coalfired power plants have attracted a lot of public attention. Hebei, Tianjin, Jiangsu and other districts published emission standards of air pollutants, and corresponding techniques have been taken to lower the temperature and moisture content of flue gas, and reduce the emission of condensable particles such as soluble salts and SO3.Taking a 630MW coalfired unit in a Jiangsu power plant as the research object, its historical data from 2017 to 2018 were obtained and analyzed with normal distribution statistical method. The coal moisture content and the probability distribution of the smoke temperature at the inlet and outlet of the absorption tower were analyzed, and the design parameters of the project were determined.

Retrofit and combustion adjustment of a lownitrogen burner in a 330MW cogeneration unit

WANG Yunpeng,DUAN Xiaoyun

2020, 42(6):  35-42. 

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In respond to the national environmental protection policy, in order to reduce the cost of denitration, alleviate the ammonia escape rate and air preheater pressure difference caused by the accumulation of ammonium hydrogen sulfate on the cold side of the air preheater, a lownitrogen burner of No.2 boiler for a 330MW cogeneration unit was modified through a lownitrogen burner retrofit.The retrofit took horizontal bias combustion technology and air staging combustion technology.The effect of the lownitrogen burner retrofit was verified by the cold aerodynamic field test and the hot combustion adjustment test.The results show that the primary air, secondary air and SOFA works well, and the furnace flame of good fullness shows no eccentricity and does not burn the furnace wall.The NOx mass concentration at the outlet of the furnace does not exceed 200mg/m3 under various conditions，which means the retrofit has met the requirement.

Application of acoustic blockage removal technique applied in urea pyrolysis furnaces

SHAO Lei，PAN Guangqiang，ZHANG Yuquan，CHU Hao，CAO Wei

2020, 42(6):  43-46. 

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Abstract:To solve the blockage of urea pyrolysis furnaces in selective catalytic reduction denitration systems in coalfired plants, 2×600MW coalfired units in Shiliquan Power Plant of Huadian Power International Corporation Limited was taken as an example.Base on the principle of acoustic blockage removal technique and operation situation of the power plant, an acoustic blockage removal system within adjustablefrequency high intensity acoustic source was installed in the hot air duct of a urea pyrolysis furnace to improve its efficiency. According to the performance test and operation efficiency, there has been no blockage in the furnace of denitration system after the application of the acoustic blockage removal system.

Comparative analysis of calculation models for thermal efficiencies of waste heat boilers in gassteam combined cycle units

WANG Zhiyong，XU He，ZHU Huimin，GE Junpei，XU Jing

2020, 42(6):  47-51. 

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To analyze the economy of power plants，performance test for a waste heat boiler in a gassteam combined cycle unit was made, and the field test data were taken to calculate the thermal efficiency of the waste heat boiler within positive and counter balance mathematical models.In the extreme situations with unknown leakage in the system, variation trends of the efficiency calculated in two models were studied. The study results showed that the counterbalance waste heat boiler thermal efficiency ranged from  85.69% to 85.92% under the rated conditions, and the efficiency calculated by positive balance ranged from 84.50% to 85.31%.Considering unknown leakage correction,the thermal efficiency of the waste heat boiler ranged from 85.30% to 85.94%. The counterbalance calculation model directly reflects the heat transfer performance of the  boiler. The positive balance calculation model reflects the actual situation of the overall thermal cycle system. These two methods can provide reference forwaste heat boilers  of the same type  under different assessment conditions.

Application of parameter identification principle in the protection of magnetic shunt reactor

XING Wu，GUO Xiao，WANG Zhe，SHI Bolun

2020, 42(6):  47-51. 

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Magnetic shunt reactors are of continuously adjustable capacity, and have wide application prospect in limiting overvoltage and reactive power compensation. At present, the protection of magnetic  shunt reactors is based on constant reactor capacity, so that the sensitivity and reliability of the protection will decline if the reactor capacity changes,which might lead to the failure to operate or unwanted operation of the protection. Applying the parameter identification principle in reactor protection, by identifying the impedance parameters of the reactor, the protection parameters will match with the operating conditions of reactors. The feasibility of this method was improved by quantitative analysis on an engineering case. Application of this method will greatly improve the sensitivity of the magnetic reactor and provide more reliable protection.

Optimization strategy of multiple output cables samephase parallel operation for gas turbine generators

WANG Dongzhen，GE Leijiao

2020, 42(6):  52-56. 

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Multiple singlecore cables are used to connect a gas turbine generator outlet and a main transformer lowvoltage side during samephase parallel operation. There is overtemperature and overrated current in cables due to uneven current distribution and high induced voltage, which poses a large safety hazard.Thus,an optimization strategy of multiple  output cables samephase parallel operation for gas turbine generators is proposed. Firstly, main causes of the overtemperature cable of the gas turbine generator are analyzed in depth. Secondly, the optimization model of the multiple singlecore cables between the gas turbine generator and the lowvoltage side of the main transformer in samephase parallel operation is constructed, and the model is solved by particle swarm optimization. Changing the arrangement of cables from the generator outlet to the main transformer lowvoltage side can effectively address the uneven current distribution and high induced voltage of the multiple singlecore cables in samephase parallel operation. Finally, the typical case of a Tianjin gasfired distributed power station is studied.The results show that optimizing the crossing layout of five outphrase cables can distribute the current of each cable evenly, so as to guide the design and operation of the parallel operation of the singlecore cables of generators.

Evaluation of prefilter improvement effect of gas turbine air intake filtration system

GAO Yong，TIAN Xin，WU Yinchen

2020, 42(6):  57-61. 

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As an important line of defense for the air taken into gas turbines, air filtration system is essential for the safe and economic operation of gasfired power generation enterprises. Huadian Qishuyan Power Generation Company Limited took an technical modification on prefilters of a air intake filtration system in a M701F4 gas turbine. By increasing the area of prefilters and updating the filtration class from G4 to M6, the dropping rate of the gas turbine compressor efficiency decreased 1.0~1.5 percentage points per 1000 operating hours, the combined cycle heat consumption rate decreased by 0.24kJ/(kW·h) per 500 operating hours, and the service life of fine filters increased from 2400~2500h to nearly 6000h. At the same time, the highest pressure differential of fine filters in rainy, foggy and other extreme weather dropped by about 40~50Pa. The modification results show that upgrading the filtration class and increase the filtration area can significantly improve the safety and economy of the unit.

Comprehensive upgrading reconstruction and performance analysis of a subcritical boiler

WU Siming，TONG Jialin，WU Yueseng，QI Yong，SUN Wuyi

2020, 42(6):  66-71. 

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In order to improve the economy and flexibility of units and meet environment requirements,it is necessary to upgrade and reconstruct energyintensive and highemission coalfired units. Taking a 600MW subcritical coalfired unit as researching object,the schemes,items and effects of the comprehensive upgrading were studied.The results indicated that the unit after reconstruction met the demands of the expansion to 630MW.Efficiency of the boiler has increased by 0.2%~0.7%, roughly and the net coal consumption rate under heating operation has been below 300g/(kW·h), the national standard.Meanwhile,the fluegas temperature at the SCR inlet during lowload running has been improved.

Analysis on heating supply retrofit of a 200MW unit by cutting off the lowpressure cylinder steam admission

LIU Shuai,ZHENG Lijun,YU Cong,GAO Xinyong,Liu Guobi,ZHAO Chunfeng,ZHANG Xiaoli,CAO Chuang,XU Jianpeng

2020, 42(6):  76-82. 

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It is essential to alleviate the conflict between heating and electricity supply, and improve the flexibility of thermal power units. A heating supply retrofit by cutting off the lowpressure cylinder steam admission was made on a 200MW unit in a domestic power generation company.In order to avoid the blade flutter under low flow conditions,guided by the test data in the literature about cutting off the lowpressure cylinder steam admission, the cooling steam flow running into the lowpressure cylinder was limited to 1.0%~1.5% of the rated exhaust gas flow. After replacing the connecting pipe butterfly valve, installing measuring points on the last two stages and adding a cooling steam bypass system with desuperheating and decompression functions, heating supply and peaking load regulating capacities of the unit were calculated.Proven by data in two heating seasons,the retrofit scheme is feasible.The scheme decouples the heating and electricity capacities, lowers the condensation loss, and improves the economy of the unit.

 Construction and implementation of intelligent, digital and networked heatsupply system

YANG Rui

2020, 42(6):  83-86.  doi:火电厂；网源一体；智慧供热；智能热网；热电联产；储热罐

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 Intelligent, digital and networked heatsupply systems integrated source with network for heatsupply systems in thermal power plants are implemented, to realize intelligent heat supply and a winwin situation for social and economic efficiency of heatsupply enterprises. By constructing subsystem platforms such as load forecasting system, thermal storage system, hydraulic balance analysis system and dynamic control system, we can achieve comprehensive analysis and evaluation on load forecasting, thermal dynamics control and energy consumption. A set of intelligent, digital and networked heatsupply system integrated source with network was taken shape initially. It confirmed that the system was of comprehensive energysaving benefits by performance tests, which can provides technical reference for similar enterprises. Intelligence, digitalization and networking are powerful techniques for the safe, scientific and economic operation of heat supply.