Marcos Telló

The Transmission Line Modeling Method to Represent the Soil Ionization Phenomenon in Grounding Systems

This paper presents an extended methodology based on the transmission line modeling method (TLM) aiming at a soil ionization representation for the simulation of grounding systems. This natural phenomenon can be represented by considering the variation of the conductive components present in the TLM circuit. The proposed analytical formulation is introduced with a focus on the computational implementation of the TLM method in one dimension. The method is not subject to divergent solutions, being numerically stable and the methodology can be incorporated into a general algorithm irrespective of the soil properties or characteristics of the grounding electrode and lightning surge.

Improved distribution feeder topology against lightning

Energy supply is a significant resource for economic and social development. Power systems statistics shows that the lightning phenomenon is one of the most important causes of power systems outage. In this context, the paper present a study of the performance of a 23kV distribution line related to the occurrence of direct lightning in a particular point of the system, with focus in a comparative analysis of different feeders and poles configurations. The analysis is based on the calculation of flashover and backflashover using ATP-Draw version of the EMTP. The differences of the performance between the horizontal and the vertical feeder configurations with grounding system are demonstrated through the comparison of the maximum lightning current withstand by the feeder. Non-linear grounding resistance and variability of the resistivity of the soil were considered. Simulation results show that the configuration with guard-wire can improve the immunity up to 100% related to the maximum lightning current that the feeder withstand.

Improvement of an overhead distribution feeder performance against lightning considering the wire-guard protection

This paper presents a study about the influence of the wire-guard as a protection system in overhead distribution line in comparison with unprotected topology against lightning. A real feeder was considered as a case study using ATP-EMTP software. Practical aspects related to the modeling of a distribution line are presented. Simulation results show that the shielding configuration ensures a protection significantly better than the actual topology, around 10 times in terms of lightning peak current. Thus, the wire-guard can improve the immunity of distribution system against atmospheric discharges.

Transient response of grounding electrode with emphasis on the Transmission Line Modeling Method (TLM)

This paper presents practical aspects of a computational implementation based on the Transmission Line Modeling Method in one dimension (TLM-1D) for the transient analysis of grounding electrodes. Initially, an introduction on the subject with a brief revision of the state-of-the-art methodologies currently used for impulsive grounding transient evaluation is made, emphasizing TLM. In the following, aspects related to the representation of the grounding conductors are reported considering the soil ionization phenomenon in the transitory analysis. Finally, simulation results are presented and discussed.

The BECM concepts applied to heal cancer

The application of Bio-Electric Circuits Model (BECM) concepts can destroy cancer cells. Complete Response (CR)+Partial Response (PR) of about 80% was obtained in more than three thousand cases from different types of human cancer. We agree that the treatment of cancer using the concepts of BECM utilizes the same principle as that of hyperthermia techniques in cancer therapy. This paper estimates the tumor temperature distribution when the BECM is applied in the cancer area. The Finite Element Method (FEM) is used to determine the temperature distribution inside the human model caused by the application of BECM in the tumor region. The simulation of the use of BECM in a tumor situated in the thorax region is presented. The aim of this work is to present a new hyperthermia technique where DC current is used directly in the tumor (contrary to irradiating the cancer area with high frequencies) to determine the temperature distribution of this area.

Effect of shielding and grounding on lightning performance of 23kV distribution feeders

This paper presents a study of the behavior of distribution feeders against lightning, where the magnitude of the surge caused by this phenomenon is calculated. The feeder model and the lightning phenomena have been implemented in the electromagnetic transients program ATP-Draw. The magnitudes of the surges are obtained by numerical simulations in this program. Simulations were performed for cases where the lightning impacts the wire-guard or the phase conductor. A sensitivity study to establish the parameters that influence the maximum values of the surge is also performed. The model is applied to a rural distribution line in southern Brazil, where very often lightning causes insulation failure and power cuts. The results show how to improve the feeder protection in order to enhance the level of system reliability.

Tumor compression due application of DC current

The aim of this paper is to evaluate the forces that appear in the tumor region when the DC current flows in it. The knowledge of the electromagnetic force distribution inside the region of study is very important because the DC current therapy (ECT) produces the destruction of tumor cells. When the DC current is applied the reduction of tumor size occurs. Additionally, the DC current flowing in the tumor promotes the micro-thromboses (desirable effect). The micro-thromboses consist of the blockade of arterial vessels that feed the malignant cells leading to regression of the tumor. So, one component responsible for these effects is the electromagnetic force distribution in the tumor area. The determination of these force distributions involves three steps of numerical evaluations: a) J/spl I.oarr/ determination, b) B/spl I.oarr/ determination and c) knowing (in the domain of study) the vectors J/spl I.oarr/ and B/spl I.oarr/ the vector F/spl I.oarr/ should be determined. Indeed, the knowledge of force distributions in the area of interest will allow a better understanding of the phenomena that occur in the cancerous cells when ECT is applied in human beings.

Comparative performance of impulsive grounding systems embedded in concrete: An experiment in reduced scale

This paper presents a comparative study of impulsive grounding systems encased in concrete (namely UFER grounding). Several topologies used in transmission and distribution networks as well as in industrial plants were evaluated considering soils with different properties. Scale measurements (in an electrolytic tank with soil) were carried out in order to quantify the performance of this grounding system. The study discusses the performance of different grounding configurations: 1 rod; 2 rods; counterweight; cross and grid embedded in concrete. The results show that the use of UFER grounding can reduce significantly the value of the grounding impulsive impedance both in soils with low and high resistivity for the different evaluated configurations.

Novel Formulation to Determine the Potential on the Soil Surface Generated by a Lightning Surge

This paper presents the development of an analytical formulation for estimating the potential on the soil surface, caused by electric current calculated on a grounding conductor. The formulation has a great significance in its use in conjunction with 1-D numerical methods, which are not able to determine such potentials directly. The proposed study focuses on lightning surges considering the frequency dependence of the soil properties. First, the subject is introduced emphasizing important aspects related to the analysis and representation of grounding systems against lightning. Afterward, the proposed analytical formulation is introduced with a focus on the computational implementation of the transmission line modeling method in 1-D. Simulations were carried out considering a typical horizontal electrode used as grounding in the power electric system. The formulation was validated by comparing the results with the solution based on the electromagnetic model (CDEGS Software), which is considered the most stringent for the solution of full Maxwell equations due to their minimum approaches. The results demonstrate that the generalized formulation presents good accuracy, contributing to an improved representation of grounding systems based on numerical techniques in 1-D.

The need for standardization of human tolerability levels for lightning currents and voltages

This paper deals with the problem of establishing limits of lightning currents and voltages tolerable to human beings. A numerical computation taking into account a representative model of the human body in contact with a lightning surge associated to a grounding system was performed considering different types of soil. The step and touch potential were evaluated in order to estimate the current and energy generated on the heart that can lead to a harmful condition in terms of ventricular fibrillation of the heart.