Shape optimisation of basin insulator for DC gas insulated switchgear/gas insulated transmission lines based on artificial bee colony algorithm

The surface charge accumulation on the basin insulator is a particular problem in high-voltage direct current(HVDC)gas insulated switchgears(GIS)and gas insulated trans-mission lines(GIL),which restricts the development and application of extra/ultra high-voltage(EHV/UHV)technology.The surface charge distribution and anti-flashover performance are closely related to the insulator shape.To obtain the optimal basin insulator,a shape optimisation model based on artificial bee colony algorithm was established,and the minimisation objective functions based on capacitive(initial)electric field distribution and resistive(steady-state)electric field distribution were respectively constructed.The optimisation results of the two objective functions were calculated,and the electric field and charge distribution on the surface of the insulator before and after optimisation were evaluated and compared using the simulation model.The results indicated that the optimisation based on the capacitive electric field can significantly inhibit the surface charge accumulation,and the optimised insulator can significantly reduce the surface normal electric field and make the distribution of the tangential electric field more uniform,and the maximum tangential electric field can be reduced by 10%;the optimisation based on resistive electric field can achieve similar results,but requires more computational resources.Based on the results,the‘anti-charge’basin insulator structure suitable for the DC field was given.

Editorial:The development of eco-friendly insulating gases and SF6-free equipment for‘net-zero’

Developing low-carbon gas insulated transmission and distribution equipment is essential to achieve the‘carbon peak,carbon neutralisation’or‘net-zero’in the power industry.Scholars have carried out various research on the eco-friendly insulating gas(such as C4F7N,C5F10O)and next-generation SF6-free equipment to gradually reduce the utilisation of strong greenhouse gas SF6.

Highly robust spatiotemporal wavefront prediction with a mixed graph neural network in adaptive optics

The time-delay problem,which is introduced by the response time of hardware for correction,is a critical and nonignorable problem of adaptive optics(AO)systems.It will result in significant wavefront correction errors while turbulence changes severely or system responses slowly.Predictive AO is proposed to alleviate the time-delay problem for more accurate and stable corrections in the real time-varying atmosphere.However,the existing prediction approaches either lack the ability to extract non-linear temporal features,or overlook the authenticity of spatial features during prediction,leading to poor robustness in generalization.Here,we propose a mixed graph neural network(MGNN)for spatiotemporal wavefront prediction.The MGNN introduces the Zernike polynomial and takes its inherent covariance matrix as physical constraints.It takes advantage of conventional convolutional layers and graph convolutional layers for temporal feature catch and spatial feature analysis,respectively.In particular,the graph constraints from the covariance matrix and the weight learning of the transformation matrix promote the establishment of a realistic internal spatial pattern from limited data.Furthermore,its prediction accuracy and robustness to varying unknown turbulences,including the generalization from simulation to experiment,are all discussed and verified.In experimental verification,the MGNN trained with simulated data can achieve an approximate effect of that trained with real turbulence.By comparing it with two conventional methods,the demonstrated performance of the proposed method is superior to the conventional AO in terms of root mean square error(RMS).With the prediction of the MGNN,the mean and standard deviation of RMS in the conventional AO are reduced by 54.2%and 58.6%at most,respectively.The stable prediction performance makes it suitable for wavefront predictive correction in astronomical observation,laser communication,and microscopic imaging.

SF_(6) decomposition behaviour under partial discharge of typical insulation defects in gas-solid insulated valve-side bushing of converter transformer

In this paper we investigated SF_(6) decomposition behaviour of typical insulation defects in gas-solid insulated converter transformer valve-side bushing under partial discharge(PD).Additionally,we compared the results with that of gas insulated switchgear(GIS).The results indicated that SF_(6) decomposition behaviour varies with the insulation defects type.For metal protrusion defects,the proportion ranking of CO_(2) and SO_(2) can be related to whether the needle tip is wrapped with epoxy resin-impregnated paper(ERIP).The proportion of carbon-containing products is much higher under contamination defect than under other defects.Moreover,the proportion of carbon-containing components is higher under flashover condition than under PD condition and is accompanied by the appearance of H2S and CS_(2).However,the yield of SO_(2)F_(2) is always low.Compared to negative DC voltages,positive DC voltages have a higher proportion of carboncontaining components,mainly in the form of more CO_(2) and less SOF_(2).Compared to the PD decomposition behaviour of typical insulation defects in GIS,when PD involves ERIP,the proportion of carbon-containing products,especially CO_(2),is significant higher,while the proportion of sulphur containing products,especially SO_(2)F_(2),is lower.

一种基于深度学习的光学合成孔径成像系统图像复原方法

光学合成孔径成像系统中光学传递函数的频率响应下降,会不可避免地导致成像模糊,因此通常需要借助维纳滤波或盲解卷积算法来实现图像复原,最终获得清晰的高分辨率图像。提出一种基于U型卷积神经网络的深度学习框架,通过MATLAB软件构建数据集,以对网络进行训练,并将所训练的U型网络与盲解卷积算法的图像复原效果进行对比。数值仿真结果表明,在弱噪声条件下,U型网络在基于光学合成孔径成像系统的图像复原中展现出较强的复原能力以及一定的泛化能力和通用性,能够实现图像的快速盲复原,因而具有潜在的应用前景。

Modulation of red-light emission from carbon quantum dots in acid-based environment and the detection of chromium(Ⅲ)ions

ⅢIn this study,the carbon quantum dots,which can emit sharp red light(R-CQDs)under optical excitation,were synthesized via simple heat treatment of wine lees.The features of the photoluminescence(PL)emission from R-CQDs in solutions with different p H values and with metal ions were examined.The intensity of the PL emission from R-CQDs depends sensitively on the p H values of the solutions with the R-CQDs.Interestingly,the p H-response of the PL intensity is reversible and can be enhanced linearly in the p H value range from 4 to 12,indicating that the R-CQDs can be applied for the p H sensor.Furthermore,the quench of the PL emission from R-CQDs can be observed when adding chromium(Ⅲ)ions into the solution with R-CQDs.This effect can be utilized for selective and quick detection of chromium(Ⅲ)ions in solutions simply via the standard PL measurement.The interesting and important findings from this work can be applied to explore more practical applications of the CQDs prepared cheaply and easily.

SF_(6)decomposition and insulation condition monitoring of GIE:A review

The statistics of the Conference International des Grands Reseaux Electriques(CIGRE)indicate that the operational reliability of SF6 gas‐insulated equipment(GIE)is very high;however,the failure rate of the GIE in operation is much higher than that of the IEC standard,and the fault occurs frequently in the GIE at a high voltage level.The reason is due to the complex and strong on‐site electromagnetic interference environment and fully enclosed structure of GIE.The key method and technology for effective on‐line monitoring and fault diagnosis of GIE are still lacking.Given the partial strong electromagnetic energy and high temperature induced by early latent insulation faults in the equipment,SF6 gas insulation presents different degrees of decomposition.The decomposition products mainly include SO_(2)F_(2),SOF_(2),SO_(2),HF,and H2S.The decomposition characteristics of SF6 are closely related to the property of insulation faults.At present,this area is attracting attention from the power industry and research institutes.This study summarises the current research on SF_(6)decomposition component analysis(DCA).The content mainly includes the latest progress of SF_(6)decomposition characteristics and mechanism under fault conditions,and fault diagnosis methods based on decomposition components.

Dynamics of surface charge and electric field distributions on basin-type insulator in GIS/GIL due to voltage polarity reversal

In this study,a simulation model of surface charge accumulation has been established.The model considers three accumulation ways,i.e.electrical conduction within the gas,through insulator volume and along the insulator surface.The generation,diffusion,drift and recombination of charge carriers are also taken into account.Based on it,the influence of polarity reversal,reversal time on surface charge and electric field distribution on a basin-type insulator are studied.The polarity of the surface charges and the direction of the electric field change after the voltage polarity reversal.When the preload voltage is equal to reversal voltage,the surface charge and the electric field distributions at steady state before and after voltage polarity reversal are all the same with opposite sign,and not affected by the reversal time.However,the time to reach the steady state varies with different reversal time.The steady-state surface charge and electric field increased with the rise of reversal voltage.The transient normal and tangential electric field would not exceed the value of the steady state,which means voltage polarity reversal has no additional influence on insulation performance.This research can provide guidance to the design and manufacture of DC GIS/GIL.

Arc decomposition behavior of C_(4)F_(7)N/Air gas mixture and biosafety evaluation of its by-products

At present,reports on the arc interruption and decomposition behavior of a C_(4)F_(7)N/air gas mixture especially the biosafety of its by-products are limited.Herein,a 57%C_(4)F_(7)N/43%air gas mixture was employed as an arc-quenching medium to conduct 200 breaking tests on a load switch(630 A/24 kV).The arc interruption and decomposition behavior of the gas mixture were evaluated,and the biosafety of the decomposition products was assessed based on an acute inhalation toxicity test.It was found that the average arcing time of the 200 breakings was about 10.1 ms and that breakings were basically completed at the zero-crossing of the second or third current half-cycle.The gas mixture after breaking decomposed dramatically(the C_(4)F_(7)N content decreased by 75.6%),generating a large number of gaseous by-products(CO,CF_(4),C_(2)F_(6),C_(3)F_(8),CF_(3)CN,C_(4)F_(8),CO_(2),C_(4)F_(10)N_(2),C_(3)F_(6),C_(2)N_(2),etc.)as well as solid by-products(carbon particles).The lethal concentration of 50%(LC50,4 h)of C_(4)F_(7)N/air after 200 breakings was 31 ppm(male mice)and 34 ppm(female mice),respectively,and the toxicity was classified as Grade 1.In general,C_(4)F_(7)N has an arc interruption capability,albeit weaker than that of SF_(6)under the same conditions.After breaking,the C_(4)F_(7)N gas mixture has a relatively high acute inhalation toxicity,and relevant safety protection measures for research or operation personnel are strictly needed.

Weighted local polynomial estimations of a non-parametric function with censoring indicators missing at random and their applications

In this paper,we consider the weighted local polynomial calibration estimation and imputation estimation of a non-parametric function when the data are right censored and the censoring indicators are missing at random,and establish the asymptotic normality of these estimators.As their applications,we derive the weighted local linear calibration estimators and imputation estimations of the conditional distribution function,the conditional density function and the conditional quantile function,and investigate the asymptotic normality of these estimators.Finally,the simulation studies are conducted to illustrate the finite sample performance of the estimators.

Correction of measurement errors on sediment concentration sampled by stirring-sampling method from traditional runoff collection tanks

Stirring-sampling method is a widely adopted method to measure sediment concentrations in collection tanks of runoff plots,but with high systematic measurement errors.This research aimed to advance an approach for building correction equations to remove measurement errors in designed sediment concentration range.Experimental data of sediment measurement from the stirring-sampling method,with four representative soils,under the designed sediment concentrations(1,2,5,8,10,20,50,80,100,200,500,800,and 1000 kg/m^(3))were used to demonstrate the correction methodological process.Two correction methods(step-wise correction and universal correction)were suggested for the trial in this study based on the distribution of measurement errors.In the step-wise correction,the correction equations were made with a series of linear functions without intercept for the low concentration group(0-20 kg/m^(3)),a series of linear functions with intercept for the high(20-200 kg/m^(3))and extremely high(200-1000 kg/m^(3))concentration groups,consecutively.The correction equations were a series of power functions in the universal correction.For the step-wise correction,most of the relative errors of correction sediment concentrations were smaller than 15%and 10%under high and extremely high concentration groups,but the corrected accuracy was not good in the sediment concentration of 1,2,5 kg/m^(3)with the corrected relative errors of 0.20%-206.07%.For the universal correction,the corrected relative errors(0.19%-31.81%)of the four soils were low under the condition of extremely high sediment concentrations,but other corrected accuracies weren’t good with the corrected relative errors of 0.68%-1154.71%.The corrected accuracy of step-wise correction is higher than that of the universal correction,but the universal correction is more convenient.These results indicated that the correction equations could efficiently revise the measurement errors of the tested soils and that this method can be generalized to other soil types and was meaningful in monitoring soil erosion.

Intelligent perception of power grid condition

In face of increasingly severe challenges in energy develop-ment,a secure,stable,green,and sustainable Energy Internet has become a development tendency,as a major technological innovation that promotes the transformation of the world's power and energy systems.The essence of Energy Internet is the deep integration of energy flow and information flow,which is the in‐depth perception and control of the energy network situation using advanced information technology.Electric energy equipment and its grid structure are the core of Energy Internet.Energy Internet needs to integrate all the information that can be collected to perceive the situation of power equipment and the entire grid deeply and accurately,so as to prevent sudden power outages caused by equipment failure or system instability,and to improve the reliability and economy of the entire Energy Internet.

Review about PD and breakdown induced by conductive particles in an insulating liquid

In insulating liquid,a conductive particle becomes charged through the interaction with a conductor exposed to an applied field.Then,it migrates in the action of both electric field and fluid and causes the enhancement of local field when it is in proximity of the conductor with opposite polarity.The enhancement will lead to partial discharge(PD)and may even ignite full gap breakdown in special cases.This study reviews comprehensive researches relevant to these topics.In the first place,several theoretical methods about how to obtain the charges held by a conductive particle with known potential are introduced,so are experimental methods.Then,forces acting on the charged particle in liquid are classified,and its migration characteristics,as well as influential factors,are described.Subsequently,PD and breakdown mechanisms of liquid initiated by conductive particles are presented.The latter involves two cases:electric-field enhancement when the particle concentration is low and bridging phenomenon when it is high.At last,two important,but frequently ignored factors,i.e.dielectric barrier and oil flow,are highlighted,and the authors’suggestions for future work are put forward.