Cable Lines Research Articles

Dynamic Simulation of Underground Cable Laying for Digital Three-Dimensional Transmission Lines

In light of the issues associated with the laying process of transmission line cables, including concealed security risks and contact collisions between pulleys and cables, which primarily stem from reliance on drawings, this paper introduces a simulation methodology for the cable laying construction process utilizing Building Information Modeling (BIM) technology. Initially, two-dimensional DWG graphic data are employed to develop a model of the target equipment and construction environment using BIM software (Solid works 2020). Subsequently, the cable is accurately modeled by applying ADAMS virtual prototype technology, the bushing force connection method, and the macro command language. This allows for the construction of a three-dimensional real cable laying system for transmission lines, enabling the simulation of the dynamic cable laying process in the field. Subsequently, an error analysis is conducted to compare the axial tension and laying speed of the cable with theoretical calculation values. The study then proceeds to analyze tension fluctuations during the cable laying process and assess the load-bearing capacity of the pulleys, thus facilitating effective control of the construction process and enhancing safety measures. The findings indicate that the proposed method can accurately and efficiently simulate the on-site cable laying construction process, with numerical errors maintained below 5%, thereby validating the integrity of the model. Furthermore, the traction overload safety protection amplification coefficient is determined to be α = 1.5. It is highlighted that the bearing capacity of the block must exceed 60% of the load carried by the conductor at constant speed. This research provides a theoretical foundation for addressing safety hazards in cable laying engineering and holds certain engineering value.

Identification of global main cable line shape parameters of suspension bridges based on local 3D point cloud

Main cable line shape measurement and parameter identification are a critical task in the construction monitoring and service maintenance of suspension bridges. 3D LiDAR scanning can simultaneously obtain the coordinates of multiple points on the target, offering high accuracy and efficiency. As a result, it is expected to be used in applications requiring rapid, large-scale measurements, such as main cable line shape measurement for suspension bridges. However, due to the large span and tall main towers of suspension bridges, the LiDAR field of view often encounters obstructions, making it difficult to obtain high-quality point clouds for the entire bridge. The collected point clouds are typically unevenly distributed and of poor quality. Therefore, LiDAR is used to monitor the local cable line shape. This paper proposes an innovative non-uniform sampling method that adjusts the sampling density based on the main cable’s rate of change. Additionally, the Random Sample Consensus (RANSAC) algorithm, the ordinary least squares, and center-of-mass calibration are applied to identify and optimize the geometric parameters of the cross-section point cloud of the main cable. Given the strong design prior information available during suspension bridge construction, Bayesian theory is applied to predict and adjust the global line shape of the main cable. The study shows that using LiDAR for cable point cloud measurement enables rapid acquisition of high-precision point cloud data, significantly enhancing data collection efficiency. The method proposed in this paper offers advantages such as highly automated, low risk, low cost, and sustainability, making it suitable for green monitoring throughout the entire main cable construction process.

Evaluation of heat mode parameters of 10 kV cable lines in different operation conditions

This paper presents a methodology for calculating thermal modes of 10 kV cable lines (CL) for different types of insulation and operating conditions, and analyzes using approximation functions of the obtained results. Regression models of dependences of estimated service life (Tsl) of CL insulation on loading factor (kzg) in different operating conditions of CL with the following types of insulation: paper-impregnated insulation (PI), insulation made of polyvinyl chloride plasticate (PVC) and insulation made of polyethylene (PE) have been developed. The results of the study can be used to clarify the parameters of CLs when selecting their cross sections. Application of the developed methodology for estimation of temperature parameters and regulation of CL operation modes will allow to reduce the number of emergency situations connected with thermal breakdowns. OBJECTIVE. To carry out research, analysis and calculations of temperature parameters of 10 kV CLs for different kzg and methods of laying in climatic conditions of the Republic of Tatarstan. METHODS. Methods of calculation of thermal parameters of 10 kV CLs in different modes and their service life, methods of statistical data processing in the Excel program complex and methods of function approximation are used. RESULTS. As a result of researches the temperature parameters of 10 kV CLs with different types of insulation for different operating conditions have been obtained, regression models of dependences of the calculated Tsl of insulation on kzg have been constructed, allowing to estimate the thermal characteristics of CLs. CONCLUSION. The results of the conducted researches and calculations can be recommended for estimation and selection of parameters of operating modes of 10 kV CL at the stages of operation and design of power supply systems.

Research on Position Detection Technology for Cross-Linked Polyethylene-Insulated Cable Production Lines

Research on Position Detection Technology for Cross-Linked Polyethylene-Insulated Cable Production Lines

A fault localization method for power communication fiber optic cable lines based on brillouin frequency shift features

A fault localization method for power communication fiber optic cable lines based on brillouin frequency shift features

Investigation of the Application of an Automated Monitoring System for Detecting Transmission Cable Deterioration in Nigeria: A Case Study of Transmission Cable Lines between Offa and Oshogbo

Investigation of the Application of an Automated Monitoring System for Detecting Transmission Cable Deterioration in Nigeria: A Case Study of Transmission Cable Lines between Offa and Oshogbo

The short-circuit analysis in multi-parallel single cable lines

The short-circuit analysis in multi-parallel single cable lines

The Choice of a Construction Arrangement for Cable Lines with a Voltage of 10 kV According to the Criterion of the Minimum Expected Cost

The article considers the issue of choosing the optimal construction arrangement of cable lines with a voltage of 10 (20, 35) kV with cross-linked polyethylene insulation. The options for using three or single-core cables laid in a triangle or in a plane are analyzed. The methodological basis of the work is the principle of minimizing the expected costs, taking into account both capital investments and annual costs, including losses of electrical energy in cables. Within the framework of the study, a nomogram of economic intervals was scheduled, which makes it possible to determine the optimal cable core sections and boundary conditions for the use of threeand single-core cables, depending on the calculated current load. It is shown that with the existing nomenclature of three-core cables with a maximum core cross-section up to 630 mm2, single-core cables can be economically feasible only with a core cross-section of 800 mm2 and above. It has been discovered that the expected costs for laying single-core cables in the plane with two-way grounding of screens always turn out to be higher than when laying a triangle. This effect is due to an increase in both capital costs and power losses in cable screens. To increase the efficiency of cable lines, it is proposed to expand the range of three-core cables by including cables with the maximum possible core cross-section. This will make possible to increase the range of current loads in which the use of three-core cables will be economically justifiable. The results presented in the article can be used in the design of new cable lines, the analysis of the effectiveness of existing ones, as well as in the modernization and reconstruction of urban medium-voltage cable networks.

Structural Analysis of Latticed Steel Transmission Towers Subjected to Nondeterministic Wind Loads

Lattice steel towers are commonly used to support overhead power transmission lines. However, the dynamic behavior of these structures is often overlooked in current design practices. Given that many accidents involving these towers occur even at basic wind speeds lower than those specified in the project, it is likely that dynamic actions play a significant role in these failures. This study proposes a method to accurately simulate the interaction between transmission line cables and towers under non-deterministic wind loads to assess displacements and forces in the steel towers. The study examines a transmission line system consisting of towers, conductors, shield wires, and insulators, featuring a central suspension tower of 32.86 m in height, flanked by two end towers with 450 m spans. Finite element modeling was developed to account for the dynamic characteristics of the wind. Wind loads were modeled as a random process based on their statistical properties. The results revealed significant differences in displacement and force values when comparing the results provided by static and dynamic analyses. The structural design of a base leg member indicated potential failure at higher wind velocities, highlighting the importance of considering the wind dynamic effects in the design.

Assessment of the Structural Response of Transmission Lines Steel Towers when Subjected to Nondeterministic Wind Loadings

The lattice steel towers have been widely used as supports for power transmission lines. In the current project practise, the structure’s dynamic behaviour usually is not considered. However, the main loading to consider in structural analysis of these steel towers is produced by wind loadings. Considering that many accidents associated to this kind of structural system occur even for wind velocities below that specified in project, it’s possible that most of these accidents have been produced by dynamic actions. This way, this investigation proposes an analysis methodology that can accurately simulate the coupled behaviour between the transmission line cables and the towers, when subjected to wind nondeterministic loadings, having in mind the assessment of the displacements and forces maximum values that occur in the steel towers. In this work, the investigated transmission line system, including the steel towers, conductors and shield wire types, presents two spans of 450 m associated to a main suspension tower in the centre with total height of 32.86 and other two towers at the ends. The conclusions of this research work pointed ou to relevant quantitative differences associated to the structural response, when was calculated based on a static linear analysis and compared to the results determined based on a geometric nonlinear and nondeterministic dynamic analysis.

Study of balancing methods for parallel cable transmission lines

Cables are of vital importance for the transmission and distribution of electricity within the power grid. However, as the demand for electricity continues to grow, the transmission capacity of a single high-voltage cable is no longer sufficient to meet the required standards. It is therefore imperative to increase the transmission capacity of cables. The deployment of parallel cable transmission represents the most effective strategy for enhancing transmission capacity. However, due to the complex electromagnetic coupling relationship between cables, there is a possibility of current imbalance between cable lines in the same phase, which will have an adverse effect on the normal operation of power equipment and pose a significant threat to the security of the power system. In light of the aforementioned considerations, this paper primarily investigates the mitigation of parallel cable line imbalance. Initially, it examines the parallel cable line current imbalance factors through a theoretical lens, encompassing cable impedance and electromagnetic coupling arrangement. Subsequently, it assesses the efficacy of two proposed methods for reducing the imbalance degree of the parallel cable, namely, the adjustable reactor in series and the addition of a magnetic ring device. Furthermore, finite element simulation software is employed to simulate the two methods and verify their efficacy. Ultimately, a parallel cable plus magnetic ring test is conducted to verify the effectiveness of the magnetic ring.

The Impact of the Shunt Reactor(s) Location on Offshore Wind Farm Power Export System on Zero-Missing Phenomenon and Switching Overvoltages—The Case of a Polish Power System

The observed development of offshore wind farms has resulted in an increasing presence of long extra-high voltage cables, with lengths ranging from 10 to 200 km. These cable lines are compensated for by a shunt reactor(s). The transient states that accompany switching operations, in this type of line, cause a number of challenges. There are slightly different and more dangerous phenomena than in classic uncompensated lines. One such phenomenon is the zero-missing phenomenon. The most effective methods for mitigating these phenomena are still under investigation and comparison to identify the optimal countermeasures. Applying a single minimization countermeasure often leads to avoiding one phenomenon (e.g., zero-missing phenomenon) while enhancing another (e.g., switching overvoltages). This can challenge designers, as they must consider the trade-offs between these competing objectives. The added value of this article is an analysis of the impact of the compensation level and its distribution (shunt reactor(s) location) in the offshore wind farm power export systems on zero-missing phenomenon and switching overvoltages. These analyses are supported by simulation cases mapping the case of the Polish power system. The results of the presented analysis are very important in light of a dynamic development of offshore wind farms and may be utilized by designers of power export systems, and can mitigate the significant risks occurring in such systems during energization cable lines.

Internet Devices and Internet Access Among Migrant and Seasonal Farmworkers, North Carolina, 2023.

Migrant and seasonal farmworkers work in rural areas where internet access may be limited. We assessed internet access, cost of access, and devices available to farmworkers through a statewide survey in North Carolina. During the 2023 agricultural season, we surveyed 1034 migrant and seasonal farmworkers during routine outreach visits in partnership with community health workers employed by 8 community health centers or by nonprofit health service agencies serving farmworkers in North Carolina. We surveyed participants aged ≥18 years by using time-venue sampling and surveyed up to 5 farmworkers at migrant housing locations. We weighted participants to the total population of farmworkers living in surveyed housing and calculated frequencies and percentages of internet access, internet speed, internet cost, available internet devices, and awareness and use of the Affordable Connectivity Program-a program that was run from 2021 through May 31, 2024, by the Federal Communications Commission to make internet access more affordable in the United States. We assessed predictors of internet access and ability to use online videos by using regression models. Participants were predominantly Spanish-speaking men who lived in housing provided by farm owners. Among participants, 9.8% had internet connections with a cable or digital subscriber line, and 23.5% did not have consistent internet access. Most participants used cellular network internet (84.9%) and mobile phone devices (93.9%). Even among farmworkers who lived in their housing year-round, few had heard of (34.4%), applied to (4.8%), or used (2.0%) the Affordable Connectivity Program. Interventions are needed to increase internet access and digital inclusion for migrant and seasonal farmworkers in North Carolina. Development of state and county broadband infrastructure should consider farmworker housing.

Electromagnetic-thermal multi-physics coupling simulation of cable joints: considering contact resistance and typical defects

As the “artery” of the urban power grid, high-voltage cables and their operating status are directly related to grid safety. Cable joint is a weak part of cable line prone to defects, leading to cable failure and jeopardizing the power supply reliability. This study constructs a three-dimensional electromagnetic-thermal multi-physics coupling model of cable joint for the analysis of contact resistance and typical insulation defects. Using an equivalent conductivity model, the thermal loss and temperature distribution of the joint were investigated under different contact coefficients. Subsequently, models for air-gap defect and water tree defect in cable joints were established to simulate the temperature and electric field distribution under these conditions. The simulation results indicate that, at an ambient temperature of 25°C, the contact resistance of a 110 kV high-voltage AC cable joint significantly increases the loss density, raising the joint temperature much higher than cable body, while not altering the temperature gradient distribution. Small air-gap has minimal impact on the temperature distribution of joint insulation but causes significant electric field distortion up to 8 kV/mm. Water tree defect considerably affects both temperature and electric field, causing a 20°C temperature rise and a 30 kV/mm electric field distortion. This research reveals the strong influence of contact resistance and water tree defect on cable joints, quantifying the resulting hazards like loss increase, temperature rise and electric field distortion.

Engineering method for quantifying the coupling effect of transmission tower-line system under strong winds

For transmission tower-line (TL) systems, the coupling effect between line cables and towers under strong winds is significant. This paper presents a method to quantify the coupling effect. Assuming that effective separation of line cables and towers is attainable, this work transforms the coupling effect into the transferred load from the line cable to the target tower, the coupling participation mass of the line cable, and the additional damping. The effective separation conditions are defined through an optimization method minimizing the residual errors of the wind-induced response and dynamic characteristics between the separated bodies and the TL system. A typical TL system is considered and analyzed for its structural dynamic characteristics and wind-induced response. Particularly, the quantities associated with the coupling effect of the TL system are estimated. It reveals that the transferred dynamic load component parallel to the line cable which is overlooked in current codes is significant and highly sensitive to the separation boundary conditions of line cables. Furthermore, the coupling participation mass of the conductor is more prominent than that of the ground wire. The proposed method is feasible for quantifying the TL coupling effect and incorporating it into the wind-induced response analysis of transmission line structures.

Fault Section Identification for Hybrid Transmission Lines Considering the Weak-Feed Characteristics of Floating Photovoltaic Power Plant Inverters

The overhead line (OHL)–cable hybrid transmission line, which connects floating photovoltaic (PV) power plants, needs to be considered regarding whether to block reclosing operations or not. However, due to the weak-feed characteristics of PV inverters, existing methods are difficult to apply in this scenario. This paper proposes a criterion for fault section identification in the transmission lines of floating PV power plants based on traveling wave power and the zero-sequence impedance angle. Firstly, the fault current characteristics of photovoltaic inverters under dual-vector control are analyzed, and the applicability of the sequence component impedance directional criterion in this scenario is discussed. Then, the transmission, refraction, and reflection processes of traveling waves in OHL–cable hybrid lines are analyzed, and a traveling wave energy criterion is designed to determine the fault section. Finally, based on the scope of application of the zero-sequence impedance angle and traveling wave energy criterion, a fault section identification method for the hybrid lines of floating PV power plants is established. A deployment method for the proposed method, based on feeder terminal units (FTUs) at the connection points between the OHL and cable is proposed. This method identifies fault sections through traveling waves and zero-sequence impedance angles, which are unaffected by PV week feed characteristics, can be applied to all the AC fault types, and do not rely on multi-terminal synchronous sampling. The proposed method is verified on a 1MW PV system built in the PSCAD.

Research on Active Power Loss Distribution of Components in Magnetic Coupling Wired Drill Pipe

Abstract The magnetic coupling wired drill pipe achieves high-speed information transmission by installing cable at the rod and embedding magnetic couplers at the joints. However, significant energy attenuation in these connected wired drill pipes necessitates the addition of relay circuit compensation every few hundred meters, increasing system complexity and cost. The equivalent circuit of magnetic coupling wired drill pipe can be regarded as a series connection of a coaxial cable line, high-frequency transformer, and terminal load. Exploring better wired drill pipe parameters to distribute signal power across different frequencies will optimize power at the terminal load and improve relay distance. This research establishes a mathematical model for active power distribution in magnetic coupling wired drill pipes based on circuit analysis. The model’s accuracy is validated through circuit simulation and numerical analysis. Reducing signal energy attenuation in the cable and coupler is achieved by increasing the coil coupling coefficient, reducing the coil resistance, and altering the characteristic impedance of the coaxial cable. This research provides a theoretical tool for analysing active power loss distribution of components in wired drill pipe.

Influence of Cable and Overhead Lines Parameters on the of Transient Recovery Voltages of High-voltage Circuit Breakers

Influence of Cable and Overhead Lines Parameters on the of Transient Recovery Voltages of High-voltage Circuit Breakers

Calculation of Maximum Permissible Load of Underground Power Cables–Numerical Approach for Systems with Stabilized Backfill

The maximum permissible load of underground power cables (known in U.S. engineering as “ampacity”) is a function of many parameters, in particular, the thermal resistivity of the native soil. If this resistivity is relatively high, thermal/stabilized backfill is applied, i.e., another material is placed around the cables, providing favourable conditions for heat transfer to the environment. It has a positive impact on the reliability of the power supply and favours the operational durability of the cables. In design practice, however, there is a difficult task—correct determination of the ampacity of the cable line depending on the thermal parameters and the geometry of the backfill. Therefore, this article presents the results of a numerical analysis to determine the ampacity of cable lines in which stabilized backfill is used. A new mathematical relationship is proposed that allows the correction of the ampacity of cable lines depending on their cross-section as well as the thermal and geometric parameters of the cable surroundings.

Effect of SF6 circuit breaker parameters on switching overvoltages evaluated based on nominal modes of converter transformers

In this work, we set out to investigate the influence of operating currents of SF6 circuit breakers on the magnitude of overvoltages during switching of converter transformers. The experience of electrical equipment operation is analyzed with a focus on the problems associated with the natural aging of insulation, overloads, and switching overvoltages. The methods of equipment diagnostics were used. According to statistical data, at present, about 37% of short circuits between phases and 42% of single-phase earth faults in electrical networks of industrial enterprises occur due to switching overvoltages. The conducted tests showed that the overvoltages emerging during switching by SF6 circuit breakers of converter transformers, which are used in aluminum smelters, may reach a three-fold rated voltage of the network. This threatens the insulation of transformer windings, cable line, and the switch itself. It was established that an increase in operating currents of an LF2 circuit breaker, not exceeding 27.8% of the rated current of the switch, leads to an increase in overvoltages during switching of converter transformers. At a further increase in the operating currents of the circuit breaker by more than 27.8% of the rated current of the circuit breaker, a sharp decrease in the value of switching overvoltages is observed. Therefore, the operating currents of SF6 circuit breakers were established to affect the level of switching overvoltages of converter transformers. The underlying mechanism of this phenomenon was determined, which should be taken into account when improving the reliability of power supply of converter transformers and, consequently, the reliability of aluminum production. The feasibly of resistive-capacitive dampers as the most effective means for limiting overvoltages during switching of converter transformers was confirmed.