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1. Measurement and Computation of Induced Noise Levels in Telephone Lines Due to Harmonics in Nearby Power Lines
J. Ma, R. D. Southey, and F. P. Dawalibi The 4th Asia-Pacific Conference on Environmental Electromagnetics (CEEM), Dalian, China, August 1-4, 2006.
Abstract: This paper presents a real case study which includes measurement and computation of noise levels on telephone cables due to harmonics in nearby power lines. The objective of the study is to find the most efficient and economic mitigation measures to reduce the noise levels. A circuit model has been built and induced noise levels computed. Computation results are compared with the measurement data and they are in general agreement. Mitigation measures are proposed and will be examined in the second phase of the study. 2. Electromagnetic Fields of Energized Conductors in Multilayer Soils
S. Fortin, Y. Yang, J. Ma and F. P. Dawalibi The 4th Asia-Pacific Conference on Environmental Electromagnetics (CEEM), Dalian, China, August 1-4, 2006. Abstract: This paper discusses the computation of electromagnetic fields due to energized thinwire conductors in a horizontal multilayer soil. The computation uses a full wave solution for the Hertz vector potential caused by an electric dipole located in the soil or in the air. The soil layers can have arbitrary resistivity, permeability,permittivity, and thickness. The field generated by a linear conductor is obtained by integrating the contribution of dipoles along the conductor. The field of an arbitrary conductor network is obtained by superposition of the contribution of all the network conductors. Both energized conductors and the calculation points can be in the air or in the soil. Numerical results are shown for several examples using a four layer soil. The results obtained with the new method are in good agreement with the analytical result for a uniform soil results in the limiting case where the resistivity of all soil layers is the same. 3. An Efficient and Automated Method for Electromagnetic Compatibility Analysis along Congested Right-of-Way
Y. Li, S. Fortin, and F. P. Dawalibi The 4th Asia-Pacific Conference on Environmental Electromagnetics (CEEM), Dalian, China, August 1-4, 2006. Abstract: One of the safety issues in a power plant grounding design is fence grounding. The main concern is the magnitudes of touch voltages at locations close to a metallic fence during a fault at the power plant. It is often necessary to decide whether a metallic fence surrounding a power plant should be connected to or isolated from the grounding system of the power plant. In many cases, both grounding and isolation of the fence have to be employed to make it safe. Presently, trial and error methods are used to determine the locations of the isolations, a process that is difficult to optimize and that is very time consuming. In this paper, we present a technique that can determine the number and locations of the isolations accurately and efficiently while avoiding overdesign or underdesign situations. The application of the technique is illustrated using a practical example of power plant grounding design. It should also be pointed out that the same technique can be used to assess safety along railways that are in proximity to power plants or electrical substations. 4. Modeling Techniques for Analyzing Electromagnetic Interference Caused by High Voltage Power Lines to Neighboring Communication Cables
J. Liu, F. P. Dawalibi, and N. Mitskevitch The 4th Asia-Pacific Conference on Environmental Electromagnetics (CEEM), Dalian, China, August 1-4, 2006.
Abstract: Advanced electromagnetic interference techniques and simulation methods, used to model a complex network that includes multiple interconnected transmission and distribution line systems, nearby communication cables, and buried metallic structures, are presented in this paper. The simulations have been conducted in order to analyze electromagnetic interference of the high voltage power lines on the communication cables. Several scenarios have been explored to determine the interference level and evaluate possible mitigative measures to effectively reduce the induced currents and voltages along the communication cables to safe levels. 5. Recent Advances in Electromagnetic Interference Analysis in Common Corridors
J. Ma and F. P. Dawalibi The 4th Asia-Pacific Conference on Environmental Electromagnetics (CEEM), Dalian, China, August 1-4, 2006. Abstract: This paper discusses recent advances made in electromagnetic interference analysis in common corridors shared by electric transmission lines and other utilities such as railways and pipelines (victim lines). They include new advances made in analysis methods and modeling techniques. These advances enable accurate modeling of extremely long common corridors along which various parameters may change, such as soil resistivity, power line current magnitude, fault location, and victim line characteristics. 6. A New Approach to Calculate the Ionized Field of HVDC Transmission Lines in the Space and on the Earth Surface
S. Fortin, H. Zhao, J. Ma and F. P. Dawalibi International Conference on Power System Technology (POWERCON2006), Chongqing, China, October 22-26, 2006. Abstract: Corona discharge is a common phenomenon in high voltage transmission lines. The corona space charge arising from HVDC transmission lines is much more significant than that from HVAC lines due to the extended distribution of the space charge, which greatly influences the electric field strength on the ground and in space. A new iterative method has been developed to solve Poisson’s equation for HVDC line systems, accounting for the presence of space charge. The electric field strength can be calculated in the space around the HVDC transmission lines or on the ground. The system can be in homopolar, bipolar or hybrid mode, and can include sky wires or non-corona conductors. The conductors in the bundles are treated individually. The treatment accounts for the different corona onset gradient of positive and negative conductors and for ion recombination in the bipolar zones. Also, the positive and negative ions can possess different mobilities. 7. Integrated Computer Approach to Analyze the Electromagnetic Impact of Transmission Lines
J. Liu, S. Fortin, H. Zhao, F. P. Dawalibi and S. Tee International Conference on Power System Technology (POWERCON2006), Chongqing, China, October 22-26, 2006. Abstract: A comprehensive and integrated computer approach to evaluate various environmental impact parameters associated with HVAC and HVDC transmission lines is presented. The environmental parameters include: the electromagnetic fields and scalar potentials generated by the lines, and corona parameters, such as electromagnetic radiative interference, acoustic noise, and corona losses. A parametric analysis of the effects of key variables on the electromagnetic impact has been carried out for several representative cases. 8. GPR Zone of Influence of a Typical Electric Power Network
N. Mitskevitch, F. P. Dawalibi, J. Ma, and J. Liu International Conference on Power System Technology (POWERCON2006), Chongqing, China, October 22-26, 2006. Abstract: The zone of influence of the ground potential rise is analyzed based on a real case scenario. It is shown that the concept of zone of influence is quite complex if not totally blurred in the context of a modern convoluted topology involving transmission lines, distribution lines, water pipes of small towns and villages, and it is difficult to predict the location of zones of high potentials without the appropriate computer simulations. 9. Grounding Analysis of a Large Electric Power Station
J. Ma and F. P. Dawalibi International Conference on Power System Technology (POWERCON2006), Chongqing, China, October 22-26, 2006. Abstract: A complete analysis of an extensive grounding system of a large electric power station is presented. Major procedures necessary for an accurate analysis of a large grounding system have been demonstrated. These procedures include constructing adequate soil structures based on short and long traverse soil resistivity measurements, measuring and interpreting the ground impedance of a large grounding system, determining if the worst fault occurs inside or outside a power station, and selecting appropriate fault locations to cover the worst scenarios in the safety evaluations of the grounding system. The procedures presented in this paper can be used as a guide when dealing with extensive grounding systems in large electric power stations. 10. Power Grounding Safety: Copper Grounding Systems vs. Steel Grounding Systems
Y. Li, J. Ma and F. P. Dawalibi International Conference on Power System Technology (POWERCON2006), Chongqing, China, October 22-26, 2006. Abstract: More and more conventional grounding systems made of steel are being replaced with copper grounding systems in Asian countries. This paper analyzes the performance of grounding systems made of steel or copper conductors, taking into account the impedances of the ground conductors. A series of computer models simulate grounding systems of different sizes in various soil structures. Numerical results such as ground impedance, ground potential rise (GPR), touch and step voltages, and potential differences between copper ground conductors are compared with those pertaining to steel grounding systems. The performance advantages of grounding grids made of copper are demonstrated throughout the comparison. This paper also presents briefly a practical grounding performance before and after the replacement of steel with copper conductors. 11. Effectiveness of the Industry Standard Peninsula Technique for Grounding the Neutrals of Shunt Capacitors in High Voltage Substations
F. P. Dawalibi, S. Tee, S. Fortin, and Nathalie Grignon (Hydro Quebec) IEEE PES Power Systems Conference & Exposition (PSCE), Atlanta, Georgio, U.S.A, October 29 - November 1, 2006. Abstract: The Industry Standard IEEE C37.99-2000 implicitly recommends the use of peninsula grounding as the preferred method to ground the neutrals of capacitor banks in high voltage substations. The basis for this recommendation is a 1972 IEEE paper by Rogers and Gillies that has remained unchallenged until now. This paper compares the overall performance of a 735/230 kV substation grounding system designed according to the Peninsula method and a more conventional design consisting of reasonably dense ground conductors in the 230 kV capacitor banks area and concludes that the conventional design offers superior performance both from a safety and EMI perspective. Although the analysis was conducted based on the full back-to-back capacitor switching transient current discharge, this paper focuses on the performance as computed based on the main resonant frequency due to the extent of the main results to be presented. A future paper will report the results of the transient analysis and will discuss resonance conditions that were observed at frequencies around 100 kHz. 12. Recent Advances in the Modeling and Mitigation of AC Interference in Pipelines
W. Ruan, R. D. Southey, S. Tee, and F. P. Dawalibi Corrosion/2007 NACE International Conference & Expo, Nashville, Tennessee, March 11 -15, 2007. Abstract: The design of mitigation to reduce AC interference levels in a pipeline is a relatively straightforward matter when the mitigation can be installed with the pipeline, at the bottom of the trench. On the other hand, retrofitting introduces design challenges, which are discussed in this paper. For one thing, the depth of burial of gradient control wires running parallel to the pipeline is often limited by practical considerations: as a result, the effectiveness of these wires is reduced by soil freezing in northern climes. A second problem is the frequent need to interrupt the gradient control wires at road crossings, water bodies, wetlands, and other such obstacles. The level of protection is obviously compromised to some degree at such locations. It is found that consideration of the exponentially decreasing nature of soil resistivity with depth, during frozen conditions, can result in a dramatically improved assessment of mitigation performance. It is also found that, depending upon the soil structure, gaps of tens of meters in otherwise continuous gradient control wires may yield acceptable performance. |
