Hybrid Dissolved Gas-in-Oil Analysis Methods

Dissolved gas analysis is the most widely used diagnostic test in power transformers. The aim of this paper is to introduce the dissolved gas analysis (DGA) methods able to diagnose the transformer conditions. The faults cause the transformer oil, pressboard, and other insulating materials to decompose and generate gases, some of which dissolve in the oil. The results of DGA must be accurate if faults are to be diagnosed reliably. There are different established methods used in industry for interpreting DGA results. We will compare the result of IEEE Key Gas Methods and Rogers’ Ratios. The transformer conditions are evaluated by the Key Gas Method with total combustible gas method (TCGM) and then verified by the Rogers’ Ratios. As result, the aging pattern and trend of the power transformer deterioration can be determined. The 30 sample data from IEEE with known faults and dissolved gas concentrations were used as the basis of comparison.

Impact of transparent exopolymer particles on the dynamics of dissolved organic carbon in the Amundsen Sea,Antarctica

The Southern Ocean is an important carbon sink pool and plays a critical role in the global carbon cycling.The Amundsen Sea was reported to be highly productive in inshore area in the Southern Ocean.In order to investigate the influence of transparent exopolymer particles(TEP)on the behavior of dissolved organic carbon(DOC)in this region,a comprehensive study was conducted,encompassing both open water areas and highly productive polynyas.It was found that microbial heterotrophic metabolism is the primary process responsible for the production of humic-like fluorescent components in the open ocean.The relationship between apparent oxygen utilization and the two humic-like components can be accurately described by a power-law function,with a conversion rate consistent with that observed globally.The presence of TEP was found to have little impact on this process.Additionally,the study revealed the accumulation of DOC at the sea surface in the Amundsen Sea Polynya,suggesting that TEP may play a critical role in this phenomenon.These findings contribute to a deeper understanding of the dynamics and surface accumulation of DOC in the Amundsen Sea Polynya,and provide valuable insights into the carbon cycle in this region.

Multivariate analysis of fluorescence and source identification of dissolved organic matter in Jiaozhou Bay, China

Hierarchical clustering analysis and principal component analysis （PCA） methods were used to assess the similarities and dissimilarities of the entire Excitation-emission matrix spectroscopy （EEMs） data sets of samples collected from Jiaozhou Bay, China. The results demonstrate that multivariate analysis facilitates the complex data treatment and spectral sorting processes, and also enhances the probability to reveal otherwise hidden information concerning the chemical characteristics of the dissolved organic matter （DOM）. The distribution of different water samples as revealed by multivariate results has been used to track the movement of DOM material in the study area, and the interpretation is supported by the results obtained from the numerical simulation model of substance tracing technique, which show that the substance discharged by Haibo River can be distributed in Jiaozhou Bay.

Continuous flow analysis of dissolved total phosphorus in seawater by UVK_(2)S_(2)O_(8) online digestion method

Several methods for analysis of dissolved total phosphorus in seawater were reviewed. Discussions were focused on UVirradiation and persulphate oxidation methods which are the most popular dissolved organic phosphorus determinationmethods presently. The compounds used for the phosphorus recovery test were categorized into three groups accordingto their chemical structure. It was found that low power UV irradiation can decompose POC or PC bonds efficientlybut may be inefficient for POP bonds. Heating-bath in acid condition is useful for decomposing POP bonds. Usingthe continuous flow analysis system (Auto-analyzer II), UV digestion and heating-bath, series experiments were carriedout based on the above analysis. Eleven model compounds were employed for the phosphorus recovery test and thefactors influencing the decomposition efficiency of dissolved compounds containing phosphorus were clarified. Finally,the optimal design for determination of dissolved total phosphorus in seawater based on the routine continuous flowanalysis system was presented. For the organic mono-phosphate, the recovery is more than 90% and a recovery of33%~51% was obtained for inorganic or organic polyphosphates. Up to now, this is the highest decompositionefficiency for dissolved phosphorus based on the continuous flow analysis system.

A Hybrid Neural Network Model for Marine Dissolved Oxygen Concentrations Time-Series Forecasting Based on Multi-Factor Analysis and a Multi-Model Ensemble

Dissolved oxygen(DO)is an important indicator of aquaculture,and its accurate forecasting can effectively improve the quality of aquatic products.In this paper,a new DO hybrid forecasting model is proposed that includes three stages:multi-factor analysis,adaptive decomposition,and an optimizationbased ensemble.First,considering the complex factors affecting DO,the grey relational(GR)degree method is used to screen out the environmental factors most closely related to DO.The consideration of multiple factors makes model fusion more effective.Second,the series of DO,water temperature,salinity,and oxygen saturation are decomposed adaptively into sub-series by means of the empirical wavelet transform(EWT)method.Then,five benchmark models are utilized to forecast the sub-series of EWT decomposition.The ensemble weights of these five sub-forecasting models are calculated by particle swarm optimization and gravitational search algorithm(PSOGSA).Finally,a multi-factor ensemble model for DO is obtained by weighted allocation.The performance of the proposed model is verified by timeseries data collected by the pacific islands ocean observing system(PacIOOS)from the WQB04 station at Hilo.The evaluation indicators involved in the experiment include the Nash–Sutcliffe efficiency(NSE),Kling–Gupta efficiency(KGE),mean absolute percent error(MAPE),standard deviation of error(SDE),and coefficient of determination(R^(2)).Example analysis demonstrates that:①The proposed model can obtain excellent DO forecasting results;②the proposed model is superior to other comparison models;and③the forecasting model can be used to analyze the trend of DO and enable managers to make better management decisions.

Trend Impact Analysis of Dissolved Nutrients Released From Soil on Water Quality in Qinglongshan Reservoir

During the storage of water and the initial running of a reservoir, part of the dissolved nutrients released from the soil in water will effect water quality. Taking Qinglongshan Reservoir as an example, estimating the value of the contribution of dissolved nutrients to the water quality and analyzing the trend or level of the dissolved nutrients effecting on the water quality under the soil nutrient inquiring, the soil nutrient monitoring, and the dissolving experiment of nutrients released from soil, also according to the capacity curve of Qinglongshan Reservoir.

Evaluation of Dissolved Organic Carbon Using Synchronized Fluorescence Emission Spectra and Unsupervised Method of Principal Component Analysis (PCA) and Independent Component Analysis (ICA)

Dissolved organic matter (DOM) can be originated from autochthonous or allochthonous sources, where allochthonous DOM can be from pedogenic sources (humic substances—HSs) or anthropogenicsources (wastewater). The analysis of fluorescence emission, excitation, synchronous or excitation-emission matrix (EEM) have been used to identify the main source or probable contribution of dissolved compounds, such as humic acids (HA), fulvic acids (FA) and dissolved organic carbon (DOC) from sewage, but does not quantify. Fluorescence emission is a powerful technique to detect and qualify organic dissolved compounds but fails in quantitative aspects. In this work, we propose an in situ method for direct determination of DOC using synchronous fluorescence spectra with independent component analysis (ICA). Well known standard solutions were used for method development and validation. In this work, we show that it is possible to predict the number of independent contributions using an unsupervised method based on iterative Principal Component Analysis and Independent Component Analysis (PCA-ICA) approach over combined matrix results. Within these results it’s also possible to see that with a very small amount of independent components it is possible to describe environmental samples of HA, FA and primary productivity (PP).

On-line monitoring of dissolved gas-in-oil with FTIR spectra

To overcome the disadvantages of conventional DGA (dissolved gas-in-oil)analysis using gas chromatography and other electrochemical sensors, initial researches werecompleted to realize on-line monitoring of dissolved gas-in-oil of power transformers using FTIR(Fourier Transform InfraRed) spectroscopy. Gas cell method is used to determine the characteristicabsorption peaks of each diagnostic gas; simple and novel devices and procedures were designed inorder to get measurable samples and spectra of mixed diagnostic gases with known concentration aretaken using long optical path gas cell. The range of wavelength is estimated to be 3.0-13.9 mum fromexperimental spectra data. Hence the corresponding sampling frequency range should be in 536-4288Hz and usable optical materials are suggested. It is concluded that a resolution of 10 cm^(-1) maywell satisfy the monitoring of all diagnostic gases and water content except hydrogen, and thelowest detection limit may be as low as 2Xl0^(-8) to acetylene with a 2.4-meter-long optical length.

Characteristics of dissolved organic matter in lakes with different eutrophic levels in southeastern Hubei Province,China

Dissolved organic matter(DOM)plays a crucial role in both the carbon cycle and geochemical cycles of other nutrient elements,which is of importance to the management and protection of the aquatic environments.To achieve a more comprehensive understanding the characteristics of DOM in the Changjiang(Yangtze)River basin,water samples from four natural lakes(Xiandao,Baoan,Daye,and Qingshan)in southeastern Hubei Province in China with different eutrophication levels were collected and analyzed.The optical characteristics were analyzed using ultraviolet-visible spectrophotometry and excitation-emission matrix spectroscopy coupled with parallel factor analysis.The results show that:(1)two humic-like components(C1 and C2)and two protein-like substances(C3 and C4)of DOM were identified in all waterbodies;(2)C3 originated primarily from the degradation of microalgae and contributed substantially to humic-like components during transformation.C4 was widely present in the Changjiang River basin and its formation was related to microbial activity,rather than algal blooms or seasons.Influenced by the water mixing,the protein-like components were more likely to be transformed by microorganism,whereas humic-like components were more easily to be photobleached;(3)the concentration of DOM and the fluorescence intensity of humic-like components gradually increased with rising lake eutrophication levels.With respect to protein-like components,only C3 showed changes along the eutrophication gradients;(4)DOM showed a high affinity with permanganate index(COD Mn)and chlorophyll a(chl a)while the relationship was variable with phosphorus.This study helps us systematically understand the DOM characteristics,microbial activities,and pollutant transformation in the Changjiang River basin and provides reference to the ecological restoration of aquatic environments.

Bacterial community succession in response to dissolved organic matter released from live jellyfish

Jellyfish blooms have increased worldwide, and the outbreaks of jellyfish population not only affect the food web structures via voracious predation but also play an important role in the dynamics of nutrients and oxygen in planktonic food webs. However, it remains unclear whether specific carbon compounds released through jellyfish metabolic processes have the potential to shape bacterial community composition. Therefore, in this study, we aimed to investigate the compositional succession of the bacterioplankton community in response to the dissolved organic matter (DOM) released by the live Scyphomedusae Cyanea lamarckii and Chrysaora hysoscella collected from Helgoland Roads of the North Sea. The bacterial community was significantly stimulated by the DOM released form live jellyfish and different dominant phylotypes were observed for these two Scyphomedusae species. Furthermore, the bacterial community structures in the different DOM sources, jellyfish-incubated media, Kabeltonne seawater, and artificial seawater (DOM-free) were significantly different, as revealed by automated ribosomal intergenic spacer analysis fingerprints. Catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH) revealed a rapid species-specific shift in bacterial community composition. Gammaproteobacteria dominated the community instead of the Bacteroidetes community for C. lamarckii, whereas Gammaproteobacteria and Bacteroidetes dominated the community for C. hysoscella. The significant differences in the bacterial community composition and succession indicate that the components of the DOM released by jellyfish might differ with jellyfish species.

Chemical composition and Pb(II)binding of dissolved organic matter in a hypersaline lake in China

Dissolved organic matter(DOM)plays a vital role in promoting carbon and nutrient cycling.It is a food source for organisms and controls the migration and transformation of trace metals and other contaminants in aquatic systems.The contributions of aquatic DOM to the environment and ecology of a system are closely related to its abundance and chemical structure.In this study,the chemical composition and binding properties of DOM in a hypersaline lake watershed were investigated for the fi rst time using dissolved organic carbon(DOC)analysis,absorption spectroscopy,Fourier transform infrared spectroscopy,pyrolysis-GC-MS(Py-GC-MS),and fl uorescence parallel factor(PARAFAC)analysis combined with Pb(II)titration techniques.The results showed that DOM from the tributaries that fl owed into the lake had a lower DOC content,higher molecular weight,and higher specifi c UV absorbance than the DOM in lake water.Protein-like fl uorophores were mainly found in tributary and lake surface water DOM(LSDOM)and humic-like substances were abundant in lake groundwater DOM(LGDOM).Using this multi-methodological approach,we found that the DOM from the hypersaline lake watershed was mainly from microbial origins,and consisted of aromatics,carbohydrates,and aliphatics.The results from quantitative analysis showed that DOM from the infl owing tributaries contained more aromatics,lower carbohydrates,and lower aliphatics than DOM in the lake.Monocyclic aromatic hydrocarbons and carbohydrates were more abundant in LSDOM than LGDOM.The results from the Pb(II)titration technique coupled with PARAFAC analysis suggested that PARAFAC-derived components had relatively low condition stability constants(log K_(M)<2).Of the two types of lake DOM,the LGDOM had a higher Pb(II)binding potential than the LSDOM.From this study we have improved our understanding of how DOM within a hypersaline lake watershed varies in its composition and potential to bind with metals.

Grey relational analysis on the relation between marine environmental factors and oxidation-reduction potential

The effects of marine environmental factors-temperature(T),dissolved oxygen(DO),salinity(S) and pH-on the oxidation-reduction potential(ORP) of natural seawater were studied in laboratory.The results show an indistinct relationship between these four factors and the ORP,but they did impact the ORP.Common mathematical methods were not applicable for describing the relationship.Therefore,a grey relational analysis(GRA) method was developed.The degrees of correlation were calculated according to GRA and the values of T,pH,DO and S were 0.744,0.710,0.692 and 0.690,respectively.From these values,the relations of these factors to the ORP could be described and evaluated,and those of T and pH were relatively major.In general,ORP is influenced by the synergic effect of T,DO,pH and S,with no single factor having an outstanding role.

Optical Characteristics of Chromophoric Dissolved Organic Matter(CDOM)in Upstream and Downstream Lakes of Taihu Lake Basin:New Insights for Water Environmental Management

Chromophoric dissolved organic matter(CDOM)is a key component of organic matter that contributes to the ecological functioning of lakes.The lakes in Taihu Lake Basin play an important role in maintaining regional ecological stabilities;however,the optical characteristics of the CDOM in the upstream and downstream lakes in this basin have not yet been systematically studied.Here,the optical characteristics of CDOM in ten lakes of upstream and downstream of the Taihu Lake Basin were studied using UV-Visible and excitation-emission matrix spectroscopies.Three different fluorophores consisting of two humic-like components(C1,C2)and one protein-like component(C3)were identified by parallel factor analysis.Soil or surface erosion was responsible for the higher abund-ance of C1 in the upstream lakes,and increased biological activities accounted for the higher abundance of C3 in the downstream lakes.Rainfall erosion in the wet season led to an increase in CDOM.We also found that the photodegradation and flocculation degree,which played a significant role in reducing CDOM,were higher in downstream lakes than in upstream lakes.Optical analysis of CDOM provides a promising method for monitoring water qualities(e.g.,total phosphorus and potassium permanganate index)in each lake.Re-ductions in soil or surface erosion in the upstream are needed to improve water quality.

基于CD-BSMOTE的D-S证据融合变压器故障诊断

针对变压器油中溶解气体数据集不均衡特性对故障诊断结果的影响,提出一种基于清除临界点改进的边界合成少数类过采样算法均衡数据集和Pearson冲突距离改进D-S证据融合的变压器故障诊断模型。首先,对少数类样本进行均衡化处理,根据K-means聚类结果清除处于临界位置的样本;其次,搭建梯度提升树、随机森林、BP神经网络的故障诊断模型,实现变压器故障初步诊断;接着引入Pearson冲突距离改进D-S证据融合模型,实现诊断结果的融合决策;最后,经实际算例分析,诊断精确率达到92.65%。结果表明,所建模型能有效解决数据不平衡对诊断结果的影响,提高故障诊断精度。

天然气净化厂废水处理过程中溶解性有机物的变化

溶解性有机物(DOM)是废水达标排放标准的重要考虑因素,综合分析废水中DOM的分子组成是对其高效去除的前提。以某天然气净化厂废水为研究对象,采用傅里叶变换离子回旋共振质谱法(FT-ICR MS)和三维荧光光谱(3D-EEMs)从分子层面深入分析氧化过程中DOM的荧光性质、分子组成、质荷比、分子转化。EEM结果表明,废水中主要以类腐殖质物质为主,其次为富里酸类物质。O_(3)/H_(2)O_(2)氧化降低了类腐殖质物质的荧光强度,但DOM降解受限于臭氧与富含电子有机物的反应特性;而O_(3)/H_(2)O_(2)-Fenton联合氧化能大幅降低总荧光强度,有效去除类腐殖质。FT-ICR MS结果表明,O_(3)/H_(2)O_(2)氧化去除了部分CHO类、CHON类DOM,但对CHOS类、CHONS类DOM的去除效果欠佳。多环芳烃和高度不饱和的化合物被臭氧降解为脂肪族类化合物,增加了CHO类DOM含氧量。O_(3)/H_(2)O_(2)-Fenton氧化对CHOS类、CHONS类DOM具有较好的去除效果,去除了大部分多酚化合物,生成具有含氧量更低和饱和度更高的DOM。同时,联合氧化极大地缓解了超滤膜污染,去除了大部分可逆污染和不可逆污染。

含钙添加剂处理下不同秸秆腐解产物可溶性有机质三维荧光特征变化

秸秆是优质的有机资源,研究含钙添加剂种类及添加量对不同秸秆腐解产物可溶性有机物(DOM)组成性质差异,可为秸秆高效腐熟利用提供理论依据和技术参考。以花生秸秆和水稻秸秆为供试物料,通过添加不同含钙添加剂草酸钙(CaC_(2)O_(4))和氢氧化钙[Ca(OH)_(2)]及不同添加量(4%、 8%),进行秸秆腐解试验。测定腐解产物养分含量,并利用三维荧光光谱(3DEEM)技术和平行因子方法(PARAFAC)探究秸秆腐解产物DOM的化学组成变化特征。结果表明:(1)总体上,草酸钙处理的秸秆腐解物总碳含量显著大于氢氧化钙处理;高量添加剂处理的秸秆腐解产物总碳含量小于低量处理;花生秸秆腐解产物的总氮、总磷和总钾高于水稻秸秆腐解产物。(2)通过3DEEM-PARAFAC方法分析腐解产物DOM组成,共识别出类胡敏酸(C1)、类胡敏酸(C2)和类色氨酸(C3)三种荧光组分;不同添加剂类型、添加量和不同秸秆类型对腐解产物DOM荧光组分的影响较为复杂,没有明显规律,但是总体上氢氧化钙处理的秸秆腐解产物DOM的C1和C2组分比例大于草酸钙处理,而草酸钙处理的秸秆腐解产物DOM的C3组分比例显著高于氢氧化钙处理;秸秆腐解产物DOM中组分C1、 C2与组分C3呈显著负相关;组分C2含量与总碳含量呈显著负相关。(3)氢氧化钙处理的秸秆腐解产物DOM的腐殖化指数(HIX)明显高于草酸钙处理,而草酸钙处理的秸秆腐解产物DOM生物源指数(BIX)明显高于氢氧化钙处理;高量草酸钙处理秸秆腐解产物DOM主要来自于微生物的转化,而其他处理DOM来自于微生物转化和陆生植物;不同添加量处理下秸秆腐解产物DOM的荧光指数没有明显变化规律;花生秸秆腐解产物DOM的HIX、 BIX和荧光指数(McKnight index)均高于水稻秸秆;秸秆腐解产物DOM中McKnight和HIX呈显著负相关,和BIX间呈极显著正相关,而秸秆腐解产物DOM中BIX和总碳含量呈显著正相关。上述结果表明,氢氧化钙可以促进秸秆腐解以及腐解产物的腐殖化,其中高量氢氧化钙处理的花生秸秆效果较好。

溶解性有机质与铅、砷相互作用研究

为研究天然水体中有机质与砷(As)、铅(Pb)相互作用,文章以标准溶解性有机质(标准DOM)为研究对象,利用光谱、超高分辨率质谱分析、平行因子分析法等方法进行分析。结果表明:(1)与类富里酸和腐殖质相比,类蛋白质酪氨酸类与As、Pb表现出更高结合能力。(2)超高分辨率质谱检测结果显示,重金属能够改变标准DOM原有特性,使得有机质发生转变,如氨基糖类组分减少,类单宁组分增加,CHO相对丰度减少,其他杂原子相对丰度增加。(3)DOM-As显示紫外特征参数a254和荧光特征参数HIX具有强正相关性,通过超高分辨质谱仪获得的氨基糖组分、CHO与紫外特征参数a254、a260、a280、荧光特征参数HIX均具有正相关性,荧光组分C1和质谱获得的不饱和烃类组分具有正相关性。研究结果可为定量评估水体中有机质-重金属相互作用机理提供理论支撑,从而减少重金属等各种污染物的环境行为。

强制对流对高压套管油介质中乙炔分子传质过程的影响

为优化对高压套管进行油中溶解气体分析时的取样质量,提升分析结果的代表性和准确性,提出一种对高压套管中的绝缘油施加强制对流的方法,通过向绝缘油施加速度场促进油中溶解气体的传质过程,进而改善油中溶解气体分析的取样质量。从仿真计算和实验验证2个方面对绝缘油中溶解乙炔气体传质过程进行研究。首先分析无强制对流情况下气体的传质过程,并测量气体从故障源到取样口的时间;然后分析在强制对流情况下气体的传质过程并测量了传质时间,在此基础上讨论气体传质时间缩短的原因;最后探究不同强制对流动作周期对传质过程影响的程度。研究成果能够为高压套管在线监测装置的研发提供参考。

极端气象条件下基于深度学习网络特征的变压器故障预测

根据极端气象条件下变压器产生故障时的环境参数,结合变压器故障预测中常用的油中溶解气体的含量,提出一种基于深度学习网络的故障预测方法。针对已有的变压器故障诊断方法泛化能力弱、时效性低、精度低等缺点,引入极端气象参数,并通过对多组数据序列进行时因分析,提取数据随着时间的变化关系;其次,设计一种新型的神经网络,将油气参数与极端气象参数的时间特征融合,并通过深度学习网络进行故障分类与预测。仿真实验结果表明,相比于其他传统故障预测方法,所提出的极端气象条件下基于深度学习网络的变压器故障预测方法准确率有显著提高。

水环境溶解性有机质溯源与表征技术研究进展

水体中的溶解性有机质(DOM)来源广泛,成分复杂,可参与水中重金属迁移转化和生物地球化学循环过程,采用相应技术手段识别水体DOM来源,实现对DOM组分和性质的表征,对理解其生态环境效应具有指示意义。简要介绍了水环境中DOM的组成、特点及当前的研究热点,重点总结归纳了紫外-可见吸收光谱、三维荧光光谱、稳定同位素、生物标志物以及傅里叶变换离子回旋共振质谱等技术方法在水环境DOM溯源与表征中的应用特点、重要表征参数、影响因素和使用局限性。结果表明:紫外-可见吸收光谱和三维荧光光谱均有操作便捷、分析速度快、不破坏样品等优点,但二者对DOM表征的侧重点不同;稳定同位素技术重点关注DOM中的碳、氮等元素同位素组成及含量,生物标志物可记录DOM分子结构的信息,而傅里叶变换离子回旋共振质谱则是从分子级别对DOM进行表征。以上各技术对DOM的研究均有广阔的应用前景,但是由于DOM成分和组成元素的复杂性以及每种技术本身的局限性,多种技术的联合使用已成为水体DOM表征与解析的发展趋势。在此基础上阐述了多技术联用条件、目标和优点,归纳了现有研究中基于多技术联用的水环境DOM研究进展及研究案例,最后展望了DOM溯源与表征的未来发展方向。