Influence of contact resistance on shielding efficiency of shielding gutters for HV cables (original) (raw)
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Magnetic shielding of buried high‐voltage (HV) cables by conductive metal plates
COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, 2008
PurposeTo study the magnetic shielding of buried high‐voltage (HV) cables by adding conductive metal plates on the ground surface above the cables.Design/methodology/approachThe field is calculated with eight rectangular conductive plates above the cables, positioned with their long edge either parallel to the cables or transversal to the cables. Here, the circuit method is used. In this method, the shield is replaced by a grid of straight filaments in which the unknown currents are searched by solving an electrical circuit.FindingsIt is observed from the calculation results that it is important to have a perfect electrical connection between adjacent plates. In the area above the shield, an “infinite” contact resistance between neighbouring plates results roughly in double field amplitude compared to the situation with contact resistance zero. The positioning of the rectangular plates (parallel or transversal to the cables) has not much influence on the shielding. The shielding eff...
Electromagnetic Losses in Magnetic Shields for Buried High Voltage Cables
Progress In Electromagnetics Research, 2011
The electromagnetic losses and shielding efficiency of shields for a buried three phase high voltage cable are studied for several shielding configurations. The shields are U-shaped gutters covered with plates, and the power cables are positioned either in trefoil or in flat configuration. The shielding efficiency and the losses are compared for shields with the same geometry but several shielding materials: aluminium, and two ferromagnetic steel grades. The numerical models are validated with experimental results. From the experiments, it is observed that the average reducing factor of the flux density is about 7 with the flat cable configuration while the average reducing factor of the flux density is about 5 with the trefoil cable configuration. But the power losses in the DX52 shield for trefoil configuration is about 40% lower compared to the flat configuration. In case of trefoil configuration, the losses are 12.14 W/m per meter length in the shield for a current of 750 A. Next to the shield material and the cable configuration, the paper investigates the influence of several parameters on both the shielding efficiency and the losses: the size of the shield, the current amplitude in the cable and the thickness of the shield.
An Investigation of Magnetic Field Influence in Underground High Voltage Cable Shields
Engineering, Technology & Applied Science Research
Magnetic fields and the shielding efficiency of the shields of underground high voltage cables are studied in this paper regarding several shielding configurations and materials. Shielding efficiency and magnetic fields are computed for shields with the same mesh but from different shielding materials, such as aluminum, ferrite, metal, and steel. In order to get the best shield configuration depending on the source characteristics and the material, a conducting ferromagnetic region with various thickness values is considered as shielding. A finite element model is introduced to investigate the influence of the parameters of magnetic fields and the shielding efficiency of underground high voltage cables. Furthermore, the reduction of the magnetic fields with or without shieldings is also presented. The developed method is performed with the magnetic vector potential formulations and validated on a practical problem.
Series Impedance and Losses of Magnetic Field Mitigation Plates for Underground Power Cables
IEEE Transactions on Electromagnetic Compatibility, 2018
This paper deals with magnetic field mitigation techniques for underground power systems by using conductive or ferromagnetic shielding plates. Two new aspects are considered in this paper beside the shielding effectiveness analysis: the contribution to the series impedance and power losses due to the conducting set formed by the shielding plate/earth return path. A finite thickness ferromagnetic or conductive shielding is assumed buried parallel to the soil/air plane surface in order to model the induction magnetic field mitigation of a power underground cable system in flat configuration. An analytical method, appropriate to deal with possible optimization procedures, is used based on the magnetic vector potential for multilayered configurations where the shielding plate is treated as a different layer. Results for the magnetic field reduction factor at the soil surface are obtained for different shielding materials, different shielding thickness values, as well as different frequency values. Results are validated by employing the finite element analysis.
Journal of Science and Technology Issue on Information and Communications Technology
Nowadays, with the development of the industries, the electrical types of equipment are used and applied widely for many different purposes. One of them is the use of power cables to transmit electricity over long distances, from generator stations to consumers. Local and global fields are usually created by the extensive presence of the types of currents following in power cables in general and underground cables in particular. Not only causes directly some unwanted effects on the body’s natural equilibrium, but electromagnetic fields can create the disturbance and cause interference with electronic devices. In this paper, a shielding plate is introduced to mitigate the local fields generated by a three phase current of underground power cables. The computation of magnetic fields is implemented with the magnetic vector potential formulations via a finite element technique. The developed method is applied to a practical problem.
2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society
In this study, the EM fields produced by high power 3-phase transmission lines are investigated. The dependence of the magnetic field with respect to vertical and horizontal distances from the transmission lines are illustrated and the minimum distance from the lines for human safety is specified according to ICNIRP standards. In addition, a quasi-static examination to the magnetic shielding of several enclosures are performed. In the analysis, the integral form of Maxwell's equations with boundary conditions are used to derive the shielding effectiveness (SE) equations. An experiment is carried out to verify the validity of the theory developed for magnetic fields of transmission lines and the SE provided by the building. An excellent agreement is obtained for experimental and theoretical results.
Magnetic Field Shielding Of Underground PowerCables In Urban Areas: A Real-life Example
2005
In this paper the authors propose a parametric analysis of a typical 150 kV underground power cable line laid in urban areas. A coupled electro-magnetic and thermal formulation based on a finite element model (FEM) has been applied to estimate the magnetic pollution due to trefoil configuration or flat configurations at the thermal operating limit of the cables (cable ampacity). We also investigate the performances of open or closed shields, made of conductive and/or magnetic materials, in order to reduce the magnetic pollution due to existing or new installations, imposing as limitation the maximum admissible operative temperature of the cables. The influence of the effective operating conditions on the magnetic pollution generated by the power line has also been investigated. The proposed formulation takes into account the real geometrical dimensions and the effective physical characteristics of the involved materials.
Effective metal shields of high voltage distribution cable lines
International Journal of Applied Power Engineering (IJAPE), 2023
The presented methodology enables determining induced currents and voltages relevant to the correct estimation of security conditions required in operating and maintenance of the metal installations surrounding highvoltage distribution cable lines. It is based on the on-site measurements of currents appearing in two phase conductors of the considered cable line during a simulated ground fault in the supplied substation. Their values are utilized to compensate for the deficiency of all relevant but unknown data concerning the surrounding metal installations. It was done by introducing an equivalent cable shield substituting, from the standpoint of inductive influence, all surrounding metal installations. Here is shown that this equivalent shield can be determined in such a way that it becomes identical from the standpoint of its appearance to the actual cable line shield but with a changed value of its longitudinal resistance. When this value is determined for single-core cables belonging to a certain cable line it becomes possible to determine the actual reduction factor, inductive influence, and sequence impedance of the considered cable line by using a standard and well-known calculation procedure.
Study about Effective Metal Shield(s) of High Voltage Distribution Cable Lines
Theory and Applications of Engineering Research Vol. 4, 2023
Peer-Review History: This chapter was reviewed by following the Advanced Open Peer Review policy. This chapter was thoroughly checked to prevent plagiarism. As per editorial policy, a minimum of two peer-reviewers reviewed the manuscript. After review and revision of the manuscript, the Book Editor approved the manuscript for final publication. Peer review comments, comments of the editor(s), etc. are available here: factor, inductive influence during a ground fault as well as during normal operation, and sequence impedance of the considered cable line by using a standard and well-known calculation procedures.
On the Power Lines—Electromagnetic Shielding Using Magnetic Steel Laminates
Energies
Protection against the electromagnetic fields around high-voltage transmission lines is an issue of great importance, especially in the case of buildings near power lines. Indeed, the developed fields can be harmful for the habitants and electrical/electronic devices, so the implementation of appropriate measures to address the above electromagnetic interference issue is necessary in order to ensure the safety of both human beings and equipment. Several practices have been proposed to reduce the electric and the magnetic fields around overhead and underground transmission lines (minimum distance, shielded cables, anechoic chamber etc.). In this context, the scope of the current paper is the use of highly permeable magnetic sheets for shielding purposes, along with the development of an appropriate procedure, based on finite element analysis (FEA) for the efficient design of passive shielding. The simulation results are compared with laboratory measurements in order to confirm the ad...