Measurement of respiratory rate (RR) is essential in the evaluation of respiratory disorders. However, the variability in RR measurement in adults has never been adequately assessed. Respiratory rate was measured twice in 245 patients; the two measurements were performed by the same observer in 137 patients, by different observers in 58 patients and simultaneously by different observers in 50 patients. The mean (SD) difference between the first and second measurements was 0.03 (3); 95% limits of agreement-4.86-4.94 breaths min(-1), -5.7-5.7 breaths min(-1), and -4.2 to 4.4 breaths min(-1) for the same observer, different observer and simultaneous observer groups, respectively. The difference in RR measurements did not vary with RR. In conclusions on average, there is very good agreement between observers in RR measurement. Inter-observer variability may account for a difference of up to 6 breaths min(-1). This is relevant when applying clinical prediction rules based on threshold RR values.
Disconnector switching operations in large gasinsulated switchgear (GIS) systems may cause very fast transients oscillations (VFTO). These VFTO surges produce dielectric stress to other apparatus of the substation. This paper describes the test technique for measuring VFTO waves straight at the high voltage entry of a 550 kV/ 840 MVA generator stepup transformer. Additionally, the signal processing for elimination the test circuit transfer effect is explained. Repetitive tests identify the reliability of test circuit and test equipment. The characteristics of recorded VFTO impulses confirm the state-ofthe art experience of other publications.Different case studies are applied for identifying the worst case configuration of busbar system regarding the effective VFTO stress for the generator transformer. Operating the closest disconnector while all busbar systems are interconnected causes the highest dielectric stress for the transformer entry.
SUMMARYThe transfer function (TF) is a comparative method to monitor the mechanical condition of transformer windings. To perform on-site diagnosis a high reproducibility of TF results is required. Consequently, there are certain restrictions for the determination of the TF using time domain records. This paper describes the effect of different signal processing procedures on the results of TF calculations. Window functions, digital filters, length and treatment of pre-trigger samples are aspects of special interest for the application of the TF method. Additionally, condition parameters of the device under test affect the results of TF measurements. The correlation of transformer temperatures and TF characteristics has been investigated as well as the dielectric effect of the insulating oil and the position of the tap changer. Finally, the effect of different test setup concepts is presented.
Transient currents can cause the mechanical displacement of transformer windings. The transfer function method is presented as a tool to detect this displacement. In order to be able to evaluate the measurements, the correlation between the characteristics of transfer functions and possible damages must be known. Axial displacement of transformer windings has been studied in this research. As test object a transformer with a primary winding of 31 double inverted disk (approx. 1.3 MVA, 10 kV) and a secondary winding with four layer concentric winding was used. A detailed mathematical model was developed for the test object and a comparison was carried out between measured and calculated results. To compare the sensitivity of transferfunctions, five different transferfunctions with different terminal conditions are simulated. It is shown that the detailed model can present the behaviour ofthe transformer winding in case of sound and displaced windings.
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