New Publications

Wind Turbine Farm Network Grounding Design Using Integrated Simulation Methods and Techniques

J. Liu and F. P. Dawalibi

2010 International Conference on Future Power and Energy Engineering (ICFPEE), Shenzhen, China, June 26 - 27, 2010.

Abstract—The design of a wind farm grounding system including the substation and wind turbine generators of the collector network is a very comprehensive task. Powerful integrated grounding simulation methods and design techniques that are appropriate for carrying out this kind of work are presented and discussed in this paper. They include soil structure model selection based on in-situ soil resistivity test data, current distribution calculations for phase-to-ground faults at the substation and wind turbines, design of the substation and wind turbine grounding systems and safety evaluations of the grounding systems. The methods and techniques presented in this paper can be used as a reference guide when designing grounding systems of a large wind farm network.

Electromagnetic Compatibility Analysis of Power Line and Railway Sharing the Same Right-of-Way Corridor: A Practical Case Study

Y. Li, F.P. Dawalibi and R. Raymond

2010 International Conference on Future Power and Energy Engineering (ICFPEE), Shenzhen, China, June 26 - 27, 2010.

Abstract —A thorough analysis of the electromagnetic compatibility of power lines and neighboring railway is presented. The railway is located close to the transmission line that consists of a combination of overhead and underground conductors and cables. Electromagnetic interference caused by high voltage power lines can endanger the proper operation of the signal and protection systems of the railways and threaten the safety of the personnel under both load and fault conditions. The performance of the system, including rail GPR (ground potential rise), rail-to-rail voltages and touch and step voltages are evaluated accurately taking into account the inductive, capacitive and conductive components. Numerical results are presented and discussed.

Validation of a Method to Remove Shield Wires’ Contribution In Ground Impedance Measurements

Jinxi Ma, and Farid P. Dawalibi

The 18th Conference of the Electric Power Supply Industry (CEPSI), Taipei, Taiwan, October 25-28, 2010.

Abstract— Validation of a method to remove the contribution of shield wires in ground impedance measurements has been carried out. It is found that even though the ground impedance obtained using this method is always higher than the true ground impedance, the method is generally acceptable. The error varies significantly as a function of soil structure. For the soil models and the system examined in the paper, the error ranges from 0.6% to 31.6%. The worst case occurs when the soil structure exhibits behaviour similar to that of a soil with low resistivity shallow-depth layers and high resistivity deeper layers. When the soil structure is similar to a soil with high resistivity shallow-depth layers and low resistivity deeper layers, the error is insignificant. Since in practice this method has to be used together with the Fall-of-Potential method for ground impedance measurement, suitable computer software packages should be used together to predict the error and thereby improve the accuracy of the measurement.

EMC ANALYSIS AND DESIGN CONSIDERATIONS OF RAILWAY SHARING THE SAME CORRIDOR WITH POWER LINES

Yexu Li, Farid Paul Dawalibi and Jinxi Ma

The 18th Conference of the Electric Power Supply Industry (CEPSI), Taipei, Taiwan, October 25-28, 2010.

Abstract—EMC analysis and design considerations of railway sharing the same corridor with power lines are discussed in this paper. The main work that has been carried out includes the analysis of the effects of the soil structure and equivalent rail ballast model, the influence of missing insulating joints on the predicted EMF levels, the impact of different types of rail unbalance conditions, such as shorted insulating joints, broken rails and moving train on aggravating the EMC problems, the effects of activated surge arrestors on the interference levels and the importance of validating the proposed mitigation scheme. Examples have been provided in this paper. The results and conclusions presented here can be used as a reference to analyze EMC issues and design appropriate mitigation to minimize EMC on railways that share the same corridor with power lines.

Inadequacies of the Industry-Standard IEEE C37.99-2000 Concerning Grounding Neutrals of Shunt Capacitors in High-Voltage Substations

Farid Paul Dawalibi, Sharon Tee, Simon Fortin and Nathalie Grignon

IEEE Transactions on PWRD, Vol. 26, No. 2, April 2011, pp. 782-789.

Abstract—The industry-standard IEEE C37.99-2000 recommends the use of Peninsula Neutral Ground 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. Many grounding designs are carried out according to this approach despite the fact that it is the least efficient one. As long as this IEEE standard is not updated to reflect the new findings reported in this paper, designers will continue to be misguided. In this paper, we demonstrate that IEEE standard C37.99-2000 recommendations have no valid scientific basis by comparing the overall performance of a 735/230-kV substation grounding system designed according to the Peninsula Neutral Ground method, the single-point neutral ground and a more conventional design consisting of reasonably dense ground conductors in the 230-kV capacitor banks area and conclude that the conventional design offers superior performance from a safety and electromagnetic-interference perspective based on the fundamental frequency and full frequency spectrum of the back-to-back capacitor switching transient current discharge.

A Parametric Analysis of Power Line Structure Response to Lightning Strikes

Winston Ruan, Robert Southey, Sharon Tee and Farid P. Dawalibi

The 18th Conference of the Electric Power Supply Industry (CEPSI), Taipei, Taiwan, October 25-28, 2010.

Abstract— Modern-day computer modeling of lightning strikes to transmission lines has concentrated for the most part on aboveground components of the system, with relatively little attention given to what happens below the earth’s surface. This paper presents a parametric analysis on how pole-top GPR and related currents vary as a function of soil resistivity (varying from 100 to 10,000 Ohm-m) and extent of grounding (varying from a pair of ground rods to a continuous counterpoise), during a 1.2 ms/50 ms lightning strike to the top of an H-frame structure. It is shown that the pole-top GPR increases when the soil resistivity increases. When the lightning channel is modeled, it also increases the pole-top GPR due to the electromagnetic field. There is little difference in the counterpoise performance as a function of counterpoise length when the soil resistivity is low. However, when the soil resistivity is high enough, a long counterpoise can make a noticeable difference in the computed pole-top GPR.

Safety Analysis of Fence Installation on a Large Power Station Concerning Inductive and Conductive Coupling from Nearby Transmission Lines

Jinxi Ma, Huiliang Zhao, Farid P. Dawalibi

Asia-Pacific Power and Energy Engineering Conference (APPEEC2011), Wuhan, P. R. China, March 25 - 28, 2011.

Abstract-This paper presents a safety analysis during the installation of a fence surrounding a large power station under construction. The safety concerns are due to both inductive and conductive coupling from nearby existing transmission lines during steady state and fault conditions. The fence must be installed during the station construction phase and before the installation of its grounding system. Different scenarios are analyzed to ensure the safety during and after the installation of the fence. Based on the analysis, procedures for installing the fence to ensure safety at all times are developed. The analysis and the procedures presented in this paper can be used as a guide when carrying out safety analysis of fence installation under similar circumstances.

Transient Response of Shielded Substations Hit Directly by a Lightning Strike

Farid Paul Dawalibi, Simon Fortin and Yexu Li

The 18th Conference of the Electric Power Supply Industry (CEPSI), Taipei, Taiwan, October 25-28, 2010.

Abstract — Electric Substations are often exposed to lighting strikes. When that happens, very fast large transient voltage stresses occur. Surge limiters can be destroyed and electronic equipment inside control rooms can be damaged. In order to develop appropriate mitigations that prevent such catastrophic damages, a model of a lightning strike hitting the top of a substation mast or shielding structure is analyzed. A field theory approach is used to solve Maxwell’s electromagnetic field equations. The transient problem is first solved by a frequency domain formulation. The time domain response is then obtained by application of an Inverse Fourier Transformation. The system analyzed consists of a shielding structure made of tall masts and horizontal shield wires that are connected to the substation grounding system. The objective of this study is to model realistic lightning strikes on various transmission and distribution substations that are shielded by masts and shield wires using an electromagnetic field approach. Based on recent studies of the electromagnetic field caused by energized conductors in horizontally layered soils, we have initiated research work on the lightning response of buried metallic structures that are partially aboveground and partially buried in multilayered soils. In this paper, the focus is placed on three dimensional structures partially buried in a uniform soil. Future work will examine the effects of soil layering structures and extended metallic networks. An internet link that shows the time domain response of the substation as an animation plot is also provided.