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This paper proposes an optimal design of Shunt-Resonance Fault Current Limiter (SRFCL) to enhance the Fault Ride-Through (FRT) capability and improve the transient stability of a grid-connected hybrid PV/wind power system. The design parameters of the SRFCL are optimized by using Particle Swarm Optimization (PSO) technique. The proposed SRFCL topology is designed in such a way that it can provide superior protection capability for limiting the fault current and supporting the grid voltage than the conventional Bridge Fault Current Limiter (BFCL). The effectiveness of the SRFCL in supporting the dynamic performance and improving the transient stability of the hybrid energy system is validated during both symmetrical and unsymmetrical faults in the electrical utility. Moreover, its credibility is evaluated compared with that of the BFCL and the FRT control schemes. Simulations have been performed using the MATLAB/SIMULINK software. The results illustrate that the proposed SRFCL augments significantly the dynamic behavior and the transient stability of the hybrid power system during the fault events. Also, when the optimal SRFCL is employed, the injected active power by the hybrid system and the grid voltage profile are improved considerably under the grid disturbances. Furthermore, the comparison confirms the superiority of the SRFCL performance to both the BFCL topology and the FRT control scheme in every aspect.

This research presents the evaluation of activated Bentonite material for treatment of used transformer oil. Different properties such as; electrical, physical, chemical and thermal of used transformer oil were meas-ured before and after purification and treatment. Two power transformers were used in this research (6.4: 4.6 MVA, 3 phases, 50 Hz). One of them was filled with purified oil and the other was filled with activated Bentonite treated oil after purification, and then the two power transformers were tested for one year under practical conditions of the operating field. Initial tests have indicated that the use of Activated BENTONITE in the treatment process for the aged transformer oil improved breakdown voltage, water content, total acidi-ty and flash point. Thus activated Bentonite gives an ideal treatment of aged transformer oil with its environmental and economic advantages. Moreover, activated Bentonite is available at many places in Egypt with low costs

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