Ayman El-Hag

Ayman El-Hag
University Waterloo

Ph.D., P.Eng., SMIEEE
Develop an educational YouTube channel for electrical engineering courses: https://www.youtube.com/user/ahalhaj/featured

About

163
Publications
39,795
Reads
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2,041
Citations
Introduction
Ayman El-Hag currently works at the Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Canada. Ayman main research interest is in high voltage engineering and currently working on several projects related to outdoor insulators monitoring and design.
Additional affiliations
June 2018 - present
University of Waterloo
Position
  • Lecturer
June 2016 - March 2018
American University of Sharjah
Position
  • Professor (Full)
June 2011 - May 2016
American University of Sharjah
Position
  • Professor (Associate)
Education
September 1999 - December 2003
University of Waterloo
Field of study
  • Electrical and Computer Engineering

Publications

Publications (163)
Article
Full-text available
Condition monitoring of high voltage apparatus is of much importance for the maintenance of electric power systems. Whether it is detecting faults or partial discharges that take place in high voltage equipment, or detecting contamination and degradation of outdoor insulators, deep learning which is a branch of machine learning has been extensively...
Article
Full-text available
This paper discusses the state of the art in the application of self-healing silicone-based materials for outdoor high-voltage insulation. Both the dynamic behavior of the dimethyl side groups of silicone rubber and the diffusion of a bulk siloxane to maintain low surface energy are respectively reported as intrinsic mechanisms responsible for the...
Article
You're welcome to read and download this article free: https://authors.elsevier.com/a/1e8mq1M7%7E0mXnf A major challenge observed for smart meters installed at North American residential premises involves the absence of reactive power consumption measurement of residential customers, which limits the accurate assessment of kVA loading for a distri...
Conference Paper
This paper presents a hardware-free novel strategy for a distribution transformer kVA load estimation, without requiring a fixed power factor assumption or reactive power load information across residential electricity consumers. The proposed strategy provides a simple and effective fixed-point iteration-based formulation for a balanced secondary d...
Article
In this letter a deep learning-based model is proposed for online inspection of silicone rubber outdoor insulators. The inclined plane tracking and erosion test is used as per ASTM D2303 in order to simulate standard erosion on silicone rubber insulation composites. Photos taken for the tested composites are used as training and testing inputs for...
Article
This paper develops a prototype quadcopter dronebased system for inspection of powerline ceramic insulators. The drone uses its onboard cameras, and Raspberry Pi singleboard computer to monitor the health condition of outdoor ceramic insulators. The main contribution of this paper is the development of a complete quadcopter-based system prototype f...
Article
Power grid failure is very costly to any modern society, and preventing upheavals like the blackout in eastern US and Canada in the summer of 2003 is extremely important. Complete power grid failure may be triggered by the failure of a transformer, underground cable, overhead line insulator or any other component of the power grid. While close moni...
Article
Full-text available
Different types of classifiers for acoustic partial discharge (PD) pattern classification have been widely discussed in the literature. The classifier performance mainly depends on the measurement conditions (location and type of the PD, acoustic sensor position and frequency response) as well as extracted features. Recent research posits that feat...
Article
Partial discharge (PD) assessment is one of the most prevalent techniques in the condition monitoring of high voltage (HV) equipment. In this regard, one of the main stages in the procedure of PD assessment is noise reduction of PD signals. Hence in this paper, a novel artificial neural network (ANN) based denoising method is introduced. Unlike the...
Article
Full-text available
This paper demonstrates the use of five different methods to estimate partial discharge (PD) location in an oil insulation system from noisy measurements. The measurements are obtained from three ultrasonic sensors located in three different places. The sensors map the PD location utilizing a nonlinear model. The estimation techniques used in this...
Article
Full-text available
This paper uses a two-layered soft voting-based ensemble model to predict the interfacial tension (IFT), as one of the transformer oil test parameters. The input feature vector is composed of acidity, water content, dissipation factor, color and breakdown voltage. To test the generalization of the model, the training data was obtained from one util...
Chapter
Accumulation of pollutants on ceramic insulators is one of the major causes of dry band arcing, a predecessor to flashovers, which may further cause major outages of electricity. It is critical to know locations of polluted insulators to prevent flashovers to make the power-grid reliable. This paper proposes a solution to detect the location of pol...
Article
Full-text available
Condition monitoring of outdoor insulation systems is crucial to the integrity of distribution and transmission overhead lines and substations. The objective of this study is to use a commercial acoustic sensor along with artificial neural network (ANN), to classify different typical types of discharges in outdoor insulation systems. First, ANN was...
Article
This work proposes a new automated inspection system that can estimate erosion in silicone rubber (SIR) samples using a computer vision-based method. In this work, we used SIR samples that were damaged under laboratory conditions. The proposed work is expected to classify SIR samples into one of three classes based on the degree of erosion followin...
Article
This paper investigates the residue formed on silicone rubber filled with natural silica in the inclined plane tracking and erosion test under AC and DC voltages. Simultaneous thermogravimetric and differential thermal analyses reveal residue formation dependent on volatilization and crosslinking in silicone rubber. Thermo-oxidation of volatiles yi...
Article
Full-text available
One of the most promising techniques for condition monitoring of high voltage equipment insulation is partial discharge (PD) measurement using radio frequency (RF) antenna. Nevertheless, the accuracy of monitoring, classification, localization, or lifetime estimation could be negatively affected due to the interferences and noises measured simultan...
Article
Full-text available
The presented paper aims to establish a strong basis for utilizing machine learning (ML) towards the prediction of the overall insulation health condition of medium voltage distribution transformers based on their oil test results. To validate the presented approach, the ML algorithms were tested on two databases of more than 1000 medium voltage tr...
Article
Insulator flashover happens when soluble and/or non-soluble contaminants cover the insulator surface which results in a reduction of the surface resistance. Significant research has been conducted to utilize leakage current (LC) to predict the contamination level on the outdoor ceramic insulators surface. This can help as a mean to warn overhead li...
Article
In this letter, a novel algorithm for high-accuracy partial discharge (PD) localization in an oil insulation system is proposed. The study aims to identify the statistics of the dynamics and measurements noise sequences in a PD localization system and employ that information in realizing better estimates. An Extended Kalman Filter (EKF) is used to...
Conference Paper
This paper investigates the effects of silica filler on the suppression of the dry-band arcing erosion of silicone rubber outdoor insulating materials. Liquid silicone rubber which was filled with silica at various levels and particle sizes were prepared and tested in the AC inclined plane test as per IEC 60587. The application of the 4.5 kV rms cr...
Chapter
The ability to monitor and detect potential faults in smart grid system components is extremely valuable. In this paper, we demonstrate the use of machine learning techniques for condition monitoring in power transformers. Our objective is to classify the three different types of Partial Discharge (PD), the identify of which is highly correlated wi...
Article
Condition monitoring (CM) techniques in the form of electrical, chemical and physical tests are conducted to assess the ageing of transformers on the basis of its oil-paper insulation strength. A thorough examination of the transformer insulation condition can only be done through a complete set of CM standard tests. Some of the conducted tests are...
Article
Leakage current (LC) has been monitored extensively to assess the surface conditions of both ceramic and non-ceramic insulators. It has been reported that LC is highly correlated with insulator surface damage and the occurrence of flashover. Hence, it is imperative to predict the LC future value. The objective of this paper is to use Bayesian regul...
Article
Full-text available
Measuring acoustic emission (AE) of partial discharge (PD) phenomena can be adopted to estimate the condition of power transformers. However, the environmental noise encountered with AE of PD measurements negatively affects the accuracy of PD localisation and classification. Thus, efficient signal denoising techniques are required for noise suppres...
Article
This letter investigates an approach based on feature selection and classification techniques to reduce assessment complexities of power transformers. This approach decreases the number of features by extracting the most influential ones when determining the transformers health index. Several filter and wrapper based feature selection methods are i...
Article
Three Hilbert fractal antenna designs are proposed in this work to capture and classify common types of partial discharge (PD) in an oil insulated system. Each antenna design shows unique characteristics in terms of resonant frequencies, inception voltage, classification capabilities and noise performance. Three types of PD signals are artificially...
Article
Defects in ceramic insulators like broken, cracked and punctured discs give rise to the initiation of partial discharge (PD) activities within the samples which has a detrimental effect on the insulator life. Hence it is important for the utilities to identify such defective samples as early as possible so that appropriate replacement strategies ca...
Article
Partial discharge (PD) can be used as an indicator of impending failure in electrical plant insulation making the accurate classification of particular occurrence patterns useful for anticipating forthcoming outages. In this paper, we propose a feature extraction method that is robust to noise and can effectively select the most discriminant featur...
Article
This paper presents the design of a wide band Hilbert fractal antenna for the purpose of detecting and classifying different common partial discharge (PD) types in an oil-paper insulated system. Three common types of PDs are considered for the multi-class classification problem, namely; PD from a sharp point to ground plane, surface discharge, and...
Article
This paper analyzes silicone rubber housing materials that have been aged in service in 200 kV and 400 kV transmission line systems in the Gulf region. Non-uniform discoloration with traces of white residue are more evident across the upper and lower sides of the 400 kV as compared to the 200 kV sheds located near both the energized and the ground...
Conference Paper
This paper discusses the use of a one arm Archimedean Sinusoidal Spiral Antenna (ASSA) to capture high frequency signals generated by Partial Discharge (PD) in an oil filled transformer. The antenna is designed such that it blocks low frequencies which corresponds to corona and noise in the transformer and allows higher frequencies which result fro...
Article
Full-text available
Polluted insulator flashover is a serious threat to the reliability of power systems. It is known that the flashover process is mainly affected by pollution and humidity levels. These are the essential parameters that influence dry-band arcing initiation on the insulator surface. This paper presents an investigation into the leakage current (LC) ch...
Conference Paper
The reliability of different power system apparatus can be maintained by minimizing the time of outage and downtime. The unexpected failure can happen due to different causes. The most important cause for transformer failure is partial discharge (PD). This paper summarizes the authors experience in both modeling and using acoustic sensors in the co...
Article
In this letter, the ranges of furan content in oil in power transformers are predicted using measurements of oil tests, such as breakdown voltage, acidity, water content, and dissolved gas analysis. Predictive models based on machine-learning techniques are trained and tested to estimate the furan level. A prediction accuracy of 90% is achieved whe...
Article
In this paper, high-accuracy estimation of partial discharge (PD) location in an oil insulation system is addressed. The study aims at forming a fault-tolerant PD localization system. Initially, the algorithm periodically and probabilistically checks for possible bias in the acoustic emission sensors' measurements. Once the detected bias is removed...
Article
Power transformers are one of the most important and expensive electrical equipment that require online condition monitoring. Partial discharge (PD) measurement is considered the most effective and non-destructive approach to observe the condition of power transformers in service. However, many sources of noise interfere with the captured PD signal...
Article
Ageing power systems infrastructure and concerns about climate change have increased interest in the next generation of grid infrastructure, known as the smart grid (SG). This study studies a particularly critical SG application: intelligent monitoring of power transformers for the early detection of insulation failure. Specifically, the focus is o...
Conference Paper
Full-text available
this paper aims to establish criteria for the automatic classification of surface conditions of outdoor insulator based on the leakage current (LC) analysis and fuzzy logic approach. The study is done in an artificial fog chamber and the LC is characterized for different stages; e.g. dry, wetted and presence of early discharge activities. Time-freq...
Conference Paper
Email Print Request Permissions We present a new method to accurately locate partial discharge by using a sequential fault detection and identification (FDI) algorithm for detecting a bias fault in the measurements of partial discharge in transformer insulation system using acoustic signals. In this paper, a novel technique is proposed to identify...
Conference Paper
Full-text available
Field aged polymeric insulators are exposed to different ageing factors such as the dry band arcing and UV radiation. In this paper, the degradation of field aged silicone rubber insulator used in both 400 and 220kV in the gulf was investigated. The samples collected from various locations near the energized and the ground ends were analyzed using...
Article
This paper presents a sequential fault detection and identification algorithm for detecting a bias fault in the measurements of partial discharge (PD) in a transformer insulation system using acoustic signals. The algorithm identifies a bias fault in any of the ultrasonic sensors by computing the probability of having that bias fault given a carefu...
Conference Paper
Measuring partial discharge (PD) phenomena in power transformers is often conducted by acoustic emission (AE) method. However, many interference sources are usually encountered with the captured PD signals which negatively affect the PD detection and classification. Thus, an effective and efficient denoising technique is required to suppress such e...
Article
High-voltage engineering is not usually an appealing area to undergraduate students because it is commonly perceived as a classical area of electrical engineering. Moreover, high-voltage (HV) engineering requires an HV laboratory, which is not usually available in universities because of high cost. In addition, several universities that already had...
Article
Online condition assessment of the power system devices and apparatus is considered vital for robust operation, where partial discharge (PD) detection is employed as a diagnosis tool. PD measurements, however, are corrupted with different types of noises such as white noise, random noise, and discrete spectral interferences. Hence, the denoising of...
Conference Paper
North American utilities are increasingly concerned with their ageing ceramic insulator assets as they are either fast approaching their expected end of life or have already exceeded them. Defects like broken, cracked and punctured discs are some of the most adverse problems that the utilities encounter. These defects give rise to the initiation of...
Article
Full-text available
This paper addresses classifying different common partial discharge (PD) types under different acoustic emission (AE) measurement conditions. Four types of PDs are considered for the multi-class classification problem, namely; PD from a sharp point to ground plane, surface discharge, PD from a void in the insulation, and PD from semi parallel plane...
Article
In this study, a novel solution is introduced to deal with excessive signal attenuation in distribution transformers for power line communication in smart grids. The results presented were not achievable before proposing this solution because of the filtering action of transformer. The solution is based on exploiting a unique frequency resonance sp...
Article
White noise is a major interference source that affects the partial discharge (PD) signal detection and recognition. Wavelet shrinkage denoising methods can efficiently reject the white noise embedded in the PD signal acquisition and measurement processes. The wavelet threshold determination is a key factor in the quality of noise suppression from...
Article
The aim of this paper is to develop an automated system to classify and assess the surface condition of silicone rubber material. Both Radon transformation and the gray-level co-occurrence matrix were examined as image processing and features extraction techniques while using the artificial neural network as a classifier. A database comprised of 35...
Article
Several transmission and distribution companies worldwide have started to replace their existing outdoor ceramic insulators with silicone rubber insulators. The use of silicone rubber insulators in outdoor insulators was first introduced in the market almost 30 years ago. Various studies have looked at the characteristics of this material under con...
Conference Paper
The presence of insulation defects results in the initiation of partial discharge (PD) activities. As insulation failure and hence a failure of power equipment can occur due to the cumulative adverse effects of partial discharges, it is important to detect PD activities at early stages. The current techniques used in PD off-line analyses are not su...
Conference Paper
Full-text available
On-line detection of partial discharge (PD) in power transformers is often performed by acoustic emission method, although this measurement can be affected by different types of noises. This paper compares the performances of three denoising methods applied to PD acoustic signals including; Wavelet Transform (WT), Singular Spectrum Analysis (SSA) a...
Conference Paper
Full-text available
The aim of this paper is to develop an automatic system to classify and assess the condition of silicone rubber insulators using image processing and pattern recognition techniques. In this research the gray-level co-occurrence matrices (GLCM) were used as an input feature vector for the classification system. Various classifiers were examined to e...
Conference Paper
Full-text available
In this paper, the characteristics of field-aged RTV silicone rubber coatings and silicone rubber insulators used in the gulf region were investigated. Samples were collected from both 220 and 400 kV field aged coated bushings and outdoor insulators. Samples taken from various positions on the insulators were analyzed using thermo gravimetric analy...
Conference Paper
This work introduces a novel solution to overcome excessive signal attenuation in distribution transformers for power line communication (PLC) in Smart Grids. The solution avoids classical hardware bypass and does not require sophisticated modulation schemes like OFDM. It explores the resonance that occurs in transformer windings at kHz range to tr...
Conference Paper
Furan content in transformer oil is highly correlated with the transformer insulation paper aging. In this paper, the ranges of furan content in power transformer is predicted using measurements of transformer oil tests like breakdown voltage, acidity and water content. Machine learning approach is adopted, and maintenance data collected from 90 tr...
Article
Full-text available
Introductory engineering courses are either programme specific or expose students to engineering as a broad discipline by including materials from various engineering programmes. A common introductory engineering course that spans different engineering programmes raises challenges, including the high cost of resources as well as the lack of backgro...
Article
The paper provides several methods to assess the condition of RTV coated porcelain/toughened glass insulators in the field. Visual observations of arcing and audible corona are the first indications that signal changes to the coating have taken place. It emphasizes that in the absence of reliable data one can use observations based on hydrophobicit...
Article
This paper presents a novel artificial neural network (ANN)-based near-field microwave nondestructive testing technique for defect detection and classification in nonceramic insulators (NCI). In this paper, distribution class 33-kV NCI samples with no defects, air voids in silicone rubber and fiber glass core, cracks in the fiberglass core, and sma...
Article
Full-text available
The goal of the research presented in this paper is to investigate the reliability of ZigBee-based wireless sensor networks in transforming existing power systems into future smart grids. The performance of the communication network for a specific propagation environment, channel modulation, and frequency band is investigated. The high-power interr...