Abdel-Maksoud I. Taalab

Modeling and experimental verification of high impedance arcing fault in medium voltage networks

A high impedance arcing fault due to a leaning tree in medium voltage (MV) networks is modeled and experimentally verified. The fault is represented in two parts; an arc model and a high resistance. The arc is generated by a leaning tree towards the network conductor and the tree resistance limits the fault current. The arcing element is dynamically simulated using thermal equations. The arc model parameters and resistance values are determined using the experimental results. The fault behavior is simulated by the ATP/EMTP program, in which the arc model is realized using the universal arc representation. The experimental results have validated the system transient model. Discrete wavelet transform is used to extract the fault features and therefore localize the fault events. It is found that arc reignitions enhance fault detection when discrete wavelet transform is utilized

DWT-Based Detection and Transient Power Direction-Based Location of High-Impedance Faults Due to Leaning Trees in Unearthed MV Networks

Electrical faults due to leaning trees are common in Nordic countries. This fault type has been studied in and it was found that the initial transients in the electrical network due to the associated arc reignitions are behavioral traits. In this paper, these features are extracted using the discrete wavelet transform (DWT) to localize this fault event. Wireless sensors are considered for processing the DWTs on a residual voltage of different measuring nodes that are distributed in the network. Therefore, the fault detection is confirmed by numerous DWT processors over a wide area of the network. The detection security is also enhanced because the DWT responded to a periodicity of the initial transients. The term for locating the faulty section is based on the polarity of a specific frequency bandpower computed by multiplying the DWT detail coefficient of the residual current and voltage at each measuring node. The fault due to a leaning tree occurring at different locations in an unearthed 20-kV network is simulated by the alternate transients program/electromagnetic transients program and the arc model is implemented using the universal arc representation. Test cases provide evidence of the efficacy of the proposed technique.

Investigation of power differential concept for line protection

In this paper, investigation of a novel fault detection concept for line protection is presented. In this concept, the difference and average quantities for phase active and reactive power entering and leaving the line are compared. Performance of the developed detector is computed under sampling misalignment as compared with conventional current differential approach. This computation is carried out via simulating a tie line connecting two power system networks using the Electromagnetic Transient Program (EMTP). The detector sensitivity for internal fault and stability for external fault are examined for wide range of fault resistance and operating conditions. The test results show distinguished performance of the proposed power differential concept in detecting high impedance faults and remarkable stability during system severe power swings.

Modeling and Experimental Verification of a High Impedance Arcing Fault in MV Networks

In this paper, a high impedance arcing fault of the tree leaning type in medium voltage (MV) networks is modeled and experimentally verified. The fault is represented as two parts; an arc model and a high resistance. The arc is generated by the tree leaning towards the network conductor and the tree resistance limits the fault current. The arcing element is dynamically simulated using thermal equations. The arc model parameters and resistance values are determined using the experimental results. The fault behavior is simulated by the ATP/EMTP program, in which the arc model is realized using the universal arc representation. The experimental results have validated the system transient model. Discrete wavelet transform (DWT) is used to extract the fault features and therefore localize the fault events. It is found that arc restrikings enhance fault detection when DWT is utilized

Detection of Partial Saturation and Waveform Compensation of Current Transformers

Derivative-based approaches have been widely used for detecting current-transformer (CT) saturation. This letter proposes an efficient approach for detecting CT saturation with a generic discrimination index without the need for setting definition. For this aim, the simultaneous samples-based multiplication of the secondary current by its derivative is only used to differentiate between saturated and unsaturated wave portions. Reconstructing the detected saturated secondary current is performed by using Kalman filtering to efficiently extract the phasor quantities of the unsaturated current portion. The results provide evidence of the efficacy of the proposed detector and of the Kalman-based waveform reconstruction.

Close Accord on DWT Performance and Real-Time Implementation for Protection Applications

In this paper, a simpler and faster algorithm of discrete wavelet transform (DWT) for a digital signal processing (DSP) implementation is proposed and intensively tested. Applicability of real-time implementation of this algorithm is verified. The computational frame in this algorithm is independent on the sampling rate, but it depends on the length of the mother wavelet filters. Therefore, signal with any sampling rate can be analyzed with the same computational effort. This implementation algorithm is exploited to investigate the DWT response experimentally. Impact of the mother wavelet, sampling frequency, fault inception angle and the signal transients on the resulted DWT levels is evaluated from the protection perspectives. Considering the DSP channel noise, these factors are strongly affect DWT response especially in high details spike, which the most of the protection applications depended on. Shortcomings of DWT application for protection relays are outlined and corrective recommendations are included.

DWT-Based Investigation of phase currents for Detecting High Impedance Faults Due to Leaning Trees in Unearthed MV Networks

In this paper, features of earth faults due to leaning trees are extracted from the network phase currents using the discrete wavelet transform (DWT). Due to the associated arc reignitions, the initial transients in the electrical network give behavioral traits. The detection security is also enhanced because the DWT is responded to a periodicity of the initial transients. The absolute sum of the DWT detail d3 coefficient corresponding to the frequency band 12.5-6.25 kHz is computed over one power cycle for each phase current of each feeder where the sampling frequency is 100 kHz. It is found that the faulty phase has the highest absolute sum when it is compared with the other healthy phases. Similarly, the absolute sum of the faulty feeder is the highest when the comparison is carried out with respect to other feeders. Therefore, two logic functions are suggested to determine the faulty phase and the faulty feeder. The fault due to a leaning tree occurring at different locations in an unearthed 20 kV network is simulated by ATP/EMTP and the arc model is implemented using the universal arc representation.

Wind Farm Protection Systems: State of the Art and Challenges

Owing to the rapid increase of the global population and their energy needs, traditional means to satisfy the burgeoning energy demands need careful reevaluation. Coupled with the uneven distribution of resources around the world, economic impacts of large-scale importation and the environmental impacts of continued dependence on nonrenewable fossil fuels, there is an imminent need to transfer, at least partly, the dependence on to renewable energy resources. Among these resources, wind electric conversion systems have emerged as the leader at the present time. According to the Global Wind Energy Council (GWEC) annual report, over 27 GW of new wind power generation capacity came on line worldwide in 2008 representing a 36% growth rate in the annual market, bringing the total global wind power capacity to over 120GW through the end of 2008 as shown in Fig. 1 [1]. This indicates that there is huge and growing global demand for emissions-free wind power, which can be installed quickly, virtually everywhere in the world.

A Gabor Transform-based universal fault detector for transmission lines

In this paper, a new fault detection scheme is proposed for transmission systems using Gabor transform (GT) for signal processing purposes instead of the conventional Fourier analysis methods. The detector uniquely detects both low impedance faults and high impedance ones with the same efficacy providing universal and precise fault detection for transmission systems. It utilizes GT as a feature extractor and artificial neural networks for pattern recognition and classification processes. The use of GT is motivated by the fact that the Gabor elementary functions have distinctively an optimal localization property in the joint time and frequency domains, which leads to optimal extraction of features from signals that is hard to be detected using conventional detectors. The generalization capability of the system allows detecting fault signals with very low fault currents and associated with, sharp and abrupt changes, dc decaying, non integer harmonics and non stationary quantities. The alternative transient program (ATP) is employed for the investigation phase. All simulation tests corroborate the superiority of the proposed detector for transmission system protection.

Generalized 1-D Gabor Transform Application to Power System Signal Analysis

In this paper, the generalized 1-D Gabor transformation and possibility of application to power system signal analysis are presented. An artificial neural network based algorithm is employed to compute the Gabor coefficients for further decomposition of the power system signals. The time-frequency resolution analysis for sinusoidal, DC decaying, sudden change and non-integer harmonic signals is carried out. Contribution of this transform to power system applications is evaluated through various simulation test cases and scenarios. Recommendations for increasing the value of Gabor transform to protection area are outlined