Ground

Abstract: The development and application of a computer model for analyzing the transient performance of grounding systems based on electromagnetic field theory is described. The use of a combination of numerical integration techniques, method of moments, adaptive interpolation, and fast Fourier transform constitutes the basis for the computation of various physical quantities such as the electric fields in the ground, longitudinal and leakage currents in the ground conductors, and ground impedances. It is shown that the analysis of conductors energized by current waves can require computations at frequencies higher than the significant frequencies in the spectrum of the excitation signal, while simpler models may fail to predict accurately the transient performance. The main limitation of the computer model is the time required for the analysis of large or complex grounding systems. >

Abstract: A comprehensive study on the effect of a lossy ground on the induced voltages on overhead power lines by a nearby lightning strike is presented The ground conductivity plays a role in both the evaluation of the lightning radiated fields and of the line parameters To be calculated by means of a rigorous theory, both fields and line constants need important computation time, which, for the problem of interest, is still prohibitive The aim of this paper is to discuss and analyze the various simplified approaches and techniques that have been proposed for the calculation of the fields and the line constants when the ground cannot be assumed as a perfectly conducting plane Regarding the radiated electromagnetic field, it is shown that the horizontal electric field, the component which is most affected by the ground finite conductivity, can be calculated in an accurate way using the Cooray-Rubinstein simplified formula The presence of an imperfectly conducting ground is included in the coupling equations by means of two additional terms: the longitudinal ground impedance and the transverse ground admittance, which are both frequency-dependent The latter can generally be neglected for typical overhead lines, due to its small contribution to the overall transverse admittance of the line Regarding the ground impedance, a comparison between several simplified expressions used in the literature is presented and the validity limits of these expressions are established It is also shown that for typical overhead lines the wire impedance can be neglected as regard to the ground impedance

Abstract: This study provides a comprehensive analysis of earthing systems as defined by international standards. It involves the calculation of fault currents and contact voltages, the selection of suitable electrical protection for each system type, and an evaluation of the currently implemented systems. The research highlights the distinctions in system performance, focusing on supply continuity and the corresponding protection mechanisms. It also addresses methods for defining neutral points in both high and low voltage networks. Furthermore, the study examines the effectiveness of protective devices during ground faults, including the implications of unearthed neutral systems. Both existing and proposed methods of protection are discussed, with particular emphasis on the utilization of derivatives of transient waves for safeguarding against atmospheric disturbances. The role of earthing in ensuring public safety during work on electrical equipment is explored, addressing the prevention of direct and indirect contact, protection against overcurrent and overvoltage, mitigation of electric shock risks, and safeguarding of both personnel and equipment from electrical discharges. This research incorporates international standards and measurements, applying them to grounding systems used globally. The findings lead to scientific, economic, and safety-related conclusions, culminating in recommendations for the optimal use of grounding devices across various settings.

Abstract: Pulse circuits for measuring the capacitance to ground of a plate may be used in control equipment to provide an indication of the proximity of a person or object to be sensed. Pulse circuits are disclosed that are made from sets of three or more electrical switching elements arranged so that each of the switching elements has one side electrically connected to either a supply voltage or to an electrical ground. These arrangements are compatible with existing integrated circuit fabrication technology. In addition, the circuitry can be configured as a proximity sensing switch that requires only a two wire connection to a host apparatus.