Kleber M. Silva

Fault detection and classification in transmission lines based on wavelet transform and ANN

This paper proposes a novel method for transmission-line fault detection and classification using oscillographic data. The fault detection and its clearing time are determined based on a set of rules obtained from the current waveform analysis in time and wavelet domains. The method is able to single out faults from other power-quality disturbances, such as voltage sags and oscillatory transients, which are common in power systems operation. An artificial neural network classifies the fault from the voltage and current waveforms pattern recognition in the time domain. The method has been used for fault detection and classification from real oscillographic data of a Brazilian utility company with excellent results

Real-Time Traveling-Wave-Based Fault Location Using Two-Terminal Unsynchronized Data

In this paper, a new two-terminal traveling-wave-based fault-location algorithm is proposed. Its main advantage over similar two-terminal algorithms lies in the fact it does not require the data from both line terminals to be synchronized. In order to do so, the algorithm is applied in real time, and a communication system is used, whose data-transmission latency is taken into account in the proposed formulation. The fault locator routines were implemented using the real-time digital simulator (RTDS), such that a wide variety of fault scenarios in a 230-kV transmission line 200 km long was evaluated in real time, considering communication systems with different latency variability levels. The obtained results indicate the proposed algorithm is able to locate faults using either synchronized or unsynchronized two-terminal data, whereas classical methods work properly for synchronized measurements only.

Two-Terminal Traveling-Wave-Based Transmission-Line Protection

This paper proposes a two-terminal traveling-wave-based transmission-line protection using only the first wavefront arrival time at each line terminal (polarity and magnitude of transients are not required), leading to a simple, accurate, and fast protection. In real time, the protection system detects internal and external faults and identifies the fault directionality. In addition, the protection zone and the protection operating time are also formulated. The effects of the sampling rate and the traveling-wave propagation velocity estimation are considered, and some paradigms, such as the need of a high-sampling frequency and an accurate traveling-wave propagation velocity estimation are properly addressed. Two traveling-wave-based protective relays were implemented and evaluated in realistic real-time hardware-in-the-loop simulations considering the communication equipment between the relays, in which reliability and protection operating time could be assessed accordingly.

A Method for Fault Classification in Transmission Lines Based on ANN and Wavelet Coefficients Energy

This paper proposes a novel method for transmission lines fault classification using oscillographic data. The scheme is based on the analysis of the current wavelet coefficients energy using an artificial neural network. In order to validate the proposed approach, both simulated and actual oscillographic data were used.

Distance protection using a novel phasor estimation algorithm based on wavelet transform

This paper presents a novel phasor estimation algorithm, which combines the filtering characteristics of the maximal overlap discrete wavelet transform (MODWT) and the least error square (LES) algorithm. Time and frequency response of the designed filters are compared to the ones of traditional discrete Fourier transform (DFT) filters. The obtained results indicate that the designed filters have time responses compatible half cycle DFT-based filters, with the advantage that their frequency responses are close to the ones of full cycle DFT-based filters. According to these characteristics, the designed filters may be used in secure high-speed distance protection.

Sampling frequency influence at fault locations using algorithms based on artificial neural networks

A sampling frequency evaluation used in digital fault recorders for fault locations was implemented. A chained structure of artificial neural networks (ANN) was adopted to locate the faults. The ATP (Alternative Transient Program) software was used in the building of the database for training, testing and validation of the ANN, with different sampling frequencies. The input to the ANN are phase quantities and zero sequence voltage and current waveform data. The fault conditions were simulated for a 230 kV transmission line. The database used was generated automatically from a standard format file, and run in batch mode. For the fault location, the transmission line was divided into 8 zones. Previous to location, classification of the fault type is performed by training the ANN with the full line data. For the location, eight ANN were trained for each fault type, each one with the data of each zone.

Traveling Wave-Based Fault Location on Half-Wavelength Transmission Lines

Transmission lines little longer than half-wavelength have been studied as an alternative for power transmission over very long distances. Recent studies about fault location procedures have proved that most impedance-based techniques are not able to correctly identify the fault point in this kind of line. In this paper, the performance of a two-terminal traveling wave-based fault location approach applied to a transmission line little longer than half-wavelength is investigated through simulations in the Alternative Transients Program (ATP), from which several fault scenarios in a 1000 kV AC line 2600 km long are analyzed. The obtained results indicate traveling wave-based approaches are robust to the atypical operation features of half-wavelength power transmission lines, being suitable for fault location applications in this kind of line.

A Wavelet-Based Busbar Differential Protection

This paper presents a new wavelet-based busbar differential protection algorithm, named as 87BW function. The instantaneous current-based differential protection fundamentals are taken into account and the well-known 1-out-of-1 and 2-out-of-2 tripping logics are mapped into the wavelet domain. Operating and restraint wavelet coefficients energy of currents are computed, regarding station configuration and bus zones boundaries. Thereby, the proposed 87BW function can be properly used in both static and dynamic busbar configuration. Its performance was evaluated through EMTP-based simulations of faults in a 230 kV power substation with double bus single breaker configuration. The obtained results reveal it provides ultra-high-fast trip for internal and evolving external-to-internal faults, guaranteeing security for normal through-load and external faults as well, even in the case of early and severe current transformer (CT) saturation.

Modified DFT-Based Phasor Estimation Algorithms for Numerical Relaying Applications

In this paper, new modifications of the conventional full-cycle and half-cycle discrete Fourier transform (DFT)-based phasor estimation algorithms are proposed. The key idea is to combine two consecutive outputs of their real and imaginary part filters to eliminate the harmful effect of the decaying dc components on phasor estimation, thereby a new strategy to estimate the exponential term is also reported. The proposed algorithms are compared with other DFT-based algorithms by using both computer-simulated and alternative transients program-generated signals. The obtained results reveal that proposed algorithms present excellent results, even taking into account multiple decaying dc components.

Performance evaluation of the phase comparison transmission line protection

In this paper, the performance of the phase comparison (PC) transmission line protection is evaluated, considering fault scenarios which are not readily analyzed in the literature on the subject. In order to do so, several faults in a 500 kV/60 Hz transmission line 200 km long were simulated using the Alternative Transients Program (ATP). Different values of power system loading, fault parameters and system-to-line impedance ratio (SIR) were taken into account. In each case, both phase and sequence elements, with and without charging current effect removal, were analyzed. The obtained results reveal the sensitivity limits of the studied PC protection algorithms, highlighting the differences on their performances when the line capacitive effect is removed from the measured currents.