scholarly journals Detecting Grounding Grid Orientation: Transient Electromagnetic Approach

2019 ◽  
Vol 9 (24) ◽  
pp. 5270 ◽  
Author(s):  
Aamir Qamar ◽  
Inzamam Ul Haq ◽  
Majed Alhaisoni ◽  
Nadia Nawaz Qadri
Keyword(s):  
Eddy Currents ◽  
Comsol Multiphysics ◽  
Electromagnetic Environment ◽  
Diagonal Branch ◽  
Transient Electromagnetic ◽  
Grounding Grid ◽  
The Status ◽  
Mesh Spacing ◽  
Grid Orientation ◽  
Inversion Calculation

The configuration is essential to diagnose the status of the grounding grid, but the orientation of the unknown grounding grid is ultimately required to diagnose its configuration explicitly. This paper presents a transient electromagnetic method (TEM) to determine grounding grid orientation without excavation. Unlike the existing pathological solutions, TEM does not enhance the surrounding electromagnetic environment. A secondary magnetic field as a consequence of induced eddy currents is subjected to inversion calculation. The orientation of the grounding grid is diagnosed from the equivalent resistivity distribution against the circle perimeter. High equivalent resistivity at a point on the circle implies the grounding grid conductor and vice versa. Furthermore, various mesh configurations including the presence of a diagonal branch and unequal mesh spacing are taken into account. Simulations are performed using COMSOL Multiphysics and MATLAB to verify the usefulness of the proposed method.

Configuration Detection of Substation Grounding Grid Using Transient Electromagnetic Method

2017 ◽  
Vol 64 (8) ◽  
pp. 6475-6483 ◽  
Author(s):  
Cigong Yu ◽  
Zhihong Fu ◽  
Gaolin Wu ◽  
Liuyuan Zhou ◽  
Xuegui Zhu ◽  
...  
Keyword(s):  
Electromagnetic Method ◽  
Transient Electromagnetic Method ◽  
Transient Electromagnetic ◽  
Grounding Grid

scholarly journals Diagnosis for Conductor Breaks of Grounding Grids Based on the Wire Loop Method of the Transient Electromagnetic Method

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Shengbao Yu ◽  
Guanliang Dong ◽  
Nannan Liu ◽  
Xiyang Liu ◽  
Chang Xu ◽  
...  
Keyword(s):  
Topological Structure ◽  
Electromagnetic Response ◽  
Height Difference ◽  
Measuring Point ◽  
Wire Loop ◽  
Loop Method ◽  
Transient Electromagnetic ◽  
Grounding Grid ◽  
Grounding Grids ◽  
The Wire

The wire loop method of the transient electromagnetic (TEM) method is used to nondestructively detect conductor breaks of grounding grid. For this purpose, grounding grids serve as an underground wire loop, and the measuring points are arranged on the ground. At each measuring point, a receiving loop is employed to detect the electromagnetic response generated by transmitting the current of the transmitting loop. Conductor breaks can be diagnosed by analyzing the slices of the electromagnetic response. We study the effect of loop size and height difference through the simulation of an intact 2×2 grounding grid, confirming that it is easier to obtain the topological structure using a small transmitting loop and a small height difference. Furthermore, simulations of an intact 4×4 grounding grid and grids with different locations of conductor breaks are also conducted with a small transmitting loop. It is easy to distinguish the topological structure of the grounding grid and the locations of conductor breaks. Finally, the detection method is applied experimentally. The experimental results confirm that the proposed method is an effective technique for conductor break diagnosis.

Impacts of Diverting Potential Difference on Armored Cables in Substations

2014 ◽  
Vol 986-987 ◽  
pp. 931-935
Author(s):  
Li Chen
Keyword(s):  
Dielectric Breakdown ◽  
Simulation Software ◽  
Potential Difference ◽  
Insulation Material ◽  
Grid Simulation ◽  
Transient Electromagnetic ◽  
Grounding Grid ◽  
Large Current ◽  
Electrical Tree ◽  
Grounding Grids

To reduce the interference on communication equipments caused by transient electromagnetic field of switching operation, the shields of cables are connected to grounding grid on both sides in the substations grounding designs. However, when the substation is stroke by lightning or shorted, the huge potential difference called diverting potential difference between the cable core and the shield is generated, which can easily destroy insulation of cables, even producing electrical tree or dielectric breakdown in insulation material. Moreover, the large current flowing through the shield of cables will cause personnel accidents and equipment damages. In this paper, the electric model of cables is established using grounding grid simulation software—CEDGS. The way diverting potential difference changes influenced by grounding grids, soil and other parameters is analyzed. Measures to reduce diverting potential difference are proposed for providing a theoretical basis of construction in practice.

Transient Simulation of Electromagnetic Forming of Aluminium Tubes

2005 ◽  
Vol 6-8 ◽  
pp. 639-648 ◽  
Author(s):  
C. Karch ◽  
Karl Roll
Keyword(s):  
Eddy Currents ◽  
High Strain ◽  
Electromagnetic Forming ◽  
Numerical Representation ◽  
Strain Rates ◽  
High Strain Rates ◽  
Forming Process ◽  
Transient Electromagnetic ◽  
Deformation Properties ◽  
Stress And Deformation

The recent push to use more aluminium in automobiles has stimulated interest in understanding electromagnetic forming (EMF), which uses induced electromagnetic fields to generate high strain rates during the forming process. The high strain rates increase the formability of aluminum materials and might reduce elastic spring-back and wrinkling of the workpiece. Primary emphasis is placed on including of all relevant physical phenomena, which govern the process, as well as their numerical representation by means of simplified electrical equivalent circuits for the EMF machine and fully coupled field approach of the transient electromagnetic and mechanical phenomena. Moreover, the thermal effects due to Joule heating by eddy currents and plastic work are considered. The numerical model predicts the electromagnetic field, temperature, stress, and deformation properties that occur during the forming process. The numerical results of the tube deformation are compared with available experimental data.

scholarly journals Measurement of the transient shielding effectiveness of shielding cabinets

2008 ◽  
Vol 6 ◽  
pp. 293-298 ◽  
Author(s):  
H. Herlemann ◽  
M. Koch
Keyword(s):  
Numerical Simulations ◽  
Electromagnetic Fields ◽  
High Frequency ◽  
Comsol Multiphysics ◽  
Magnetic Shielding ◽  
Shielding Effectiveness ◽  
Transient Electromagnetic ◽  
Electric And Magnetic Fields ◽  
Numerical Tools ◽  
Gtem Cell

Abstract. Recently, new definitions of shielding effectiveness (SE) for high-frequency and transient electromagnetic fields were introduced by Klinkenbusch (2005). Analytical results were shown for closed as well as for non closed cylindrical shields. In the present work, the shielding performance of different shielding cabinets is investigated by means of numerical simulations and measurements inside a fully anechoic chamber and a GTEM-cell. For the GTEM-cell-measurements, a downscaled model of the shielding cabinet is used. For the simulations, the numerical tools CONCEPT II and COMSOL MULTIPHYSICS were available. The numerical results agree well with the measurements. They can be used to interpret the behaviour of the shielding effectiveness of enclosures as function of frequency. From the measurement of the electric and magnetic fields with and without the enclosure in place, the electric and magnetic shielding effectiveness as well as the transient shielding effectiveness of the enclosure are calculated. The transient SE of four different shielding cabinets is determined and discussed.

scholarly journals Damage detection of cracks in carbon fibre reinforced composites by pulsed eddy-current testing

2018 ◽  
Vol 191 ◽  
pp. 00003
Author(s):  
Abdeslam Aoukili ◽  
Abdellatif Khamlichi
Keyword(s):  
Carbon Fibre ◽  
Eddy Currents ◽  
Design Feature ◽  
Electromagnetic Response ◽  
Depth Of Penetration ◽  
Scientific Publications ◽  
Theoretical Understanding ◽  
Transient Electromagnetic ◽  
Pulsed Eddy Currents ◽  
Non Destructive

Non-destructive evaluation techniques that are based on electromagnetic methods are commonly used for inspection of metallic and carbon fibre reinforced plastics parts. Some of these inspection methods are based on eddycurrents which are generated by the electromagnetic induction phenomenon occurring under variable magnetic induction field. In eddy-currents testing, the depth of penetration into the material is controlled by the conductivity of the tested material and also the work frequency. Transient eddy-currents, also called pulsed eddy-currents, is an emerging non destructive technique that employs a pulsed excitation to induce a transient electromagnetic response from defects lying deep within a conducting structure. Such defects are difficult to inspect by conventional techniques, such as harmonic eddy-currents or ultrasonics. A large number of recent scientific publications have dealt with the theoretical understanding of the pulsed eddy-currents phenomenon and have also undertaken the design feature of appropriate probes. Finite element solution of the governing equations has been used to simulate the output signals as function of the input electrical excitation signal. Considering a B-scan strategy, simulation of a pulsed eddy-currents based probe is performed in this work with the objective to assess detectability of small defects through monitoring impedance changes of a detection probe.

scholarly journals Derivative Method Based Orientation Detection of Substation Grounding Grid

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1873 ◽  
Author(s):  
Aamir Qamar ◽  
Muhammad Umair ◽  
Fan Yang ◽  
Muhammad Uzair ◽  
Zeeshan Kaleem
Keyword(s):  
Magnetic Flux ◽  
Flux Density ◽  
Critical Parameters ◽  
Magnetic Flux Density ◽  
Main Peak ◽  
Diagonal Branch ◽  
Grounding Grid ◽  
Derivative Method ◽  
Grounding Grids ◽  
Orientation Detection

The grounding grid is a key part of substation protection, which provides safety to personnel and equipment under normal as well as fault conditions. Currently, the topology of a grounding grid is determined by assuming that its orientation is parallel to the plane of earth. However, in practical scenarios, the assumed orientation may not coincide with the actual orientation of the grounding grid. Hence, currently employed methods for topology detection fails to produce the desired results. Therefore, accurate detection of grounding grid orientation is mandatory for measuring its topology accurately. In this paper, we propose a derivative method for orientation detection of grounding grid in high voltage substations. The proposed method is applicable to both equally and unequally spaced grounding grids. Furthermore, our method can also determine the orientation of grounding grid in the challenging case when a diagonal branch is present in the mesh. The proposed method is based on the fact that the distribution of magnetic flux density is perpendicular to the surface of the earth when a current is injected into the grid through a vertical conductor. Taking the third order derivative of the magnetic flux density, the main peak coinciding with the position of underground conductor is accurately obtained. Thus, the main peak describes the orientation of buried conductor of grounding grid. Simulations are performed using Comsol Multiphysics 5.0 to demonstrate the accuracy of the proposed method. Our results demonstrate that the proposed method calculate the orientation of grounding grid with high accuracy. We also investigate the effect of varying critical parameters of our method.

Prediction of transient electromagnetic environment in power networks

1994 ◽  
Vol 30 (5) ◽  
pp. 3745-3748 ◽  
Author(s):  
B. Nekhoul ◽  
R. Feuillet ◽  
J.C. Sabonnadiere ◽  
L. Quinchon ◽  
F. Morillon
Keyword(s):  
Power Networks ◽  
Electromagnetic Environment ◽  
Transient Electromagnetic

The effect of a conductive half‐space on the transient electromagnetic response of a three‐dimensional body

Geophysics ◽  
1985 ◽  
Vol 50 (7) ◽  
pp. 1144-1162 ◽  
Author(s):  
William A. SanFilipo ◽  
Perry A. Eaton ◽  
Gerald W. Hohmann
Keyword(s):  
Half Space ◽  
Free Space ◽  
Eddy Currents ◽  
Three Dimensional ◽  
Vertical Component ◽  
The Body ◽  
Electromagnetic Response ◽  
Loop Current ◽  
Transient Electromagnetic ◽  
Space Response

The transient electromagnetic (TEM) response of a three‐dimensional (3-D) prism in a conductive half‐space is not always approximated well by three‐dimensional free‐space or two‐dimensional (2-D) conductive host models. The 3-D conductive host model is characterized by a complex interaction between inductive and current channeling effects. We numerically computed 3-D TEM responses using a time‐domain integral‐equation solution. Models consist of a vertical or horizontal prismatic conductor in conductive half‐space, energized by a rapid linear turn‐off of current in a rectangular loop. Current channeling, characterized by currents that flow through the body, is produced by charges which accumulate on the surface of the 3-D body and results in response profiles that can be much different in amplitude and shape than the corresponding response for the same body in free space, even after subtracting the half‐space response. Responses characterized by inductive (vortex) currents circulating within the body are similar to the response of the body in free space after subtracting the half‐space contribution. The difference between responses dominated by either channeled or vortex currents is subtle for vertical bodies but dramatic for horizontal bodies. Changing the conductivity of the host effects the relative importance of current channeling, the velocity and rate of decay of the primary (half‐space) electric field, and the build‐up of eddy currents in the body. As host conductivity increases, current channeling enhances the amplitude of the response of a vertical body and broadens the anomaly along the profile. For a horizontal body the shape of the anomaly is distorted from the free‐space anomaly by current channeling and is highly sensitive to the resistivity of the host. In the latter case, a 2-D response is similar to the 3-D response only if current channeling effects dominate over inductive effects. For models that are not greatly elongated, TEM responses are more sensitive to the conductivity of the body than galvanic (dc) responses, which saturate at a moderate resistivity contrast. Multicomponent data are preferable to vertical component data because in some cases the presence and location of the target are more easily resolved in the horizontal response and because the horizontal half‐space response decays more quickly than does the corresponding vertical response.

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