Search results for " Fault"
showing 10 items of 239 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…
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…
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.
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…
A simple unsynchronized two‐end algorithm for faults location and identification in electrical distribution systems
2012
PurposeThe purpose of this paper is to identify a new and simple two‐end algorithm for fault location identification and characterization, in electrical distribution systems.Design/methodology/approachThe developed diagnostic algorithm is based on a simple model of the network using a lumped parameters representation.FindingsTest results have proved the approach to be efficient, allowing a precise fault identification and location while not requiring synchronized measures from the two ends.Research limitations/implicationsThere is a need for measurement systems at all MV/LV substations.Practical implicationsApplicability with limited investments is not possible where metering systems are no…
Investigation of motor current signature and vibration analysis for diagnosing rotor broken bars in double cage induction motors
2012
This paper investigates the detectability of rotor broken bars in double cage induction motors using current signature and vibration analysis techniques. Double cage induction motors are commonly used for applications where successive loaded starts-up are mandatory. Experimental results were performed under healthy and faulty cases, and for different load conditions using each technique. Rotor broken bars fault detection based on sideband current components may fails due to the presence of inter bar currents that reduce the degree of rotor asymmetry, yielding to a decrease of the magnitude of these spectral components. But inter bar currents produce core vibrations in the axial direction, w…
A robust calibration methodology for an On-Board Diagnostic car system
2006
New car models are now by law equipped with on-board diagnostic (OBD) systems aimed at monitoring the state of health of strategic components that ensure low levels of polluting exhaust emissions. During development phases, for each new car model, the OBD system must be finely calibrated. This article presents a robust calibration methodology taking into account sources of variability mainly due to production process, operating, and environmental conditions. The methodology enables us to evaluate the false alarm and failure to detect risks intrinsically related to the adopted calibration. An application concerning an upstream oxygen sensor monitored by the OBD is presented.
Controlled Fault-Tolerant Power Converters for Power Quality Enhancement
2013
Power quality depends generally on the interaction of electrical power with electrical equipments. If electrical equipments operate correctly and reliably without being damaged or stressed, a suitable level of power quality is assured. On the other hand, if the electrical equipment malfunctions, is unreliable, or is damaged during normal usage, power quality is poor and probably the economical loss could be important like the technical one. In the scenario of the Distributed Generation, power quality issues will be moreover important because an higher dissemination of power conditioning equipment will be requested and this obviously increases the sources of vulnerability of the electrical s…
Data-driven design of robust fault detection system for wind turbines
2014
Abstract In this paper, a robust data-driven fault detection approach is proposed with application to a wind turbine benchmark. The main challenges of the wind turbine fault detection lie in its nonlinearity, unknown disturbances as well as significant measurement noise. To overcome these difficulties, a data-driven fault detection scheme is proposed with robust residual generators directly constructed from available process data. A performance index and an optimization criterion are proposed to achieve the robustness of the residual signals related to the disturbances. For the residual evaluation, a proper evaluation approach as well as a suitable decision logic is given to make a correct …