China’s 10-year progress in DC gas-insulated equipment: From basic research to industry perspective

The construction of the future energy structure of China under the 2050 carbon-neutral vision requires compact direct current (DC) gas-insulation equipment as important nodes and solutions to support electric power transmission and distribution of long-distance and large-capacity. This paper reviews China's 10-year progress in DC gas-insulated equipment. Important progresses in basic research and industry perspective are presented, with related scientific issues and technical bottlenecks being discussed. The progress in DC gas-insulated equipment worldwide (Europe, Japan, America) is also reported briefly

Optimal decisions in reducing loss rate of returnable transport items

International audienceReturnable transport items (RTI) have been commonly used due to their advantages in reducing packaging waste and improving supply chain sustainability. However, RTI loss will result in a mismatch between the products flow and the RTI supply, which will affect operational continuity. This paper studies a RTI supply chain consisting of a single manufacturer and a single retailer, assuming that the retailer can reduce RTI loss by investing in staff training. We first develop an inventory model to minimize the total cost of the system. Then we analyze the optimal decision of the closed-loop supply chain of RTI. We compare the case where the retailer invests in reducing RTI loss and the case where the retailer does not. The results show that the supply chain will be more efficient if the retailer invests in reducing RTI loss, and the total cost of the system will be reduced. However, the retailer will invest only when its cost decreases. Thereby, we consider side payments as an available incentive to stimulate the retailer to invest. Moreover, we build an asymmetric Nash bargaining model considering investment cost sharing to coordinate the RTI supply chain. We compare the total optimal cost of the manufacturer and the retailer. The results show that the system can be coordinated, and the optimal total costs of both the manufacturer and the retailer are reduced.<br/

Optimal decisions in reducing loss rate of returnable transport items

International audienceReturnable transport items (RTI) have been commonly used due to their advantages in reducing packaging waste and improving supply chain sustainability. However, RTI loss will result in a mismatch between the products flow and the RTI supply, which will affect operational continuity. This paper studies a RTI supply chain consisting of a single manufacturer and a single retailer, assuming that the retailer can reduce RTI loss by investing in staff training. We first develop an inventory model to minimize the total cost of the system. Then we analyze the optimal decision of the closed-loop supply chain of RTI. We compare the case where the retailer invests in reducing RTI loss and the case where the retailer does not. The results show that the supply chain will be more efficient if the retailer invests in reducing RTI loss, and the total cost of the system will be reduced. However, the retailer will invest only when its cost decreases. Thereby, we consider side payments as an available incentive to stimulate the retailer to invest. Moreover, we build an asymmetric Nash bargaining model considering investment cost sharing to coordinate the RTI supply chain. We compare the total optimal cost of the manufacturer and the retailer. The results show that the system can be coordinated, and the optimal total costs of both the manufacturer and the retailer are reduced.<br/

Moisture Prediction of Transformer Oil-Immersed Polymer Insulation by Applying a Support Vector Machine Combined with a Genetic Algorithm

The support vector machine (SVM) combined with the genetic algorithm (GA) has been utilized for the fault diagnosis of transformers since its high accuracy. In addition to the fault diagnosis, the condition assessment of transformer oil-immersed insulation conveys the crucial engineering significance as well. However, the approaches for getting GA-SVM used to the moisture prediction of oil-immersed insulation have been rarely reported. In view of this issue, this paper pioneers the application of GA-SVM and frequency domain spectroscopy (FDS) to realize the moisture prediction of transformer oil-immersed insulation. In the present work, a method of constructing a GA-SVM multi-classifier for moisture diagnosis based on the fitting analysis model is firstly reported. Then, the feasibility and reliability of the reported method are proved by employing the laboratory and field test experiments. The experimental results indicate that the reported prediction model might be serviced as a potential tool for the moisture prediction of transformer oil-immersed polymer insulation

Analysis of low‐frequency polarisation behaviour for oil‐paper insulation using logarithmic‐derivative spectroscopy

Abstract The low‐frequency polarisation information of oil‐paper insulation could be easily obscured by the conductance effect, and the contained polarisation information thus can not be readily extracted from the frequency domain spectroscopy (FDS). Given this issue, an alternative idea is reported to extract the low‐frequency polarisation information by using logarithmic‐derivative spectroscopy (LDS). The present findings proved that the parameters extracted by using the LDS can be applied for studying the low‐frequency polarisation behaviour under the moisture effect. In that respect, the novelty of this work is in the exploration of the LDS as a potential tool to extract feature parameters for analyzing the low‐frequency polarisation information of transformer oil‐paper insulation

Numerical Studies on the Performance of the PCM Mesh-Finned Heat Sink Base on Thermal-Flow Multiphysics Coupling Simulation

Operating temperature is an important parameter of thyristors to ensure the stable operation of power electronic devices. Thermal management technology is of great significance for improving the reliability of thyristors. In this study, the performance of a phase change material (PCM) mesh-finned heat sink is investigated for the thermal management of thyristors. A multi-physical coupling model of the PCM mesh-finned heat sink is established to analyze the effects of different power losses, air velocities, heights of fins, and thickness of PCM on the thermal performance of the PCM heat sink. The influence of thermal and flow fields on PCM is considered in this model. Furthermore, the heat sink design is optimized to improve the thermal performance based on the calculation results of thermal network parameters. The results show that the power losses, the air velocity, the height of fins, and the thickness of PCM significantly affect the protection ability of the PCM heat sink. After optimizing the heat sink, the PCM heat sink provides 80 s protection time and 100 s recovery time. The PCM mesh-finned heat sink demonstrated good potential for the thermal management of thyristors

A Modified Aging Kinetics Model for Aging Condition Prediction of Transformer Polymer Insulation by Employing the Frequency Domain Spectroscopy

The aging kinetics model is of great interest to scholars since it is capable of describing the variation law between the degree of polymerization (DP) and the aging duration of transformer polymer (cellulose) insulation. However, it is difficult to determine the moisture content inside the transformer polymer insulation without destroying it, so that the model parameters cannot be confirmed. Such limitation greatly restricts its application. It is interesting to note that as long as the moisture content of the transformer polymer insulation could be characterized (replaced) by a certain feature parameter, the above issue will be solved naturally. The existing researches indicate that the Frequency Domain Spectroscopy (FDS) is sensitive to moisture. Consequently, the feature parameter that could characterize the moisture inside transformer polymer insulation (extracted from the FDS curve) can be used to report a modified aging kinetics model, which could perform the aging condition prediction of transformer polymer insulation under various test conditions, including aging duration, aging temperature, and initial moisture. In that respect, the average relative error of prediction results of prepared samples is equal to 7.41%, which reveals that the reported model might be serviced as a potential tool for the aging condition prediction of transformer polymer insulation