W. L. A. Neves

A Traveling-Wave Detection Method Based on Park's Transformation for Fault Locators

A novel algorithm for transient detection based on Parks transformation is proposed. It is very simple, self-adapts to electrical noise and phase imbalances, and is appropriate to be used in connection with traveling-wave fault location (TWFL) methods. The proposed technique is evaluated through Electromagnetic Transients Program simulations. A 230-kV transmission system case study is carried out, in which power system voltage and current waveforms are picked up one sample at a time. It is shown that the method is very reliable and suitable for multiterminal TWFL algorithms.

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.

An Approach for Controlled Reclosing of Shunt-Compensated Transmission Lines

An approach for controlled reclosing of transmission lines with shunt reactive compensation is proposed here to reduce switching surge overvoltages. It consists on applying Karrenbauers transformation as a matrix operator for the analysis of voltage signals required to control switching operations. The procedure also determines the arc extinction time for single and double-phase to ground faults which may avoid unsuccessful reclosing. A device to control the line reclosing was implemented and evaluated through real time simulations. An offline version was implemented for parametric and sensitivity analysis through the EMTP using actual parameters from the Brazilian Power System Grid. Several field oscillographic data, obtained from Brazilian power transmission lines with different transposition schemes were used to validate the proposed approach and the results attest its efficiency.

Sampling rate of digital fault recorders influence on fault diagnosis

A case study of fault classification in transmission lines using artificial neural networks (ANN) is presented. The database is built from current and voltage waveform samples obtained from fault simulations with the ATP. Utility companies usually have digital fault recorders with different sampling rates, so it is important to evaluate how good the classifier is when the sampling rate changes, this is the main purpose of the paper. A routine to reduce the sampling rate with no loss of accuracy in classifying faults was implemented.

Transmission line shunt conductance from measurements

In this work, sensitivity studies were performed using electromagnetic transients program (EMTP)-type programs in order to show how shunt conductance values affect the characteristic impedance and the propagation function of overhead transmission lines. Time-domain simulations were carried out using modal and phase-domain line models. It is shown that, in some situations, simulation results are very sensitive to shunt conductance values. Laboratory measurements were carried out to provide better estimates for overhead line shunt conductances. Measurements were carried out for two voltage classes, considering different insulator types and arrangements. The estimated values can be used as default values for overhead transmission lines in EMTP-type programs.

Transients detection in EHV transmission lines using park's transformation

Among various algorithms used to diagnose electrical disturbances, the transient detection is considered one of the most important functions. The objective of this paper is to present the Parks transformation (Tdq0) as a simple and efficient tool to detect transients in EHV transmission lines. The evaluation of such technique is performed with actual records from a Brazilian power system utility. The results reveal that the Tdq0 can detect accurately the transient occurrence and, thus, may be used to give support to various protective applications based on the detection of travelling waves.

A comparative investigation of electromechanical stresses on transformers caused by inrush and short-circuit currents

This paper presents the mechanical effect on transformers when subjected to one of the power quality indicators, i.e., the electromagnetic transients. A common reason for internal faults in transformers windings is the weak insulation. This effect can be caused and accelerated by the electromechanical efforts produced by the inrush and short-circuit currents. Even though the transformer energizing is considered a normal operation, it produces high currents and this phenomenon significantly reduces the transformer life expectancy and may even lead to its instantaneous or timing destruction. Moreover, taking into account the same magnitude of current, the inrush currents can produce greater forces than those caused by short-circuit currents. Therefore, this papers aims to present and compare the electromechanical effects produced by the inrush and short-circuit currents in the transformers windings. To conduct this research, FLUX software in its 3D version, based on the finite element method (FEM) will be used. To highlight the overall model and the software performance, a laboratory 15 kVA transformer is utilized. It has been built with concentric double-layer windings and ferromagnetic core with three columns.

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.

A transient based approach to diagnose high impedance faults on smart distribution networks

This paper presents a transient based approach to diagnose high impedance faults (HIFs) on smart distribution grids. The algorithm does not require the knowledge of the feeder parameters and uses the discrete wavelet transform (DWT) to monitor fault-induced transients at strategic points of the power system, taking advantages of available Smart Grid communication channels. It allows the HIF detection and then the identification of the area in which the fault occurred. The proposed methodology is evaluated through Electromagnetic Transients Program (EMTP) simulations of HIFs in a 13.8 kV system, which was modeled using actual data of a Brazilian distribution network. Obtained results show that the method is able to detect HIFs practically at the disturbance inception as well as to provide a great reduction of the fault search field using a small computational burden.

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.