Electromagnetic Field Analysis and Shielding Method of Underground Variable Frequency Power Cable

The transmission and radiation of underground variable frequency electromagnetic waves will seriously interfere with the operation of the power cable and its surrounding environment. At present, the test methods for power cables basically require the impedance of the test system to match the characteristic impedance of the cable. The defect is that the process of designing and making the impedance matching impedance network is relatively complex and requires high manufacturing accuracy. In order to solve these problems, this paper puts forward the electromagnetic field fast detection formula and electromagnetic field shielding method of underground variable frequency power cable. The research method of this paper is the principle of shielding electromagnetic field materials and the suppression principle of shielding layer for electromagnetic coupling. The function of the two principles is to study the reflection, absorption, and multiple reflection of electromagnetic waves and to study the cut-off frequency of the nonmagnetic shielding layer. These two principles guide the experiment. In this paper, the measurement formula of the shielding performance of mismatched cables is derived through experiments. The results show that the error of the measurement formula is no more than 8 dB. Then, through the experiment of restraining the interference of magnetic materials on the electromagnetic field, it is concluded that the magnetic field shielding performance can reach 20 dB. Then, through the performance test of electromagnetic field shielding materials, the shielding efficiency of metal fiber antiradiation materials is the largest, and the average efficiency reaches 76.4 dB.

Cable Temperature Alarm Threshold Setting Method Based on Convolutional Neural Network

Power cable is used more and more in the power network, and its significance to the safety and stability of the power network is increasingly prominent. Especially in the urban power grid, the high voltage cable is related to the normal production and life of the city. Because of the particularity of the laying environment, it is very difficult to find and eliminate the fault points once the cable faults occur, which seriously affects the reliability of the power grid. Currently, 25% of cable faults are caused by elevated cable temperature, so it is important to set the cable temperature alarm threshold accurately. In this paper, a method of setting temperature alarm threshold using convolutional neural network is proposed. Experiments show that this method is 60% more accurate than other methods.

Online Life Forecasting Method and State Assessment Architecture of Power Cable Based on Recurrent Neural Network and Internet of Things

For the purpose of increasing the accuracy of power cable life forecasting and status assessment, improving its life cycle management process, this paper proposes a power cable online life forecasting method and status assessment system based on recurrent neural network and Internet of Things (IoTs). Power cable electrical insulation online monitoring system is established on the first place. Then, recurrent neural network and fuzzy analytical hierarchy process are used in the IoTs based power cable online status assessment architecture to proceed life forecasting and status assessment process. Lastly, example analysis is presented to verify the effectiveness and superiority of the methodology introduced in this paper. It is shown that artificial intelligence and IoTs will also have broad development and application prospect when combined with power cable life cycle management.

NEURAL NETWORK INFORMATION-MEASURING SYSTEM IN TASKS OF RESOURCE PREDICTION

It was established that methods based on artificial neural networks (HC) find the most widespread in predicting thermal processes in power cable networks. Analysis of influence of various functions of HC activation on forecast error of thermoflux processes in power cable networks was carried out. It is established that the minimum error of thermal processes prediction in power cable networks is HC with function of logsig activation in hidden layer and pureline in output layer.

CAD FOR SOLVING EDUCATIONAL RESEARCH PROBLEMS WHEN DESIGNING MODERN HIGH AND EXTRA HIGH VOLTAGE CABLE LINES

The development of teaching and research version of the computer aided design of cable lines of high and extra-high voltage is at the final stage. For TR CAD CL, software has been developed that allows solving design and research problems for a power cable for a voltage of 35-500 kV with XLPE insulation. The development of the documentary subsystem TR CAD CL, which fully meets the regulatory requirements, has been completed.

Control of EMI in High-Technology Nano Fab by Exploitation Power Transmission Method with Ideal Permutation

There are many high-power electrical cables around and within semiconductor foundries. These cables are the source of extremely low-frequency (ELF < 300 Hz) magnetic fields that affect the tools which operate by the function of electronic beams. Miss operation (MO) happens because the ELF magnetic fields induce beam shift during the measurement or process for cutting-edge chips below 40 nm. We present the optimal permutation of power transmission lines to reduce electromagnetic influence in high-technology nano fabs. In this study, the magnetic field was reduced using a mirror array power cable system, and simulation results predicted the best permutations to decrease the electromagnetic interference (EMI) value to below 0.4 mG in a working space without any shielding. Furthermore, this innovative method will lower the cost of high-technology nano fabs, especially for the 28 nm process. The motivation behind this paper is to find the ideal permutation of power transmission lines with a three-phase, four-cable framework to decrease the EMI in high-technology nano fabs. In this study, the electromagnetic interference was diminished using the ideal-permutation methodology without investing or using additional energy, labor, or apparatus. Moreover, this advanced methodology will help increase the effectiveness and reduce the costs of nano fabs. The mathematical and experimental results of the study are presented with analysis.

THE DISTRIBUTION OF MAGNETIC AND THERMAL FIELDS, POWER LOSSES IN ELECTROMAGNETIC SHIELD OF UNDERGROUND TWO-CIRCUIT CABLE LINE

In the article, the magnetic and thermal field distributions generated by underground two-circuit extra-high voltage power cable line in the environment, particularly near the cables and flat aluminum shield, which is located at a different distance from the cables and has different thicknesses, are analyzed. The unique features of the magnetic field and temperature distributions inside the shield are computed and studied. For the cases under consideration, the Joule losses in the external shield do not exceed 3% of the losses in the cables. The primary electromagnetic characteristics are compared for the aluminum shield (shielding efficiency is 1,94) and the shield with lower conductivity (shielding efficiency is equal to 1,2). As shown, the thicker shield helps to increase the ampacity of the cable line owing to lower heating. The actual operating current of the cable line under consideration depends on the distance of the shield from the cables owing to the relation between their maximum temperature and this distance. Ref. 15, fig. 7, table.

Evolution of Temperature Field around Underground Power Cable for Static and Cyclic Heating

Power transmission covering long-distances has shifted from overhead high voltage cables to underground power cable systems due to numerous failures under severe weather conditions and electromagnetic pollution. The underground power cable systems are limited by the melting point of the insulator around the conductor, which depends on the surrounding soils’ heat transfer capacity or the thermal conductivity. In the past, numerical and theoretical studies have been conducted based on the mechanistic heat and mass transfer model. However, limited experimental evidence has been provided. Therefore, in this study, we performed a series of experiments for static and cyclic thermal loads with a cylindrical heater embedded in the sand. The results suggest thermal charging of the surrounding dry sand and natural convection within the wet sand. A comparison of heat transfer for dry, unsaturated and fully saturated sand is presented with graphs and colour maps which provide valuable information and insight of heat and mass transfer around an underground power cable. Furthermore, the measurements of thermal conductivity against density, moisture and temperature are presented showing positive nonlinear dependence.