Underground Lines Research Articles

Lightning Protection of Distribution Power Systems: Arrester Development and Application Over the Years

As the demand for higher quality power increases, the development of more lightning resistant distribution systems is required. This article is an overview of the challenges and opportunities we now face in the lightning protection of electric power distribution systems. Specific topics are lightning protection of underground circuits, overhead circuits, system equipment, and lines of all configurations.

Basement Design for Vibration Reduction of High-Rise Buildings under Metro Operation

Vibration induced by metro operation on the underground line is transmitted to the buildings above the line, which adversely affects on the normal life and work of human in the building. To study this problem, based on the plate-shell vibration theory, a plate-column-plate coupled model is constructed to analyze the influence of plate thickness, plate elastic modulus and column arrangement on the vibration in mechanism firstly. Relying on a practical engineering problem, two models are established, namely a train-track coupled dynamic model and a monolithic track bed-tunnel-soil-building model, loading fastener force from the train-track coupled dynamic model on the monolithic track bed, vibration propagates to high-rise building through soil-building coupling. Field test is conducted to verify the reliability of the numerical model. On the basis, the vibration law of building under different basement floor thicknesses, basement floor material and arrangement of non-permanent columns are studied. Results show that changing the basement design parameters has different effects. The Z vibration level of building floor decreases with the increase of basement floor thickness. Basement floor thickness increases by 0.02 m, the Z vibration level of the floor decreased by 1.4–2.2 dB at most. The decrease of elastic modulus leads to a slight decrease of the Z vibration level of building, the change is less than 1 dB. Without changing the arrangement of basement load-bearing columns, reducing non-permanent structural columns significantly reduces the Z vibration level, with attenuation of up to 5.1 dB.

Seasonal Subsidence and Heave Recorded by Borehole Extensometers in Houston

Seasonal ground movements, particularly subsidence and heave, present a great challenge for the design of roadways, parking lots, underground utility lines, and buried culverts. The US Geological Survey has been operating 13 deep borehole extensometers in Houston, Texas, for land subsidence monitoring since the 1970s and the early 1980s. The half-century extensometer datasets provide direct and continuous measurements of seasonal ground movements in the vertical direction. The Houston global positioning system (GPS) network (HoustonNet) provides independent measures for the timely evaluation of extensometer data. According to this study, shallow expansive soils can induce up to 4 cm (peak-to-trough) seasonal subsidence and heave, and deep sediments can further produce up to 2 cm seasonal subsidence and heave. The latter is primarily caused by the seasonal fluctuations of hydraulic heads in the lower Chicot and upper-Evangeline aquifers, varying considerably over time and space. The results from this study are important for determining potential vertical movement (PVM) for the design of pavements and shallow foundations and for the optimization of groundwater management in the Houston region.

Improving distribution system resilience by undergrounding lines and deploying mobile generators

To improve the resilience of electric distribution systems, this paper proposes a stochastic multi-period mixed-integer linear programming model that determines where to underground new distribution lines and how to coordinate mobile generators in order to serve critical loads during extreme events. The proposed model represents the service restoration process using the linearized DistFlow approximation of the AC power flow equations as well as binary variables for the undergrounding decisions of the lines, the configurations of switches, and the locations of mobile generators during each time period. The model also enforces a radial configuration of the distribution network and considers the transportation times needed to deploy the mobile generators. It is shown that long-term line undergrounding decisions which are cognizant of short-term mobile generator deployments yield superior results relative to undergrounding decisions made without considering mobile generators. Using an extended version of the IEEE 123-bus test system, numerical simulations show that combining the ability to underground distribution lines with the deployment of mobile generators can significantly improve the resilience of the power supply to critical loads. • Resilience can be improved via mobile generators and underground lines. • Stochastic optimization for siting underground lines and operating mobile generators. • Show benefits from jointly considering undergrounding and mobile generator decisions.

Retracted: Design of an Underground Transmission Line Condition Fault Monitoring System for Power Grids Based on Data Analysis Algorithms

Retracted: Design of an Underground Transmission Line Condition Fault Monitoring System for Power Grids Based on Data Analysis Algorithms

Mathematical modeling of road heating system with underground distribution line based on nonlinear ODE model

In regions with heavy snowfall, there has long been a serious problem of great inconvenience and danger to people's lives caused by the snowfall. To tackle this problem, a novel framework for efficient snowmelting should be proposed, which can be useful in the control systems design for the considered road healing systems. In this paper, we propose a road heating system using underground power distribution lines. As a main result, we derive a mathematical model of the system. The nonlinear ordinary differential equation (ODE) model is introduced to describe the spatial and temporal variation of the voltage of the distribution line. The validity of the model is verified by numerical simulations using actual data of solar radiation and PV power generation of Toyama Prefecture, Japan in winter.

«Птицы и ЛЭП» в России: наследие СССР, современные достижения и вопросы

«Птицы и ЛЭП» в России: наследие СССР, современные достижения и вопросы

Development of models of the electromagnetic environment in buildings and urbanized areas

A set of measures and means to control the electromagnetic situation of the environment in the territories of urban development, in buildings and individual premises has been substantiated and developed. The simulation tools show the ability to rationalize the parameters of overhead lines with voltages of 220 kV and below, which will reduce the electromagnetic load in the territories. Modeling the propagation of fields from underground high-voltage lines has established that the values of magnetic fields compared to overhead lines are lower up to 30 times. Models of propagation of electromagnetic fields of very high and ultrahigh frequency were built. Sources of electromagnetic fields of non-production origin in industrial buildings have been investigated. Uncompensated currents in power networks with nonlinear electric consumers generate magnetic fields by induction of 0.35−1.20 μT, which exceeds the maximum permissible levels of operation of computer equipment. Leakage currents on grounded metal structures generate magnetic fields with 1.52−6.75 μT. Simulation of the propagation of electric and magnetic fields of components of personal computers of controlled ranges according to the MPRII standard was carried out. Models of propagation of the magnetic field of industrial frequency around electric motors and generators with their cross sections were built. On the basis of such models, design schemes for placing equipment in production areas are selected or places of safe stay and movement of personnel are selected. The expediency of using shielding to reduce field levels to safe values due to coating surfaces with liquid protective mixtures was shown. Metal-containing composition based on water-dispersion paint makes it possible to reduce the level of magnetic field of industrial frequency by 2.5−2.6 times, electric field by 1.6−1.7 times, electromagnetic field of industrial frequency – by 1.2−1.3 times.

Study of the Effect of External Magnetic Fields on the Parameters of the Electrical Communications Probing System for a Microtunneling Shield

The issues were reviewed in assessing external electromagnetic fields’ effect on the parameters of an electrical power line probing system based on three-component ferroprobes for detecting active underground power cable lines during microtunnel construction using the thrust boring method (by tunneling shield) in densely populated urban areas. A study was conducted on the change in the topology of the energized cable magnetic field located in the external magnetic field area created by operating electrical equipment under the influence of an external electromagnetic field and a tunneling shield with installed magneto-sensitive detectors. Experimental studies of the probing system were made. Options have been proposed for compensating the inductance component of the external magnetic field during tunnel driving in urban development and industrial area conditions.

Insights into the Thermal Performance of Underground High Voltage Electricity Transmission Lines through Thermo-Hydraulic Modelling

In this paper, a flexible numerical framework to provide thermal performance assessment for the underground buried cables, considering different geological and meteorological conditions, has been presented. Underground cables tend to retain the heat produced in the conductor, so complex coupled thermo-hydraulic response of the porous medium surrounding the cables needs to be assessed to prevent cable overheating and the associated reduction in cable capacity for carrying current. Applying a coupled thermo-hydraulic model within the developed numerical framework to conduct a health assessment on a subset of National Grid Electricity Transmission’s underground cables, this study provides novel insights into the thermal behaviour of buried circuits. The results indicate that backfill and surrounding native soil have the dominant effect on the thermal behaviour of cables, while the amount of precipitation and ambient temperature were found to have less impact on cable’s thermal behaviour. The findings strongly infer that the nature of the overloading which is undertaken in practice would have no ongoing negative impact, suggesting that more frequent or longer duration overloading regimes could be tolerated. Overall, this study demonstrates how the developed numerical framework could be harnessed to allow safe rating adjustments of buried transmission circuits.

Particulate air pollution in the Copenhagen metro part 1: Mass concentrations and ventilation

The Copenhagen Metro comprises four lines, the M1, M2, M3 and M4, with 25 subterranean stations and an additional 14 stations above ground, serving ca. 80 million passengers annually. In this study we measure fine particulate matter (PM2.5) and carbon dioxide (CO2) concentrations in stations and in trains across the entire system. In partially underground lines, high PM2.5 concentrations with an average of 109 μg m−3 are found in below-ground stations. The observed correlation between PM2.5 concentration and distance between a station and a tunnel exit is attributed to ventilation via the piston effect. The piston effect via tunnel draught relief shafts was therefore found to be relatively limited. Filter samples of particulate matter are analysed using particle-induced X-ray emission and show an iron content of 88.6 % by mass which is quite different from above-ground particulate matter and consistent with particle production by train wheels, rails and brakes. The average concentration measured at the stations of a recently opened (2019) fully underground M3 closed loop line is 168 μg m−3, further demonstrating that while piston effect-driven ventilation is effective in close proximity to tunnel openings, it is relatively limited via tunnel draught relief shafts. Measurements onboard trains show even higher PM2.5 concentrations and the patterns in CO2 concentrations suggest carriage ventilation by tunnel air. Ventilation via doors during platform stops caused a drop in observed PM (and CO2) at stations, but the system is surprisingly polluted despite its recent construction. CO2 mixing ratios ranged from ambient to around 600 ppm. Measures should be taken to control PM levels using a combination of source control and increased clean air supply of the Copenhagen and other similar metro systems.

PAHs exposure and its association with oxidative stress and neurotransmitter levels in coal miners

Objective: To learn the investigate of polycyclic aromatic hydrocarbons (PAHs) and to explore the association between PAHs exposure and oxidative stress' neurotransmitter levels in coal miners. Methods: A cross-sectional survey was conducted in 652 coal miners (239 in the underground first line group, 280 in the underground auxiliary group and 133 in the surface group) from April to June 2017. The levels of urinary monohydroxy PAHs metabolites (OH-PAHs) , oxidative stress and neurotransmitters in blood were determined. A linear regression model was used to evaluate the correlation between OH-PAHs and oxidative stress' neurotransmitter levels. The mediating role of oxidative stress between urinary OH-PAHs and neurotransmitters change was assessed by mediation analysis. Results: The levels of 2-hydroxynaphthalene (2-NAP) 、2-hydroxy uorene (2-FLU) 、1-hydroxypyrene (1-OHP) in urine OH-PAHs of coal miners in different workplaces were significantly different (H=33.64, 9.63, 26.82, P<0.01, =0.008, <0.01) . The levels of neurotransmitters [5-hydroxytryptamine (5-HT) , norepinephrine (NE) , epinephrine (E) , dopamine (DA) , acetylcholine (Ach) , acetylcholinesterase (AChE) ] and oxidative stress [malondialdehyde (MDA) (F=36.81, 15.58, 79.16, 179.58, 33.48, 67.63, 4.96, P<0.01) ] in the blood of three groups of coal miners were significantly different. After controlling the potential confounding factors, NE content was negatively correlated with 2-FLU level, and AChE activity was also negatively correlated with 1-OHP level (β=-134.99, 95% CI: -250.74~-19.23, P=0.02; β=-0.80, 95%CI: -1.54~-0.05, P=0.036) . Positive correlation was found between Ach content and 9-hydroxyphenanthrene (9-PHE) level, AChE activity was also positively correlated with 2-NAP level and 9-PHE level (β=0.96, 95%CI: 0.26~1.64, P=0.007; β=1.78, 95%CI: 0.75~2.82, P=0.001; β=0.77, 95%CI: 0.07~1.47, P=0.031) . In addition, superoxide dismutase activity was correlated with 1-OHP level and AChE activity (β=0.32, 95%CI: 0.02~0.62, P=0.034; β=-0.23, 95%CI: -0.43~-0.02, P=0.032) . Mediation analysis indicated that 1-OHP level may directly affect AChE activity (P<0.05) . Conclusion: The level of PAHs in underground coal miners is relatively higher, and may lead to changes of neurotransmitter levels. The mediating effect of oxidative stress has not been observed.

Design of an Underground Transmission Line Condition Fault Monitoring System for Power Grids Based on Data Analysis Algorithms

With the continuous expansion of the scale, capacity, and coverage of the modern transmission network, the role of the power system in the national economy is increasingly prominent, and the disconnection of the power system will have a huge impact on society and people’s lives. Due to the long transport distance and wide coverage of transmission lines, natural conditions and human factors have caused great difficulties in line operation and maintenance. How to effectively improve the operation and maintenance of transmission lines to ensure the stability and safety of the power grid has become a common problem for the power industry and scientific researchers to discuss. In recent years, the information society has stepped into the era of big data, and big data has developed rapidly, becoming a hot area favored by academia and industry, and is widely used. Through big data analysis, potential operation rules can be discovered from a large amount of grid information, providing maintenance personnel with corresponding maintenance decision support. Using big data technology for transmission line fault analysis can effectively reduce accident processing time and avoid accident expansion. Therefore, this paper combines the underground transmission line fault of power grid with the fuzzy KNN algorithm model to apply the underground transmission line state intelligent monitoring system and conducts the study of real-time data collection and fault diagnosis analysis of the underground transmission line fault of power grid, and this paper conducts the transmission line fault analysis experiment, which fully confirms the feasibility and effectiveness of the algorithm model proposed in the paper and concludes that the data analysis model proposed in this paper. The proposed data analysis model has good innovation and practical feasibility.

Prediction method and experimental verification of vibration response caused by underground high-speed railways

Aiming at the problem of vibration caused by underground high-speed railways, this paper proposes a vibration prediction method based on the multi-point transfer ratio in the frequency domain. The transmission information of vibration signals from the tunnel to the surface was obtained by an in situ hammer excitation test, and the acceleration response near the vibration source was calculated via high-precision vehicle-track coupling analysis and a finite element model of the tunnel. Then, the superposition operation was carried out in consideration of the position change of the train, and the surface vibration response caused by the underground high-speed railway was finally predicted. An in situ vibration test was carried out near an underground high-speed railway line and the measured data were compared with the predicted data. The results demonstrate that the predicted and measured time domain peaks were similar, and the main vibration frequencies were both located in the range of 30–70 Hz. Moreover, the 1/3-octave spectra were also very similar, and the root mean square error of acceleration and the Z vibration level error were less than 1.9%. The comparison results show that the proposed method can be used to predict the vibration response caused by the operation of underground high-speed railways with high precision.

Surface Settlement during Tunneling: Field Observation Analysis

We address the effect of three groups of factors on supplementary ground surface displacements during tunnel construction. The first group of factors includes the engineering and geological properties of the massif in which the tunneling is conducted; the second group includes the structural features of the designed tunnels and surrounding buildings, and the third group includes the engineering parameters of the tunneling process. The research takes advantage of the geotechnical monitoring data obtained during the construction of underground facilities and the engineering parameters of shield tunneling during construction of single- and double-track Moscow underground lines by using EPB (earth pressure balance)–TBM (tunnel boring machines) in different soils. The dependence of additional displacements, occurring above the designed tunnel, on the TBM pressure, is addressed in detail. The presence of a close interdependence is evidenced by a correlation coefficient equal to 0.77. No dependence of the settlement on the diameter or depth of the designed tunnel, the distance from the tunnel axis to the monitored object, the loading that comes from a building in the affected area, or the boring rate was identified. The consideration of this parameter can be used to predict the soil displacement around the tunnel at construction facilities having similar geological profiles and boring parameters.

1,500 ㎾ 유도발전기를 배전선로에 연결할 때 발생하는 전압강하에 대한 분석

Induction generators, like induction motors, have a disadvantage in that a voltage drop occurs due to a high current during starting. Induction generators are often connected to the ends of distribution lines. When the induction generator is started and connected to the distribution line through the generated transformer, a voltage drop occurs in the distribution line as well as the transformer terminals. When an induction generator is applied to a hydroelectric power plant, it is necessary to accurately consider substations, distribution lines, loads, transformers for generators, and induction generators to know whether the voltage drop allowed by the system is satisfied.BRIn this paper, we analyzed the application of induction generators with accurate data on substations, underground and overhead distribution lines, customer loads, transformers, and generators for power plants currently installed and operating in Korea. As a result of the analysis, the voltage drop was high in the premises of the power plant, but the voltage drop was low in the distribution line, confirming that it is possible to apply the induction generator to the distribution line.

Modelling and Stress Analysis of Shaft Work Subsidence of Underground Power Transmission Line Tunnel

This research presents an analysis of soil subsidence around shaft work under its construction process and drilling tunnel by finite element method (FEM). The study is focused on the underground power transmission tunnel in the Chao Phraya River construction project (Southern Bangkok Station to Suksawat Road, Thailand) of the Metropolitan Electricity Authority. This research aims to provide information for designing shaft work and preventing drilling tunnel problems. The research analyzed the soil subsidence around shaft work with 12 m of inside diameter and 1 m of thickness that located 33 m underground during constructing a tunnel chimney by sinking method. It is assumed that the analyzed horizontal reaction is the net resistance of the lateral earth pressure around the shaft work. This study found that the subsidence of soil around shaft work during the construction and drilling process had the value between 0.80 - 53.30 mm. In the part of the base slab, the soil subsidence value is between 3.40 - 16.00 mm. It can be concluded that the top of shaft work during the construction and drilling process had a soil subsidence value of 53.30 mm with dmax/H ratio of 0.00162.&#x0D; HIGHLIGHTS&#x0D; &#x0D; The Metropolitan Electricity Authority has an underground power transmission tunnel in the Chao Phraya River Construction (Southern Bangkok Station to Suksawat Road, Thailand) project which used to distribute electricity from the source station to the other side of the Chao Phraya River&#x0D; This research studied the behavior of the shaft work in sinking reinforced concrete shaft work and drilling tunnel process by finite element method (FEM) with the Midas Gen 2021 program&#x0D; The analysis results of the maximum soil subsidence around the shaft work wall occurred in the top area (very soft to medium stiff clay layer)&#x0D; &#x0D; GRAPHICAL ABSTRACT

FEM-based Arrhenius modeling of the thermal effects of a heating pipeline and pavements on underground power cables

It is well-known that, in thermal aging management of underground power cables, analytical Arrhenius models can include the thermal effect of a heating pipeline on the lifespan of power cables through a rise in the soil temperature and an appropriate ampacity de-rating factor. However, the thermal effect of a pavement on the lifespan of power cables installed below that pavement cannot be taken into account using any de-rating factor. Accordingly, this paper proposes FEM-based Arrhenius models to analyze the thermal effects of one heating pipeline and several different types of pavements on the thermal lifespan of an underground line of 110 kV consisting of cables with cross-linked polyethylene (XLPE) insulation. Each proposed Arrhenius model is created using both IEC 60287 and IEC TR 62095, as well as combining the traditional Arrhenius model with an appropriate FEM-based steady-state thermal model. An experimental background consisting of the existing thermal aging tests with XLPE insulation is also used. Different pavements are represented by different values of thermal and surface radiation properties, namely: thermal conductivity, solar absorptivity, and thermal emissivity. The pavement surface radiation properties are specified within the frames of the most unfavorable summer conditions, and the most common winter conditions. Moreover, different distances between the 110 kV cables and the heating pipeline are considered. Finally, it is found that: the considered thermal effects can shorten the expected total service lifespan of the 110 kV cables in the area adjacent to the heating pipeline by up to 297.5 h; the pavement surface radiation properties do not affect the consumption of total thermal lifespan; as well as the largest consumption of total thermal lifespan occurs when the 110 kV cables are at the smallest distance from the heating pipeline.

Development of an Intelligent Based Water Pipelines Damage Control System at the Supply Unit of the Federal Polytechnic Offa, Kwara State

Water is the most valuable means of life sustainability because it is a basic need of all households. The incessant water leakage levels in the water supply network on the mini campus, Federal Polytechnic Offa, is one of the most vital issues to address by the work unit on the School campus. Works unit provides services to all departments on campus, covering an area of the landmass of 1050 hectares with a population of staff and students of approximately 13 000. The work unit is in charge of correctional facilities and operation. The sub-service of the work unit on water supply system comprising a network of 1km of water pipes and 1500 litres capacity storage tower across units. The input system volume in the lose of water supply is approximately 56%, from which a significant proportion is about physical losses. This paper focused on intelligent-based leakage control to replace the traditional method used on campus parameters for backtesting tracing when physical damage becomes visible. However, the result of the study revolves around the design and implementation of a prototype system. The study created a management console as an intelligent decision support system. The realism of the study summarizes various operations by developing intelligent reporting software with data warehouse techniques to facilitate underground leak line pipes tracking.

Methods for the implementation of automatic reclosing on combined overhead and underground cable power lines 110-500 kV

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.