Cable Shield Research Articles

Application of the Fast Marching Method for Path Planning of Long-haul Optical Fiber Cables With Shielding

This paper provides a method for optimal shielding design and path planning of a long-haul optical fiber cable between two locations on the Earth’s surface. The method allows minimization of the cable laying cost including material and labor and the risks of future cable break associated with laying the cable through various areas, including earthquake-prone or other risky areas. Both costs per unit length and risk of cable damage may be different at different locations. Expensive shielding may be important in certain high-risk areas and unnecessary in lower risk areas. We use ground motion intensity to estimate future cable repair rate (our measure of earthquake-related cable damage risk), and a triangulated manifold to represent the surface of the Earth. With laying cost and expected total number of repairs of the cable as the two objectives, we formulate the problem as a multiobjective variational optimization problem. This formulation incorporating multiple design levels for cable shielding is converted into a single objective variational optimization problem by assigning different weights to each objective. The solution path of the later problem is obtained by using the Fast Marching Method (FMM) with an additional minimization step. A new proof of the optimality of FMM for the problem is provided. Numerical results demonstrate that the FMM-based method outperforms existing raster-based algorithms. With billions of US dollars spent yearly on new cables, the potential savings are substantial. Furthermore, the computational complexity of the FMM-based method is $O(N \log (N))$ , making it applicable to cables of realistic length.

Open source cable models for EMI simulations

One of the most significant coupling paths for electromagnetic interference into systems is via cables [1], This may be cable to cable coupling within a bundle of conductors or coupling from an illuminating electromagnetic field [2]–[4], These coupling effects may be enhanced by non-ideal cable terminations such as pigtail connections of shields or by crosstalk within connectors [5], In addition, imperfect cable shields allow coupling via transfer impedance and transfer admittance [6][7].

Active cathodic protection for HV power cables in undersea application

This paper focuses on the performance analysis of the corrosion protection system of HV power cables for undersea applications. The aim of the work is to describe the relations between the main electrical parameters affecting the electric potential distribution in the cable layers and in the surrounding medium, when an active cathodic protection (CP) arrangement is used. In particular, the analysis focuses on the design of an active CP for reducing corrosion phenomena of the cable metallic shield. This study is based on a 2D analytical approach supported by a detailed 3D finite element analysis (FEM). It gives evidence to the relation between the electrical variables and the design criteria of the active cathodic protection system.

Analysis and suppression measures of lightning transient overvoltage in the signal cable of wind turbines

AbstractLightning strikes are a major threat to the secure operation of wind turbines. When lightning strikes a wind turbine, the lightning current flows through the blade and the tower and then the induced overvoltage will damage sensors and signal cables. In this study, a comprehensive transient surge impedance model of a wind turbine was built to analyze the causes of the overvoltage in the signal cable. The model that studies the overvoltage caused by both capacitive coupling and electromagnetic induction included the blade, nacelle, tower, signal cable, power cable, and grounding system using π networks. The influences of the cable shielding layer, soil resistivity, and lightning current waveform on the overvoltage were also analyzed. Then, 2 overvoltage suppression measures, ie, grounding at 2 ends of the outer shielding layer and installation of a surge protective device, were tested. Results show that a signal cable with double shielding layers reduced the overvoltage in the signal cable, and higher soil resistivity resulted in increased voltage on the tower base. In addition, the peak and the front time of the lightning current significantly influenced the overvoltage on the tower and the cable. The effectiveness of the 2 suppression measures was also verified. The calculation results will provide guidance for a reasonable lightning protection design.

Performance of a multi leaf collimator system for MR-guided radiation therapy.

The purpose of this study was to investigate and characterize the performance of a Multi Leaf Collimator (MLC) designed for Cobalt-60 based MR-guided radiation therapy system in a 0.35 T magnetic field. The MLC design and unique assembly features in the ViewRay MRIdian system were first reviewed. The RF cage shielding of MLC motor and cables were evaluated using ACR phantoms with real-time imaging and quantified by signal-to-noise ratio. The dosimetric characterizations, including the leaf transmission, leaf penumbra, tongue-and-groove effect, were investigated using radiosensitive films. The output factor of MLC-defined fields was measured with ionization chambers for both symmetric fields from 2.1 × 2.1 cm2 to 27.3 × 27.3 cm2 and asymmetric fields from 10.5 × 10.5 cm2 to 10.5 × 2.0 cm2 . Multi leaf collimator (MLC) positional accuracy was assessed by delivering either a picket fence (PF) style pattern on radiochromic films with wire-jig phantom or double and triple-rectangular patterns on ArcCheck-MR (Sun Nuclear, Melbourne, FL, USA) with gamma analysis as the pass/fail indicator. Leaf speed tests were performed to assess the capability of full range leaf travel within manufacture's specifications. Multi leaf collimator plan delivery reproducibility was tested by repeatedly delivering both open fields and fields with irregular shaped segments over 1-month period. Comparable SNRs within 4% were observed for MLC moving and stationary plans on vendor-reconstructed images, and the direct k-space reconstructed images showed that the three SNRs are within 1%. The maximum leaf transmission for all three MLCs was less than 0.35% and the average leakage was 0.153 ± 0.006%, 0.151 ± 0.008%, and 0.159 ± 0.015% for head 1, 2, and 3, respectively. Both the leaf edge and leaf end penumbra showed comparable values within 0.05 cm, and the measured values are within 0.1 cm with TPS values. The leaf edge TG effect indicated 10% underdose and the leaf end TG showed a shifted dose distribution with 0.3 cm offset. The leaf positioning test showed a 0.2 cm accuracy in the PF style test, and a gamma passing rate above 96% was observed with a 3%/2 mm criteria when comparing the measured double/triple-rectangular pattern fluence with TPS calculated fluence. The average leaf speed when executing the test plan fell in a range from 1.86 to 1.95 cm/s. The measured and TPS calculated output factors were within 2% for squared fields and within 3% for rectangular fields. The reproducibility test showed the deviation of output factors were well within 2% for square fields and the gamma passing rate within 1.5% for fields with irregular segments. The Monte Carlo predicted output factors were within 2% compared to TPS values. 15 out of the 16 IMRT plans have gamma passing rate more than 98% compared to the TPS fluence with an average passing rate of 99.1 ± 0.6%. The MRIdian MLC has a good RF noise shielding design, low radiation leakage, good positioning accuracy, comparable TG effect, and can be modeled by an independent Monte Carlo calculation platform.

Characteristics of Electromagnetic Disturbance for Intelligent Component Due to Switching Operations via a 1100 kV AC GIS Test Circuit

Switching operation of the disconnector in gas-insulated switchgear (GIS) results in very fast transient overvoltage in GIS pipes. In a smart substation, this process induces disturbance voltage on the port of the intelligent component fixed on GIS pipes or placed in the local cabinet nearby, which then may lead to the failure of the equipment. The experimental results of the port disturbance voltage during the switching operation via a 1100 kV test circuit are first reported in this paper. The test arrangement, including both 70 opening operations and 70 closing operations, had been performed. The influences of different grounding schemes of cable shield on port disturbance had been investigated. Three different cases of the terminal load had also been considered: open circuit, short circuit, and 50 Ω. Over 100 000 micro-pulses had been extracted from the disturbance voltage waveforms. The waveform characteristics including peak voltage, rise-time, oscillation frequency, and decaying had been obtained by statistical analysis of these micro-pulses. Furthermore, the differences between measured waveforms and the IEC 61000-4-18 immunity test standard waveform had been discussed.

Impact of the disconnection of cable shields on the thermal stress reduction in case of cross-country faults

Impact of the disconnection of cable shields on the thermal stress reduction in case of cross-country faults

A Seismic Resistant Design Algorithm for Laying and Shielding of Optical Fiber Cables

This paper considers a long-haul optical fiber cable, connecting two points on the Earth's surface that passes through earthquake-prone or other sensitive areas. Different segments of the cable are characterized by different protection levels, where a higher level through shielding represents a more costly and more resilient segment. This leads to a multi-objective optimization problem, where the two objectives are 1) the total cost of the cable and 2) the total number of potential repairs along the cable likely to be caused by earthquakes. As a measure of seismic risk, we use the concept of cable repair rate used in the civil engineering community. In our models, ground motion intensity data are used to estimate the cable repair rate, and a graph of a triangulated irregular network is used to represent the Earth's surface. We formulate this optimization problem as a multi-objective shortest path problem and solve it by a variant of the label setting algorithm. Two approximate algorithms, an interval-partition-based label-setting algorithm and an evolutionary algorithm, are also presented as methods of computational cost reduction for large-scale cases, and their results are compared. The solution leads to a Pareto front or an approximate Pareto front that enables us to choose the path and protection of the cable to either minimize cost for a given risk level or minimize risk for a given budget.

DETERMINATION OF ANALYTICAL CALCULATION ERROR OF MAGNETIC FIELD OF HIGH-VOLTAGE CABLE LINES WITH TWO-POINT BONDED CABLE SHIELDS CAUSED BY NON-UNIFORM CURRENT DISTRIBUTION IN THE SHIELDS

This paper deals with the determination of analytical calculation error of magnetic field of high-voltage cable lines in two-point bonded cable shields caused by non-uniformity of the current distribution in the shields. The relative error is determined by comparing numerical calculation of magnetic field obtained in the COMSOL Multiphysics software with the analytical one. It is shown that the maximum value of relative error does not exceed 8 %. The obtained error values are verified by testing the numerical calculation and confirmed by results of experiment. In paper proves the correctness of the analytical calculation of magnetic field of cable lines at the points of its normalization, which is carried out without taking into account the non-uniform current distribution in the cable shields.

IMPROVING CALCULATION ACCURACY OF CURRENTS IN CABLE SHIELDS AT DOUBLE-SIDED GROUNDING OF THREE-PHASE CABLE LINE

This paper deals with the calculation of currents in shields of single-core cables at double-sided grounding of three-phase cable lines. We consider flat and trefoil cable lines and receive the analytical expressions for RMS currents in the shields of cables. These expressions allow reducing the shield current calculation error to value of 5 %. We analyze the known approximate expressions for RMS currents in the shields of cables and represent dependencies of corresponding calculation errors on cable line dimensionless parameters. These dimensionless parameters are determined by the distance between the axes of the cables, the radius and the resistance of shields.

Circuit models of Lossy Coaxial Shielded cables to Analyze Radiated and Conducted Susceptibilities with unmatched line loads

This paper studies the variation effects of incident plane wave on shielded coaxial cables, using Branin’s method, which is called the method of characteristics. That model can be directly used for the time-domain and frequency-domain analyses. Moreover, it had the advantage of being used without the need of setting the preconditions of the charges applied to its ends. This makes it easy to insert in circuit simulators, such as SPICE, SABER, and ESACAP. The results obtained under ESACAP were remarkably similar to other results, which reinforce the validity of the model. Finally, we will discuss the effects of the variation of the incident plane wave.

New method for estimating the grounding reliability test of aircraft cable shield

New method for estimating the grounding reliability test of aircraft cable shield

Modeling of Power Cables with Arbitrary Cross Section: From Parameter Calculation to Electromagnetic Transients Simulation

A full computer-based methodology is proposed for electromagnetic transient simulations in power cables characterized by an arbitrary cross-section geometry. The frequency-dependent parameters of the cables are calculated using finite element method, and the three-phase cable modeling is carried out using modal decoupling and fitting techniques. The multiconductor representation of a sector-shaped cable is possible from the calculation of a constant and real modal transformation matrix, resulting four independent propagation modes (three phases and cable shield), which are modeled from the inclusion of frequency effect in the classic Bergeron method. The currents and voltages are expressed as a system of differential equations, which are presented as state equations and solved using numerical integration methods. The proposed modeling technique allows the inclusion of time-variable and nonlinear elements during electromagnetic transient simulations in the time domain, which is not possible from frequency-domain models that are solved using inverse transforms. The proposed model is validated from results simulated using numerical Laplace transform and exact modal transformation matrix for calculation of phase currents and voltages.

Equivalent Circuit Model of Soft Shield Defects in Coaxial Cables Using Numerical Modeling

This paper presents a three-dimensional modeling study to investigate the effects of one type of soft fault problem in electrical fault diagnosis, the impacts of partial degradation in the coaxial cable shielding or other shielded lines. At first, a time domain nodal discontinuous Galerkin method is used to solve Maxwell's equations and simulate reflectometry responses of soft faults. Then, the numerical simulation results for soft defects in cable shields are compared with experimental measurements for validation purposes. Finally, the shield defects that can arise on coaxial cables are modeled by an equivalent circuit and compared to illustrate their impacts on the electrical characteristic parameters as a function of their severity.

A Study for Control Power System Load Flow by Shield Control of High-TC Superconducting Cable

Objectives: HTS cable was shown high temperature characteristic of the superconducting tape by sharp increase resistance on fault state. This paper proposes by controlling the HTS shield part to stable transmission in power system. Methods/Statistical Analysis: HTS cable was divided mainly three parts that was former, conductor, and shield part. To be performance the HTS cable designed by comparison low error value with real HTS cable property and, developed by controlling shield parts by using mutual inductance change. Findings: The HTS power cable was controlled load flow by adjusting the shield part. Improved the HTS cable was limited current above 64% better than HTS cable in installed the fault current limiter. Therefore, HTS cable could be improved power stability in the power system. Improvements/Applications: The HTS shield control might be controlled power flow and limited fault current. It wasn’t necessary for installing other device by controlling HTS cable shield part. So, proposed the HTS cable model was applied in economic and effective device in power system.

Influence of LV Neutral Grounding on Global Earthing Systems

International Standards define a Global Earthing System as an earthing net created interconnecting local Earthing Systems (generally through the shield of MV cables and/or bare buried conductors). In Italy, the regulatory authority for electricity and gas requires distributors to guarantee the electrical continuity of LV neutral conductor. This requirement has led to the standard practice of realizing “reinforcement groundings” along the LV neutral conductor path and at users’ delivery cabinet. Moreover, in urban high-load scenarios (prime candidates to be part of a Global Earthing System), it is common that LV distribution scheme creates, through neutral conductors, an effective connection between grounding systems of MV/LV substations, modifying Global Earthing System consistency. The aim of this paper is to evaluate the effect, in terms of electrical safety, of the aforementioned LV neutral distribution scheme when an MV-side fault to ground occurs. For this purpose, simulations are carried out on a realistic urban test case and suitable evaluation indexes are proposed.

Mutual inductive interference of 400 kV cable systems

The paper proposes a suitable model for the calculation of the mutual inductive and ohmic interference of 400 kV cable systems particularly of the induced currents and voltages in cable shields, cross bonding joints and earthing systems. Based on practical relevant examples, typical scenarios were defined and the effects of parallel laid 400 kV cable systems are shown and discussed. For the calculation of voltages and currents due to mutual inductive and ohmic coupling of parallel laid underground cable systems, the following parameters have to be considered: electrical symmetry of the cable systems, cable laying arrangement, distances between systems and phases, system and cross-bonding section length, influencing current, cross-section arrangement with detailed sub-section design, earthing configuration of the cable shields and joint cases, parallel earth continuity conductors, specific soil resistivity and laying depth. Considering the isolation materials of cables, the distances between phases and related cable shields, between phases themselves and between three-phase systems are much lower than the distances on overhead lines. Therefore, the mutual coupling, the symmetry of the entire system and the earthing arrangement play an essential role regarding induced voltages and currents. Not only the number of sections, but also the section length varies in many cases. For each of these sections, the impedance matrix is computed by using the self-impedances of all conductors and the coupling-impedances between all conductors using Dubanton’s approximation. These coupled cable sections are combined with the earthing resistances of the joints to form a chain model. The voltage and current distribution across 400 kV cable systems through the inductive interference can be finally calculated in all accessible places. Measurements at 400 kV cable systems of a DSO in Austria were carried out to validate the simulation model and the calculation results, respectively. The presented results show a good correlation with the measurement results.

Electromagnetic Emission Modeling in Case of Shielded Cabling With Respect to the Ground Dielectric Properties

Satellites and spacecraft subsystems in general are vulnerable in terms of electromagnetic interference. Shielded cables, connecting these subsystems as well as the subsystems themselves, are major sources of electromagnetic (EM) emission. The minimization of these emissions is critical in order to achieve EM cleanliness. An accurate model predicting these emissions could offer great insight and enable interference minimization. In this study, a shielded cable model for predicting EM emission via decomposition of contributing phenomena is presented including the ground dielectric properties. The model is built based on a standardized measurement setup and validated for different cases of ground material and cable's position.

Influence of the shield grounding system on choice of section

The choice of the ground circuit of a shield that gets rid of capacity losses is becoming especially urgent to increase the transmission capacity of lines with cross-linked polyethylene insulation. Ground systems of shields of the single-phase high-voltage power cables are studied. A mathematical model to select the section of the electric conductor for single-wire power cables for a voltage of 6–500 kV is suggested which takes into account the connection circuit of the shield permits allows one to determine the capacity losses and induced voltage on the shield. The method of selection of energy-efficient grounding systems of the shield of the three-phase group is found on the basis of the mathematical model. A selection criterion is suggested determining the relative rate of return of the “open” ground system with no currents in the shields over against the “closed” system in the shields of which parasitic currents flow.

Voltage Distribution of a Wind Turbine Transformer Under Direct Lightning Strike: Effects of the Grounding of Cable Shield

In this paper we consider wind energy generators as tall structures, thus the reflections of the current of a direct lightning strike, at various interfaces, have been included in the computational model. A significant effect of such reflections on the voltage distribution has been observed thus, inclusion of the reflections in the computation model has been justified. The study focuses on over voltage at critical locations that have been reported in the literature as having high probability of lightning damage. All parts related to the power generation in a wind turbine, including the step up transformer are modeled by lumped parameters using the Matlab/Simulink software. The transient response is obtained by applying the lightning impulse current to the equivalent circuit under several values of grounding resistance and several cable sheath grounding methods with different lightning strike waveforms. The results show that the location of the cable shield grounding and the grounding resistance values have significant influence on the produced over voltage waveforms at the input and output of transformer terminals. Appropriate surge protection devices for avoiding dangerous over voltage are proposed to reduce harmful effects.