Fault Current Profile Research Articles

High impedance fault detection based on current harmonic analysis using Chirp Z transform

High Impedance Fault (HIF) is a problematic fault of feeders which its fault current is lower as compared to normal current in power system. Likewise, due to magnitude of impedance engaged in fault area and behavior of fault current is specific and not the same as the usual fault current profile which cannot be identified by standard relays. The HIF is created whenever a live conductor contacts with objects owning large impedance. The HIFs Signal has high index of similarity with some normal cases in feeders like Nonlinear loads (NL) waveform, or instant of switching of linear loads (LL), capacitor banks (CB) and full load transformers (FLT), which provided methods must distinguish them. So, the paper utilized a novel method with ability of recognizing HIF from all possible events in feeders with high accuracy. The Chirp Z Transform (CZT) has been applied to extract the features of HIF and/or other usual network events signal. It is possible to appropriately detect fault by low order harmonics of current signal extracted by means of CZT. Maximum discrepancy of detection is nearly 7 ms which is accurate enough. Also, absence of threshold values in algorithm makes it simple and can be used in each type of distribution and even transmission systems. Working in low-frequency harmonics is another advantage of this method because needs lower sampling frequency. The evaluated signals of HIF, NLs, LLs, capacitors and FLT are acquired by a simulated 13.8 kV distribution system in MATLAB/Simulink.

Fault Location in Radial Distribution Network Based on Fault Current Profile and the Artificial Neural Network

Abstract Electricity distribution systems are subject to a variety of faults such as permanent and transient short circuits due to the extent and multiplicity of equipment. In principle, short circuit fault causes the existing protective equipment to operate and to no electricity the various parts of the distribution network. Rapid and accurate determination of fault location, repair and recovery, it has not prevented the distribution of energy. This will satisfy consumers and prevent the losses of electricity companies. In this paper, the artificial neural network and fault current profiles are used to determine the distance of the fault, determine the type of fault and detect the short circuit. This method provides the information needed to locate the fault by sampling the current before and after the fault occurs from the SCADA system. The effect of connectivity local resistance changes and the effect of load changes on fault location were evaluated. The results show that this method is more accurate than the voltage droop profile variation method in determining the fault distance and short circuit breakdown. If only the net fault current changes profile is used, the effect of the load changes in determining the short-circuit breakdown is much less.

Fault Analysis on Distribution Feeders With High Penetration of PV Systems

Fault current profile on a PV-dominated distribution feeder is rather different than a conventional feeder. To estimate the fault current profile on such a feeder, the paper proposes a new method which extends the capability of conventional short-circuit analysis method. The paper also shows that this time-varying fault current profile makes it also more difficult to estimate the time it will take for an overcurrent relay/device to interrupt such a fault current. The paper proposes a method for estimation of this operating time also. Performance of the proposed methods has been assessed by simulations on a sample distribution feeder.

Accommodating High PV Penetration on Distribution Feeders

This paper investigates the operation and protection issues on distribution systems with high penetration of residential PV systems. Residential PV systems represent small scale resources and therefore they have different impacts on a distribution circuit than larger scale resources. The paper considers a typical residential distribution system and shows that determining the fault current profile and voltage variations on such systems becomes more challenging. However, the impacts on system protection and voltage variation are not severe on such systems, and thus, high level penetration can be accommodated provided that proper revisions are made to the protection and voltage control schemes.

A breaker-oriented fault analysis methodology

SUMMARY This paper presents a methodology for fault analysis of multiphase systems with the following innovations: (i) a breaker-oriented modeling approach that enables the computation of fault currents through any circuit breaker in a system and (ii) the use of a three-phase model with explicit representation of neutrals, ground wires, and grounding systems. Explicit grounding models allow the simulation of faults to neutrals and to ground wires and help evaluate ground potential rise. The proposed breaker-oriented fault analysis is utilized in a Monte Carlo simulation to provide a statistical profile or distribution of fault currents through any circuit breaker. Such fault current profiles permit an evaluation of the risk of breaker failures caused by increased fault current levels that result from the expansion of power systems. The proposed fault analysis methodology is illustrated using a three-phase, breaker-oriented 24-substation test system. Copyright © 2012 John Wiley & Sons, Ltd.

Transient Model of Short Circuit Fault on Subway Traction Power Supply System

Accurate analysis and modeling of DC side short circuit transient is important for design of DC traction power supply system and assessment of the suitability of protection arrangement. In recent years, the overshoot and swing in short-circuit fault current profiles of subway traction power supply system can not be correct explained by the existing subway traction power supply system fault model. The second-order transient model on subway traction power supply system is presented by analyzing short-circuit fault current recorder, the commissioning test waveform and electrical parameters of subway train. Using this model, the simulation results are consistent with the fault recorder and the commissioning test current profiles. Also the origin of the overshoot and swing on the waveform is explained.

Six-pulse three-phase rectifier bridge models for calculating closeup and remote short circuit transients on DC supplied railways

Short circuits applied close to substations cause large transient peak fault currents, but remote faults are difficult to detect because the fault current may be less than a normal train load. It is important to be able to predict the form of both closeup and remote fault currents for design of new protection systems and to assess the suitability of particular protection arrangements for specific railways sites. The model of the substation rectifier is an essential part of any means of predicting the current profiles. A detailed rectifier model based on a piecewise linear digital simulation, particularly suitable for prediction of fault current profiles owing to closeup faults is presented. The accuracy is demonstrated by comparison with a case study of a practically measured fault current profile. It is shown that commonly used models based on simpler equivalent circuits can not match the accuracy of the detailed model. It is also shown that a simple DC power source model of a rectifier is appropriate for remote fault calculations because the profile is not significantly affected by the switching action of the rectifier. The validity of the simpler model is demonstrated by comparing the simple model with the more detailed one.