To investigate the fouling characteristics of the composite insulator surface under the salt fog environment,the FXBW-110/120-2 composite insulator was taken as the research object.Based on the field-induced charge me...To investigate the fouling characteristics of the composite insulator surface under the salt fog environment,the FXBW-110/120-2 composite insulator was taken as the research object.Based on the field-induced charge mechanism,the multi-physical field coupling software COMSOL was used to numerically simulate the fouling characteristics,explored the calculation method of ESDD,and demonstrated its rationality.Based on this method,the pollution characteristics of the composite insulator under the pollution fog environment were studied,and the influence of wind speed,droplet size,and voltage type on the pollution characteristics of the composite insulator was analyzed.The results showed that:with the increase in wind speed,the amount of accumulated pollution of insulator increases in the range of droplet size,and the relationship between wind speed and accumulated pollution is approximately linear;at the same wind speed,the amount of accumulated pollution increases with the increase of droplet size under the action of DC voltage;when there is no voltage,the amount of dirt on the upper surface of the insulator is more than that on the lower surface,while it is the opposite under DC voltage.展开更多
LS-SVM （least squares support vector machines） are a class of kemel machines emphasizing on primal-dual aspects in a constrained optimization framework. LS-SVMs aim at extending methodologies typical of classical su...LS-SVM （least squares support vector machines） are a class of kemel machines emphasizing on primal-dual aspects in a constrained optimization framework. LS-SVMs aim at extending methodologies typical of classical support vector machines for problems beyond classification and regression. This paper describes a methodology that was developed for the prediction of the critical flashover voltage of polluted insulators by using a LS-SVM. The methodology uses as input variables characteristics of the insulator such as diameter, height, creepage distance, form factor and equivalent salt deposit density. The estimation offlashover performance of polluted insulators is based on field experience and laboratory tests are invaluable as they significantly reduce the time and labour involved in insulators design and selection. The majority of the variables to be predicted are dependent upon several independent variables. The results from this work are useful to predict the contamination severity, critical flashover voltage as a function of contamination severity, arc length, and especially to predict the flashover voltage. The validity of the approach was examined by testing several insulators with different geometries. Moreover, the performance of the proposed approach with other intelligence method based on ANN （artificial neural networks） is compared. It can be concluded that the LS-SVM approach has better generalization ability that assist the measurement and monitoring of contamination severity, flashover voltage and leakage current.展开更多
Equal Salt Deposit Density (ESDD) is a main factor to classify contamination severity and draw pollution distribution map. The precise ESDD forecasting plays an important role in the safety, economy and reliability of...Equal Salt Deposit Density (ESDD) is a main factor to classify contamination severity and draw pollution distribution map. The precise ESDD forecasting plays an important role in the safety, economy and reliability of power system. To cope with the problems existing in the ESDD predicting by multivariate linear regression (MLR), back propagation (BP) neural network and least squares support vector machines (LSSVM), a nonlinear combination forecasting model based on wavelet neural network (WNN) for ESDD is proposed. The model is a WNN with three layers, whose input layer has three neurons and output layer has one neuron, namely, regarding the ESDD forecasting results of MLR, BP and LSSVM as the inputs of the model and the observed value as the output. In the interest of better reflection of the influence of each single forecasting model on ESDD and increase of the accuracy of ESDD prediction, Morlet wavelet is used to con-struct WNN, error backpropagation algorithm is adopted to train the network and genetic algorithm is used to determine the initials of the parameters. Simulation results show that the accuracy of the proposed combina-tion ESDD forecasting model is higher than that of any single model and that of traditional linear combina-tion forecasting (LCF) model. The model provides a new feasible way to increase the accuracy of pollution distribution map of power network.展开更多
Stability and reliability of distribution system are able to be improved by many protective devices including insulators, relay and surge arrester (SA). SA is used for protection of lightning and switching surge in Pr...Stability and reliability of distribution system are able to be improved by many protective devices including insulators, relay and surge arrester (SA). SA is used for protection of lightning and switching surge in Provincial Electricity Au-thority (PEA). This paper presents an experimental investigation of 22 kV distribution SA electrical performances under pollution conditions according to IEC 60507. The experimental results of leakage currents more than 6 mA at Equiva-lent Salt Deposit Density (ESDD) 0.6 mg/cm2 at nominal voltage. These data will be useful to be guideline for solving problems and reducing power loss from leakage current on the surface of SAs as a result of surface dirt and pollution. Moreover, it will be useful to select or design suitable SAs for using in places with salt conditions, high rainfall, high wind speeds and high humidity.展开更多
硅橡胶复合绝缘子的憎水性迁移特性使其污层具有憎水性,污层中盐分的溶出和流失过程都变得复杂。绝缘子的污闪特性与表面污层受潮时溶解并参与导电的盐分紧密相关,对有效附盐密度(effective equivalent salt deposit density,EESDD,标...硅橡胶复合绝缘子的憎水性迁移特性使其污层具有憎水性,污层中盐分的溶出和流失过程都变得复杂。绝缘子的污闪特性与表面污层受潮时溶解并参与导电的盐分紧密相关,对有效附盐密度(effective equivalent salt deposit density,EESDD,标记为ρEESDD)进行了更深入的研究。用溶出盐密减去流失盐密来表征有效附盐密度,通过试验研究了憎水性迁移时间和绝缘子表面灰密对ρEESDD的影响,以及自然积污绝缘子受潮过程中的ρEESDD。结果发现:绝缘子受潮时ρEESDD先增大后减小,最终趋于稳定;污层憎水性导致受潮时有效附盐密度的变化过程持续时间更长;灰密的增大会导致有效附盐密度的最大值更晚出现;自然积污绝缘子ρEESDD的最大值仅为污层总等值盐密的15%,说明较低的等值盐密也是复合绝缘子污闪电压高的原因之一。展开更多
利用自建的自然污秽试验站,对自然条件下带直流电压运行2个积污季节的复合绝缘子的积污特点进行了试验研究,分析了直流绝缘子的伞裙表面积污规律、降水对积污(等值附盐密度(equivalent salt deposit density,ESDD)和不溶性污秽物质密度(...利用自建的自然污秽试验站,对自然条件下带直流电压运行2个积污季节的复合绝缘子的积污特点进行了试验研究,分析了直流绝缘子的伞裙表面积污规律、降水对积污(等值附盐密度(equivalent salt deposit density,ESDD)和不溶性污秽物质密度(non-soluble deposit density,NSDD))的影响,表面污秽不均匀度、表面灰盐比、ESDD和NSDD的直交比等。研究表明:并不是所有降水都会对绝缘子表面污秽产生明显的清洗效果;降水量和雨强均为清洗效率的重要影响因素;复合绝缘子最大污秽度出现在夏季多雨季节来临前。建议直流外绝缘设计中充分考虑这些积污特点。展开更多
用有效盐密(EESDD)法表征输变电设备污秽程度能够弥补等值盐密(ESDD)法与污闪电压相关性不大的缺陷,对输变电设备进行更好的污秽评估。为此介绍了新的有效盐密的测量设备,并通过一系列人工污秽试验研究了探头尺寸、用水量以及盐成分对...用有效盐密(EESDD)法表征输变电设备污秽程度能够弥补等值盐密(ESDD)法与污闪电压相关性不大的缺陷,对输变电设备进行更好的污秽评估。为此介绍了新的有效盐密的测量设备,并通过一系列人工污秽试验研究了探头尺寸、用水量以及盐成分对有效盐密测量的影响,最终选择外半径为5.13 mm,内半径为1.00 mm的探头,并选择0.02 m L/cm^2的用水量。最后将有效盐密的测量应用于实际运行的输变电设备中,对不同地区运行绝缘子表面的等值盐密和有效盐密进行了比较,用等值盐密与有效盐密的比值探讨了不同地区的污秽特征,为有效盐密的进一步推广提供了依据。结果表明,有效盐密是一个很好的表征污秽度的参数,是等值盐密很好的补充。展开更多
文摘To investigate the fouling characteristics of the composite insulator surface under the salt fog environment,the FXBW-110/120-2 composite insulator was taken as the research object.Based on the field-induced charge mechanism,the multi-physical field coupling software COMSOL was used to numerically simulate the fouling characteristics,explored the calculation method of ESDD,and demonstrated its rationality.Based on this method,the pollution characteristics of the composite insulator under the pollution fog environment were studied,and the influence of wind speed,droplet size,and voltage type on the pollution characteristics of the composite insulator was analyzed.The results showed that:with the increase in wind speed,the amount of accumulated pollution of insulator increases in the range of droplet size,and the relationship between wind speed and accumulated pollution is approximately linear;at the same wind speed,the amount of accumulated pollution increases with the increase of droplet size under the action of DC voltage;when there is no voltage,the amount of dirt on the upper surface of the insulator is more than that on the lower surface,while it is the opposite under DC voltage.
文摘LS-SVM （least squares support vector machines） are a class of kemel machines emphasizing on primal-dual aspects in a constrained optimization framework. LS-SVMs aim at extending methodologies typical of classical support vector machines for problems beyond classification and regression. This paper describes a methodology that was developed for the prediction of the critical flashover voltage of polluted insulators by using a LS-SVM. The methodology uses as input variables characteristics of the insulator such as diameter, height, creepage distance, form factor and equivalent salt deposit density. The estimation offlashover performance of polluted insulators is based on field experience and laboratory tests are invaluable as they significantly reduce the time and labour involved in insulators design and selection. The majority of the variables to be predicted are dependent upon several independent variables. The results from this work are useful to predict the contamination severity, critical flashover voltage as a function of contamination severity, arc length, and especially to predict the flashover voltage. The validity of the approach was examined by testing several insulators with different geometries. Moreover, the performance of the proposed approach with other intelligence method based on ANN （artificial neural networks） is compared. It can be concluded that the LS-SVM approach has better generalization ability that assist the measurement and monitoring of contamination severity, flashover voltage and leakage current.
文摘Equal Salt Deposit Density (ESDD) is a main factor to classify contamination severity and draw pollution distribution map. The precise ESDD forecasting plays an important role in the safety, economy and reliability of power system. To cope with the problems existing in the ESDD predicting by multivariate linear regression (MLR), back propagation (BP) neural network and least squares support vector machines (LSSVM), a nonlinear combination forecasting model based on wavelet neural network (WNN) for ESDD is proposed. The model is a WNN with three layers, whose input layer has three neurons and output layer has one neuron, namely, regarding the ESDD forecasting results of MLR, BP and LSSVM as the inputs of the model and the observed value as the output. In the interest of better reflection of the influence of each single forecasting model on ESDD and increase of the accuracy of ESDD prediction, Morlet wavelet is used to con-struct WNN, error backpropagation algorithm is adopted to train the network and genetic algorithm is used to determine the initials of the parameters. Simulation results show that the accuracy of the proposed combina-tion ESDD forecasting model is higher than that of any single model and that of traditional linear combina-tion forecasting (LCF) model. The model provides a new feasible way to increase the accuracy of pollution distribution map of power network.
文摘Stability and reliability of distribution system are able to be improved by many protective devices including insulators, relay and surge arrester (SA). SA is used for protection of lightning and switching surge in Provincial Electricity Au-thority (PEA). This paper presents an experimental investigation of 22 kV distribution SA electrical performances under pollution conditions according to IEC 60507. The experimental results of leakage currents more than 6 mA at Equiva-lent Salt Deposit Density (ESDD) 0.6 mg/cm2 at nominal voltage. These data will be useful to be guideline for solving problems and reducing power loss from leakage current on the surface of SAs as a result of surface dirt and pollution. Moreover, it will be useful to select or design suitable SAs for using in places with salt conditions, high rainfall, high wind speeds and high humidity.
文摘硅橡胶复合绝缘子的憎水性迁移特性使其污层具有憎水性,污层中盐分的溶出和流失过程都变得复杂。绝缘子的污闪特性与表面污层受潮时溶解并参与导电的盐分紧密相关,对有效附盐密度(effective equivalent salt deposit density,EESDD,标记为ρEESDD)进行了更深入的研究。用溶出盐密减去流失盐密来表征有效附盐密度,通过试验研究了憎水性迁移时间和绝缘子表面灰密对ρEESDD的影响,以及自然积污绝缘子受潮过程中的ρEESDD。结果发现:绝缘子受潮时ρEESDD先增大后减小,最终趋于稳定;污层憎水性导致受潮时有效附盐密度的变化过程持续时间更长;灰密的增大会导致有效附盐密度的最大值更晚出现;自然积污绝缘子ρEESDD的最大值仅为污层总等值盐密的15%,说明较低的等值盐密也是复合绝缘子污闪电压高的原因之一。
文摘用有效盐密(EESDD)法表征输变电设备污秽程度能够弥补等值盐密(ESDD)法与污闪电压相关性不大的缺陷,对输变电设备进行更好的污秽评估。为此介绍了新的有效盐密的测量设备,并通过一系列人工污秽试验研究了探头尺寸、用水量以及盐成分对有效盐密测量的影响,最终选择外半径为5.13 mm,内半径为1.00 mm的探头,并选择0.02 m L/cm^2的用水量。最后将有效盐密的测量应用于实际运行的输变电设备中,对不同地区运行绝缘子表面的等值盐密和有效盐密进行了比较,用等值盐密与有效盐密的比值探讨了不同地区的污秽特征,为有效盐密的进一步推广提供了依据。结果表明,有效盐密是一个很好的表征污秽度的参数,是等值盐密很好的补充。
