Transmission Cables Research Articles

Research on Cable Head Monitoring Technology for Transmission Lines

Buried cables are located in harsh environments with high corrosion, uneven soil acidity and alkalinity, and groundwater immersion, resulting in complex structures. Especially for long-distance 10 kV transmission cables, the path planning is relatively long and cannot be connected at once, requiring a connection at the middle end of the cable. The production of cable joints is generally carried out in the foundation pit or well, with complex processes and manual production throughout the entire process, which cannot avoid manual technical deviations. Therefore, cable line faults mostly occur in the intermediate joints. Due to the uneven distribution of the temperature field caused by the accumulation of the electric field, the heat is transferred outward from the peeling chamfer point, resulting in uneven heating. In addition to the skin effect and proximity effect of current, the accumulation of electric field at the chamfer process point of the main insulation and outer semiconducting layer is intensified, and then the insulation is gradually broken down, causing a short circuit or ground fault. This article first studies the temperature and electric field distribution at the cable joint, and considers installing a small temperature sensor at the middle joint of the cable. The sensor is powered by a small electromagnetic energy coil, which can monitor abnormal temperature and electric field changes at the joint in real-time.

Functional significance of lamellar architecture in marine sponge fibers: Conditions for when splitting a cylindrical tube into an assembly of tubes will decrease its bending stiffness

Numerous ingenious engineering designs and devices have been the product of bio-inspiration. Bone, nacre, and other such stiff structural biological materials (SSBMs) are composites that contain mineral and organic materials interlaid together in layers. In nacre, this lamellar architecture is known to contribute to its fracture toughness, and has been investigated with the goal of discovering new engineering material design principles that can aid the development of synthetic composites that are both strong and tough. The skeletal anchor fibers (spicules) of Euplectella aspergillum (Ea.) also display a lamellar architecture; however, it was recently shown using fracture mechanics experiments and computations that the lamellar structure in them does not significantly contribute to their fracture toughness. An alternate hypothesis—the load carrying capacity (LCC) hypothesis—regarding the lamellar architecture’s functional significance in Ea. spicules is that it enhances the spicule’s strength, rather than its toughness. From an ecology perspective the LCC hypothesis is certainly plausible, since a higher strength would allow the spicules to more firmly anchor Ea. to the sea floor, which would be beneficial to it since it is a filter feeding animal. In this paper we present support for the LCC hypothesis from a solid and structural mechanics perspective, which, compared to the support from ecology, is far harder to identify but equally, if not more, compelling and valid. We found that when the spicule functions in a knotted configuration a reduced bending stiffness benefits its load carrying capacity and that sectioning a cylindrical tube into an assembly of co-axial tubes can reduce the tube’s bending stiffness for a wide class of materials that are consistent with the spicules’ axial symmetry. The mechanics theory developed in this paper has applications beyond providing support for the LCC hypothesis. For example, it makes apparent many design strategies for reducing the bending stiffness of large industrial cables (e.g., undersea optical data transmission cables) while maintaining their tensile strength, which has benefits towards the handling, storage, and transportation of such cables.

Trajectory tracking control for a cable-driven space manipulator using time-delay estimation and nonsingular terminal sliding mode

Trajectory tracking control is critical for cable-driven manipulators to achieve long-distance operation. However, the uncertainties and deformations caused by long-distance transmission cables make the existing trajectory tracking control methods for cable-driven space manipulators unable to meet the demand for high accuracy and strong robustness in practical engineering. In this paper, the trajectory tracking control for a new type of cable-driven large space manipulator is investigated. First, the kinematics and dynamics models of the cable-driven space manipulator are established by using the principle of virtual work. Then, a trajectory tracking control scheme is designed for the cable-driven space manipulator based on the time-delay estimation and the nonsingular terminal sliding mode control approach. The main advantage of the proposed control scheme is to improve the performance of the time-delay estimator by rationally introducing a tuning parameter, which improves the performance of the whole control system. The asymptotic stability of the resulting closed-loop system is proven by the Lyapunov stability theory. The simulation and experiment results show that the proposed control scheme can effectively overcome the influence of disturbance and achieve high-precision trajectory tracking control of the cable-driven space manipulator.

Design of Grid-Connected rooftop Photovoltaic system for leakage current reduction using optimization algorithms

Rooftop solar power systems refer to the organization of photovoltaic (PV) panels on the rooftop of a building. They are a feasible substitute for land-based solar arrays, and they are being used in different Asian countries. Thus regulations, grid connectivity, off-take, and land acquisition are the main obstacles that renewable energy plant owners face. At high penetration of rooftop PV, this voltage variability reduces the stability of the grid due to transient imbalance in load and generation and causes voltage and frequency to exceed set limits if not countered by power controls. To reduce this power loss in the transmission cable, a Manta Ray Foraging Optimization (MRFO) process is presented in this research. This method also enhances the PV system's performance. A Non-isolated Buck-Boost Converter is connected between the PV and the grid. For renewable energy applications, a new non-isolated Buck-Boost converter with high voltage gain and positive output voltage has been developed. This converter receives the voltage of input from the PV and gives the output as boosting or lowering the voltage. To improve the current tracking with high power conversion efficiency, a Finite Control Set Model Predictive Controller (FCS-MPC) is introduced for this converter. The proposed optimization algorithm is utilized to tune the controller and improves the dynamic process of the power plant system connected to the grid. This algorithm is simulated using the Matlab Simulink software. The voltage and power generated by the proposed rooftop PV are 560 V and 495.25 kW/sec. The voltage and electricity produced by the ground-mounted are very low compared to the proposed method, therefore, utilizing this rooftop solar PV model, that study generates more power than the ground-mounted PV. This study contributes to the field by improving the energy production of roof-top solar PV systems based on roof design.

Design and analysis of a cable-driven gravity compensation mechanism for spatial multi-DoF robotic systems

The gravity compensation mechanisms (GCMs) are widely used in robotic manipulators and exoskeletons. This paper presents a cable-driven GCM applied in a spatial multi-degree-of-freedom (DoF) robotic system. By combining the cable transmission with the spring-based GCM, the whole compensation system is placed outside the main body of the robotic system, including the movable links and revolute joints. Therefore, the complexity and inertia of the robotic system's main body are reduced, and the motion range will not be limited by the mechanism for compensation, such as parallelogram linkages. Here presents the application example of a cable-driven four-DoF exoskeleton to demonstrate the development of the proposed GCM. The GCM is analyzed based on the space mapping method, and the mechanical models are designed based on theoretical analysis to evaluate the technical feasibility. The effectiveness of the proposed GCM is validated by calculating and analyzing the cable tension required by the exoskeleton and generated by the GCM in several specific movements. Finally, some limitations and potential applications of this cable-driven GCM are discussed.

Fault Location Study of Overhead Line–Cable Lines with Branches

A new fault location method based on the three-terminal travelling wave method is proposed for the fault location problem of multi-branch overhead line–cable transmission lines. Firstly, the process of fault travelling wave propagation in overhead transmission lines and the phenomenon of refraction are analysed, and an improved phase-mode transformation is introduced to decouple the electromagnetic coupling and perform fault phase selection. Secondly, the Pearson correlation coefficient is introduced to compare the similarity of the current travelling waveforms at different measurement points in order to implement fault segmentation. To solve the problems of the complexity of the fault travelling wave propagation process and the difficulty of identifying the travelling wavehead, the Hilbert–Huang transform is used to extract the fault signal characteristics, and the travelling wave arrival moment is accurately calculated by the sampling error correction method to determine the fault location. Finally, the accuracy and stability of the method are verified via a simulation test on the MATLAB/Simulink platform. The results show that the proposed positioning method combining the three-terminal travelling wave method with HHT and sampling error correction can locate the fault location more accurately, and it has good potential for application in the engineering field. It provides a new technical means for fault location in overhead transmission lines, which is expected to become one of the most important technologies in the future power system.

Initial Study on Press Welding With Indium Applied to High-Temperature Superconducting DC Feeder Cables

High-temperature superconducting (HTS) DC feeder cable has been proposed for reducing energy loss in railway systems. The feeder cables are required to be installed during the night using a quickly-fabricable low-resistive joint. A soldering technique has been widely used for connecting HTS round-shaped cables in transmission or feeder cable systems. In this study, we proposed applying press welding with indium at room temperature (cold pressure welding) or with heat treatment at 90–120 °C as an alternative candidate for the cable-to-cable joint. First, we examined the necessity of the pre-joint process, polishing the HTS tape, and pickling indium foil with 10% HCl as well as the joining temperature. The examination was performed using tape-to-tape joints with copper-alloy-laminated Bi-2223 tapes. The joint resistance and mechanical strength for railway application were satisfied even by a joint fabricated at room temperature skipping the above two pre-joint processes. Then, we fabricated straight and spiral joints of the model cable made of copper-alloy-laminated Bi-2223 tapes with various joining processes and spiral pitches. The joint resistivity for the model cable joint was less influenced by the joining process and spiral pitch and it was comparable to that of a single tape-to-tape joint. As a conclusion, press welding with indium with a simplified process, joining at room temperature, and skipping some of pre-joint processes can be applied to quick and simple joint fabrication of HTS DC feeder cable.

Reduction of Overvoltages under Connection on a High-Voltage Cable Line Due to Optimal Controlled Switching

The purpose of the work is to develop a mathematical model of a cable transmission line, which allows modeling and choosing the optimal conditions for controlled switching to limit overvoltage at the development and design stage. The goal is achieved by solving the problem of determining the initial angle of each phase, so that each phase has an initial switching angle equal to zero with a time delay. A high-voltage cable line for a voltage of 330 kV, implemented using Matlab, has been chosen as the object of study. The most significant result is the method of numerical simulation of the cable line that allows you to analyze transients when each phase of a three-phase cable line is connected to a three-phase source with a time delay, the switching angle of all phases is zero. This, in turn, makes it possible to limit switching overvoltages. The significance of the results obtained lies in the possibility of the proposed technique to choose the optimal conditions for controlled switching, which makes it possible to use it in the design of switching nodes, as well as the use of controlled switching to eliminate unwanted electrical transients during planned switching. The simulation results showed that the greatest effect of using numerical simulation is when each phase of a three-phase cable line is connected to a three-phase source with a time delay of 1/150 second, then the switching angle of all phases is zero, which makes it possible to limit switching overvoltages. Keywords: three-phase cable line, switching overvoltage, transient processes, controlled switching, theory of multipoles, modeling of electrical engineering objects.

Experimental investigation on the performance of Cable-Girder anchorage structure of hybrid Cable-Stayed suspension bridges

As the key component of the stay cable connecting the girder and tower in the hybrid cable-stayed suspension system, the cable anchorage structure needs to bear the powerful cable force transmission function. Compared with normal anchorages, the structural features of a new type of anchor box structure cable-girder anchorage (CGA) that has strong bearing capacity and more uniform stress distribution for a long-span hybrid cable-stayed suspension bridge with steel box girder was investigated by a 1:2 scale specimen test and a series of finite-element analysis. Through finite element analysis (FEA) and test results, the stress distribution and cable load transfer pathway of anchor box structure are obtained. The test results show that the CGA design is reasonable and reliable. The four welds connected to the anchor box support plates and the steel box girder webs bear 87% of the cable force load transfer, and the remaining 13% of the cable load is delivered from the anchor box bearing plate to webs. A large stress concentration in the six welds, but the maximum von Mises stress (VMS) of welds is 130–151 MPa. According to the parametric studies,the installation angle of the anchor box considerably affects the stress characteristics. Also, the thickness and length of the anchor box plate are changed, the transmission and distribution proportion of the cable force between the main welds of the anchor box increase alternately.

Passivity enforcement of wideband model through a new and full perturbation formulation

Passive component models are necessary to ensure numerical stability in the simulation of electromagnetic transients in power systems. However, it is challenging to represent transmission lines and cables with frequency-dependent wideband models that are accurate, efficient, and passive. This paper proposes a new method for the passivity enforcement of wideband line and cable models. The wideband models rely on pole-residue identification of characteristic admittance and propagation function in rational forms. In case the resulting models are not passive, the proposed method simultaneously applies perturbation to the residue matrices of characteristic admittance and propagation function. The set of equations related to passivity enforcement through the residues of propagation function in phase domain is complex and presented for the first time in this paper. The proposed approach minimizes the overall perturbation for maintaining passivity as opposed to the existing simplified approaches that rely on the perturbation of the residues of either characteristic admittance or diagonal elements of propagation function. The performance of the method is validated with application cases, and it is shown that it outperforms the existing methods that seek simplification in problem formulation.

Modelling and Experimental Investigation on the Differential Protection of Transmission Line

Due to the significant impact of the fault on power systems and the failure of protection devices, power system operators and researchers have given reliability a great deal of consideration. The modern IEC 61850 standard is used recently to improve communication systems in digital substations and allow signals to be shared between the devices. Differential protection is used to protect the transmission lines, cables, and transformers, as it detects the faults by comparison of the currents flowing into and out of the protected devices. In this research, MATLAB/Simulink has been utilized to simulate the differential protection by using two current transformers (CTs) and to analyze the current waveforms of CTs. A model of the transmission line has been implemented in Taylor’s University Lab to validate the simulation results and measure the differential current, which equals the current summation of two CTs. The outcomes of the research show that the phase shift in the secondary side of CTs between two terminal points is zero and the value of differential current is zero under normal operating situations. However, the differential current has increased in each of the following cases: one CT is connected to the system with the wrong polarity or under an internal fault.

A feasibility study of the reflection readout method of Resistive-Plate Chambers

The conventional readout method of Resistive-Plate Chambers uses two sets of orthogonal readout strips placed at both sides of the detector to collect signals of opposite polarities, which can be processed to reconstruct the hit position of incident muons. A new readout method utilising the reflected signal is proposed with only one set of readout strips. This reflection readout method exploits the difference in the arrival time of the original and the reflected signal to determine the hit position. Customised transmission cables are used to extend the propagation distance of the reflected signal to ensure sufficient time separation of the two signals. Compared to the conventional readout method, this reflection readout method can increase the geometrical acceptance of the detector and reduce the number of readout channels, which is particularly appealing for experimental applications with strict space limit. A preliminary feasibility study of this new method has been conducted. Experimental setup and test results are shown in this paper, and it is demonstrated that a spatial resolution of sub-centimetre can be achieved.

Measurement method for electromagnetic radiation generated during a high-capacity warhead explosion

To study the impact of explosion electromagnetic radiation on electronic equipment and to improve the anti-interference ability of electronic equipment in an explosion electromagnetic environment, it is necessary to understand the characteristics and laws of explosion electromagnetic radiation. An explosive electromagnetic measurement test is necessary to study this problem. In view of the measurement conditions of the explosive field and the interference factors in the process of a warhead explosion, protection and improvement measures have been proposed. It designs a repeater to compensate for excessive transmission loss of explosive electromagnetic signal. It enhances the anti-interference ability of the measurement system by adopting electromagnetic shielding methods for signal transmission cables. The closed aperture method was used to solve the field line coupling problem in the measurement system. By analyzing the law of seismic wave propagation, equivalent simulation test of instrument vibration and optimization of test point layout, which are conducted to deal with adverse effects such as explosive seismic wave and fragment strike. Finally, an electromagnetic radiation measurement method suitable for the environment of a high-capacity warhead explosive field has been formed.

Ice Adhesion Evaluation of PTFE Solid Lubricant Film Applied on TiO2 Coatings

Ice formation affects the performance of many industrial components, including aircraft wings, spacecraft, and power transmission cables. In particular, ice build-up on airplane components increases drag and fuel consumption. A large number of studies have been carried out to reduce ice adhesion by developing passive methods such as icephobic coatings and active ice removal approaches such as mechanical vibrations or chemical-based solutions. Despite remarkable recent breakthroughs in the fabrication of icephobic coatings, passive ice removal solutions require higher durability to resist cyclical mechanical ice detachment treatments. Functionalized TiO2 coatings, applied using the suspension plasma spray (SPS) technique, have been shown to be robust and to have dual-scale characteristics in an ice accretion analysis. In this study, the icephobicity and mechanical durability of a novel duplex coating consisting of polytetrafluoroethylene (PTFE) solid lubricant films on TiO2-coated substrates were evaluated. Notably, various amounts of PTFE were applied on top of the TiO2 coating to identify the ideal quantity required to obtain optimal icephobic properties. Ice was generated in an icing wind tunnel, and the amount of accreted ice was evaluated to assess the anti-icing properties. Wettability parameters, including static water contact angle and contact angle hysteresis, were measured to determine the water mobility and surface energy. Ice shear adhesion to the PTFE-TiO2 duplex coating was measured using a custom-built test rig. The mechanical durability was assessed by measuring the ice shear strength for almost twenty icing–deicing cycles, and after five cycles, the roughness parameters and images taken from the surface of the samples were compared. The combination of PTFE solid lubricant film and TiO2 coating reduced ice adhesion by 70%–90% compared to that of a bare aluminum substrate (reference material). Additionally, the results showed that the application of a uniform layer of PTFE solid lubricant film on dual-scale TiO2 coating significantly reduced ice adhesion and maintained mechanical durability for 25 deicing cycles, making this combination a promising candidate for deicing approaches.

Modeling and analysis of a cable-driven serial-parallel manipulator

Cable-driven serial-parallel (CDSP) manipulators have a small size and large load/mass ratio and represent an ideal scheme for humanoid manipulators. However, owing to the multilevel mapping relationship among the end-effector, joints, cables, and motors, as well as the complex cable transmission path and cable–pulley contact, the modeling and control of such manipulators are highly complex. In this study, the kinematics and dynamics models for a CDSP manipulator were established, and a dynamic controller was proposed. First, the structure and cable transmission path of a CDSP manipulator were described. A kinematics equivalent method was used to equate the cable-driven parallel joint in the manipulator to an Equivalent pair. Using the proposed equivalent method, along with analytical and numerical methods, the kinematic equations were derived. In addition, the dynamic equations including those for the cable–pulley contact, cable tension, and joint variables were derived. Considering the actual control requirements, the cable tensions were optimized to obtain the minimum solution. Moreover, a dynamic control strategy was formulated. Finally, a prototype of the proposed manipulator was fabricated, and the cable tension of its joints and the pose accuracy of its end-effector were tested to verify the models and dynamic control method. The experiment results demonstrated that the kinematic and dynamic models are valid, and the dynamic controller is effective.

Fabrication and properties of n-SiO2/m-SiO2/PU superhydrophobic coatings

In order to eliminate the adverse effects of icing on the surface of mechanical devices such as power transmission cables and wind turbine blades due to low temperature, nano-silica (n-SiO2) and micron-silica (m-SiO2) modified by silane coupling agent were blended with a mass ratio of 5:1 and subsequently compounded with polyurethane (PU) to obtain n-SiO2/m-SiO2/PU superhydrophobic coatings. It is shown that the tight bonding of m-SiO2 with PU avoids the cracking of the coating due to the agglomeration of n-SiO2 and improves the stability of the coating. n-SiO2 makes the surface of n-SiO2/m-SiO2/PU coating form a dense and rough structure, which increases the air-liquid contact area by trapping more air. The contact angle reached 158.10° at a low filling ratio(40 wt%), indicating that the prepared n-SiO2/m-SiO2/PU coating has excellent superhydrophobic properties. The superhydrophobic n-SiO2/m-SiO2/PU coating is very helpful in solving the low-temperature icing problem of outdoor power and wind equipment in rain and snow.

An experimental study of rime ice accretion on bundled conductors

The dynamic ice accretion process on bundled electrical power conductors and icing-induced effects on the aerodynamic forces acting on the conductors were examined experimentally. An Icing Research Tunnel was used to generate a typical atmospheric rime icing condition experienced by power transmission cables. Two pieces of Aluminum-Conductor-Steel-Reinforced (ACSR) cables were mounted in the icing wind tunnel with different spacing and angular displacements with respect to the incoming airflow. While ice accretion was found to take place primarily on the frontal surfaces of the bundled conductors, the accreted ice layers resembled well the twisted outer strands of the ACSR conductors. Averaged outer profiles of the iced conductors were elliptical with the semi-minor axis being the radius of the conductors and the semi-major axis passing through the foremost frontal points of the accreted ice layers. The icing process on the windward conductor was almost unaffected by the existence of the leeward conductor. The ice accretion and resultant aerodynamic force acting on the leeward conductor were found to vary significantly, depending on the spacing and angular displacements between the bundled conductors. The windward conductor was found to induce a “shadowing effect” by intercepting airborne supercooled water droplets to prevent them from impinging onto the leeward conductor, resulting in much less ice accretion and smaller aerodynamic drag acting on the leeward conductor. The aerodynamic force measurements were correlated with the acquired ice accretion images and wake flow field around the bundled conductors to elucidate the underlying physics.

Characterization and Mitigation of Conducted Emissions in a SiC Based Three-Level T-Type Motor Drive for Aircraft Propulsion

This paper presents the full-scale high power inverter design considerations that are needed for minimum conducted noise propagation throughout the system. Specifically, system design issues pertaining to high current and high altitude, high switching transients during commutation process, ribbon cables for high-speed signal transmission, strict conducted emissions requirements and motor side bearing/leakage currents are discussed. Based on the underlying deficits for high power motor drives, layout and circuit design methodologies are proposed to tackle such problems, while keeping costs at a bare minimum. Subsequently, modeling and prediction of common-mode (CM) and differential-mode (DM) noise is made possible using accurate lumped inverter and filter models, allowing for a better understanding of the sensitive components contributing to peak CM-DM noise. A high power (211 kW) rated three level T-type inverter prototype is used to demonstrate the viability of the proposed design techniques for reliable system operation and conducted electromagnetic interference (EMI) emissions mitigation.

Stories From China

On December 22, 2021, the world's first 35-kV kilometer-class superconducting cable demonstration project was put into operation in the business core area of the Xuhui District in Shanghai. It is a fully commercialized 35-kV superconducting cable transmission project with the longest distance and the largest transmission capacity in the world. The project is located in the center of Shanghai, connecting two 220-kV substations in Xuhui's business core area with a total length of 1.2 km. The rated current is 2,200 A, and the rated capacity is 133 MW [1].

Особенности моделирования воздушных и кабельных участков линий электропередачи 110–750 кВ при использовании фазного координатного базиса

Power system steady state and transient analysis require correct modeling of overhead transmission lines and cables operating at 110–750 kV. The key difficulties to model sections of overhead and cable lines are caused by complex conductor geometry, their transposition, as well as grounding schemes of ground wires of overhead lines and screens of underground cables. The paper covers various aspects of 110–750 overhead line and cable modeling that must be taken into consideration to obtain a reliable mathematical model in a phase domain. Modern software does not provide a universal solution to determine line parameters. The 110–500 kV cable line modeling issues have not been worked out properly and require careful analysis of specialized foreign literature. Thus, the task to develop the algorithms of calculating the parameters of overhead and cable power lines is relevant, taking into account the various configuration options of these lines which are possible in operational practice. To derive overhead transmission line and cable line models, electric circuit theory and matrix algebra methods have been used. The ATP/ATPDraw and MATLAB/Simulink software environment has been used to investigate what tools are available to determine line parameters, as well as to verify some of the calculation results. Analysis has been carried out to reveal the options available in the ATP/ATPDraw and MATLAB/Simulink software to compute line parameters in a phase domain. An algorithm has been developed and verified to calculate overhead line parameters regardless of the number of parallel circuits. The key features of the calculation of the matrix of linear resistances of overhead power transmission lines are outlined. The main features of modern cable lines operating at 110–500 kV are also described. The paper presents various cable layouts possible in real-field conditions, as well as provides expressions that allow obtaining correct impedances and admittances for a system of cable line conductors. Study of the options of various software tools dedicated to overhead line parameter calculation in a phase domain has revealed that these tools cannot be deemed universal to represent an overhead line of whatever configuration. However, the developed algorithm is universal as it allows computing line parameters regardless the ground wire grounding approach. The expressions presented in this paper consider various layouts of 110–500 kV cable lines that could be encountered in the Russian power system.