Search results for "Ground"
showing 10 items of 2432 documents
A Simple Method for Evaluating Ground-Fault Current Transfer at the Transition Station of a Combined Overhead-Cable Line
2008
When a substation is fed by a combined overhead-cable transmission line, a significant part of the ground fault current flows through cable sheaths and is discharged into the soil at the transition station where cables are connected to the overhead line. Such a phenomenon, known as ldquofault application transfer,rdquo may result in high ground potentials at the transition station which may cause shocks and equipment damage. The scope of this paper is to present new analytic formulas which can be used for the direct calculation of the fault current transferred at the transition station and its ground potential rise as well as the substation earth current. The proposed formulas allow evaluat…
Finite-Difference Time-Domain Simulation of Tower and Grounding Subjected to Lightning
2015
In this paper the behavior of a tower and its grounding system, subjected to a lightning, is faced. Finite difference time domain (FDTD) method has been chosen in order to study the non-linear time domain behavior of the system. The electromagnetic problem has been described by using two type of first order time derivative equations: Maxwell's equations and Telegraph equations. Aim of this work is to evaluate the possibility of a flashover between tower and power line, by considering different cases of study.
A Method to Evaluate Voltages to Earth During an Earth Fault in an HV Network in a System of Interconnected Earth Electrodes of MV/LV Substations
2008
An easy and swift method to evaluate, in a system of interconnected earth electrodes, earth potentials on earthing systems of medium-voltage/low-voltage (MV/LV) substations, in an event of single-line-to-earth fault inside a high-voltage/medium- voltage (HV/MV) station, is presented. The advantage of the method is the simplicity of the mathematical model for solving complex systems of any size with a sufficient accuracy for practical purposes. This paper shows the results of simulations, performed on networks with different extensions and characteristics, organized in easy-to-read graphs and tables. A comparison of these results with the values obtained according to the procedure explained …
DOUBLE EARTH FAULT EFFECTS IN PRESENCE OF INTERCONNECTED EARTH ELECTRODES
2009
The paper presents a study on the effects of double earth faults in Medium Voltage (MV) networks, in presence of electrical interconnection of the earthing systems of the secondary substations. In urban areas, indeed, the earth electrodes of the secondary substations are interconnected and, in many cases, they are also connected to the earth electrodes of the primary stations, in order to realize quasi-equipotential surfaces, intrinsically safe against electric shocks, named Global Earthing Systems (GES). The concept of GES has been introduced in the technical literature ten years ago in the Document HD 637 S1 by CENELEC, with the aim of providing a solution to the problems of designing and…
The Quest for Global Safety
2007
The authors present a systematic study on the factors that have influence on the establishment of the safety conditions ensuring the rise of Global Earthing Systems. Starting from the definition of Global Earthing System given by CENELEC Document HD 637 SI and from the results of the studies done on the last years on the interconnected earthing systems inside MV networks, the paper proposes some directions of deepening on the topic of Global Safety. Some of the themes whom the paper deals with are: the correct definition of proximity, interconnection and quasi-equipotentiality of the earth electrodes belonging to a Global Earthing System; the influence of the presence of HV/MV stations on h…
On the effects of HV/MV stations on global grounding systems
2016
The METERGLOB project has faced the issue of the identification of Global Grounding Systems. One of the main point of the problem is to define if an interconnection of single grounding systems gives place to a Global Grounding System in any condition and for every kind of ground fault. This paper focuses the attention on what happens in the case of single line to ground fault inside a HV/MV station whose ground electrode is connected to the cable' shields of the MV lines outgoing the station and supplying the secondary substations of a given area.
Attenuation of low frequency magnetic fields produced by HV underground power cables
2015
High-voltage underground cable systems are becoming more common as the demand for electrical power within urban centers increase, also considering the difficulties in building new overhead power lines in the vicinity of city centers because of authorization issues. Therefore, interest towards the evaluation of magnetic fields produced by high-voltage power lines has been triggered during the last decade and concern about effects on human health of exposure to extra low frequency (ELF) magnetic fields due to power lines has been increasing as well. Hence, the evaluation of the magnetic field produced by underground power cables is important in order to develop methods for mitigating their in…
Ground-Fault Current Transfer at the Transition Station of a Combined Overhead-Cable Line. A Parametric Analysis
2007
When a substation is fed by a combined overhead-cable transmission line, a significant part of the ground fault current flows through the grounded cable sheaths and discharges into the earth at the transition station, where cables are connected to the overhead line. If the transition station is a dead-end steel pole structure, the local ground electrode, small and of high resistance, could be inadequate to maintain the ground potential rise within safety limits in case of a fault to ground at the receiving end substation. Based on a circuit model approach, the paper presents a parametric analysis of the fault current distribution between the faulted substation and the transition station, ta…
Incremental dynamic based fragility assessment of reinforced concrete structures: Stationary vs. non-stationary artificial ground motions
2017
Abstract Artificial and natural records are commonly employed by researches and practitioners to perform refined seismic assessments of structures. The techniques for the generation of artificial records and their effectiveness in producing signals which are significantly representative of real earthquakes are still debated as well as results of the consequent seismic assessment to expect from their application. The paper presents an in-depth comparative study highlighting the effect of employing different typologies of artificial ground motion records on seismic assessment results, especially addressing seismic fragility curves. Three sets of 50 stationary, nonstationary evenly modulated a…
HybridPLAY: A New Technology to Foster Outdoors Physical Activity, Verbal Communication and Teamwork
2015
This paper presents HybridPLAY, a novel technology composed of a sensor and mobile-based video games that transforms urban playgrounds into game scenarios. With this technology we aim to stimulate physical activity and playful learning by creating an entertaining environment in which users can actively participate and collaborate. HybridPLAY is different from other existing technologies that enhance playgrounds, as it is not integrated in them but can be attached to the different elements of the playgrounds, making its use more ubiquitous (i.e., not restricted to the playgrounds). HybridPLAY was born in 2007 as an artistic concept, and evolved after different phases of research and testing …