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The magnetizing current inrush appears in electrical power units equipped with transformers in case of no-load energizing of the power transformers and in a number of other cases. This phenomenon could cause a false triggering of the current protection. To prevent incorrect actions of the current protection during the magnetizing current inrush a protection blocking is carrying out. The blocking principle operation is based on the fact that in a three-phase system in normal mode and in case of symmetrical short circuit the first harmonics contained in the phase currents of electrical installations form a direct sequence and the second ones – the negative sequences. In case of an asymmetric mode, including an asymmetric short circuit, the negative sequence appears, formed by the first harmonics that are part of the phase currents of the specified system. In magnetizing current inrush modes, second harmonics of significant magnitude are present in phase currents, which form the negative sequence. Based on the analysis of the information parameters of the specified sequences currents, identification of the magnetizing current inrush and short-circuit modes is performed with the implementation of the protection blocking if necessary. The study of the current protection blocking functioning was performed using computational experiment by analyzing the calculated changes of blocking parameter compared with the threshold setpoint. The specified researching is done by using the digital model that is implemented in the dynamic modeling environment MatLab-Simulink. As a result of the performed calculations, the principal operability of the proposed current protection blocking was confirmed that provides a fairly reliable identification of the magnetizing current inrush and short-circuits modes, regardless of the degree of saturation of current transformers. It was found that the proposed principle of the current protection blocking has a higher sensitivity in comparison with the classical one based on the estimation of the ratio of the second and first harmonics of the phase currents. In short-circuit modes in an electrical power units the proposed blocking causes a current protection operation delay that can be reduced by digital filters performance improvement.

The OBJECTIVE of the study was to evaluate the effectiveness of the use of «early» (up to 3 days) valve bronchial blocking in the complication of postoperative period in patients with bullous emphysema. MATERIAL AND METHODS. For the period from 2009 to 2017, 32 patients with bullous pulmonary emphysema had a long (more than 3 days) air leakage from the pleural cavity. Depending on the time of the valve bronchial blocker installation, the patients were divided into 2 groups: 1 group («late» blocking): the valve bronchial blocker was placed later than 3 days after the operation (11 patients); 2 group («early» blocking): the valve bronchial blocker was placed for 2–3 days from the operation (21 patients). RESULTS. During the first two days, air discharge through the pleural drainage was discontinued in 16 patients of the «early» blocking group and in 2 patients of the «late» blocking group (р=0.0022). The duration of air leakage in the «early» blocking group was 1.59 days less (44.91 %) than in patients of the «late» blocking group (р=0.0024). The positive blocking effect was fixed in 85.71 % (18) of the patients of the group with «early» blocking, which was 3.6 times higher than in the patients of the «late» blocking group (р= 0.04). The frequency of repeated intervention in the «early» blocking group was 3.81 times less than in the «late» blocking group (54.54 % vs. 14.28 %) (р=0.08). CONCLUSION. «Early» valve bronchoblocation (performed on the 2–3rd day of the postoperative period) had an indisputable advantage in comparison with bronchial blocking performed at the time of more than 3 days postoperative period, allowing reliably faster lung dilatation and eliminating air discharge through drainage from the pleural cavity, without resorting to repeated interventions, which was important, both for the surgeon and for the patient.

Principles of implementation of current protection of elements of electric power systems with power transformers are considered. In some cases, in facilities with power transformers there could be an inrush of a magnetizing current that can cause a false positive current protection. The special measures of blocking of current protection ought to be taken to avoid this. The methods of implementation of blocking digital current protection when magnetizing current inrush takes place are described. The main way of blocking protection from magnetizing current inrush is tuning-out by harmonics content. The presence of lower harmonics content serves as a criterion of permitting operation of the protection and the higher harmonics content, on the contrary, indicates the appearance of magnetizing current inrush and is used to block the protection action. The operation condition of blocking of digital protection from magnetizing current inrush is presented. A realization of digital part of implementation of current protection blocking is described and the functional scheme of the latter is considered. The scheme contains conditioners of orthogonal components of signals of the first and second harmonics as well as the filters of positive and reverse sequences and blocks of determination of amplitudes. The blocks compute current amplitudes of first harmonic of positive sequence and the negative sequence current of the second harmonic with the use of the orthogonal components. By these values the characteristic quantity of blocking is calculated, which is compared with the activation setpoint. The improvement of performance of the principles of blocking current protection of electric transformers with current magnetizing inrush has been suggested by incorporating the digital part the block of the maximum value formation that determines the maximum amplitude of the first harmonic of the total current into the functional block scheme.