Wide-area disturbances are power outages occurring over large geographical regions that dramatically affect the power system reliability, causing interruptions of the electric supply to residential, commercial, and industrial users. Historically, wide-area disturbances have greatly affected societies. Virginia Tech directed a research project related to the causes of the major disturbances in electric power systems. Research results showed that the role of the power system's protection schemes in the wide-area disturbances is critical. Incorrect operations of power system's protection schemes have contributed to a spread of the disturbances. This research defined hidden failures of protection schemes and showed that these kinds of failures have contributed in the degradation of 70-80 percent of the wide-area disturbances. During a wide-area disturbance analysis, it was found that hidden failures in protection schemes caused the disconnection of power system elements in an incorrect and undesirable manner contributing to the disturbance degradation. This dissertation presents a methodology to assess and rank the effects of unwanted disconnections caused by hidden failures based on Regions of Vulnerability and index of severity in the protection schemes. The developed methodology for the evaluation of the Region of Vulnerability found that the indicator that most accurately reflects the relationship of the Region of Vulnerability with the single line diagram is kilometers. For the representation of the Region of Vulnerability in the power system, we found segments in the transmission line in which the occurrence of faults do make the relay to operate, producing the unwanted disconnection caused by hidden failure. The results in the test system show that the infeed currents restrain the Region of Vulnerability from spreading along power system elements. Finally the methodology to compute the index of severity is developed. The index of severity has the objective of ranking the protection schemes, considers the dynamics of the protection schemes, and evaluates the overall disturbance consequence under the static and dynamic perspectives. / Ph. D.

Background: Financial constraints challenge evidence of the effectiveness of dermatological inpatient management. Objective: To evaluate the effectiveness of hospitalization in atopic dermatitis and psoriasis regarding initial and sustained benefits. Methods: Prospective study on adults with psoriasis vulgaris (n = 22) and atopic dermatitis (n = 14). At admission, discharge, and 3 months after discharge, validated outcomes of objective and subjective disease severity were assessed by trained investigators. Results: Hospitalization resulted in substantial benefit in quality of life and clinical disease severity. Looking at mean scores, the observed benefit appeared stable until 3-month follow-up. The analysis of individual patient data revealed significant changes in disease severity between discharge and 3-month follow-up with some patients relapsing, others further improving. Reasons for hospitalization and treatment performed were not related to sustained benefit. Conclusions: In psoriasis vulgaris and atopic dermatitis, hospitalization effectively improved quality of life and clinical disease severity. Further research should focus on prognostic factors for sustained improvement. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.