André Darós Filomena

Extended Fault-Location Formulation for Power Distribution Systems

In this paper, an extended impedance-based fault-location formulation for generalized distribution systems is presented. The majority of distribution feeders are characterized by having several laterals, nonsymmetrical lines, highly unbalanced operation, and time-varying loads. These characteristics compromise traditional fault-location methods performance. The proposed method uses only local voltages and currents as input data. The current load profile is obtained through these measurements. The formulation considers load variation effects and different fault types. Results are obtained from numerical simulations by using a real distribution system from the Electrical Energy Distribution State Company of Rio Grande do Sul (CEEE-D), Southern Brazil. Comparative results show the technique robustness with respect to fault type and traditional fault-location problems, such as fault distance, resistance, inception angle, and load variation. The formulation was implemented as embedded software and is currently used at CEEE-Ds distribution operation center.

Hybrid Fault Diagnosis Scheme Implementation for Power Distribution Systems Automation

Power distribution automation and control are important tools in the current restructured electricity markets. Unfortunately, due to its stochastic nature, distribution systems faults are hardly avoidable. This paper proposes a novel fault diagnosis scheme for power distribution systems, composed by three different processes: fault detection and classification, fault location, and fault section determination. The fault detection and classification technique is wavelet based. The fault-location technique is impedance based and uses local voltage and current fundamental phasors. The fault section determination method is artificial neural network based and uses the local current and voltage signals to estimate the faulted section. The proposed hybrid scheme was validated through Alternate Transient Program/Electromagnetic Transients Program simulations and was implemented as embedded software. It is currently used as a fault diagnosis tool in a Southern Brazilian power distribution company.

Ground Distance Relaying With Fault-Resistance Compensation for Unbalanced Systems

Fault resistance is a critical variable in distance relaying. If not considered due to underreaching phenomenon, it may cause the misoperation of ground distance relays for internal faults. Still, as a consequence of the overreaching phenomenon, the unbalanced nature of loads and asymmetry of lines can affect the distance protection operation efficiency. Mainly due to these aspects, there is low precision in protection zone limits of ground distance relays. In this paper, a new algorithm is proposed to increase the precision of these limits, improving efficiency in the distance protection process. The proposed method is based in phase coordinates and uses a fault resistance estimate to develop the trip decision procedure. The results show that the algorithm is suitable for online applications, and that it has an independent performance from the fault resistance magnitude, the fault location, and the line asymmetry.

Unbalanced Underground Distribution Systems Fault Detection and Section Estimation

This paper presents a novel fault detection and section estimation method for unbalanced underground distribution systems (UDS). The method proposed is based on artificial neural networks (ANNs) and wavelet transforms (WTs). The majority of UDS are characterized by having several single/double phase laterals and non-symmetrical lines. Also, Digital Fourier Transforms (DFT), used in the majority of traditional protection relays, supplies a low level of robustness to the fault diagnosis process due to its inversely proportional time-frequency characteristic. These characteristics compromise the traditional fault diagnosis methods performance. ANNs are capable of learning and generalizing, whereas WTs are robust tools capable of evaluating a signals frequency range that can characterize the fault phenomenon. This paper describes the proposed diagnosis method and discusses the results obtained from simulated implementation. The obtained results demonstrate the capability and robustness of the technique indicating its potential for on-line applications.

Extended impedance-based fault location formulation for unbalanced underground distribution systems

Underground distribution systems are commonly exposed to permanent faults. Due to specific construction characteristics, visual inspection for fault location cannot be performed. To overcome this limitation, accurate fault location techniques must be applied. In this paper, an extended impedance-based fault location formulation for unbalanced underground distribution systems is described considering single line-to-ground faults. The technique uses only local voltages and currents as input data. An iterative algorithm for cable capacitive current compensation in the fault location formulation is proposed. The formulation focuses an easily practical implementation and is based on typical available systempsilas data, as lines impedance and admittance matrices, and also system loads. Test simulations on a real data underground distribution system demonstrate the proposed extensions improvements. The algorithm performance presents negligible fault resistance, distance, and inception angle variation effects.

Electrical power systems fault location with one-terminal data using estimated remote source impedance

In this study, a fault location algorithm for electrical power systems is presented. The proposal consists in an accurate impedance-based fault location algorithm by utilizing voltage and current measurements from local terminal and estimated remote source impedance. In order to evaluate the fault location algorithm a numerical analysis is made. Phase-to-ground faults are simulated in a 230 kV Brazilian transmission line using the software ATP/EMTP and MATLAB. The algorithm is tested considering the fault distance, fault resistance, and the variation of short-circuit capacity of remote system effects. The results show that the fault resistance and fault distance affect the estimated fault distance, but with minor errors. More, the proposed algorithm is not sensitive to the remote system short-circuit capacity variation.

Park's transformation analitycal approach of transient signal analysis for power systems

A rapid change in power system states leads to appearing of electromagnetic transients signals in system variables. Such transients are in the form of DC offset or frequencies above de fundamental and have information about its producer phenomenon. Thus, system signals can be recorded using adequate equipment in order to diagnose the phenomenon. Within the previous contextualization, this paper present an analytical study of Parks transformation applied in the framework of power system three-phase signals. Furthermore, this paper highlights the potential use of such transformation as a filter that could be useful to improve the transient signal analysis. By means of a numerical implementation of Parks transformation taken on Matlab environment, four cases are analyzed. Three of them consist on studying synthetics and controlled signals, whereas the last analyze the phase voltages of a faulted power system simulation performed in ATP-EMTP.