Characterization of super-low frequency electromagnetic fields produced by an undersea transmission cable in a homogeneous fluid By Jordan Pommerenck A PROJECT submitted to Oregon State University College of Science in partial fulfillment of the requirements for the degree of Baccalaureate of Science in Physics Presented 6 May 2014 Commencement June 2014 An ABSTRACT of the thesis of Jordan Pommerenck in partial fulfillment of the degree of Baccalaureate of Science in Physics presented on 6 May 2014. Title: Characterization of super-low frequency electromagnetic fields produced by an undersea transmission cable in a homogeneous fluid. Abstract approved: _____________________________________________________ Alexandre F. T. Yokochi Offshore renewable energy, an untapped energy resource in the United States, has the potential to stimulate job creation and diversify the world’s energy portfolio. Transmission cables are used to transfer electrical power to the mainland. These cables carry a harmonic time-dependent current. This current in turn generates both an electric and magnetic field. Although the electric field can be shielded from the marine environment, it is not economically feasible to use high permeability materials to shield the magnetic field. The magnetic field induces an electric field in the water surrounding the transmission cable. The sensory perception and migration of fish and mammalian species can be caused by perturbations in the electric and magnetic fields. This research focuses on determining the magnitude of both the magnetic field and the induced electric field. It is hoped that through a better understanding of the fields created by these transmission cables, marine conservation can be promoted and renewable wave energy can be further developed. Several analytic models are compared for the radial and axial electric field. The magnitude of the magnetic field and its induced electric field in seawater are experimentally measured, and the ability to predict the electric field through a derivation of Maxwell’s equation similar to the statement by Shakur et al is evaluated experimentally. A derivation using polarization potentials (Hertz vectors) employed by Sommerfeld et al is used to model the induced electric field. The magnetic field is measured using a Hall magnetometer. Electric fields are measured using standard reference graphite electrodes. The magnetic field is modeled using Maxwell’s equations; there is excellent overlap of the experimental data and theoretical model. The traditional model of dealing with the fields directly fails to accurately model the data for a single copper conductor in both the near and far field regions. There is excellent correlation between the model proposed by Sommerfeld and the measured data. Keywords: Electric and magnetic fields, polarization potential, under-sea transmission cable, offshore ocean energy, renewable, electric wave generation, marine life Corresponding email address: [email protected] i © Copyright by Jordan Pommerenck 6 May 2014 All images are the intellectual property of Jordan Pommerenck unless otherwise cited in the caption. Images may not be used without express written consent of the author. All Rights Reserved ii Acknowledgements I would like to thank Dr. Yokochi for providing the opportunity and the environment in which to conduct this exciting research. The freedom to conduct research in a very independent way helped me to gain a great deal of responsibility and intellectual maturity. This research experience has really taught me to motivate myself. I am deeply indebted to Justin Pommerenck for the many hours spent taking measurements on this project. Working on several different research projects has been a wonderful experience. I would like to thank Dr. Tate for the time well spent in the PH403 working and reworking my undergraduate thesis. The opportunity to work in a collaborative environment with fellow students was an invaluable learning experience. Being able to learn about each other’s research and professionally present our own research was an important part of my undergraduate experience. THANK YOU! I would like to express my gratitude to Dr. Yokochi, Dr. Tate, and Dr. Minot for writing letters of recommendation for graduate school. Also, I would like to thank Dr. Jansen and Dr. Tate for making time to discuss graduate school with me. This material is based upon work supported by the Department of Energy under Award Number DE- FG36-08GO18179. iii Table of Contents 1. Abstract.....................................................................................................................................................i 2. Acknowledgements ................................................................................................................................iii 3. Introductory Material.............................................................................................................................1 3.1 Physics of wave generation .................................................................................................................1 3.2 Introduction to the problem..................................................................................................................3 4. Theoretical Methods ...............................................................................................................................4 4.1 Theoretical background to problem ....................................................................................................4 5. Methods....................................................................................................................................................9 5.1 Setup of the water containment system ...............................................................................................9 5.2 Measuring the current drawn by the thermal fan ...............................................................................10 5.3 Magnetic field measurement techniques............................................................................................10 5.4 Instrument analysis of the digital multi-meter ...................................................................................12 5.5 Direct electric field measurement techniques ....................................................................................13 5.6 Induced electric field measurement techniques .................................................................................14 6. Results and Discussion..........................................................................................................................15 6.1 The magnitude of the magnetic field .................................................................................................15 6.2 The direct electric field from copper conductor.................................................................................17 6.3 Electric field strength induced by magnetic field ..............................................................................18 6.4 Electromagnetic impacts on marine life.............................................................................................21 7. Conclusions ............................................................................................................................................22 8. References ..............................................................................................................................................22 9. Appendices.............................................................................................................................................24 iv Table of Figures Figure 1: The image shows the global distribution of wind speed as observed by TOPEX/Poseidon's dual-frequency radar altimeter from October 3 to October 12, 1992 [2].......................................................1 Figure 2: Shown is a topographical map of wave energy per meter capable of being harvested for the world [4].........................................................................................................................................................2 Figure 3: Shown in the figure [14] is a finite current source oriented along the z axis and a source point P. ........................................................................................................................................................................4 Figure 4: The water containment unit in the laboratory setting. The rack is free to slide in the horizontal direction. ......................................................................................................................................................10 Figure 5: The blue radial field lines surrounding the wire correspond to the magnetic field. The magnetic probe is shown above the wire. The red, blue, and green arrows represent the standard basis in a Euclidean space. The red arrow points in the positive z direction, the green arrow points in the positive y direction, and the blue arrow points in the positive x direction...................................................................11 Figure 6: Attached to the Keithley multi-meter are the two sensitive probes used to measure the electric field. The device generates data in tabular format that is exported Excel or csv worksheets. ...................13 Figure 7: Shown is the experimental technique used to measure the radial electric field. The two graphite rods are shown on a line perpendicular