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Nasr, A., D. K. Ibrahim, and M. Gilany, "Accurate Fault Location Algorithm for Series-Compensated Transmission Lines Using Synchrophasor Measurements", 17th International Middle East Power Systems Conference, MEPCON 2015; Mansoura University, Egypt, December, 15-17, 2015., 2015. Abstract

Reliable and accurate fault location algorithms for series-compensated transmission lines are challenges that arise in most of modern electrical power transmission grids. This paper proposes an accurate fault location algorithm for series-compensated transmission lines. Distributed parameters long transmission line model is used in this study to account for practical travelling waves’ effect during fault incidence. The proposed algorithm uses wavelet transform for only one cycle data window length of post-fault voltage signals to detect the faulted line, then Fast Fourier Transform for voltages and currents signals of three post-fault cycles (including the 1st cycle) to locate the fault. Only positive sequence network is used for the fault location calculations, hence, the algorithm does not depend on the zero sequence parameters (i.e., ground resistivity) which are depending on moisture, temperature, etc. Different types of grounded and ungrounded faults, fault locations, fault resistances, fault inception angles are applied to validate the robustness of the algorithm. The algorithm is tested using a real case study for a 380 kV, 400 km series compensated transmission line in Saudi Arabia using MATLAB and SIMULINK software. Extensive Simulation results show the effectiveness and robustness of the proposed algorithm under various fault conditions.

Eldin, E. M. T., M. I. Gilany, M. M. Abdel Aziz, and D. K. Ibrahim, "An accurate fault location scheme for connected aged cable lines in double-fed systems", Electrical Engineering, vol. 88, issue 5: Springer, pp. 431-439, 2006. AbstractWebsite

This paper presents an adaptive fault location scheme for aged power cables using synchronized phasor measurements from both ends of the cable. The proposed fault location scheme is derived using the two terminal synchronized measurements incorporated with distributed line model, modal transformation theory and Discrete Fourier Transform. The proposed scheme has the ability to solve the problem of cable changing parameters, especially the change of the relative permittivity over its age and thus for the operating positive, negative, and zero-sequence capacitance changes. Extensive simulation studies are carried out using Alternative Transients Program ATP/EMTP. The simulation studies show that the proposed scheme provides a high accuracy in fault location calculations under various system and fault conditions. The results show that the proposed scheme responds very well to any fault insensitive to fault type, fault resistance, fault inception angle and system configuration. The proposed scheme solves the problem of aged cables with the change of the electric parameters. In addition to, it gives an accurate estimation of the fault resistance.

Gilany, M., E. S. T. El Din, M. M. Abdel Aziz, and D. K. Ibrahim, "An accurate scheme for fault location in combined overhead line with underground power cable", Power Engineering Society General Meeting, 2005. IEEE: IEEE, pp. 2521-2527, 2005. Abstract

This paper presents an accurate fault location scheme for transmission systems consisting of an overhead line in combination with an underground power cable. The algorithm requires phasor measurements data from one end of the transmission line and the synchronized measurements at the most far end of the power cable. Fault location is derived using distributed line model, modal transformation theory and Discrete
Fourier Transform. The technique can be used on-line or off-line using the data stored in the digital transient recording apparatus. The proposed scheme has the ability to locate the fault whether it is in the overhead line or in the underground power cable. Extensive simulation studies carried out using MATLAB show that the proposed scheme provides a high accuracy in fault location under various system and fault conditions.

El-Sayed, L. M. A., D. K. Ibrahim, M. I. gilany, and A. ’F. El’Gharably, "An Accurate Technique for Supervising Distance Relays during Power Swing", Indonesian Journal of Electrical Engineering and Computer Science, vol. 21, issue 3, pp. 1279-1290, 2021. AbstractWebsite

Power swing is a power system transient phenomenon that arises due to several reasons including line switching, line outage, sudden increment or decrement in load, faults, etc. Unnecessary tripping during power swing and unnecessary blocking for faults occur during power swing result in distance relay maloperation. Several cascaded outages and major worldwide blackouts have occurred due to maloperation of distance relays. This paper proposes a technique for supervising distance relays during power swing. The proposed
online technique discriminates real faults and power swing accurately. It relies on constructing a locus diagram for the current and voltage differences (ΔI-ΔV) between the two ends of the protected line. The locus is estimated at every power frequency cycle to continuously monitor the state of the line by utilizing the synchrophasor measurements at the sending and receiving ends of the line. The proposed technique is tested for two-area, four-machine power system under faults at different locations of zone-1 and zone-2 regions of distance relays, fault resistances, fault inception angles and slip frequencies using MATLAB software. The simulation results proved the superior improvement of distance relay performance for handling power swing blocking and unblocking actions.

Abo-Hamad, G. M., D. K. Ibrahim, E. A. M. Zahab, and A. F. Zobaa, "Adaptive Mho Distance Protection for Interconnected Transmission Lines Compensated with Thyristor Controlled Series Capacitor", Energies , vol. 14, issue 9, pp. Article 2477, 2021. Abstract

This paper proposes an adaptive dynamic Mho distance relay based on a phase comparator scheme for protecting interconnected transmission networks compensated with a Thyristor Controlled Series Capacitor (TCSC). The proposed relay uses an impedance index factor to initiate the fault detection subroutine. The RMS of the positive sequence current of the faulted loop and the TCSC terminal current are compared for TCSC zone identification. A phase comparator for ground and phase distance elements is proposed, relying on the positive sequence voltage as a polarized memory quantity, while the operating and polarizing quantities are developed using estimated TCSC impedance to mitigate its negative impact. The proposed scheme is easy in implementation and independent on synchronized data transfer, as minimum communication requirements are needed. To evaluate the performance of the proposed scheme, extensive simulation studies were carried out on an IEEE9 bus system compensated with TCSC for different firing angles covering four modes of TCSC operations, different fault types, and fault locations. In addition, an IEEE-39 bus network, as a large interconnected system, is tested for validation purposes. The achieved results designate the precision of the proposed scheme. Moreover, the results indicate its effectiveness for fault resistance tolerance, close-in three phase faults, and stable power swing phenomenon compared with conventional relays.

Atta, M. E. E. - D., D. K. Ibrahim, M. I. gilany, and A. F. Zobaa, "Adaptive Scheme for Detecting Induction Motor Incipient Broken Bar Faults at Various Load and Inertia Conditions", Sensors, vol. 22, issue 1, pp. Article 365, 2022. Abstract

This paper introduces a novel online adaptive protection scheme to detect and diagnose broken bar faults (BBFs) in induction motors during steady-state conditions based on an analytical approach. The proposed scheme can detect precisely adjacent and non-adjacent BBFs in their incipient phases under different inertia, variable loading conditions, and noisy environments. The main idea of the proposed scheme is monitoring the variation in the phase angle of the main sideband frequency components by applying Fast Fourier Transform to only one phase of the stator current. The scheme does not need any predetermined settings but only one of the stator current signals during the commissioning phase. The threshold value is calculated adaptively to discriminate between healthy and faulty cases. Besides, an index is proposed to designate the fault severity. The performance of this scheme is verified using two simulated motors with different designs by applying the finite element method in addition to a real experimental dataset. The results show that the proposed scheme can effectively detect half, one, two, or three broken bars in adjacent/non-adjacent versions and also estimate their severity under different operating conditions and in a noisy environment, with accuracy reaching 100% independently from motor parameters.

Rashad, B. A. - E., D. K. Ibrahim, M. I. Gilany, and A. ’F. El’Gharably, "Adaptive Single-End Transient-based Scheme for Detection and Location of Open Conductor Faults in HV Transmission Lines", Electric Power Systems Research, vol. 182, issue May 2020, pp. Article 106252, 2020. Abstract

Detection and location of open conductor in transmission systems using single-end data is a challenging task. This paper proposes a novel integrated scheme to detect and locate different types of open conductor faults (OCFs) in HV transmission systems. The proposed scheme unit (PSU) applies Discrete Wavelet Transform (DWT) with single-level decomposition on local current signals to detect OCFs correctly using adaptively estimated threshold values. PSU is also capable of dealing correctly with various normal transient conditions such as load capacitor switching. To ensure quick repair of OCFs, PSU captures the transient voltage surges and applies a fault location scheme using DWT and Clark Transformation to accurately estimate the location of different OCFs types. Extensive ATP simulations are employed to check the PSU performance under various OCFs conditions on a 345 kV, 100 km transmission line. The achieved results confirm the effectiveness, robustness, and reliability of PSU in detecting correctly OCFs as well as the low-impedance faults within only 1.25 cycles. Moreover, the percentage error in estimating OCFs location is less than 1%. PSU has also confirmed its capability to be applied in cascaded lines without any communication or synchronization between PSUs.

Shafei, M. A. R., D. K. Ibrahim, and M. Bahaa, "Application of PSO tuned fuzzy logic controller for LFC of two-area power system with redox flow battery and PV solar park", Ain Shams Engineering Journal, vol. 13, issue 5, pp. Article No. 101710, 2022. Abstract

Nowadays, integrating large scale renewable energy sources, like solar PV parks, raises challenges for Load Frequency Controllers (LFC). The output of PV varies continuously, which requires a robust LFC deals
logically without continuous tuning and parameters optimization. In this paper, a fuzzy logic controller (FLC) is proposed to act as the main LFC instead of the traditional proportional–integral–derivative (PID) controller. The dynamic performance of FLC is enhanced by optimizing its parameters for different cost functions using particle swarm optimization technique (PSO). Another two FLCs will be added to PV system to act as an output controller instead of maximum power point tracker (MPPT) to enhance the overall system performance. To increase system reliability, a fast active power source called redox flow battery (RFB) is added in the proposed model as a frequency stabilizer. RFB can deeply discharge up to 90% with theoretically limitless number of duty cycles and has fast time response for severe load changes. The
importance of these proposed controllers side by side with RFB is to avoid disconnecting solar parks during
heavy cloudy days while preserving on maximizing its output during these periods. The superiority of the proposed FLC is examined by evaluating its performance compared to another control approach called PID-P (PID controller with P controller in the inner feedback loop). Finally, a comprehensive sensitivity analysis is also presented to investigate the controller robustness for extensive changes in power system parameters and loading.

Alham, M. H., M. F. Gad, and D. K. Ibrahim, "Applying Marine Predators Algorithm for Optimizing the Layout of Wind Turbines", International Journal of Renewable Energy Research, vol. 13, issue 2, pp. 730-740, 2023. AbstractWebsite

The extracted power from wind is clean, plentiful, and completely renewable. All over the world, researchers keep looking for the best layouts of wind parks to maximize captured energy. To design wind farms suitably, forecast their performance, and understand the strain loads of wind turbines, there is a persistent need to catch a perfect wake model. Wind turbine wakes are one of the most vital factors in the meteorology of wind power due to reducing the power production and the necessity to raise the downstream capacity of wind turbines. This study is divided into two main aspects: firstly, enhancing the optimal layout for the wind turbines at a farm using Marine Predators Algorithm (MPA). The Jensen wake model is applied to get the extracted power for each turbine, which is one of the mutual analytic models used to reach the optimized layout. By comparing the performance of the proposed algorithm with the previous studies achieved by several techniques, the obtained results revealed that the MPA achieves promising results. Secondly, the proposed algorithm is applied for four sites in Egypt as the fraction of occurrence for the selected locations has been adequately calculated using wind speed over five years.

Metwally, M. A., A. Aboshosha, D. K. Ibrahim, and E. E. L. - D. A. EL-Zahab, "Applying Neurofuzzy Computing for Safety Improvement of Nuclear Power Reactor", 14th International Middle East Power Systems Conference (MEPCON’10), Cairo University, Egypt, 2010. Abstract

Nuclear Power Reactors (NPRs) are large in scale and complex, so the information from local fields is excessive, and therefore plant operators cannot properly process it. When a plant malfunction occurs, a great data influx is occurred, so the cause of the malfunction cannot be easily or promptly identified.
A typical NPR may have around 2,000 alarms in the Main Control Room (MCR) in addition to the display of analog data. During plant transients, hundreds of alarms may be activated in a short time. Hence, to increase the plant safety, this paper proposes a support system based on neurofuzzy that assists alarming and diagnosis systems. Throughout this framework the neurofuzzy fault diagnosis system is employed to fault diagnosis of nuclear reactors. To overcome weak points of both linguistic and neuro learning based approaches, integration between the neural networks and fuzzy logic has been applied by which the
integrated system will inherit the strengths of both approaches.

Ali, H. A. E. ‑S., M. H. Alham, and D. K. Ibrahim, "Big data resolving using Apache Spark for load forecasting and demand response in smart grid: a case study of Low Carbon London Project", Journal of Big Data, vol. 11, issue 1, pp. Article no. 59, 2024. Abstract

Using recent information and communication technologies for monitoring and management initiates a revolution in the smart grid. These technologies generate massive data that can only be processed using big data tools. This paper emphasizes the role of big data in resolving load forecasting, renewable energy sources integration,
and demand response as significant aspects of smart grids. Meters data from the Low Carbon London Project is investigated as a case study. Because of the immense stream of meters’ readings and exogenous data added to load forecasting models, addressing the problem is in the context of big data. Descriptive analytics are developed using Spark SQL to get insights regarding household energy consumption. Spark MLlib is utilized for predictive analytics by building scalable machine learning models accommodating meters’ data streams. Multivariate polynomial regression and decision tree models are preferred here based on the big data point of view and the literature that ensures they are accurate and interpretable. The results confirmed the descriptive
analytics and data visualization capabilities to provide valuable insights, guide the feature selection process, and enhance load forecasting models’ accuracy. Accordingly, proper evaluation of demand response programs and integration of renewable energy resources is accomplished using achieved load forecasting results.

Shafei, M. A. R., D. K. Ibrahim, A. El-Zahab, E. El-Din, and M. A. A. Younes, "Biogeography-Based Optimization Technique for maximum power tracking of hydrokinetic turbines", Renewable Energy Research and Application (ICRERA), 2014 International Conference on: IEEE, pp. 789–794, 2014. Abstract

Hydrokinetic energy, referring to the energy contained in moving water, is a renewable energy source that gained much consideration in the past years and expected to play a significant role in the future. The energy is initiated in all moving water masses, but is significantly economic to convert for water masses moving with high velocity. Nonlinear characteristics of water speed and generator model in hydrokinetic energy conversion systems require an optimal controller for achieving optimal performance and high efficiency of the system. Here, the field oriented control method is proposed to set the PI controllers which their coefficients are optimized based on Biogeography- Based Optimization technique (BBO). In order to use BBO to solve this problem, the problem has to be formulated as an optimization problem. Numerous simulation studies are carried out to verify the effectiveness of the proposed controller scheme. Achieved results for different patterns of water speed changes in time domain show the capability of the proposed control.

Atta, M. E. E. - D., D. K. Ibrahim, and M. I. gilany, "Broken Bar Fault Detection and Diagnosis Techniques for Induction Motors and Drives: State of the Art", IEEE Access, vol. 10, pp. 88504 - 88526, 2022. AbstractWebsite

Motors are the higher energy-conversion devices that consume around 40% of the global electrical generated energy. Induction motors are the most popular motor type due to their reliability, robustness, and low cost. Therefore, both condition monitoring and fault diagnosis of induction motor faults have motivated considerable research efforts. In this paper, a comprehensive review of the recent techniques proposed in the literature for broken bar faults detection and diagnosis is presented. This paper mainly investigates the fault detection methods in line-fed and inverter-fed motors proposed after 2015 and published in most relevant journals and conferences. The introduced review has deeply discussed the main features of the reported methods and compared them in many different aspects. Finally, the study has highlighted the main issues and the gaps that require more attention from researchers in this field.

Atta, M. E. E. - D., D. K. Ibrahim, and M. Gilany, "Broken Bar Faults Detection under Induction Motor Starting Conditions Using the Optimized Stockwell Transform and Adaptive Time-Frequency Filter", IEEE Transactions on Instrumentation and Measurement, vol. 70, pp. Article 3518110, 2021. Abstract

Most of the published research studies for detecting induction motor broken bar faults (BBFs) use a time–frequency (t − f ) decomposition tool to characterize the fault-related components. However, the identification and the assessment of these components in (t − f ) domain require skilled user or powerful pattern recognition technique. Moreover, a relatively long starting duration is necessary. This article introduces an automated scheme to detect BBFs and distinguish fault severity in induction motors under startup conditions regardless of the user experience and even under short starting duration and in a noisy environment. This scheme is based on the analysis of the starting current using optimized Stockwell transform (ST). An active set algorithm is applied to maximize the energy concentration of the left-side harmonic (LSH) component. Then, an adaptive time–frequency filter is applied to extract the LSH component from the (t − f ) domain, where the energy of the right part of LSH (RLSH) is utilized as an effective index for BBFs detection and for discriminating BBFs severity. Both real experimental data and simulation-based tests on 0.746- and 11-kW motors are used to extensively verify the performance of the proposed scheme. The achieved results have ensured that the proposed scheme can achieve a high accuracy with the minimum data and shortest acquisition time in comparison with some recent methods in the literature.

Mohamed, M. S., M. A. R. Shafei, A. A. Mansour, and D. K. Ibrahim, "Coils design and parallel resonant H-bridge inverter for inductive power transfer to recharge low-power portable devices", 21st International Middle East Power Systems Conference, MEPCON , Tanta University, Egypt, December 17-19, 2019. Abstract

The capability of the inductive power transfer (IPT) for wireless charging mainly depends on both coil structure and inverter topology. The paper presents the resonant inverter based on the concept of energy injection and free oscillation which are applied to increase the resonant frequency without raising the switching frequency. The implemented inverter utilizes the variable frequency zero current switching (ZCS) control strategy for parallel configuration that ensure the high operating frequency at multiplies of the inverter switching frequency. Consequently, it will result in decreasing the inverter switching loss and also reducing the coil size that operates at resonant frequency. The coil design methodology is introduced in details while studying the different factors affecting the coil behavior. The performance of the overall designed system is evaluated via simulation tests carried out using ANSYS Maxwell and MATLAB SIMULINK.

Afifi, M. K., H. M. Sharaf, M. M. Sayed, and D. K. Ibrahim, "Comparative Study between Single-Objective and Multi-Objective Optimization Approaches for Directional Overcurrent Relays Coordination Considering Different Fault Locations", 13th IEEE PES PowerTech Conference, Milano, Italy, 23-27 June 2019. Abstract

In this paper, a comparative study of single-objective and multi-objective optimization approaches for directional overcurrent relays (DOCRs) coordination is presented. Singleobjective optimization approach is investigated using two methods; the fmincon function which is the gradient-based method, while the second method is the Genetic Algorithm which is a meta-heuristic technique. Multi-objective optimization approach is investigated using fmincon function and Goal Attainment method. All the methods are available in the MATLAB Optimization Toolbox. Different fault locations on the meshed power distribution network of the IEEE 14 bus system are considered for the investigated methods. The results of singleobjective and multi-objective approaches are compared regarding total relays operating times, mean fault clearing time, maximum primary and backup relays operating time and maximum coordination time interval. The results show that using the multi-objective optimization approach in solving the DOCRs coordination problem achieved less total relays operating time and coordination time intervals which ensure faster fault clearing.

Ibrahim, D. K., M. M. Abd-elaziz, and M. B. Youwakim, "Comparison of Maximum Power Point Tracking Techniques for Different Types of Photovoltaic Models", Proceedings of the 7th International Conference on Electrical Engineering, (ICEENG) Conference, 25-27 May, Cairo, Egypt, 2010, 2010. Abstract
Ibrahim, D. K., G. M. Abo-Hamad, A. E. E. M. Zahab, and A. F. Zobaa, "Comprehensive Analysis of the Impact of the TCSC on Distance Relays in Interconnected Transmission Networks", IEEE Access, vol. 8, pp. 228315 – 228325, 2020. Abstract

This article extensively investigates the calculations of the compensation factor of the thyristor-controlled series compensator (TCSC), which are used to accurately evaluate the negative impacts of the TCSC on the performance of conventional distance relays. To broadly evaluate the distance protection performance, the TCSC was adapted to the IEEE 9-bus system as one of the interconnected transmission networks that are increasingly spreading to improve service reliability, reduce reserve capacity, and enhance system efciency. In addition, IEEE 39-bus system, as a large interconnected system, is also examined to generalize the TCSC impact on different interconnected systems. To determine the precise impact, the impedance of the TCSC was calculated based on its practical design parameters. The impedance of the TCSC was examined as a function of transmission line impedance and ring angle. Both Mho and Quadrilateral distance relays were tested using the MATLAB/Simulink environment for different types of faults, fault locations, fault resistances, and ring angles for capacitive, inductive, and blocking modes of TCSC operation. In addition, distance relay performance was evaluated during power swing phenomenon in the presence of the TCSC. Simulation tests indicated the negative impacts of the TCSC on distance relay operation, which are not limited to over-reach and under-reach in faulty conditions but also to maloperation in dynamic disturbances that cause power swing phenomena on the protected line.

Ibrahim, D. K., E. E. - D. A. El-Zahab, and A. Galal Ahmed, "Comprehensive Fault Location Scheme for Power Transmission lines", 16th International Middle East Power Systems Conference, MEPCON 2014, 2014. Abstract

A comprehensive two-terminal impedance based fault location scheme is presented in this paper which takes into account the distributed parameter line model. The scheme utilizes unsynchronized measurements of voltages and currents from the two ends of a line. The synchronization angle is calculated using symmetrical components transformation theory. The proposed scheme integrates several fault location algorithms. In one of them, Takagi method is used taking into account the effect of distributed capacitance when the communication link between sending end and receiving end fails.
Another algorithm is embedded in the proposed scheme to accurately locate ground and phase nonlinear high impedance faults using zero and negative sequence currents gathered from the two terminals within a maximum time of 2 cycles. The proposed fault-location scheme has been thoroughly tested using ATP versatile simulations of faults on transmission lines. The presented evaluation shows the validity of the developed fault-location scheme and its accepted accuracy.

Atta, M. E. E. - D., D. K. Ibrahim, and M. I. gilany, "Detection and Diagnosis of Bearing Faults under Fixed and Time-Varying Speed Conditions Using Persistence Spectrum and Multi-Scale Structural Similarity Index", IEEE Sensors Journal, vol. 22, issue 3, pp. 2637 – 2646, 2022. Abstract

With the widespread use of variable speed drives, a robust scheme that can detect and diagnose bearing faults under fixed and variable speed conditions becomes essential for reliable operation. Unfortunately, most of the reported methods in the literature are dedicated to working under fixed speed and will face challenges under variable speed conditions. Besides, most of them require detailed bearing information that may be unavailable in the real world. Therefore, in this paper, a new scheme is proposed for bearing faults detection and diagnosis under fixed and time varying speed conditions. The proposed scheme is based on the analysis of vibration signals using the persistence spectrum that can provide images rich with health-related features largely independent from rotating speed. Then, the produced image is compared with priorly stored images of the persistence spectrum of a healthy case. This comparison is performed using the multi-scale structural similarity index, which is a robust basis for images comparison without the need for training or expert knowledge. The obtained index is compared against an adaptive threshold for fault detection. Upon detecting a fault, the persistence spectrum image is compared with that of stored different fault types for fault diagnosis. The proposed scheme is extensively validated using three experimental datasets under different speed conditions. The results show that it can detect bearing faults in an earlier stage without the need for bearing specifications or shaft speed. Moreover, it can successfully diagnose bearing faults severity with accuracy reaching 100% with the minimum required data.

Ibrahim, D. K., M. M. Abdel Aziz, N. M. Abdel Fattah, and A. Ramadan, "Detection and Location of Distribution Systems Faults using Wavelet Packet Transform Based Overcurrent Relay", Proceedings of the 8th International Conference on Electrical Engineering, ICEENG Conference, Military Technical College, Cairo, Egypt, 29-31 May, 2012., Egypt, 2012. Abstract

This paper presents a scheme to increase the sensitivity of overcurrent protection. The proposed scheme applies wavelet packet transform, since it can preserve both time and frequency information with high resolution. The proposed scheme demonstrates its feasible performance in detecting short circuit faults, calculating fault location with moderate accuracy and detecting nonlinear high impedance faults. In addition, the proposed scheme examines the load current continuously and has the ability of changing the relay pick up value adaptively. The examined tested cases include different internal short circuit fault conditions, different nonlinear high impedance faults, and non fault situations such as normal load changing. The obtained results indicate that the developed scheme is fast, robust, reliable and suitable for power distribution systems.

Mohamed Sharaf, H., H. H. Zeineldin, D. K. Ibrahim, and E. E. L. - D. A. EL-Zahab, "Directional Inverse Time Overcurrent Relay for Meshed Distribution Systems with Distributed Generation with Additional Continuous Relay Settings", 12th International Conference on Developments in Power System Protection, 31 March - 3 April 2014 Copenhagen., Copenhagen, IET, 2014. Abstract

Coordination between inverse time overcurrent relays within meshed systems are achieved by adjusting two relay settings; pick up current and time multiplier settings. The operating time of these relays is also a function of two additional constants; one represents the constant for relay characteristics and the other one represents the inverse time type. For typical relays, each of these two constants has four definite values and choosing between them indicates the selected relay operating curve: either standard inverse, very inverse, extremely inverse or long time standby earth fault time-current relay characteristics. In this paper, a coordination strategy, that takes advantage of the available capabilities in microprocessor based relays, is proposed by considering the two relay characteristic constants as continuous variable settings that can be adjusted in addition to the conventional pickup current and Time Dial Setting (TDS). The protection coordination problem is formulated as a nonlinear programming problem where the main objective is to minimize the overall time of operation of relays taking into account protection coordination constraints. The proposed approach is applied to the IEEE 14 bus system and is compared with the conventional two setting relay.

Mostafa, S. A. E. A., D. K. Ibrahim, and E. E. - D. A. El-Zahab, "Directional Overcurrent Relays Coordination Restoration By Reducing Minimum Fault Current Limiter Impedance", Proceedings of the 15th International Middle East Power Systems Conference, MEPCON 2012; Alexandria, Egypt, December, 23-25, 2012, 2012. Abstract
Mostafa, S. A. E. A., D. K. Ibrahim, and E. E. - D. A. El-Zahab, "Directional Overcurrent Relays Coordination Restoration By Reducing Minimum Fault Current Limiter Impedance", Journal of Energy and Power Engineering, vol. 8, pp. 1132–1141, 2014. AbstractWebsite

FCL (fault current limiter) is used to solve relays miscoordination problem arises from DG (distributed generation) installation. In most published researches, different optimization methods are developed to obtain optimal relay settings to achieve coordination in case of not installing DG, then depending on the achieved optimal obtained relay settings, FCL impedance is deduced to ensure relays coordination restoration in case of installing DG. Based on original optimal relay settings, obtained FCL impedance is not the minimum one required to achieve relay coordination. The contribution of this paper is the generation of multi sets of original relay settings that increase the possibility of finding FCL impedance of minimum value which is lower than the calculated value based on original optimal relay settings. The proposed method achieves better economic target by reducing FCL impedance. The proposed approach is implemented and tested on IEEE-39 bus test system.

Yousef, W. H., D. K. Ibrahim, and E. Abo El-Zahab, "Discrimination of Internal Faults and Inrush Currents For Large Modern Power Transformer", 14th International Middle East Power Systems Conference (MEPCON’10), Cairo University, Egypt, 2010. Abstract

This paper presents a differential protection approach for large high quality power transformers that have
low inrush currents of about 3.14 times rated currents. Such transformers have low second harmonic level, which results in conventional differential protection malfunction. A scheme for internal faults and inrush currents discrimination based on both discrete Fourier transform DFT and discrete Wavelet Transform
DWT is proposed. The proposed method has been designed based on the percentage of the sum of wavelet transform coefficients D1 and fundamental differential current (based on a 1 kHz sampling
rate). It has been tested by extensive EMTP/ ATP simulations for different faults and switching conditions on El Tebbin Power Plant 220/21 kV generator/power transformer. It is proved that it has a high capability for discrimination even in the case of inrush with low second harmonic content and internal fault currents with high second harmonic component. All tests proved that the proposed scheme is reliable, accurate, and fast.