Naser Tarhuni

Bayesian Selectivity Technique for Earth Fault Protection in Medium-Voltage Networks

In Nordic countries, distribution networks are unearthed or compensated. Earth faults, particularly in compensated networks, provide fault currents that are low compared to the load currents. Identification of the faulty feeder is therefore difficult. A preliminary description of discrete wavelet transform (DWT)-Bayesian selectivity technique was introduced in reference 1 to identify the faulty feeder. It was dependent on a conditional probabilistic method applied to transient features extracted by using the DWT. However, a practical setting for this technique has not yet been presented. Furthermore, its sensitivity is limited to 1.5-k fault resistances, and is further reduced to 170 when considering current transformer and network noise. In this paper, the ratio between the absolute sums of the DWT detail level from each feeder is used as an input to the conditional probability approach, providing an enhanced selectivity decision. This input contributes to discriminating the faulty feeder during high resistance faults. The relay setting is introduced as a function of the number of feeders and their characteristic impedances, as the proposed algorithm is dependent on the discharges initial transients. The performance is evaluated taking into account current-transformer and network noises. A digital implementation is experimentally verified by using two digital signal processing boards.

Evaluation of probabilistic-based selectivity technique for earth fault protection in MV networks

In [1], a Bayesian selectivity technique has been introduced to identify the faulty feeder in compensated medium voltage (MV) networks. The proposed technique has been based on a conditional probabilistic method applied on transient features extracted from the residual currents only using the Discrete Wavelet Transform (DWT). In this paper, the performance of this selectivity technique is evaluated when the current transformers (CTs) impacts are considered. The CTs are modeled considering their frequency characteristics. Furthermore, network noises are added to the simulated signals. Therefore, the algorithm can be tested at different practical conditions, such as nonlinear characteristics of the measuring devices and the impact of noise as well. The fault cases occurring at different locations in a compensated 20 kV network are simulated by ATP/EMTP. Results show a reduction in the algorithm sensitivity with considering CT and noise effectiveness.

Performance Evaluation of OFDM Based Watermarking Robust to Multipath Spatial Shifts

A digital watermark is a visible or invisible pattern embedded in a digital image which can be used for copyright protection, authentication, broadcast monitoring, telemedicine and many more. This paper describes how an efficient CDMA based spread spectrum technique can be combined with the most prominent spectrum efficient OFDM technology to formulate a robust watermarking algorithm which is suitable for image distortions due to time delays and spatial shift that may occur during the transmission of watermarked images. A detailed simulation of embedding and decoding algorithm was performed and compared the performance with the existing DCT, DWT and FWHT based techniques. Simulation results reveal that the proposed algorithm is computationally efficient, robust and is well suited for wireless multipath fading channel. The algorithm was tested against a number of possible noises in the wireless channels and various geometric and signal processing operations. The proposed algorithm is proved to be robust enough to extract a good quality watermark compared to well-known techniques.

Computationally Efficient Robust Color Image Watermarking Using Fast Walsh Hadamard Transform

Watermark is the copy deterrence mechanism used in the multimedia signal that is to be protected from hacking and piracy such a way that it can later be extracted from the watermarked signal by the decoder. Watermarking can be used in various applications such as authentication, video indexing, copyright protection and access control. In this paper a new CDMA (Code Division Multiple Access) based robust watermarking algorithm using customized 8 × 8 Walsh Hadamard Transform, is proposed for the color images and detailed performance and robustness analysis have been performed. The paper studies in detail the effect of spreading code length, number of spreading codes and type of spreading codes on the performance of the watermarking system. Compared to the existing techniques the proposed scheme is computationally more efficient and consumes much less time for execution. Furthermore, the proposed scheme is robust and survives most of the common signal processing and geometric attacks.

Computationally Efficient, Robust Watermarking Using Fast Walsh Hadamard Transform

Nowadays, anonymous manipulation of digital data with malicious intention is increasing at an enormous rate. With the advent of various technologies, multimedia signal can easily be downloaded, copied and manipulated at any point of time without much effort. Watermark is the pattern of bits added to the multimedia signals, such as audio, video or images, such that this can be extracted and used to check the authenticity of the received signal. The field of watermarking is growing at a fast pace. Watermarking techniques can be used for a variety of applications such as authentication, video indexing, copyright protection and access control. In this paper, CDMA based robust watermarking algorithm using Discrete Cosine Transform is modified for more robust and computationally efficient applications using Walsh Hadamard Transform. Performed a detailed simulation of both the techniques and compared the results. Compared to the existing technique the proposed technique is proved to be more resistant to attacks, computationally and cost wise more efficient. The new technique results in a good quality extracted watermark even at a low embedding gain even though the information hiding capacity is comparatively less.

On-line denoising of motor speed control loop using order statistics filtering

In real-time motor speed measurements and control, severe noise spikes cause unacceptable performance degradation of the control loop. In this work, we propose a real-time filtering mechanism to reduce the unwanted effects of spiky noise. A Hardware-In-the-Loop (HIL) experimental setup was used to measure the noisy motor speed and an online order statistics filtering was applied to mitigate the effect of the noise. We tested and evaluated experimentally several orders of the applied on-line filtering algorithm. We showed that larger windows tend to enhance the smoothness of the response but at the expense of extra delay that can lead to oscillatory responses when a feedback controller is used. For the implemented system, we showed experimentally that a window size of 5 samples achieves a good compromise between impulsive noise rejection and acceptable oscillatory response.