Samy M. Ghania

The switching surges arising due to integrating renewable energy resources with power grids have become the major factor in the insulation coordination of the power systems. Consequently, it is urgent to perform proper risk analysis of the switching surges appear over the power systems integrating with large-scale renewable energy resources. The main contribution of the current research is to develop a full comprehensive study of the risk of failure for the power transformer’s insulators due to the switching overvoltages arising from integrating large – scale renewable anergy resources with the power grids. For this objective, the IEEE 40 Bus power grid and two large-scale PV and Wind systems are simulated using EMTP-RV integrated with MATLAB. Furthermore, the probability risk assessments are performed for insulators of the interconnecting power transformer under different conditions (dry/wet) using four different probability distribution schemes. The effects of switching different power capacities of the renewable energy resources are demonstrated. The main factors affecting the risk of failure of the insulators are evaluated. The effects of the numbers of the interconnected transformers working in parallel and operating conditions are elaborated. Moreover, the effects of the switching overvoltages mitigation techniques on the risk of failure are considered.

Integration of the renewable energy sources with utility grids is receiving more impressive concerns to provide extra-green energy sources to work in parallel or to phase out the sources with fossil fuels. The effects of the transient surges are the most vital parameters that are used in the insulation coordination studies for integrated systems of smart grid. Therefore, the electromagnetic transient overvoltages caused by switching surges and faults on the smart grids are the competitive design issues. Moreover, the contingency analysis of either sources or loads patching/dispatching is one of the major issues in the design process of the power system grid. The transient overvoltages imposed over the integrated grid systems need to be more properly investigated using most sophisticated numerical methods. Although, the transient surges have relatively short durations, but it may cause severe overvoltages stresses for the insulation systems and consequently may yield to insulation failure. This paper presents the simulation of large-scale renewable energy resources integrating with the utility grid. The transient overvoltages appear over the utility grids due to different renewable energy resources are investigated. Moreover, the different methods that proposed to be used to suppress, mitigate, and control these overvoltages and to minimize their probable sever effects over the permissible insulation level (BIL) are elaborated. Furthermore, the full simulation of the IEEE 39 grid integrated with large Photovoltaic and wind farms using EMTP-RV /MATLAB is developed. In addition, different proposed methods to mitigate and to control internal surges are investigated. Finally, the obtained results are presented with very good consistency level and compliance with other research studies found in literature and with the different standards related to the renewable energy sources.

Proper operation of any power system depends on robust and continuous performance of the substations. The design of the substation grounding system plays vital role. Since the grounding system should preserve safe and effective protective schemes. This work is to investigate the different grounding systems design of a 500/220 kV substation in Egypt. The design of grounding system to get the optimum values of the desired parameters is performed by developing many M-Scripts of Matlab program. To verify the obtained results, the substation grounding system is designed using developed Ground Grid System. The obtained results are verified by using Module of the Electrical Transient and Analysis Program (ETAP). The best grounding system of the substation is advised to be used to achieve the minimum risk for equipment and workers inside the substation during normal and abnormal conditions.

The modern methods of insulation coordination make use of probabilistic concepts and statistical procedures especially for very high voltage systems. This paper presents, a proper approach to calculate the switching surge flashover rate (SSFOR) using Adaptive Neuro Fuzzy Interface System (ANFIS). The switching overvoltages distribution along the power transmission line under different conditions are investigated. The statistical distributions of energization overvoltages for a typical Egyptian 500 kV double-line from High-Dam to Samalut are derived based on the results of 100 energization scenarios by randomly switching using alternate transient program (ATP). The statistical distributions and its key values, such as mean value, standard deviation and 2% statistical overvoltages values have been recorded. The effects of the line length, source strength and shunt reactors for controlling the switching surge overvoltages are demonstrated. The developed ANFIS system is used to estimate the SSFOR for different input parameters for both of the switching overvoltages and the insulation strength distributions with high and comparable accuracy.