Doaa Khalil Ibrahim

Discrimination and location of faults in Flexible Alternating Current Transmission Systems (FACTS) have several challenges in power systems. This is because of the errors in the measured impedance due to FACTS control actions. The presence of series FACTS in a transmission line complicates both the fault location and discrimination between faults behind and in front of the FACTS device. This paper proposes an integrated solution for both fault zone discrimination (either in front of or behind the FACTS device) and fault location for series FACTS-compensated transmission lines. Online calculations are carried out to estimate the percentage of compensation. After fault inception, a wavelet-based algorithm is used to decide whether the fault is in front of the FACTS device or behind it. Then, a conventional distance protection algorithm is used to estimate the fault zone. After that, synchronized data signals from both ends are used to locate the exact location offline. The algorithm is tested using a real data for a 380 kV, 400 km series-compensated line in Saudi Arabia using MATLAB/SIMULINK. Different types of faults are applied to validate the effectiveness of the algorithm. Metal-Oxide Varistor (MOV) nonlinearity is also considered. Simulation results show the effectiveness of the algorithm.

Digital filters of electrical protective relays play primary roles in calculating the fundamental phasors of electrical power signals. In most fault cases, large amounts of decaying DC components are included in the current signals during the fault period. Decaying DC component significantly reduces the precision and convergence speed of all conventional frequency-domain filters such as Fourier and Walsh filters. In this investigation, this paper introduces a new frequency-domain filtering algorithm to remove the decaying DC components and accurately capture the fundamental power system phasors for digital protective relays. This is executed by means of a mathematical procedure using digital signal processing techniques. The proposed filter is tested for a wide variety of current signals during different fault conditions to assess its performance. The simulation results show that the proposed filtering algorithm has a superior performance at a wide range of decaying components.

Sympathetic tripping is a common challenge that affects the proper operation of the earth fault relays in distribution networks. It likely occurs when healthy feeders are exposed to an unnecessary trip operation in response to an actual fault occurring on an adjacent feeder. The sympathetic tripping phenomena of overcurrent and earth fault (EF) relays in the distribution networks and their causes are studied in this paper. Real recorded data of affected healthy feeder(s) for different sympathetic trip scenarios reported from an Egyptian distribution network are extensively analysed. A custom logic protection scheme is proposed to detect the sympathetic tripping phenomena using the existing features of IED relays without any additional cost. In addition to the captured real disturbance records, simulated scenarios of sympathetic tripping are modelled using MODELS language in ATP/EMTP program to evaluate the proposed schemes. The achieved results ensure the suitability of the proposed protection program in order to avoid the unnecessary false sympathetic tripping for both incoming and outgoing feeders.

The presence of DGs in power system networks tends to negatively affect the protective relays coordination. The proposed method introduces an approach to minimize the numbers of relays that acquire new settings on contrary to their original settings (case without DG), to achieve relays coordination in case of adding DG, since relays coordination with minimum number of relays of readjusted settings represents economical target, especially in networks containing mixture of electromechanical and adaptive digital relays. The scheme decides the possible minimum number of re-adjusted relays and their locations in an optimum manner to achieve proper relays coordination in case of adding DGs. The proposed approach is divided into two successive phases; the first phase is stopped when the first relays coordination solution is achieved. The second phase increases the possibility to keep higher number of relays at their original settings than that obtained in first phase through achieving multi solutions of relays coordination. The proposed approach is implemented and effectively tested on the well-known IEEE-39 bus test system.

The presence of DGs in power networks tends to negatively affect relays coordination. Adding fault current limiters FCLs is one of the possible solutions to mitigate negative impacts of DGs addition on protection systems. Traditional schemes have estimated the minimum value of FCL to restore relays coordination when adding DGs without resetting of any relays. That minimum value of FCL in such case is called a critical value, where below this value the relays coordination will be lost.
Nowadays, designing FCL to simultaneously achieve two conflicted objectives of good performance and low cost is considered a great challenge. The paper introduces a new scheme to determine to what extent we could decrease FCL impedance value below its critical value with re-adjusting the original settings of only one adaptive relay to get relays coordination. Decreasing FCL value below its critical value will reduce the cost especially for superconductivity FCL. The proposed scheme can determine the location of that selected relay to be an adaptive one and estimate its re-adjusted new settings to be applied when DGs are added while inserting the reduced value of FCL.
Actually the proposed scheme can be applied for any networks irrespective of the number of added DGs and their capacities; while having an adaptive relay is the only requirement to implement it. The proposed approach is implemented and effectively tested on the large well-known interconnected IEEE-39 bus test system with 84 relays. Its results are compared with other approaches where, no readjusted relays settings are applied. A noteworthy advantage of the proposed scheme is the ability to implement a reduced FCL value than the critical value, by adjusting only one relay settings in the whole network. The proposed scheme may also be extended to re-adjust settings of more than one relay and get further reduced value of FCL. Furthermore, it is also shown that a more optimum value of the total operating time of all primary relays for near end faults is achieved when applying the proposed method rather than other traditional schemes.

This paper proposes an analytical impedance-based fault location scheme for distribution systems. The approach is based on voltage and current measurements extracted at only one-end feeding substation.Modal transformation is implemented to decompose the coupled three phase equations due to mutual effects into decoupled ones, and hence directly calculating fault distance in each section without iterative processes. The proposed approach considers various aspects of distribution systems: intermediate loads along the feeder, tapped laterals and sub-laterals at various nodes, time varying loads, and unbalanced operations. The proposed algorithm is extensively investigated on a typical real 11 kV distribution system,South Delta electricity sector, Egypt using MATLAB environment. Different cases are studied considering various loading conditions, varied fault resistance values and different fault types. The achieved results ensure the effectiveness of the proposed fault locator irrespective to fault conditions. Besides, the robustness of the proposed scheme against unbalanced loading, network topology change and non homogeneous network sections is also confirmed.

The high penetration of the wind energy in the power systems raises some issues such as ramping and mismatch between the wind power and power demand. One of the possible solutions to these issues is the demand side management (DSM). In this paper, dynamic economic dispatch (DED) incorporating different penetration levels of wind energy and utilizing the DSM is proposed to solve the issues related to high penetration of wind energy. The effect of utilizing the DSM on the operation cost with different test cases is discussed. The General Algebraic Modeling System (GAMS) using BARON as a solver and genetic algorithm (GA) with hybrid function are used to solve the proposed DED model and a comparison between them is assessed. The proposed model is applied to a six units’ generation system to test the effectiveness of the proposed model.

In this contribution, the three-phase underground cable is modelled using COMSOL Multiphysics software to evaluate the steady state and transient thermal performances. Finite element technique is applied using the heat conduction equation to study the temperature distributions in power cables components and the surrounding environment for both linear and non-linear loads. A real case study of 220 kV, 340 MVA three phase single core copper cables insulated by XLPE is studied. Other types of insulation such as oil, and SF6 gas and their contributions of convection and radiation are investigated at trefoil and flat configurations. The loading capability under different ambient conditions for average moisture soil and dry soil with low moisture content are also evaluated taking into account the unfavourable effect of dry zones formation. Moreover, the challenge of predicting the accurate thermal performance and estimating the required derating factor in the presence of odd harmonics is considered. The effect of the change of the frequency spectrum of the non-linear load current by involving different simultaneous harmonic orders for the same total harmonic distortion is extensively investigated for both flat and trefoil configurations. It is concluded that all harmonics contributions should be considered, to accurately calculate the required cable derating.

This paper describes a proposed busbar protection scheme immune to the impact of the outflow current during internal faults based on the combination of magnitude and phase angle comparisons. The effective relay performance is achieved by implementing the phaselet approach and the adaptive digital mimic filter. The performance of the proposed scheme is extensively analyzed for different fault conditions on a breaker and a half bus substation to ensure its proper response during internal, external and evolving faults. Tests are carried out to investigate the impact of the circulating current, CT saturation, fault inception angle and high fault resistance. ATP simulations ensure that the proposed scheme can fulfill all busbar protection requirements within quarter cycle operation time and is not affected by the outflow current during internal faults.

This paper presents an automated fault location scheme for MV overhead distribution networks. The scheme utilizes only the measurements of voltage signals at the main substation. Clarke and Fast Fourier transformations are applied to get the frequency of the travelling wave generated during the
fault. A simple automation system is implemented to identify the faulted lateral. A typical 22 kV distribution system is used to test and validate the proposed scheme. ATP program is used to simulate the tested network while the required calculations are performed by MATLAB developed algorithms. Extensive fault cases are carried out at different fault positions, inception angles, fault resistance and load levels. The calculated errors indicate that the proposed scheme has low sensitivity to the change of the fault conditions that ensures the effectiveness and robustness of the proposed scheme.

Reducing carbon emissions is an important goal for the whole world; a high penetration of wind energy can help in reducing emissions. However, great increase in wind energy usage raises some issues concerning its variability and stochastic nature. These issues increase the importance of studying methods of wind energy representation, and in the same time studying the effect of using some flexible resources in decreasing those issues. This paper proposes a dynamic economic emission dispatch (DEED) model incorporating high wind penetration considering its intermittency and uncertainty. Energy storage system (ESS) and demand side management (DSM) are implemented in order to study their effect on the cost, emission, and wind energy utilization. The GAMS software has been utilized to solve this DEED problem. The achieved results show the importance of using ESS and DSM in decreasing both cost and emission, and increasing the wind energy utilization.

This paper presents a deep analysis for the energy system in Yemen, which consists of thermal power plants taking into account the strengths and weaknesses of its power system. The investigation results show that Yemen power system suffers lacking of energy efficiency (EE), weak institutional capacity, high losses in the generation, transmission and distribution grids, and currently the disability to invest in renewable energy (RE). Yemen should focus on foundational activities to build institutional capacity and mobilize resources to initiate suitable energy efficiency policies and measures. Yemen should also focus on exploring the opportunities of designing innovative energy systems based on decentralized small-scale power generation. Microgrids could enable power supply to remote areas at lower costs than required by traditional infrastructure.

With increasing global great concern over greenhouse gas emissions and their harmful effects on environment, huge number of wind turbines are recently connected to electrical grids. Nowadays, Egypt has continuous development of wind energy projects; it makes a great effort at Gulf of Suez area especially in Al Zafarana district. This paper focuses on studying the dynamic performance of the 5th phase of Al-Zafarana wind farm, which is made of 100 Gamesa G52/ 850kW Doubly Fed Induction Generator (DFIG) machines, using Digsilent /PowerFactory simulation tool as an advanced simulation package. As DFIG is currently one of the most common types employed for Wind Energy Conversion System (WECS), the paper also implements a dynamic model for 850 kW DFIG machine based WECS in Matlab / Simulink environment. A dual reference frame control strategy is applied here to improve the dynamic system performance during balanced and unbalanced grid voltage conditions.

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.

This paper presents modeling and impact analysis of Al-Mukha wind farm (MWF) on Yemen power system, which is made of thermal power plants. In this paper, four kinds of major components are modeled: a 60MW wind farm, a transmission network, thermal power plants, and the Yemen power system load. To analyze the impact of the wind power generation to the Yemen power system, simulations are carried out for two case studies by using the DIgSILENT program. The first is the case of grid impact studies: impact on thermal limits, voltage variations, and system stability, in which an aggregated model of the wind farm is used. The other is the dynamic performance of the wind farm by analyzing low-voltage ride through LVRT, harmonics and flicker impact on the basis of the detailed wind farm layout with 30 wind turbines (WTs) arranged in four stands and the external grid of 2175MVA short-circuit capacity. The simulation results show that the loading of most lines and voltage variations are slightly reduced. In addition, there is no harmful effect on the system stability and also the wind farm is capable to ride through the grid fault. Finally, it is shown that the wind farm contributes voltage and current harmonics higher than the permissible limits while the flicker levels are far below any critical values. 

Synchronous generator in electric power plants –as well as the power transformer - is very important and expensive element so it should be provided with fully protection system to protect it against any abnormal conditions. Failure can occur in a generator or transformer due to different reasons. The protection system must prevent the protected equipment from being affected by external faults in addition to prevent evolving damage in case of internal faults. Repeated breaks of generation power stations in last few years are recorded. Because of their great impact on the Egyptian unity network (500 kV and 220 kV), it is essential to deeply review the efficiency of various existing protection schemes designed for generating stations. Detailed analyses of some of the major and destructive real faults recorded at some stations are carried out. Accordingly, modifications for the power plant protection schemes are recommended.

By 2017, Egypt is expected to finish its sixth hydropower plant which is associated with the new Assiut barrage. Based on any hydraulic structure's design, there is enormous kinetic energy created downstream of the gates. This super power water jet generated under dams/barrage gates creates a destructive scouring effect downstream of the gates. In this work, a novel approach for hydrokinetic energy application is presented. The new approach proposes installing a farm of hydrokinetic turbines on the stilling basin of the spillways of the barrage's gate. This approach does not only magnify the total electric energy which was untapped in the past but also dissipates the enormous kinetic energy downstream of the gates. The total expected captured electric power from the barrage reaches 14.88 MW compared to 32 MW rated value of the existing hydropower plant.

In the presence of distributed generation (DG), it is important to assure a fast and reliable protection system for the distribution network to avoid unintentional DG disconnection during fault conditions. In this paper, dual setting directional over-current relays are proposed for protecting meshed distribution systems with DG. Dual setting relays are equipped with two inverse time-current characteristics whose settings will depend on the fault direction. The protection coordination problem for the dual setting directional relay is formulated as a nonlinear programming problem where the objective is to minimize the overall
time of operation of relays during primary and backup operation.
The proposed protection coordination scheme using dual setting relays is compared against the conventional approach, which relies on the conventional one setting directional relay. The proposed scheme is applied to the power distribution network of the IEEE 30-bus system equipped with synchronous and inverter-based DG. The results show that the proposed protection coordination scheme with dual setting relay can significantly reduce the overall relay operating time, making it an attractive option for distribution systems with DG.

In this paper, coordination strategy that considers using user defined characteristics for the inverse time overcurrent relays is proposed. Typically, the coordination between relays operating times within meshed systems are achieved by adjusting two relay settings; pick up current and time multiplier setting (TDS and Ip). The equation that models the digital inverse time overcurrent relay operation has two constants; one of them represents the constant for relay characteristics (A) and the other one represents the inverse time type (B). The proposed coordination strategy considers the two relay characteristics constants as continuous variable settings that can be adjusted. These (A and B) values are chosen optimally in addition to (TDS and Ip) to achieve coordination. The coordination problem is formulated as a nonlinear programming problem where the main objective is to minimize the overall time of operation of relays during primary and backup operation considering faults at different locations. The results are compared against the relay coordination using the conventional settings. The problem is applied to the meshed power distribution network of the IEEE 30 bus systems equipped with synchronous based DGs. The results show that the proposed strategy can significantly reduce the overall relay operating time and thus making it an attractive option for meshed distribution systems with DG.

In medium voltage distribution network, the phenomena of having a simultaneous false trip on healthy feeder/feeders during a real fault on another feeder is common. It affects badly the continuity of service. In this paper, three different causes of this unnecessary simultaneous tripping in distribution networks are discussed. The earth fault element problems caused by these phenomena are also evaluated. A practical solution for this problem is proposed by using the custom logic scheme exists in the digital protection relay. The proposed method is applied to an actual system utilizing the existing protective digital relays. Actual records for faulty phase current and calculated zero sequence currents were captured and analyzed by means of digital fault recorders exist in the protection relay. The obtained results are encouraging and indicate the suitability and advantages of the proposed method.