Emad Farrag - Academia.edu (original) (raw)

Papers by Emad Farrag

2016 51st International Universities Power Engineering Conference (UPEC), 2016

Transformer failure in electricity supply grids has a high financial impact, due to failure to me... more Transformer failure in electricity supply grids has a high financial impact, due to failure to meet commercial contract and possibility of transformer replacement cost. Therefore, detecting fault inception is very important in order to keep the transformer operating with recommended efficiency, hence ensuring stability of the electric network. Dissolved gas analysis (DGA) of a transformer can provide clear indication of thermal and electrical stresses on power transformer insulation and is considered as one of the most effective tools for oil-filled power transformer diagnostics. DGA is used to detect incipient faults in order to manage the fault severity. Both on-line and offline condition monitoring methods can be applied to obtain gas content, thereafter there are many interpretation techniques for DGA results. The accuracy of these techniques is dependent on the operator's experience and knowledge of the materials and equipment involved. In this work, a combined fuzzy logic analysis technique for monitoring of power transformers based on DGA analysis is proposed, the system uses the 7 key gases to diagnose the health of the transformer and, where applicable, fault type. Initially, gas levels are considered using the IEEE standard as a basis to indicate the health of the transformer. A combined fuzzified analytical tool, based on Duval Triangle, Doernenburg ratio and Key gas method, are analysed to identify the fault type, improving on the accuracy of the individual interpretation techniques. The analytical tool has been applied to 444 sample faults reported in the literature to assess the accuracy of the proposed system. Results presented show the system's overall decision has improved capability of identifying the transformer condition over individual methods. The proposed system is proved to have 99 % accuracy in identifying the transformer normality. For cases where transformers were faulty, the approach has 98.76% accuracy in recognising the actual fault, superior to individual approaches.

2018 Twentieth International Middle East Power Systems Conference (MEPCON), 2018

Dissolved Gas Analysis (DGA) of liquid insulation is an effective means for diagnosing power tran... more Dissolved Gas Analysis (DGA) of liquid insulation is an effective means for diagnosing power transformers. The gas contents in insulating oil can be gathered on-line and off-line to indicate the health condition of the transformers, thereafter there are many interpretations of the gas contents. In this work, Seven-fuzzy interpretation modules are individually established, tested and lately combined to monitor power transformers' health. The developed method incorporates trending of the concentration of the dissolved gases over the operating life. The approach processes current and/or historical DGA data, using the 7developed logic modules, to determine the current state of a transformer, provide information regarding the fault type, fault probability, fault severity and recommended future sampling interval in addition to operating procedure, consistent with industry standards. The developed diagnosis system has been validated using 1290 samples from fresh and previously tested mineral oil filled transformers. The proposed system is proved, based on field data, to be 99% accurate in identifying transformers being in normal or abnormal operation. For the cases where a transformer fault was known, the proposed technique has less than 2% inaccuracy in recognizing the fault's type in comparison to other approaches discussed in literature.

2017 52nd International Universities Power Engineering Conference (UPEC), 2017

Concerns over global climate changes coupled with growing demand for energy are leading to increa... more Concerns over global climate changes coupled with growing demand for energy are leading to increased penetration of distributed generation from intermittent sources into low voltage networks. In such cases distribution network (DN) operation will be affected. Consequently, there have been serious concerns over reliability and satisfactory operation of these power systems which contain distributed generation (DG) equipment. Distributed power generated from renewable sources is variable particularly in the case of wind generation or solar energy. The variability affects the stability of the system between supply and consumers. In DN, the losses and voltage drop across the network are significant matters and the DG location has a critical impact on the network operation. So, there is a clear need to optimise the DG size and location in the DN; for example, optimising the number of DG's and coordinating their operation can improve voltage drop and network losses. In this paper, an optimisation technique based on the genetic algorithm (GA) in conjunction with the power flow (PF) method is used to improve the DN performance and to identify the best location and size of the DG's. The main goal of the optimisation function is to reduce both the network losses and regulate the voltage level under different loading conditions.

2017 First International Conference on Latest trends in Electrical Engineering and Computing Technologies (INTELLECT), 2017

The micro-hydro based interconnected power system performance in terms of stability is generally ... more The micro-hydro based interconnected power system performance in terms of stability is generally affected by the dynamic characteristic of its components during and after when it is subjected to physical disturbances such as quick change in electric load, occurrence of fault etc. These disturbances sometimes cause large variations in frequency, voltage, power flows and other system constraints; thereby, invoking the actions of processes, controls, and protections that are incompletely and inappropriately modeled in conventional stability studies. Thus, complete and precise modeling of these processes, controls and protections is essential to diagnose the system response during and after instability. However, this research work focuses on the generating unit controls of micro-hydro deployed to regulate and sustain the frequency, voltage and power output for system stability and reliability. This paper presents an approach for appropriate modeling of a micro-hydro based interconnected power system scheme and its generating unit controls using SIMULINK. Furthermore, this work also analyzes the dynamic performance of micro-hydro generation and its associated controls during and after the occurrence of transient disturbances due to load changes and fault.

Renewable Energy and Power Quality Journal, 2011

Power quality has become a matter of growing concern in recent years owing to a daily rise in use... more Power quality has become a matter of growing concern in recent years owing to a daily rise in use of non-linear loads at domestic level. In addition, fast growing technologies like distributed generation and electric vehicles are emerging as part of modern distribution systems. Therefore, it is necessary to evaluate and analyze the power quality issues due to various non-linear home appliances to give a clear picture of the current scenario. So that future technologies can be accommodated in the distribution systems while coping with existing power quality issues. The experimentally developed harmonic models, of various commonly deployed domestic appliances, are used for the simulation of a practical distribution system in Electrical Transient Analyzer Program (ETAP). Experimental results combined with simulation results show an alarmingly high level of harmonic distortion, breaching the recommended standard practices, in both current and voltage at not only point of common coupling (PCC) but also at the consumer's end. In addition to increase in losses, this also degrades power factor giving rise to distortion power. While discussing other impacts of harmonic distortion, true power factor (PF true) and distortion power (D) has also been evaluated at PCC.

International Journal of Smart Grid and Clean Energy, 2014

The probabilistic power flow method has previously been used for voltage violation quantification... more The probabilistic power flow method has previously been used for voltage violation quantification in residential distribution networks (RDNs) with small wind turbines (SWTs) and battery electric vehicles (BEVs). An improved statistical time series approach is developed in this paper to account for factors which impact on system conformity. In addition to consideration of variations in wind speed over time and BEV charging, using a statistical time series approach, the novel method takes into account variations in system load caused by the randomness of load switching by customers. The method has been applied to a generic UK distribution network. Results show that the proposed method provides a closer indication of daily probability distribution of voltage violations in a RDN, based on physical data, than the previous statistical time series approach.

2013 48th International Universities' Power Engineering Conference (UPEC), 2013

ABSTRACT This paper investigates the impact of unbalanced loads and SWT penetrations over three p... more ABSTRACT This paper investigates the impact of unbalanced loads and SWT penetrations over three phases on voltage violation of residential distribution networks (RDNs). In this research, the point estimate method (PEM) is applied to identify the voltage violation of the network with various SWT penetration and distribution scenarios, taking into account the time varying characteristics of loads and wind speeds. The results quantify the voltage violation that will help distribution network operators to assess and constrain SWT impact on network configuration and operation.

International Journal of Smart Grid and Clean Energy, 2013

Harmonic distortion has garnered a lot of interest in the recent past due to the high advent of t... more Harmonic distortion has garnered a lot of interest in the recent past due to the high advent of the non-linear electronic loads. Moreover, newer technologies including distributed generation and electric vehicles are anticipated to be part of the distribution systems at a mass scale in the near future. This makes it of utmost importance to evaluate the existing power distribution systems and analyze the possible constraints. This research study makes an effort to evaluate the harmonic distortion in the distribution systems caused by the various non-linear residential loads. The experimentally developed harmonic spectrums, of several home appliances, are deployed for the simulation of a typical UK distribution system using Electrical Transient Analyzer Program (ETAP). The results show high level of harmonic distortion, at the Point of Common Coupling (PCC), in the distribution system which becomes even more aggravated when a higher loading level, of the distribution transformer, is considered.

2012 Asia-Pacific Power and Energy Engineering Conference, 2012

ABSTRACT Distributed generation is becoming an integral part of electrical distribution systems, ... more ABSTRACT Distributed generation is becoming an integral part of electrical distribution systems, which implies a subsequent increase in the induction of power electronic inverters into the power systems. These inverters being non-linear in nature produce harmonic distortion in voltage. To worsen the scenario, the present day distribution systems are already frazzled by many non-linear domestic loads. The adverse effects of high level of harmonic distortion are well established in the theory. Therefore, it is of utmost importance to investigate the impacts of distributed generation on the harmonic distortion level of a residential distribution system already stressed by non-linear domestic appliances. This research work makes an effort to address the very same issue. The experimentally developed harmonic model of an inverter is deployed to perform the simulation of a typical UK distribution system in Electrical Transient Analyzer Program. The results show a remarkable increase in the total harmonic distortion in the voltage and third individual harmonic in voltage, in the presence of distributed generation, at the point of common coupling. However, the total harmonic distortion in the current reduces which subsequently reduces the line losses.

IEEE Transactions on Power Systems, 2013

Voltage violation tends to be one of the dominant constraints or critical factors that limit the ... more Voltage violation tends to be one of the dominant constraints or critical factors that limit the penetration of small wind turbines (SWTs) and battery electric vehicles (BEVs) in distribution networks. To quantify the voltage violation, a statistical time series based approach is developed in this paper. The daily time varying characteristics of electric loads, wind speeds and BEV charging loads have been taken into consideration in a statistical manner. The method has been compared with the conventional time series approach. It is proven that the proposed methodology, while providing a global picture on voltage violations, can potentially be used for fast evaluation of the probability of a voltage violation occurring in a network. The methodology has been applied to an example distribution network. Results show that the proposed methodology can reduce the computational requirement by over 98%, while the difference between the results obtained using the proposed method and applying the conventional time series approach is within 12.5%.