Distance and overcurrent relay coordination considering non standardized inverse time curves

Protective relaying comprehends several procedures and techniques focused on maintaining the power system working safely during and after undesired and abnormal network conditions, mostly caused by faulty events. Overcurrent relay is one of the oldest protective relays, its operation principle is straightforward: when the measured current is greater than a specified magnitude the protection trips; less variables are required from the system in comparison with other protections, causing the overcurrent relay to be the simplest and also the most difficult protection to coordinate; its simplicity is reflected in low implementation, operation, and maintenance cost. The counterpart consists in the increased tripping times offered by this kind of relays mostly before faults located far from their location; this problem can be particularly accentuated when standardized inverse-time curves are used or when only maximum faults are considered to carry out relay coordination. These limitations have caused overcurrent relay to be slowly relegated and replaced by more sophisticated protection principles, it is still widely applied in subtransmission, distribution, and industrial systems. In this work, the use of non standardized inverse-time curves, the model and implementation of optimization algorithms capable to carry out the coordination process, the use of different levels of short circuit currents, and the inclusion of distance relays to replace insensitive overcurrent ones are proposed methodologies focused on the overcurrent relay performance improvement. These techniques may transform the typical overcurrent relay into a more sophisticated one without changing its fundamental principles and advantages. Consequently a more secure and still economical alternative can be obtained, increasing its implementation area

Initial approach to irst-time seizures in pediatrics

Objective: Prove that conducting complementary studies at laboratories and imaging studies are unnecessary in irst-time unprovoked seizures, since there is no change in the evolution and prognosis of the disease, as well as the study of our population, the incidence rate and the proportion of our patients that have been studied and given maintenance treatment, so it can be determined whether or not our population should follow the suggestions of the American Academy of Pediatrics and the Spanish Pediatric Association. Methods: An observational study, including patients diagnosed with irst-time unprovoked seizures. They were followed up on by the emergency department and information was collected from their clinical history and compared with the results of the different studies between patients that suffered just one seizure and the ones that had recurrent seizures. Results: Thirty one patients were included, 14 males and 17 females. The average age was 5.5 years old. The 100% of patients were studied, and the groups were compared. The signiicant study was the electroencephalogram (EEG) with a p=0.02 (signiicance p<0.05), incidence of 41%. Conclusions: The study and diagnosis of irst-time unprovoked seizures is based on clinical manifestations. The EEG is important in the study and classiication of unprovoked seizures. Our population has an incidence and recurrence rate similar to that in the bibliography, and for that reason, this study suggests that the diagnostic and therapeutic guidelines of the American Academy of Pediatrics and the Spanish Pediatric Association should be followed.