Doaa Khalil Ibrahim

Increasing energy demand worldwide has resulted in more penetration of renewable sources for developing non-polluted electric energy despite their prices are not economically competitive to traditional generation systems due to intermittent nature of renewable resources. Energy storage systems are used to counteract the intermittent nature of renewable sources. Therefore, the optimal sizing and design of stand-alone renewable generating systems is a significant concern to get a more cost-effective system. This paper focuses on achieving the optimum design and size of a microgrid to meet the load requirements and reducing the total cost including capital, investment, operational and maintenance costs. For this aim, the sizing problem is formulated to be solved using three well-known metaheuristic algorithms, namely, Particle Swarm Optimization (PSO), Grey Wolf Optimization (GWO) and Cuckoo Search Optimization (CSO). The employed microgrid comprises hybrid renewable energy sources of PV/Wind systems integrated with a hybrid energy storage system of Battery and FC/Electrolyzer set for supplying AC loads located in Zafarana, Egypt. On the basis of real meteorological data of the studied location, the produced energies from the renewable sources are estimated using MATLAB developed algorithms. The simulation results showed that the optimized design using CSO can robustly and efficiently yield the optimal design of a microgrid.

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.

The main purpose of this paper is focused upon the enhancement of transient stability and improvement of the dynamic behavior of Egyptian electrical power grid including new nuclear power station in Dabaa area. This target is achieved via employing only one device as a first approach of solution. That device is the Static VAR Compensator (SVC). Capability of that device to provide synchronizing torque is tested at different implementation conditions, as well as, different locations of feedback signals. For that purpose, singular value decomposition is used and siting index program is created. A second approach of solution is also proposed, in which a Power System Stabilizer (PSS) is added as a more effective device in providing damping torque. For the two proposed approaches, devices' time constants and gains are set using genetic algorithm optimization technique (GA).

Connection of distributed generation (DGs) powered by renewable energy resources in power systems has numerous benefits. However the presence of these (DGs) increase the fault current levels in different points, and disturb the protection coordination of the existing relays. Two approaches are proposed for coordination of directional overcurrent relays (DOCRs) in power systems with (DGs), depending on the types of system relays either adaptive or non adaptive. For adaptive protection system, the first proposed approach is based on linear programming technique which used to calculate the relay settings in case of DGs existing or not. For non-adaptive protection system, the second proposed approach is introduced, in which minimum impedance of fault current limiter is calculated to restore the coordination of relays without altering the original relay settings. The two proposed approaches are implemented and tested on IEEE-39 bus test system.

This paper proposes a differential protection scheme for transmission lines using the energy conservation law. The real power signals at both ends (sending and receiving) of the line are compared with a prespecified value, if the resultant is more than this value, an internal fault is indicated in the transmission line zone. The proposed technique is evaluated using PSCAD/EMTDC program configurated to model the effect of faults on typical 500 kV transmission line. Extensive simulation studies show that this protection scheme has the ability to discriminate internal faults fast and accurately, and is more reliable than conventional biased differential protection scheme, and suitable for all types of lines. Details of the proposed relay design are given in the paper; also results of some performance studies are given.

Abstract—This paper presents a novel wavelet-based fault-location scheme for aged cable systems when synchronized digital fault recorded data are available at the two terminals of each cable. The proposed scheme estimates the fault location in multiend-aged cable systems using the theory of wavelet singularity detection as a powerful signal processing tool. The arrival of the first and second voltage traveling waves at both ends of the power cables can be identified reliably. The developed wavelet processing scheme is applied on the modal coordinates instead of the phase coordinates. The proposed scheme has the ability to eliminate the impact of the change in the propagation velocity of the traveling waves on the fault-location calculations. This will help solve the problem of cable changing parameters, especially the change of the relative permittivity of the cable with age. The method is valid even with faults that are very close to busbars. Characteristics of the proposed fault-location scheme are analyzed by extensive simulation studies using Alternative Transients Program/Electromagnetic Transients Program. The results indicate an accepted degree of accuracy for the suggested fault locator.

This paper presents a novel wavelet-based fault-location scheme for aged cable systems when synchronized digital fault recorded data are available at the two terminals of each cable. The proposed scheme estimates the fault location in multiend-aged cable systems using the theory of wavelet singularity detection as a powerful signal processing tool. The arrival of the first and second voltage traveling waves at both ends of the power cables can be identified reliably. The developed wavelet processing scheme is applied on the modal coordinates instead of the phase coordinates. The proposed scheme has the ability to eliminate the impact of the change in the propagation velocity of the traveling waves on the fault-location calculations. This will help solve the problem of cable changing parameters, especially the change of the relative permittivity of the cable with age. The method is valid even with faults that are very close to busbars. Characteristics of the proposed fault-location scheme are analyzed by extensive simulation studies using Alternative Transients Program/Electromagnetic Transients Program. The results indicate an accepted degree of accuracy for the suggested fault locator.

This paper presents a novel wavelet-based travelling wave fault location algorithm for aged underground cables in transmission systems. Such transmission systems consist of overhead lines combined with underground power cables. Applying the singularity detection feature of wavelets as a powerful signal processing tool, the first and second initial arrival of the voltage travelling waves at the first end of the overhead as well as at the terminal end of the aged cable line can be identified reliably without the need for detection the sign of these waves. In this paper modal signals, rather than the phase signals, are
the inputs to the relay. The proposed algorithm is capable of eliminating the effect of the change in the propagation velocity of the travelling waves over the age of the cable. It can be used on-line
following the operation of digital relays or off-line using the data stored in the digital transient recording apparatus. Extensive simulation studies carried out using ATP/EMTP show that the proposed algorithm provides an accepted degree of accuracy in fault location under different fault conditions.