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Dynamic thermal rating assessment of oil-immersed power transformers for multiple operating conditions

High Voltage 2024年第1期9卷 195-205页

作者： Chen Zhang Xuzhu Dong Jiangjun Ruan Yongqing Deng School of Electrical Engineering and Automation Wuhan UniversityWuhanHubeiChina

In this article,the dynamic thermal rating assessment method of oil-immersed power transformer with multiple operating conditions is proposed,considering the constraints of hot spot temperature(HST),top oil temperature,losses of life and the maximum allowable current of on-load tap changer(OLTC)or bushing,which can determine the dynamic load curves under different operating conditions and give the most sensitive constraints to limit the dynamic load *** improve the accuracy of HST estimation,the temperature estimation model is also improved and the thermal parameters are optimised using the HST measured by optical ***,several application examples are studied for transformers in different *** results show that the normal cyclic dynamic transformer rating(DTR)is mainly limited by the losses of life when the ambient temperature is high,and the average load factor can be increased to 0.82 with a maximum load capacity of *** main limiting factor of short-term DTR is the OLTC or bushing current constraint,and the average load factor can be increased to *** maximum load capacity of the transformer under both operating conditions is 23%and 50%higher than its rated load capacity,indicating that the transformer still has a large load potential available.

关键词： load thermal power

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Experimental study on ice monitoring method for 10 kV transmission line with tangent tower in alpine landform

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High Voltage 2024年第1期9卷 182-194页

作者： Lin Yang Zhiqiang Chen Yanpeng Hao Xinhao Lin Lei Yu Yue Li Zhiyong Yuan Licheng Li School of Electric Power South China University of TechnologyGuangzhouChina Electrical Power Research Institute China Southern Power GridGuangzhouChina Electric Power Research Institute of Guizhou Power grid Co.Ltd. GuizhouChina

Ice monitoring methods were applied for 110 kV and above transmission lines with tangent ***,the change in the vertical span is not considered,and a significant difference lies in the tower-conductor structure of 10 kV transmission *** this reason,a proposal is made about the ice monitoring method for the 10 kV transmission line with tangent tower in alpine landform,which includes the ice monitoring system based on pressure measurement and corresponding equivalent ice thickness calculating *** methods calculate the vertical span under different height difference coefficients.A finite element simulation model and a simulated ice load experiment system are established based on real conductors and *** and simulations under four simulated terrains are conducted within 2.5–20 mm ice thickness *** comparison is made between this method and the method without considering the change in vertical *** results show that the two methods are consistent and the relative errors are lower than�4%in simulation and�10%in experiment when the height difference coefficient is *** it is not 0,the relative errors of this method fall between t0.38%and t6.78%in simulation and−6.40%to t6.60%in experiment,while the relative errors of the method without considering the change in vertical span ranges between−11.13%and−20.23%in simulation and−11.65%to−23.20%in experiment.

关键词： methods tangent method

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Contamination degree prediction of insulator surface based on exploratory factor analysis-least square support vector machine combined model

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High Voltage 2021年第2期6卷 264-277页

作者： Jiaxiang Sun Hongru Zhang Qingquan Li Hongshun Liu Xinbo Lu Kaining Hou Shandong Provincial Key Laboratory of uHV Transmission Technology and Equipment School of Electrical EngineeringShandong UniversityJinanChina

This study presents a combined model based on the exploratory factor analysis(EFA)and the least square support vector machine(LSSVM)to predict the contamination degree of insulator ***,EFA method is utilised to reduce numerous influence factor variables of the insulator contamination into a few factor variables,which could decrease the complexity of the ***,regarding the above factor variables as new input variables,LSSVM model is established to predict the insulator contamination *** order to obtain the optimal predictive value,the non-dominated sorting genetic algorithm II is applied on the optimization of LSSVM model *** proposed EFA-LSSVM combined model is compared with the models of LSSVM,back propa-gation neural network,and multiple linear regression on the model *** indicate that the EFA-LSSVM combined model in this study effectively overcomes the shortcomings of the other three models mentioned above in computational time,pre-diction accuracy and generalization ***,the feasibility of the proposed model in predicting contamination degree of insulator surface is verified by adopting the radar map of the evaluation indexes of model performance.

关键词： sorting insulator prediction

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Transient electric field of the combined insulation structure under positive periodic square waveform voltage:Analytical analysis and application

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High Voltage 2022年第5期7卷 877-889页

作者： Teng Wen Xiang Cui Xuebao Li Sijia Liu Zhibin Zhao state Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijingChina

The working voltage of the high-voltage high-power electronic devices is the positive periodic square waveform(PPSW)voltage,which is much different from the conventional AC or DC *** the composite insulation structure of devices,it is important to analyse the transient electric field under the PPSW ***,the existing investigations are often conducted under the electrostatic field due to the high frequency of the PPSW ***,the transient characteristics of the electric field are *** obtain some qualitative conclusions,this paper focusses on the theoretical analysis of the transient characteristics of electric field for the composite insulation structure under the PPSW ***,the formula of the electric field intensity and the interfacial charge density are derived ***,the influence of the cycle and the duty cycle on the transient characteristics are ***,the maximum of the electric field intensity and the interfacial charge density in the positive square waveform steady-state are discussed in ***,the engineering calculation methods for obtaining these maximum values are also ***,an actual model is employed to testify the validity of the analytical *** work is significant for the numerical calculation of the transient electric field of composite insulation structure under the PPSW voltage in engineering.

关键词： composite insulation field

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